HomeMy WebLinkAboutPermit L92-0025 - CITY OF TUKWILA - 1991 COMPREHENSIVE SEWER SYSTEM PLAN: ANNEXATION AREASL92-0025
1991 COMPREHENSIVE SEWER SYSTEM PLAN
ANNEXATION AREAS
COMPREHENSIVE PLAN COMPREHENSIVE LAND USE PLAN
Responsible Official
City of Tukwila, (206) 431 -3680
6300 Southcenter Boulevard
Tukwila, WA 98188
CITY OF TUKWILA
DETERMINATION OF NONSIGNIFICANCE (DNS)
DATE: Mar 23, 1992
DESCRIPTION OF PROPOSAL:
CITY OF TUKWILA 1991 COMPREHENSIVE SEWER SYSTEM
PLAN AND INCLUDING SUPPLEMENT A - ANNEXATION AREAS
PROPONENT: CITY OF TUKWILA
LOCATION OF PROPOSAL, INCLUDING STREET ADDRESS, IF ANY:
LEAD AGENCY: CITY OF TUKWILA FILE NO: L92 -0025
The City has determined that the proposal does not have a probable
significant adverse impact on the environment. An environmental impact statement (EIS) is not required under RCW 43.21c.030(2)(c).
This decision was made after review of a completed environmental
checklist and other information on file with the lead agency. This
information is available to the public on request.
COMMENTS MUST BE SUBMITTED WITHIN 10 DAYS.
******************************************** * * * * * * * * * * * * * * * * * * * * * * * * * * * * * **
This determin. '•, is final and signed this
199Z. _
day of
You may appeal this determination to the City Clerk at City Hall, 6200
Southcenter Boulevard, Tukwila, WA 98188 no later than 10 days from the
above signature date by written appeal stating the basis of the appeal for
specific factual objections. You may be required to bear some of the
expenses for an appeal.
Copies of the procedures for SEPA appeals are available with the City
Clerk and Department of Community Development.
Address:
Permit No: L92 -0025
Type: P -SEPA
Location:
Parcel #:
CITY TUKWILA
COMMENTS
Status: PENDING
Applied: 03/02/1992
Issued:
******************************************** * * * * * * * * * * * * * * * * * * * * * * * * * * * * * **
Permit Comments:
PLAN CONTEMPLATES THE ADOPTION OF THE 1991 CITY OF TUKWILA
COMP. SEWER SYSTEM PLAN, WITH SUPPLEMENT A - ANNEXATION
AREAS. THESE DOCUMENTS ADDRESS FUTURE SEWER SERVICE TO ALL
ARES OF THE EXISTING TUKWILA CITY LIMITS AND PROPOSE A CAPIT
AL IMPROVEMENTS SCHEDULE FOR SYSTEM IMPROVEMENT IN
ACCORDANCE WITH SEWER SYSTEM FLOW PROJECTIONS DEVELOPED AS
PART OF THE PLAN. THE EFFICIENT PLANNING AND DESIGN OF
UTILITIES & MINIMIZING THE USE OF PUMP STATIONS WILL ASSIST
IN CONSERVATION OF ENERGY. THIS IS FUNDAMENTAL TO THE COMP
PLAN. THE PLAN WILL NOT IMPACT DEMANDS ON TRANSPORTATION OR
PUBLIC UTILITIES, BUT WILL PROVIDE A GUIDELINE FOR FUTURE
DEVELOPMENT OF THE CITY'S SEWER SYSTEM. THE INTENT OF THE
MENT OF THE CITY'S SEWER SYSTEM. THE COMP. PLAN INTENT
DOES NOT INCLUDE SPECIFIC SEWER SYSTEM INFRASTRUCTURE.
PROJECTS. ENVIRONMENTAL ANALYSIS INCLUDING EVALUATION OF
POTENTIAL ALTERNATIVES WILL BE CONDUCTED WITH INDIVIDUAL
PROJECTS PROPOSALS DURING PLAN IMPLEMENTATION.
None Known.
None Known.
Ross Earnst, Director of Public Works
6300 Southcenter Blvd.
Tukwila, Washington 98188
(206) 433 -0179
4. Date checklist prepared:
November 15, 1991.
5. Agency requesting checklist:
City of Tukwila.
6. Proposed timing or schedule (including phasing, if applicable):
1 021Z1{1 —
ENVIRONMENTAL CHECKLIST 1 FE812 1992
A. BACKGROUND Lcl 2 Q ,
CIT ,,,A
1. Name of proposed project, if applicable: PLANNING DEPT.
City of Tukwila
1991 Comprehensive Sewer System Plan, including Supplement A - Annexation Areas.
2. Name of applicant:
City of Tukwila.
3. Address and phone number of applicant and contact person:
A suggested Capital Improvement Schedule is included in Chapter 6 of the Base Sewer System
Plan and Chapter 5 of Supplement A - Annexation Areas. Specific timing of improvements will
depend on the availability of funding, scheduling of developer extensions and sewer system
demands.
7. Do you have any plans for future additions, expansion, or further activity related to or
connected with this proposal? If yes, explain.
Please refer to Chapter 6 of the base plan and Chapter 5 of the supplement for detailed
information on future improvements contemplated for the Tukwila sewer system. The sewer system
plan does not propose any land use expansions or changes and only considers the system
improvements which are required to meet existing and projected sewer system flows.
8. List any environmental information you know about that has been prepared, or will be
prepared, directly related to this proposal.
9. Do you know whether applications are pending for governmental approvals of other proposals
directly affecting the property covered by your proposal? If yes, explain:
Tukwila City Council Approval.
State of Washington Department of Ecology review.
10. List any government approvals or permits that will be needed for your proposal, if known.
11. Give brief, complete description of your proposal, including the proposed uses and the size
of the project and site. There are several questions later in this checklist that ask you to describe
certain aspects of your proposal. You do not need to repeat those answers on this page. (Lead
agencies may modify this form to include additional specific information on project description.)
This proposal contemplates the adoption of the City of Tukwila 1991 Comprehensive Sewer System
Plan, with Supplement A - Annexation Areas. These documents address future sewer service to
all areas of the existing Tukwila city limits and propose a capital improvements schedule for
system improvements in accordance with sewer system flow projections developed as part of the
Plan.
12. Location of the proposal. Give sufficient information for a person to understand the precise
location of your proposed project, including a street address, if any, and section, township, and
range, if known. If a proposal would occur over a range of area, provide the range or boundaries
of the site(s). Provide a legal description, site plan, vicinity map, and topographic map, if
reasonably available. While you should submit any plans required by the agency, you are not
required to duplicate maps or detailed plans submitted with any permit applications related to this
checklist.
The City of Tukwila is generally located south of the City of Seattle, east of the City of Sea Tac
and west of the City of Renton as indicated on Figure 1 -1 of the Plan. The City is within all or
part of the following Sections: Section 33, Township 24 North; and, Sections 3, 4, 9, 10, 14, 1 5,
22, 23, 24, 25, 26, 35, and 36, Township 23 North, Range 4 East.
B. ENVIRONMENTAL ELEMENTS
1. Earth
a. General description of the site (circle one): Flat, rolling, hilly, steep slopes,
mountains, other
Topography of the area is characterized by the flat topography of the Duwamish River
Valley floor, with slopes leading up to a plateau in the western portion of the City.
b. What is the steepest slope on the site (approximate percent slope)?
Not Applicable.
c. What general types of soils are found on the site (for example, clay, sand, gravel,
peat, muck)? If you know the classification of agricultural soils, specify them and note
any prime farmland.
The majority of the area consists of alluvial soils composed of silt, clay and some peat
with some bedrock outcroppings.
d. Are there surface indications or history of unstable soils in the immediate vicinity?
If so, describe.
2. Air
Not Applicable.
Not Applicable.
Not Applicable.
3. WATER
a. Surface:
... :
•
Unstable soils may occur along the banks of the Duwamish River or in steep slopes
leading to the valley floor.
e. Describe the purpose, type, and approximate quantities of any filling or grading
proposed. Indicate source of fill.
f. Could erosion occur as a result of clearing, construction, or use? If so, generally
describe.
g. About what percent of the site will be covered with impervious surfaces after project
construction (for example, asphalt or buildings)?
Not Applicable.
h. Proposed measures to reduce or control erosion, or other impacts to the earth, if any:
Not Applicable.
a. What types of emissions to the air would result from the proposal (i.e., dust,
automobile, odors, industrial wood smoke) during construction and when the project is
completed? If any, generally describe and give approximate quantities if known.
b. Are there any off-site sources of emissions or odor that may effect your proposal?
If so, generally describe.
Not Applicable.
c. Proposed measures to reduce or control emissions or other impacts to air, if any:
Not Applicable.
1) Is there any surface water body on or in the immediate vicinity of the site
(including year -round and seasonal streams, saltwater, lakes, ponds, wetlands)?
If yes, describe type and provide names. If appropriate, state what stream or
river it flows into.
The Green - Duwamish River, flows through the City of Tukwila as indicated on the
maps included in the Plan. Other small streams and wetland areas are within the
city limits. This proposal does not impact any surface waters.
2) Will the project require any work over, in, or adjacent to (within 200 feet)
;
No.
b. Ground
the described waters? If yes, please describe and attach available plans.
Not Applicable. This proposal contemplates adoption of the Plan only. Specific
project construction documents will address surface water considerations as
required.
3) Estimate the amount of fill and dredge material that would be placed in or
removed from surface water to wetlands and indicate the area of the site that
would be affected. Indicate the source of fill material.
Not Applicable.
No.
4) Will the proposal require surface water withdrawals or diversions? Give
general description, purpose, and approximate quantities if known.
5) Does the proposal lie within a 100 -year floodplain? If so, note location on
the site plan.
Not Applicable. This proposal does not contemplate any activity relating to
floodplains.
6) Does the proposal involve any discharges of waste materials to surface
waters? If so, describe the type of waste and anticipated volume of discharge.
1) Will ground water be withdrawn, or will water be discharged to ground
water? Give general description, purpose, and approximate quantities if known.
No.
2) Describe waste material that will be discharged into the ground from septic
tanks or other sources, if any (for example: Domestic sewage; industrial,
containing the following chemicals ... agricultural; etc.). Describe the general
size of the system, the number of such systems, the number of houses to be
served (if applicable), or the number of animals or humans the system(s) are
expected to serve.
None.
c. Water Runoff (including storm water):
1) Describe the source of runoff (including storm water) and method of
collection and disposal, if any (include quantities, if known). Where will this
water flow? Will this water flow into other waters? If so, describe.
Not Applicable.
4. PLANTS
..
•
'*'
2) Could waste materials enter ground or surface waters? If so, generally
describe.
Not Applicable.
d. Proposed measures to reduce or control surface, ground, and runoff water impacts,
if any:
This Comprehensive Plan has been developed to address the provision of sanitary sewer
service to all areas of the City. Provision of such service will protect surface and ground
water quality by reducing the hazards associated with on -site sewage disposal.
a. Check or circle types of vegetation found on the site:
X deciduous tree: alder, maple, aspen, other
X evergreen tree: fir, cedar, pine, other:
X shrubs,
grass
X pasture
_ crop or grain
X wet soil plants: cattail, buttercup, bulrush, skunk cabbage, other
water plants: water lily, eelgrass, milfoil, other
_ other types of vegetation:
b. What kind and amount of vegetation will be removed or altered?
None.
c. List threatened or endangered species known to be on or near the site.
None Known.
d. Proposed landscaping, use of native plants, or other measures to preserve or enhance
vegetation on the site, if any:
Not Applicable.
5. ANIMALS
a. Circle any birds and animals which have been observed on or near the site or are
known to be on or near the site:
birds: hawk, heron, eagle, songbirds, other:
mammals: deer, bear, elk, beaver, other:
fish: bass, salmon, trout, herring, shellfish, other:
b. List any threatened or endangered species known to be on or near the site.
None Known.
c. Is the site part of a migration route? If so, explain.
Puget Sound Flyway.
......
c. What kinds of energy conservation features are included in the plans of this proposal?
List other proposed measures to reduce or control energy impacts, if any:
Future sewer system projects have been designed to minimize the use of energy for
pumping of sewage flows.
7. ENVIRONMENTAL HEALTH
a. Are there any environmental health hazards, including exposure to toxic chemicals,
risk of fire and explosion, spill, or hazardous waste, that could occur as a result of this
proposal? If so, describe.
There is a minimal hazard associated with the operation of sanitary sewer systems.
1) Describe special emergency services that might be required.
Sewer system monitoring and emergency response procedures are employed by the
City in accordance with the State Department of Ecology requirements.
2) Proposed measures to reduce or control environmental health hazards, if any:
Provision of sanitary sewer service is in itself a mitigation measure for protection
of the environment.
b. Noise
1) What types of noise exist in the area which may affect your project (for
example: traffic, equipment, operation, other)?
Not Applicable.
2) What types of levels of noise would be created by or associated with the
project on a short -term or a long -term basis (for example: traffic, construction,
operation, other)? Indicate what hours noise would come from the site.
None.
3) Proposed measures to reduce or control noise impacts, if any:
None Required.
8. LAND AND SHORELINE USE
a. What is the current use of the site and adjacent properties?
The existing land use of the area is identified in Chapter 2 of the Base Plan and
Supplement A - Annexation Areas. As indicated, land use within the City of Tukwila
ranges from single and multi family residential uses to Boeing Field airfield. Southcenter
Shopping Center is a regional shopping area located in the heart of Tukwila. Other
commercial, industrial and warehouse uses also exist in the Southcenter area.
b. Has the site been used for agriculture? If so, describe.
Not Applicable.
c. Describe any structures on the site.
Not Applicable.
d. Will any structures be demolished? If so, what?
No.
e. What is the current zoning classification of the site?
Zoning is consistent with land use and is identified in Chapter 2 of the Base Plan and
Supplement A.
f. What is the current comprehensive plan designation of the site?
Please refer to Chapter 2 of the Base Plan and Supplement A. Comprehensive Plan
designations reflecting the diverse land uses within the City are appropriately assigned.
g. If applicable, what is the current shoreline master program designation of the site?
Not Applicable.
h. Has any part of the site been classified as an "environmentally sensitive area? If so,
specify.
Sensitive areas are identified by the City of Tukwila Department of Community
Development. This Comprehensive Water System Plan will not impact such areas.
i. Approximately how many people would reside or work in the completed project.
Not Applicable.
j. Approximately how many people would the completed project displace?
None.
9. HOUSING
None.
k. Proposed measures to avoid or reduce displacement impacts, if any:
Not Applicable.
1. Proposed measures to ensure the proposal is compatible with existing and projected
land uses and plans, if any:
This Comprehensive Sewer System Plan was developed to address the future sewer system
needs of the City of Tukwila based on existing and projected land use patterns and
associated sewer system capacity requirements.
a. Approximately how many units would be provided, if any? Indicate whether high,
middle, or low- income housing.
b. Approximately how many units, if any, would be eliminated? Indicate whether high,
middle, or low- income housing.
None.
c. Proposed measures to reduce or control housing impacts, if any:
Not Applicable.
10. AESTHETICS
^;+ "_'
a. What is the tallest height of any proposed structure(s), not including antennas: what
is the principal exterior building material(s) proposed?
Not Applicable.
b. What views in the immediate vicinity would be altered or obstructed?
None.
c. Proposed measures to reduce or control aesthetic impacts, if any:
Not Applicable.
11. LIGHT AND GLARE
a. What type of light or glare will the proposal produce? What time of day would it
mainly occur?
None.
b. Could light or glare from the finished project be a safety hazard or interfere with
views?
Not Applicable.
No.
Not Applicable.
Not Applicable.
Not Applicable.
13. HISTORIC AND CULTURAL PRESERVATION
c. What existing off -site sources of light or glare may affect your proposal:
Not Applicable.
d. Proposed measures to reduce or control light and glare impacts, if any:
Not Applicable.
12. RECREATION
a. What designated and informal recreational opportunities are in the immediate vicinity.
Not Applicable.
b. Would the proposed project displace any existing recreational uses? If so, describe.
c. Proposed measures to reduce or control impacts on recreation, including recreation
opportunities to be provided by the project or applicant, if any:
a. Are there any places or objects listed on, or proposed for, national, state, or local
preservation registers known to be on or next to the site? If so, generally describe.
b. Generally describe any landmarks or evidence of historic, archaeological, scientific,
or cultural importance known to be on or next to the site.
Not Applicable.
c. Proposed measures to reduce or control impacts, if any:
Not Applicable.
14. TRANSPORTATION
a. Identify public streets and highways serving the site, and describe proposed access to
the existing street system. Show on site plans, if any.
See Figure 1 -1 and 2 -1 of the Base Plan and Supplement A - Annexation Areas.
Interstate Highways 5 and 405, the Burlington Northern Railroad, and State Route 99
bisect the City.
b. Is site currently served by public transit? If not, what is the approximate distance to
the nearest transit stop?
None.
No.
No.
Signature:
Date Submitted:
c. How many parking spaces would the completed project have? How many would the
project eliminate?
d. Will the proposal require any new roads or streets, or improvements to existing roads
or streets, not including driveways? If so, generally describe (indicate whether public or
private).
e. Will the project use (or occur in the immediate vicinity of) water, rail, or air
transportation? If so, generally describe.
f. How many vehicular trips per day would be generated by the completed project? If
known, indicate when peak volumes would occur.
None.
g. Proposed measures to reduce or control transportation impacts, if any:
Not Applicable.
15. PUBLIC SERVICES
a. Would the project result in an increased need for public services (for example: fire
protection, police protection, health care, school, other)? If so, generally describe.
No.
b. Proposed measures to reduce or control direct impacts on public services, if any.
Not Applicable.
16. UTILITIES
a. Circle utilities currently available at the site: electricity, natural gas, water, refuse
service, telephone, sanitary sewer, septic system, other.
b. Describe the utilities that are proposed for the project, the utility providing service,
and the general construction activities on the site or in the immediate vicinity which might
be needed.
This proposal establishes a plan for the future development of sewer systems within the
City of Tukwila and assures that adequate facilities are provided to meet projected sewer
system capacity requirements.
C. SIGNATURE
The above answers are true and complete to the best of my knowledge. I understand that the lead
agency is relying on them to make its decision.
•
D. SUPPLEMENTAL SHEET FOR NONPROJECT ACTIONS
1. How would the proposal be likely to increase discharge to water; emissions to air; production,
storage, or release of toxic or hazardous substances; or production of noise?
No Increases.
Proposed measures to avoid or reduce such increases are:
Not Applicable.
2. How would the proposal be likely to affect plants, animals, fish or marine life?
No Impacts.
Proposed measures to protect or conserve plants, animals, fish or marine life are:
None Necessary.
3. How would the proposal be likely to deplete energy or natural resources?
Construction of new sewer facilities will require the use of construction materials typical to this
type of construction.
Proposed measures to protect or conserve energy or natural resources are:
Efficient planning and design of utilities and minimizing the use of pump stations will assist in
conservation of energy.
4. How would the proposal be likely to use or affect environmentally sensitive areas or areas
designated (eligible or under study) for governmental protection; such as parks, wilderness, wild
and scenic rivers, threatened or endangered species habitat, historic or cultural sites, wetlands,
floodplains, or primelands?
This proposal will not impact any of the above listed areas.
Proposed measure to protect such resources of to avoid or reduce impacts are:
Any future work done on the Tukwila sewer system will be consistent with the regulations and
policies governing the protection of such resources.
5. How would the proposal be likely to affect land and shoreline use, including whether it would
allow or encourage land or shoreline uses consistent existing plans?
This proposal will not affect, allow or encourage land and shoreline uses.
Proposed measures to avoid or reduce shoreline and land use impacts are:
Not Applicable.
Not Applicable.
6. How would the proposal be likely to increase demands on transportation or public services
and utilities?
This proposal will not impact demands on transportation or public utilities but will provide a
guideline for future development of the City's sewer system.
Proposed measures to reduce or respond to such demands are:
7. Identify, if possible, whether the proposal may conflict with local, state or federal laws
requirements for the protection of the environment.
This proposal is not in conflict with any such laws.
TO BE COMPLETED BY APPLICANT'+.- Evaluation for
Agency Use Only
E. SUPPLEMENTAL SHEET FOR ALL PROJECT AND NON PROJECT
PROPOSALS
The objectives and the alternative means of reaching the
objectives for a proposal will be helpful in reviewing the
aforegoing items of the Environmental Checklist. This
information provides a general overall perspective of the
proposed action in the context of the environmental infor-
mation provided and the submitted plans, documents, suppor-
tive information, studies, etc.
1. What are the objective(s) of the proposal
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3. Please compare the alternative means and indicate the
preferred course of action:,
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2. What are the alternative means' of accomplishing these
objectives?
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4. Does the proposal conflict with policies of the Tukwila
Comprehensive Land Use Policy Plan? If so, what poli-
cies of the P1 Plan?
Proposed measures to avoid or reduce the conflict(s)
are: , _
-23-
Evaluation for
Agency Use Only
COPIES
DATE
NO.
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ATTN: Jack Pace, Senior PLanner
DESCRIPTION
SUBJ:
Department of Community DeveL.
1
City of TukwiLa
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LETTER OF TRANSMITTAL
DATE 01 -10 -92
JOB NO.A9z
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ATTN: Jack Pace, Senior PLanner
TO: Jack Pace /Rick E3eeLer
SUBJ:
Department of Community DeveL.
SEWER COMPREHENSIVE PLAN
City of TukwiLa
& ANNEXED AREA UPDATE
WE ARE SENDING YOU:
ri Shop drawings
❑ Copy of letter
THESE ITEMS ARE TRANSMITTED AS CHECKED BELOW:
❑ As requested
n For your information
For your use
n For bids due (date):
COPIES TO:
City of Tukwila Public Works Department
6300 Southcenter Blvd., Tukwila, Washington 98188
(206) 433 -0179
17<1 Attached n Under separate cover via the following items:
n Prints ❑ Plans ri Samples Ti Specifications
❑ Change order bn Other: Gory,
C'for review ❑ Approved as submitted
Rtor approval n Approved as noted
ssuance of ❑ Returned for corrections
DNS
REMARKS:
SIGNED: ,
TITLE: .. io.4.
If enclosures are not as noted, please notify us at once. Thank you.
❑ Resubmit copies for approval
❑ Submit copies for distribution
❑ Return corrected prints
❑ Prints returned after loan to us
CITY. OF TUB
COMPREHENSIVE SEWER SYSTEM PLAN
1991
CITY OF TUKWILA
COMPREHENSIVE SEWER SYSTEM PLAN
1991
PREPARED BY:
Horton Dennis & Associates
Consulting Engineers, Planners & Surveyors
320 Second Avenue South
Kirkland Washington
EXECUTIVE SUMMARY
EXECUTIVE SUMMARY
Summary
The City of Tukwila is authorized by the State of Washington, under RCW 35.27 to operate and maintain
public utility systems for the benefit of its population. This report is the Comprehensive Sewer Plan
Intended to guide the City through future operation of sanitary sewer systems within the city. This
document updates the previous Comprehensive Sewer Plan which was adopted in 1984 and addressed
sewer service to all areas within the 1984 city limits. This update has been prepared under a contract
with Horton Dennis and Associates, Inc. of Kirkland, Washington.
This update includes changes to the sewer service area, projected population and employment,
development plans zoning and new developments since adoption of the 1984 Plan. The main body of the
Plan addresses sewer service within the Tukwila city limits as of January 1988. Since that date, the City
has completed five major annexations, including: Fire District No. 1; Riverton; Foster; Thorndyke; and
Cascade View. Sewer service to these areas is addressed in Supplement A - Annexation Areas. This
summary addresses the findings and recommendations of the complete Comprehensive Sewer Plan,
including Supplement A.
The intent of this Plan is to enable the City to be better prepared to meet its long range sanitary sewer
system needs. In this effort, the Plan addresses a number of elements in accordance with State
Department of Ecology guidelines and accepted engineering and planning practices. The following briefly
highlights each of these elements:
* Planning Considerations and Service Area Characteristics
This element describes the background conditions of the sewer service area, including a brief history of
the City as well as descriptions of the planning area, adjacent sewer systems, service agreements, physical
features, human environment, land development potential, and projected growth scenarios. The growth
scenarios identified in this section establish the baseline data for addressing the adequacy of the existing
sewer system to meet projected needs. The City's ultimate sewer service area has been defined as
including all areas within the existing city limits, including the recently annexed areas.
* Existing Sanitary Sewer System
The existing sanitary sewer system of the City of Tukwila, METRO and others operating within the City
of Tukwila have been inventoried and mapped. The Plan also includes discussion of the history, existing
facilities and general condition and characteristics of systems within the planning area.
* Design Criteria and Construction Standards
A complete discussion of the minimum sanitary sewer system design criteria and service criteria as
required by the City of Tukwila has been included. Average wastewater flow rates and peaking factors
for various types of land use activity developed as part the 1984 Comprehensive Sewer Plan were utilized
in system analysis and future flow projections.
* System Analysis
A detailed analysis of the system was performed as part of the 1984 Comprehensive Sewer Plan and
reviewed for the purpose of this update. Comprehensive sewer system plans of other systems operating
within the City limits were reviewed to identify problems associated with those systems.
* Proposed Improvements
Based on analysis of the Tukwila system and review of other system's comprehensive plans, recommended
improvements, improvement schedules and cost estimates have been identified. Recommended
improvements include: improvements to the sewer system in the Central Business District area;
installation of sanitary sewers in the Allentown area; completion of other sewer system extensions to
developed properties as identified; upgrading certain existing lateral sewer, trunk line pumping facilities;
and, construction of additional gravity sewer facilities wherever feasible to reduce pump station
requirements in the system.
* Implementation
This section of the Plan discusses financial considerations for implementing the proposed improvements.
Topics reviewed include: general obligation and revenue bonds; general facilities charges; developer
financing, combination financing; grant funding and loans; rates; and, administration and coordination
* Operations and Maintenance
The typical operations and maintenance procedures of the City have been documented in this section to
identify operations responsibilities and emergency repair and maintenance procedures for the system.
Recommendations
The following recommendations are made to the City of Tukwila regarding provision of sewer service:
* The City adopt this Comprehensive Sewer Plan Update, with the ultimate sewer service area
defined as the existing city limits, as the official guide for sewer system development and
improvements.
* The City adopt a policy for the elimination any point or non -point pollution sources associated
with sewage disposal systems. In areas of continuous septic and drainfield sewage system
failures, installation of sanitary sewer facilities should be accomplished. Future septic system and
drainfield applications should be considered individually based on soils, past on -site sewage
disposal system failure and other environmental considerations, and appropriate recommendations
forwarded to the Seattle -King County Department of Public Health, the agency having jurisdiction
over acceptance of such applications.
* The City continue monitoring infiltration and inflow through a routine schedule of television
inspection of lines and construct improvements as required to limit the infiltration and inflow
currently occurring in the sanitary sewer system.
* The City adopt and implement a grease trap ordinance for the regulation of this type of material
being discharged into the sanitary sewer system.
* The City initiate a program for water quality monitoring in the Allentown area of the City in
order to determine the effectiveness of existing on site sewage disposal systems in that area.
* The City continue to negotiate with other sewer systems operating within the city limits to
determine the feasibility, terms and scheduling of transfer of sewer system facilities. In addition,
sewer service providers operating facilities within the city limits should be required to obtain a
franchise for operation which details the terms and conditions for sewer system operation.
* The City proceed with other studies as required to facilitate design and construction of proposed
capital improvements and the transfer of customers within the city limits which are presently
served by others or without sanitary sewer service.
* The City review and increase when needed monthly sewer rates sufficient to fund necessary
engineering, environmental and financing studies, and cover necessary immediate repairs to the
system. In conjunction with the rate study, implementation of a general facility charge and the
penalties associated with unauthorized discharge into the system should also be evaluated.
* The City adopt a uniform sewer system extension policy for extension of systems both inside and
outside of the city limits. This document would govern all new developer extension activities and
would establish minimum and uniform design standards.
* The City extend sewer service to areas that can be economically and feasibly served when
requests are made and where it does not adversely affect existing sewer service levels.
EXECUTIVE SUMMARY
TABLE OF CONTENTS
ENGINEERS CERTIFICATION
CITY OF TUKWILA
1991 COMPREHENSIVE SEWER PLAN
TABLE OF CONTENTS
Page No.
CHAPTER 1 - INTRODUCTION
Authorization 1 -1
Location 1 -1
Authority, Management and Place of Business 1 -1
Planning Goals and Objectives 1 -2
CHAPTER 2 - PLANNING CONSIDERATIONS AND
SERVICE AREA CHARACTERISTICS
Background 2 -1
Tukwila's Planning Area 2 -1
Adjacent Sewer Districts and Cities 2 -2
Future Sewer Service Area Expansion 2 -2
Sewer Service Agreements 2 -2
Physical Features of the Sewer Service Area 2 -5
Topography 2 -5
Geology and Soils 2-6
Surface and Ground -Water Resources 2-6
Human Environment 2 -13
Land Use 2 -13
Residential Population Projections 2 -13
Employment Projections 2 -14
Housing Characteristics 2 -15
Land Development Potential 2 -15
Single Family Residential 2 -15
Multiple Family Residential 2 -16
Commercial and Industrial 2 -16
Employee Density Factors 2 -16
Puget Sound Council of Governments (PSCOG) Employment Forecasts 2 -16
Role of the City's Comprehensive Land Use Plan and Zoning 2 -17
Transportation Corridors 2 -17
Chapter 2 (Continued)
Growth Management Scenarios 2 -17
Scenario I - Existing Conditions 2 -18
Scenario II - Vacant Land Buildout 2 -18
Scenario III - Redevelopment Buildout 2 -20
CHAPTER 3 - EXISTING SANITARY SEWER SYSTEM
Sewer System History 3 -1
Existing Collection System 3 -1
Sewage Lift Stations 3 -1
Metro Facilities 3 -2
Sanitary Sewer System Drainage Basins 3 -5
Drainage Basin No. 1 3 -5
Drainage Basin No. 2 3 -5
Drainage Basin No. 3 3-6
Drainage Basin No. 4 3-6
Drainage Basin No. 5 3-6
Drainage Basin No. 7 3 -7
Drainage Basin No. 8 3 -7
Drainage Basin No. 9 3 -7
Drainage Basin No. 10 3 -8
Drainage Basin No. 11 3 -8
Drainage Basin No. 12 3 -8
Drainage Basin No. 13 3 -8
South Service Area Basin No. 14 3 -9
North Service Area Basin No. 15 3 -9
Industrial Waste Surcharge Program 3 -10
National Pollutant Discharge Elimination System (NPDES) 3 -10
CHAPTER 4 - DESIGN CRITERIA AND CONSTRUCTION STANDARDS
General 4 -1
Minimum Sanitary Sewer Design Requirements 4 -1
System Design 4 -1
Wastewater Flow Rates 4 -2
Peaking Factors 4 -2
Collection System Design Criteria 4 -3
Reference Datum 4-4
Sewer Location 4-4
Materials 4-4
Pipe Design and Construction 4-4
Manhole Design and Construction 4 -5
Overflows 4 -5
Chapter 4 (Continued)
Grease Traps 4 -5
Lift Stations 4-6
Pumps 4-6
Wet Wells 4-6
Infiltration and Inflow 4 -7
CHAPTER 5 - SEWER SYSTEM HYDRAULIC ANALYSIS
Methodology 5 -1
Sewage Lift Station Considerations 5 -1
Sanitary Sewer Drainage Basins 5 -2
Drainage Basin No. 1 5 -2
Drainage Basin No. 2 5 -2
Drainage Basin No. 3 5 -3
Drainage Basin No. 4 5-4
Drainage Basin No. 5 5 -5
Drainage Basin No. 6 5 -5
Drainage Basin No. 7 5 -5
Drainage Basin No. 8 5 -5
Drainage Basin No 9 5-6
Drainage Basin No. 10 5-6
Drainage Basin No. 11 5 -7
Drainage Basin No. 12 5 -8
Drainage Basin No. 13 5 -9
South Service Area Basin No. 14 5 -11
North Service Area Basin No. 15 5 -13
CHAPTER 6 - PROPOSED IMPROVEMENTS
General 6 -1
Proposed Improvements 6 -1
Drainage Basin No. 1 6 -1
Drainage Basin No. 2 6 -2
Drainage Basin No. 3 6 -2
Project 1 - Gravity Sewer to Northern Area of Basin No. 3 6 -3
Project 2A - Gravity Sewer Under 1-405 to Tukwila Sewer System 6 -3
Project No. 2B - Gravity Sewer Under the Railroad to Metro 6 -3
Drainage Basin No. 4 6-4
Drainage Basin No. 5 6-4
Drainage Basin No. 6 6-4
Drainage Basin No. 7 6-4
Drainage Basin No. 8 6-4
Drainage Basin No. 9 6-4
Chapter 6 (Continued)
Drainage Basin No. 10 6 -5
Project 3A - Gravity Sewer Service to Basin No. 10 6 -5
Project 3B - Service to Basin No. 10 via a Lift Station 6 -5
Drainage Basin No. 11 6-6
Drainage Basin No. 12 6-6
Project 4 - 21 -inch Trunk Line on Andover Park West 6-6
Drainage Basin No. 13 6 -7
Project 5 - Increase Lift Station No. 2 Capacity 6 -7
Project 6 - 12 -inch Gravity Trunk Sewer on Andover Park West 6 -7
Project 7 - 8 -inch Lateral Sewers on Andover Park West 6 -7
Project 8 - 18 -inch Gravity Sewer on Minkler Boulevard 6 -7
Project 9 - Gravity Sewer to South 178th Street 6 -7
South Service Area Basin No. 14 6 -8
Project 10 - 18 -inch Gravity Sewer on Southcenter Parkway 6 -8
Project 11 - 21 -inch Gravity Sewer on Southcenter Parkway 6 -8
Project 12 - 21 -inch Gravity Sewer on 57th Avenue South 6 -8
Project 13A - 21 -inch Gravity Sewer on South 200th Street 6 -8
Project 13B - 1.0 MGD Lift Station at 57th and 200th 6 -9
Project 14 - 10 -inch Gravity Sewer on South 200th Street 6 -9
North Service Area Basin No. 15 6-9
Project 15A - 8 -inch Gravity Sewer to Allentown 6 -9
Project 15B - Sewer Service to the Existing Tukwila System 6 -10
Schedule 6 -10
Cost Estimates 6 -10
CHAPTER 7 - IMPLEMENTATION
General 7 -1
Authority 7 -1
Sewer System Expenses 7 -1
Sewer System Revenue 7 -2
Sewer Rates 7 -2
Sewer Connection Fees 7 -3
Annual Financial Report 7 -3
Classes of Capital Improvements 7 -7
General Facilities 7 -7
Local Facilities 7 -7
Individual Service Lines 7 -8
Methods of Financing Improvements 7 -8
General Obligation or Revenue Bonds 7 -8
Local Improvement District 7 -8
Developer Extension Agreements 7 -9
City Financed Projects 7 -9
Government Grants 7 -9
Chapter 7 (Continued)
CITY OF TUKWILA
COMPREHENSIVE SEWER SYSTEM PLAN
SUPPLEMENT A - ANNEXATION AREAS
Rates, Fees, Policies and Ordinances 7 -10
Application for Sewer Service 7 -10
Individual Sewer Service Connections 7 -10
Installation of the Sewer Connection 7 -10
Side Sewer Permit Fee 7 -10
Sewer Stub Charges 7 -11
General Facility Charges and Local Lateral Charges 7 -11
Charges for City Labor, Materials, Equipment and Overhead 7 -14
City Rates 7 -14
Definitions 7 -14
Permits and Inspections 7 -14
Special Charges for Wastewater Dumping or Discharge 7 -15
Industrial Wastewater Discharge 7 -15
Wastewater Batch Dumping 7 -15
CHAPTER 8 - OPERATIONS AND MAINTENANCE
Sewer System Responsibility and Authority 8 -1
System Operation and Control 8 -2
System Components 8 -2
Records 8 -2
Preventative Maintenance Program 8 -2
Problem Areas 8 -3
Emergency Procedures 8-4
Emergency Telephone Numbers 8-4
System Vulnerability 8-4
CHAPTER 1 - INTRODUCTION
Authorization Al -1
Location Al -1
Authority A1-2
Planning Goals and Objectives Al -2
CHAPTER 2 - PLANNING CONSIDERATIONS AND
SERVICE AREA CHARACTERISTICS
Background A2 -1
Planning Area A2 -1
Sewer Service Areas and Agreements A2 -1
Supplement A - Chapter 2 (Continued)
Physical Features of the Sewer Service Area A2 -2
Topography A2 -2
Geology and Soils A2 -2
Surface Water Resources A2 -7
Human Environment A2 -8
Land Use Calculations A2 -8
Population A2 -12
Land Development Potential A2 -13
Growth Management Scenarios A2 -15
Scenario I - Existing Conditions A2 -15
Scenario II - Vacant Land Buildout A2 -15
CHAPTER 3 - EXISTING SEWER SYSTEM
General A3 -1
City of Tukwila A3 -1
Drainage Basin No. 18 A3 -1
Val Vue Sewer District A3 -1
Drainage Basin No. 7 A3 -3
Drainage Basin No. 16 A3-4
Drainage Basin No. 17 A3-4
Drainage Basin No. 19 A3-4
Drainage Basin No. 21 A3-4
CHAPTER 5 - RECOMMENDED SERVICE AREAS AND IMPROVEMENTS
Introduction A5 -1
City of Tukwila A5 -1
Drainage Basin No. 18 A5 -1
Drainage Basin No. 20 A3 -9
Drainage Basin No. 21 A3 -9 ;,;
Supplement A - Chapter 5 (Continued)
Drainage Basin No. 20 A5 -1
Project No. 27S. - Allentown Sewers A5 -2
-... Drainage Basin Nos. 23 and 24 A5-6
Metro Facilities A5 -7
CHAPTER 6 - IMPLEMENTATION
Service Areas and Interlocal Agreements A6 -1
City of Seattle Service Area A6 -1
Allentown Sewers A6 -1
Metro Facilities A6-2
Val Vue Sewer District Area A6 -2
Existing Sewer Rates A6 -2
APPENDIX A - INTERLOCAL AGREEMENTS
APPENDIX B - SEPA DOCUMENTATION
APPENDIX C - SANITARY SEWER SYSTEM CONSTRUCTION STANDARDS
SANITARY SEWER SYSTEM PLAN MAP (Map Pockets)
ENGINEERS CERTIFICATION
CITY OF TUKWILA
1991 COMPREHENSIVE SEWER SYSTEM PLAN
ENGINEERS CERTIFICATION
The technical material and data contained in this report were prepared under the supervision and
direction of the undersigned, whose seal as a professional engineer licensed to practice as such in the
State of Washington is affixed below.
Martin L. Penhallegon, P.E.
President
Horton Dennis & Associates, Inc.
CHAPTER 1
INTRODUCTION
Authorization
In 1984, the City of Tukwila adopted their Comprehensive Sewer Plan to regulate the sewer system
service area which includes most of the land within the 1984 corporate limits. The City Council,
recognizing that the plan requires regular revision, has contracted Horton Dennis and Associates, Inc. of
Kirkland, Washington to review and update the Comprehensive Sewer Plan. This update incorporates
changes in service area, projected population, projected employment, development plans, zoning and new
development. This report addresses the Tukwila sewer service area as of January 1988. Since that date,
Tukwila annexed five major areas including Fire District No. 1, Riverton, Foster, Thorndyke, and
Cascade View. A comprehensive sewer plan for these annexed areas presented as Supplement A -
Annexation Areas. Supplement A is included at the back of this Document.
Location
The City of Tukwila is located south of the City of Seattle and east of the Seattle Tacoma International
Airport in the vicinity of the intersection to Interstate Highway 5 and Interstate Highway 405. Tukwila
is bordered on the north by the City of Seattle, on the east by the Cities of Renton and Kent, on the south
by unincorporated King County and the City of Kent, and on the west by the City of SeaTac and
unincorporated King County as shown on Figure 1 -1.
Authority, Management and Place of Business
The City of Tukwila is a Code Class City and is authorized by the State of Washington under RCW 35.27
to operate and maintain public utility systems for the benefit of the population. The City has the authority
to take over the ownership, operation and maintenance of all utility systems within its boundaries.
The City of Tukwila operates under mayoral system of an elected mayor and seven (7) elected council
members. By ordinances and resolutions, the City Council makes and establishes City policies that govern
operation of the sanitary sewer system. The City's elected officials, City Administrator and Public Works
Director are identified as follows:
Mayor John "Wally" Rants
City Council Joe H. Duffle Allen E. Ekberg
Joan Hernandez Steve Lawrence
Steve Mullet Dennis L. Robertson
Charles Simpson
City Administrator John McFarland
Public Works Director Ross Earnst
The overall responsibility for all Public Works projects including sanitary sewer, water, storm sewer,
streets and all new public development falls under the authority of the Director of Public Works. The
Public Works staff work directly under the Public Works Director to provide review of all new
development designs, accomplish some designs of ongoing work, and provide administration for ongoing
improvements in the City. The Public Works Superintendent is responsible for the operation and
maintenance of the City utilities and streets. Outside consultants are used to augment the efforts of the
City staff.
The Public Works Department is located at 6300 Southcenter Boulevard, in the office building east of City
Hall. All administration, engineering, plan review, billing etc. is accomplished at this location. The
Utilities Operations Center is located at 600 Minlder Boulevard. The Operations and Maintenance staff
and equipment are located at the Operations Center.
Planning Goals and Objectives
The purpose of the Comprehensive Sewer Plan update is to meet the following goals and objectives:
Goals:
o Reflect present land use, future growth and redevelopment.
o Provide an ecologically sound and efficient sanitary sewer system for the City of Tukwila.
o Provide a Comprehensive Sewer Plan that can be implemented considering community values,
funding limitations, political and environmental constraints and geographic scale in its priorities.
Objectives:
o Review and assimilate all available information regarding the City's historic sewer system
development and forecast logical areas of expansion.
o Review present land use and project future growth and redevelopment.
o Inventory and assess the condition of the existing sewer collection system.
o Develop population and employment forecasts to appraise the capability of the existing sanitary
sewer system to handle projected loadings.
o Address state and local regulatory agency requirements with regards to sanitary sewer systems
and treatment.
o Review Metro and other surrounding jurisdiction projections and policies with regards to the
Tukwila sanitary sewer system.
o Review Developer Extension policies.
o Using the area topography, land use, population and employment projections and the hydraulic
performance of the system develop a Capital Improvement Program to upgrade the sewer system
to meet City and State standards.
o Assess the financial resources of the utilities department and determine sources of funding for the
Capital Improvement Program.
1-2
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HORTON DENNIS & ASSOCIATES, INC.
CONSULTING ENGINEERS, PLANNERS
& SURVEYORS
Kirkland, WA 98033.6687 (206) 822.2525
TUKWILA
• KENT
Proj. No.5030.061 Orwn. mg I Date 5-31-91
RENTON
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KING CO. _
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PRE-ANNEXATION TUKWILA
CITY LIMITS
LK. SAMMAMISH
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FIGURE 1-1
VICINITY MAP
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PLANNING CONSIDERATIONS
AND SERVICE AREA CHgRACIERISTICS
�• CHAPTER 2
.._ Tukwila's Planning Area
PLANNING CONSIDERATIONS AND SERVICE AREA CHARACTERISTICS
Background
The City of Tukwila was incorporated in 1908. At that time, Tukwila included 418 acres of land adjacent
to what is now known as Interurban Road. From September 1957 to August 1959, the City went through
an ambitious annexation program including 10 annexations for a total of 1,739 acres. Some minor
annexations since 1959 have brought the City to approximately 2880 acres or 4 1/2 square miles in 1988.
Another wave of annexations took place in 1989 which nearly doubled the area of Tukwila from 2,880
acres to 5,176 acres. The 1989 annexations included the areas of Fire District No. 1, Riverton, Foster,
Thorndyke and Cascade View. The annexed areas are discussed in Supplement A - Annexation Areas.
This main report pertains only to the 1988 Tukwila sewer service area.
In conjunction with these major annexations, the population quadrupled from 800 in 1950 to 3,160 in
1978, to 4,760 in 1987, to 10,793 in 1989 and to 14,631 in 1991. Aside from the annexations, Tukwila's
growth has closely paralleled that of other adjacent south King County communities of Kent, Renton and
Auburn. The construction of Southcenter, a major regional shopping center, and several large industrial
parks in the area, have created additional population pressures.
The City of Tukwila's Planning Area shown on Figure 2 -1 encompasses both land within the corporate
limits and land outside its limits but within its sphere of influence for a total of 6,275 acres. The area
includes 2,700 acres of alluvial lowlands lying west of the Green River, 2,800 acres of glacial plateau,
and 750 acres of steep wooded hillsides connecting the lowlands to the plateau area to the west. Probably
the most succinct description of the Planning Area is found in the 1977 Comprehensive Plan:
...the Tukwila Planning Area is situated at the bottleneck of the lower Green - Duwamish River
Valley where the wider Green River Valley meets the narrower Duwamish Valley. North -
trending glacial uplands border the Valley on both sides, rising steeply from the valley floor. On
the west side, the Planning Area reaches up to the valley wall to include a portion of these
uplands...
Source: 1977 Comprehensive Land -Use Policy Plan, p. 21
2 -1
The Planning Area is divided into two (2) distinct areas, as follows:
City of Tukwila
Unincorporated Areas
Tukwila Planning Area
3.85 square miles
5.95 square miles
9.80 square miles
Tukwila's Existing Sewer Service Area
The Tukwila sewer system service area shown on Figure 2 -2 covers the industrial area around Southcenter
and the residential area just north of I-405 that is considered old Tukwila.
Adjacent Sewer Districts and Cities
The adjacent sewer district's and cities are shown on Figure 2 -2. The 80 -acre unincorporated portion of
the Planning Area to the west of the City of Tukwila known as McMicken Heights neighborhood is served
by the Val Vue Sewer District. This system connects directly to the Tukwila sewer system for
transmission to the Metro Renton sewage treatment facilities. To the east and south, the Cities of Renton
and Kent provide sewer service to area businesses, industries and residents. To the north, the City of
Seattle has a sewer system that serves industrial and residential areas.
A review of the sewer service area boundaries with regards to adjacent systems indicates that the only
existing conflict in sewer service areas occurs in the southern part of the Planning Area, where the City
of Kent has shown it's future service area to overlap with Tukwila's proposed sewer service area.
Future Sewer Service Area Expansion
Expansion of the City's sanitary sewer service area into the annexation areas is discussed in Supplement
A - Annexation Areas. Most likely, expansions within the study area covered by this report would occur
in the unincorporated areas of the Planning Area and the industrial area to the south, although expansion
into this area is only anticipated by specific requests for service.
Sewer Service Agreements
The City of Tukwila maintains an agreement with Metro for the treatment and disposal of wastewater.
Metro has several major wastewater interceptors which cross through the City and extend to the Renton
Treatment Plant. Also, the Renton Effluent Transfer System (RETS) flows through the City on its way
to ultimate discharge into the Puget Sound. The Tukwila sewer system flows into Metro trunk sewers
at seventeen different locations. The agreement between the City and Metro specifies the charges and
conditions of the disposal into the system. Metro charges are detailed in Chapter 8 of this document.
2-2
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FIGURE 2 -I
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MARSHY SOILS
OUTWASH SOILS
ROUGH, BROKEN & STONY LAND
ALLUVIAL SOILS
TILL SOILS OVER HARDPAN
TILL SOILS OVER BEDROCK
MAJOR FILL AREAS
SOIL GROUPS
FIGURE 2-3
TUKWILA ?LAMMING NPARTIKENT 1975
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MODERATE SUITABILITY FOR URBAN DEVELOPMENT
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FIGURE 2-4
TUKWILA PLANNING DEPARTMENT 1915
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Within LID 26, the McMicken Heights area within the City Limits, Val Vue operates and maintains
sewers originally constructed by and paid for by the City of Tukwila. At the completion of construction,
Tukwila deeded this sewer system over to Val Vue. In this area, Val Vue directly bills all customers even
though the area is within the City limits of Tukwila.
No sanitary sewer interties exist between the City of Tukwila and the Cities of Renton and Kent.
Physical Features of the Sewer Service Area
The three elements of the physical environment which are important considerations for future development
of the sewer system include topography; soils and geology; and, surface and groundwater resources and
related floodplains. These factors are discussed below.
Topography
The topography of a sewer service area determines how the sewer system is laid out. The most
economical sewer system utilizes the natural drainage patterns of the land to minimize the number
of lift stations and, therefore, pumping requirements. By designing sewer mains to follow the
drainage patterns of the service area topography, the depth of sewer lines can also be minimized.
The topography of Tukwila is dominated by the Duwamish /Green River, which flows the full
length of the City, generally following the eastern boundary. The existence of the river has
resulted in a flat river bottom area that covers a large portion of the City. From the river bottom
area the topography rises sharply in the north and west on both sides of the River up to a plateau.
In some areas, steep slopes have restricted development potential.
2-5
Geology and Soils
The geology of the planning area is an important factor in the development of a Comprehensive
Sewer Plan for several reasons: the stability of the soils could constrain development in certain
areas, and the quality of the soils could affect the pipeline routes, the design, and the methods of
construction of sewer mains, directly affecting the cost of improvements. The soils within the
planning area are shown on Figure 2 -3, and the characteristics of each type of soil are
summarized on Table 2 -1. The three physiographic units for the planning area are shown on
Figures 2-4 and 2 -5.
The two predominant soils in the Planning Area are alluvial and till. Alluvial Soils dominate the
entire area south of Interstate 405 and along the Green River west to Southcenter Boulevard.
These soils, mainly silt, clay and peat, have two severe developmental constraints: 1) low bearing
capacity and 2) high water table. These soils types are naturally suited to light- weight buildings.
Till soils, underlain by a considerable depth of Vashon Till or bedrock, cover the portion of the
Sewer Service Area north of Interstate 405. These soils are excellent for large- building
construction, and are considered to have foundation, seismic, and slope stability.
Looking at other portions of the Planning Area, the area lying west of Interstate 5 and north and
south of Interstate 405, the soils are identical to those on Tukwila Hill. These soils are ideal for
all types of construction, being covered by a one to four foot mantle of till soils underlain by
impermeable glacial till or bedrock. These soils provide foundation, seismic, and slope stability
for all buildings, however the undulating terrain may limit industrial buildings.
The steep hillsides, with slopes between 15 and 70 percent, have a high potential for landslides,
and tend to be unstable naturally or become unstable when modified. These limitations make the
hillsides difficult to build on without considerable engineering expedients.
Surface and Ground Water Resources
Four significant surface waters and eight unnamed creeks exist in the Planning Area. There are
two large man-made ponds and several smaller natural ponds. The Green - Duwamish River, the
major river within the area, drains 90 percent of the Planning Area. The remaining ten percent
of the area drains to Puget Sound via Des Moines Creek. Overall, the Green River drains 483
square miles (309,120 acres) of which about 9 sq. mi. (5,670 acres) are within the Planning Area.
2-6
..
Before 1906, the Green River drainage basin was considerably larger because it received the flows
of the White and Black Rivers. This changed during a 1906 flood when the White River was per-
manently diverted southward. In 1916, the Black River lost its identity when the construction of
the Lake Washington Ship Canal lowered the Lake Washington water level by 9 feet, shutting off
flow through the Black River.
Two types of floods have occurred on the Green River. Historically, overbank flooding occurred
in early winter and early spring, coinciding with periods of heavy precipitation and snowmelt.
Construction of the Howard Hanson Dam all but eliminated this problem in 1962, regulating peak
flows to 12,000 cfs at the Auburn gaging station (Source: pg. 17, Data \Inventory, Tukwila
Planning Area [1975]).
More recently, increased runoff from commercial and industrial expansion on the lowlands and
residential development on the uplands has created localized flooding in the form of standing
water. To remedy this problem, the U.S. Soil Conservation Service has proposed creating a
circuit of drainage canals to collect valley storm runoff and direct it to one of several pumping
stations along the Green River. The runoff would then be pumped into the river when flow in
the river allowed. Levies have been improved on portions of the river south of Interstate 405 to
control flooding.
The Green River, which originates in the Cascades 50 miles southeast of Tukwila and discharges
into Puget Sound five miles downstream, is designated as a Class A water by the Washington
State Department of Ecology. The Green River complies with three Class A standards a)
dissolved oxygen, b) ph level, and c) lead concentration. The River also complies with two other
class A standards, temperature and turbidity, the majority of the time. In the summer, as a result
of removal of bank trees, water temperatures increase and produce a stressful condition for
aquatic life. Acceptable turbidity levels are exceeded during periods of high flows. The river
does not comply with the coliform content standard, due in part to agricultural and human activity
along the river.
Two man-made lakes, Angle Lake (96 acres) and Bow Lake (12 acres), exist in the
unincorporated uplands portion of the Planning Area. Both lakes function as natural detention
ponds, capturing the runoff from adjacent hillsides. Angle Lake is spring -fed.
2 -7
Two natural ponds, Tukwila Pond and P -17, exist in Andover Park area of the City. The
Tukwila Pond is within the Andover Industrial Park and drains to Pond P -17, which is located
east of Andover Park East near Minlder Blvd. The P -17 pond serves as a holding basin for storm
runoffs and water is pumped from P -17 to the Green River during off peak flow periods. Several
other seasonal ponds and marshes in the Planning Area function as part of the natural system.
Several natural drainage basins exist in the Planning Area and each of the basins is drained by
one or more unnamed creeks. Most of the runoff from the area is conveyed to the Green -
Duwamish river. The Des Moines Creek, however, drains directly to the Puget Sound. Creek
head- waters originate in open ditches in upland areas combining into creeks that flow down steep
ravines to the valley floor. When the storm water reaches the lowlands, it is carried by the storm
drainage system to the Green River. Specific information on drainage basins and facilities can
be obtained from the City of Tukwila Department of Public Works, Surface Water Utility.
Ground -water is a needed resource but it can also be a constraint on development due to land
slides caused by saturated soil conditions. The Tukwila area has many slide -prone areas.
Hillsides in the area typically have a permeable layer of sand and gravel underlain by a less
permeable layer of clay. When the upper layers become saturated with ground- water, they slide
off the lower stratum.
The runoff from the uplands, combined with impermeable under layers of glacial till and bedrock,
cause the valley soils to be saturated, creating a seasonal high water table and surface ponding.
This excessive groundwater condition can cause problems during the construction of sanitary
sewers and lift stations. These problems can be controlled by dewatering the area of construction,
however, this requirement increases costs of construction.
Another concern with groundwater is excessive infiltration and inflow (I & I) into the sewer
system. Excessive I & I will increase wastewater flows and can overload the sewer system. In
areas where the sewers are old and in disrepair, the bad pipe joints can contribute large amounts
of water to the system. Excessive infiltration can be repaired and controlled, however this is a
costly process.
2 -8
General Soil
Type
General
Description
Bearing Capacity Low
Erosion Hazard Slight
Internal Drainage Poor
Arability Fair
Characteristics
related to urban
development
Marshy Soils
Wet areas, depres-
sions of peat and
muck. Level, gen-
erally shallow
soils.
High water table
and low bearing
capacity require
filling prior to
development. These
areas serve to
store runoff, and
if drained, an in-
crease in peak
storm runoff will
occur.
Alluvial Soils
Low
Slight
Poor
Good
High water table
and low bearing
capacity require
much site prepar-
ation prior to
development.
High fertility of
soil will suited
to agriculture.
erosion, increas-
ing to moderate
erosion in slopes
exceeding 15%.
TABLE 2 -1
SOIL CHARACTERISTICS
Deep sedimentary
soils of silt,
clay and some peat
developed in valley
alluvium.
Till Soils
Based on: Soil Conservation Service, U.S. Department of Agriculture,
Soil Survey of King County, Washington, 1973.
Thin soil layer
developed over
impermeable glac-
ial till or bedrock
Relief generally
rolling or hilly.
High
Slight
Fair
Fair
Hardpan occurs
only a few feet
from soil surface
and restricts
downward percola-
tion of water.
Soils will sup-
port heavy struc-
tures. Slight
tank drainfields,
but may cause
possible ground-
water pollution.
Outwash Soils
Gravelly, dry
soils developed
over glacial out -
wash deposits.
Relief generally
rolling or hilly.
High
Moderate
Good
Poor
Excessively dry
soils which are
subject to ero-
sion if cleared.
Good soils for
buildings with
basements. Pro-
vide good drain-
age for septic
vegetative cover.
Soils are gen-
erally unstable.
Rough, Broken
and Stony Land
Variety of soil
types found on
steep slopes
Low
Severe
Fair
Poor
Steep slope pre-
cludes construc-
tion of roads.
Intense develop-
ment imparactical.
High erosion
hazard in these
soils, especial-
ly if stripped of
iii
/ ///
•
•
/��. "�/ " �ii /iii / i i
_:
�
/ l age --- raiiinfle
MARSHY SOILS
OUTWASH SOILS
ROUGH, BROKEN & STONY LAND
ALLUVIAL SOILS
TILL SOILS OVER HARDPAN
TILL SOILS OVER BEDROCK
MAJOR FILL AREAS
SOIL GROUPS
PLAHN1H_
<
i
it
_
•
ri
FIGURE 2 -3
7111p7LA PLIAIWIC WEE 1915
3
SurrABLE FOR. RESIDENTIAL.
R.E.c.REAnor-,ANo com-
maRcum-
L.
STEEP SLOPV5 MAKE L.Z..YEL 5LOF'e t PEC.IALLY SUrT-
THIS 4 Gra:02XL? Et, FOR INDUSTRIAL AND AC2.1-
UNSUTAEO...E. FOR Urr..AN CULTURAL USE.S
USES I.Cr-AUMD RAV-
I CAN eE
%/MOPED 15DR Ra:405.1-
t R.RF-1(110NALI.:
PHYS1OGRAPHIC SECTION
Figure 2 - 5 Physiographic Areas: Plateau, Valley Wall, Lowland.
Source: City of Tukwila Planning Department
Human Environment
This section examines the human elements of the Sewer Service Area including land use, zoning,
population, housing and employment. Three growth management scenarios are presented in order to
project sewer system demands and needs.
In compiling information on the human environment of the study area, a variety of information sources
were used. Some of the most important documents reviewed include:
- City of Tukwila Comprehensive Land Use Policy Plan, 1977;
- City of Tukwila Zoning Ordinance, 1982;
- City of Tukwila 1980 Employment Survey;
- City of Tukwila Land Use and Zoning Matrix, 1985;
- City of Tukwila 1984 Comprehensive Sewer Plan;
- City of Tukwila, Fire District No. 1 Annexation Draft Environmental Impact Statement,
February 1988;
- King County Supply - Demand Study, November 1979;
- Puget Sound Council of Governments, Population and Employment Forecasts, 1988;
- Puget Sound Council of Governments, Population and Housing Estimates, April 1, 1987;
- King County Comprehensive Plan, 1985;
- Val Vue Comprehensive Sewer Plan, July, 1985.
Land Use
City of Tukwila 1985 land use and zoning acreage are presented in Table 2 -2 shown on the next
page. As indicated, nearly one third of the City's total area is used for commercial and industrial
uses, while only about 12% is used for housing. Later in this Chapter, future land uses are
discussed and projected in the form of development scenarios.
Residential Population Projections
The majority of the City's residents is within U.S. Census Tract No. 262 (approximately 88 %).
The remaining 12% is scattered throughout adjoining Census Tracts. The population data con-
tained in Table 2 -3 were generated from the Puget Sound Council of Governments (PSCOG) 1987
population data. The data were adjusted to reflect the actual 1988 City limits. Population data
for the annexation areas is presented in Supplement A of this document.
Note: All figures for 1988 city limits.
2
Note: All figures are for 1988 city limits.
2 -14
TABLE 2 -3
RESIDENTIAL POPULATION PROJECTIONS
CITY OF TUKWILA
Year 1980 1987 1990 2000 2020
Population 3,983 4,760 4,741 5,790 7,415
Source: "Population and Employment Forecasts, 1988 "; and "Population and Housing Estimates,
April 1, 1987 "; PSCOG.
Employment Projections
Existing and projected employment for the City are presented in Table 2-4 shown later in this
chapter. This information was compiled from both City records and PSCOG information. These
projections suggest that the number of people employed in the City will increase dramatically
between 1984 and 1990 (52 %), with the rate of increase slowing some between 1990 and 2000
(26%). Between the years 2000 to 2020 an increase of 34% is projected.
TABLE 2 -4
EMPLOYMENT PROJECTIONS
CITY OF TUKWILA
Category Employment
1980' 1984' 1990 2000 2020
Commercial Service 6,816 6,343 12,591 16,860 24,548
Retail 6,816 6,301 9,282 11,539 14,787
Whol/Transp 4,565 4,846 8,086 9,670 11,651
Comm /Util
Process /Manuf. 1,825 1,806 4,664 4,540 4,524
Govt /Public Ser. 252 368 348 614 1,055
Total 20,274 19,664 34,971 43,223 56,565
1980 and 1984 figures are from "City of Tukwila Number of Year Round Employees
by Employment Category" and based on unpublished Tukwila business license data
between 1975 and 1984.
1990, 2000 and 2020 projections are from "Population and Employment Forecasts,
1988 ", Puget Sound Council of Governments, and have been adjusted to reflect actual
City area.
2020 7,415 1.64 1,005 3,516 4,521
Based on: "Population and Employment Forecasts, 1988" and "Population and
Housing Estimates, April 1, 1987 ", PSCOG
Housing Characteristics
Table 2 -5 shown on the next page shows the general housing trends for the City. This infor-
mation represents the Puget Sound Council of Government projections, which have been adjusted
to reflect the actual City area. This information indicates that the projected increase in population
will require addition of more than 1,100 housing units before the year 2000; the City anticipates
the majority of those units will be multi - family.
TABLE 2 - 5
HOUSING TRENDS - NUMBER OF HOUSEHOLDS (1111)
CITY OF TUKWILA
Note: All figures are for 1988 city limits.
Development Potential
ased on analysis of the foregoing data, the following conclusions are made about the development
otential of the City of Tukwila. These conclusions are inherent to the development of realistic scenarios
and formulation of an effective Comprehensive Sewer Plan.
Single Family Residential
In 1985, approximately 130 acres of vacant single family zoned land within the City was available
which would permit approximately 725 additional residences to be constructed. Based on the
historical consumption rate of this type of land, the supply of low density residential land appears
to be adequate for at least 40 years.
2 -15
Multiple Family Residential
In 1985, approximately 11 acres of vacant multi - family zoned residential land was available which
could yield 324 apartment units. At the historical consumption rate, this supply of multi - family
land would be exhausted by the year 2000.
Commercial and Industrial
Approximately 233 acres of land zoned for commercial or industrial use was available for devel-
opment in 1985. More than 35 acres of commercial - industrial zoned land is used as residential.
Employee Density Factors
The King County "Supply -Demand Study" suggests employee densities of 12.5 employees per
acre for industrial uses and 23.8 employees per acre for professional offices. This seems low
based on recent employee -to -floor area ratios in Tukwila and extremely low for the intensity of
development expected in the future. Recommended employee densities are listed in Table 2-6
are applied in developing vacant land build -out and high growth /redevelopment scenarios. To
determine gross floor areas in these scenarios, it was first assumed that all land in these scenarios
was developed. Total acreage by projected land use was then multiplied by average employee
densities. The average gross floor area to employee ratio was then applied to determine the
estimated gross floor area under each land use classification.
TABLE 2 -6
EMPLOYEE DENSITIES
CITY OF TUKWILA
Employees Building Gross Floor Area
per Acre Factors per Employee
Activity (Average) (Average) (Average)
Retail 30.0 0.30 435
Office /Service 65.0 0.45 300
Warehousing/Light
Indust./Wholesale 14.5 0.40 1,200
Process /Manufact. 29.0 0.40 600
Puget Sound Council of Governments ( PSCOG) Employment Forecasts
A breakdown of the PSCOG figures for the City of Tukwila area forecasts a 52% increase in
employment from 1984 to 1990 and 26% increase from 1990 to 2000. These forecasts reinforce
2 -16
calculations made elsewhere in this report that the City would essentially be "built -out" when it
reaches the forecasted employment plateau between 1990 and 1995. To grow beyond this build-
out, the City must undergo extensive redevelopment, converting uses with low employment
densities under 15 employees /acre to uses with high employees /acre (e.g. office with 65
.._. employees /acre).
Role of the City's Comprehensive Land Use Plan and Zoning
The 1977 Comprehensive Land Use Policy Plan is the official guide to the future development
of the City while the Zoning Ordinance provides the means of realizing the goals listed in the
Land Use Plan. All scenarios for future development must be in conformance with the
Comprehensive Land Use Plan, except where the City is envisioning the future beyond the scope
and assumptions underlying the Comprehensive Plan.
Transportation Corridors
Significant traffic improvements proposed for the Tukwila area include the extension of
Southcenter Parkway to South 200th Street, and the creation of an alternate east -west corridor on \„
either South 200th or South 188th Street, linking both arterials to Interstate 5. The net effect of
these improvements on the developing land use scenario could be enormous. Freeway access
would enhance the development potential of the entire south end of the City, especially for high
intensity office and retail uses along Southcenter Parkway and for industrial sites in the area South
of South 180th Street. Additionally, the two improvements would create a continuous loop
through the industrial area south of South 180th Street. The Southcenter Parkway extension
would provide needed north -south access to the area, relieving traffic pressure from SR -181. If
the South 188th or South 200th Street corridor is developed, it would provide an alternate east -
west route and improve access from the valley to Interstate 5. The proximity of all high intensity
development along major and secondary arterials is the strongest design consideration in
developing utility corridors throughout the City.
Growth Management Scenarios
The section presents three growth scenarios for the purpose of evaluating and planning the sewer systems.
The scenarios are existing conditions, vacant land buildout and redevelopment buildout and are shown in
Tables 2 -7, 2 -8 and 2 -9. The vacant land buildout and redevelopment scenarios are illustrated on Figures
2-6 and 2 -7. Maps pertaining to the existing land use conditions can be obtained from the City of
Tukwila Department of Community Development.
2 -17
Scenario I - Existing Conditions
This scenario is based on 1985 land use, and population, housing and employment data. The
elements of this Scenario were presented as existing conditions earlier in this Chapter. This
Scenario is offered for the purpose of evaluating deficiencies in the existing sewer system.
Defining the status quo provides a basis of determining the adequacy of present facilities and the
need for immediate improvements. Tables 2 -2 and 2 -7 present the City's general land use
characteristics. Specific mapping of land uses associated with Scenario 1 can be obtained from
the City of Tukwila Department of Community Development.
TABLE 2 - 7
CITY OF TUKWILA
PROJECTED DEVELOPMENT SCENARIOS
Land UsQ
Single Family
Multi - Family
Office Service
Retail
Light Industry
Process /Manual
Total Housing Units
Total Commercial/
Industrial
HU = Housing Unit
GFA = Gross Floor Area
Scenario I
Existing
Conditions
665 HU
1,494 HU
3,083,794 GFA
3,835,147 GFA
6,546,337 GFA
213,400 GFA
2,182 HU
13,678,278 GFA
Scenario II - Vacant Land Buildout
Scenario II assumes that the City would develop according to the Zoning Ordinance by filling in
the vacant land and that the land use configuration would move toward that projected in the
Comprehensive Land Use Plan. All new land uses are assumed to correspond exactly with the
associated zoning; this Scenario does not take into account any existing development which differs
from zoning designation
2 -18
Scenario II Scenario III
Vacant Land Redevelopment
Build -Out Build -Out
2,336 HU 2,198 HU
2,544 HU 3,129 HU
928,500 GFA 7,749,900 GFA
4,449,640 GFA 5,255,235 GFA
16,180,800 GFA 10,448,400 GFA
300,000 GFA 447,000 GFA
4,880 HU 5,327 HU
21,858,940 GFA 23,900,535 GFA
Tables 2 -7 and 2 -8 and Figure 2-6 show the maximum population, employment and building
square footage possible under Scenario II. To achieve this the population would increase by
nearly 150% to 9,868 residents in 2,336 single family units and 2,544 apartment units.
Employment within the City would increase by 52% to an estimated 29,931.
Based on employment rates and land consumption trends, vacant land build -out could occur at
1995 or later. Assuming this is so, the populations projected under Scenario II is considerably
higher than those put forth by the Puget Sound Council of Governments. For wastewater flow
projections, it is recommended that the PSCOG estimated 1995 population of 5,265 be used.
TABLE 2 -8
SCENARIO 11 - VACANT LAND BUILDOUT
Population by Employment Unit (Areas)
(In People)
1 2 3. 4 5 6 7 $ To
Single Family 15 — 4,004 — 411 — 730 1,146
Multi - Family — 3,444 118 — -- 3,562
Total 15 7,448 118 411 730 1,146 9,868
Employment (in People)
1 2 2 4 5 6 7 1 Total
Retail -- -- 1,191 285 8,349 -- -- 9,825
Professional
Office /Service -- -- 2,119 566 410 -- -- 3,095
Light Industrial -- 1,807 1,012 -- 6,408 2,326 1,937 -- 13,490
Process /Man — -- 3,521 -- 3,521
Total 1,807 4,322 851 15,167 2,326 5,458 — 29,931
Underdeveloped Land
1 2 2 4 5 6 7 $ Total
Agriculture /Open
Space (Acres) 3.6 -- 127.0 -- — 16.2 — 146.8
Note: Areas or "Units are defined in Tukwila's 1980 Employment Survey except Unit 8 and are shown
on the Growth Scenario Maps.
2 -19
Scenario III - Redevelopment Buildout
Scenario III shown in Figure 2 -7 assumes that the City would develop according to the Zoning
Ordinance by redevelopment to maximum build -out by the year 2020. Population would increase by
156 percent from 4,015 in 1987 to 10,315 people in 2,198 single - family residences and 3,129
apartments. Employment would increase by 140 percent from 19,664 in 1984 to approximately 47,366
in 2010. Redevelopment of industrial lands with 6 to 8 story office buildings and 3 to 4 story retail
buildings would occur under Scenario III. It is generally assumed that this scenario could occur as
early as 2010, making the population projections contained in Tables 2 -7 and 2 -9 much higher than
those anticipated by the Council of Governments.
TABLE 2 -9
GROWTH SCENARIO III - REDEVELOPMENT BUILDOUT
Population by Employment Unit (areas)
(in people)
1 2 3 4 5 6 7 1 Total
Single Family 15 4,004 -- 411 653 851 5,934
Multi - Family 3,444 118 - 819 4,381
Total 15 7,448 118 411 - 653 1,670 10,315
Employment (in People)
1 2 3 4 5 6 7 1 Total
Retail 1,878 285 8,349 -- 1,569 -- 12,081
Professional
Office /Service -- 2,600 995 566 13,891 - 7,781 -- 25,833
Light Industrial 1,227 1,012 -- 3,400 2,326 742 -- 8,707
Process /Man - - 745 -- 745
Total 3,827 3,885 851 25,640 2,326 10,837 -- 47,366
Agriculture /Open
Space (Acres)
Underdeveloped Land
1 2 3 4 5 6 7 $ Total
3.6 -- 127.0 --
2-20
-- 16.2 -- -- 146.8 Acres
Note: Areas or "Units are defined in Tukwila's 1980 Employment Survey except Unit 8 and are shown
on the Growth Scenario Maps.
•
\u/LiJitx
EUCEI
UNIT 4
TUKWILA WEST
MULTI FAMILY 2.8 AC.
OFFICE 8.7 AC.
RETAIL COMM. 9,5 AC.
UNIT 5
5f4Th5
UNIT 8
McMICKEN HEIGH1S
SINGLE FAMILY 75.8 AC.
SOUTHCENTER
SINGLE FAMILY 27.2 AC.
OFFICE 6.3 AC.
RETAIL 274.3 AC.
LIGHT INDUSTRIAL 441.9 AC.
54
3 .7
UNIT 1 EARLINGTON
SINGLE FAMILY 1.0 AC.
AGRICULTURE 3.6 AC.
UNIT 2 FOSTORIA
LIGHT INDUSTRIAL 124.6 AC.
QO , �s •
a
, j , RETAIL
"19
4
t
FIGURE 2 -6
SCENARIO 1
VACANT LAND BUI DOUT
SINGLE FAMILY RESIDENTIAL
■ MULTI FAMILY RESIDENTIAL
COMMERCIAL SERVICES
WHOLESALE DISTRIBUTION
PROCESS MANUFACTURING
■ PARKS AND PUBLIC SERVICES
UNDEVELOPED
UNIT 3 INTERURBAN
AGRICULTURE
SINGLE FAMILY
MULTI FAMILY
RETAIL COMMERCIAL
OFFICE
LIGHT INDUSTRIAL
127.0 AC.
264.8 AC.
82.0 AC
39.7 AC,
32,8 AC.
89.8 AC.
UNIT 6
BURLINGTON
AGRICULTURE 16.2 AC.
LIGHT INDUSTRIAL 180.4 AC.
UNIT 7 TUKWILA SOUTH
SINGLE FAMILY " 48.3 AC.
LIGHT INDUSTRIAL 133.6 AC.
PROCESS MANUF. 121.4 AC.
-I-
.1111zzi_t‘\
UNIT 4
TUKWILA WEST
MULTI FAMILY 2.8 AC.
OFFICE 8.7 AC.
RETAIL COMM, 9.5 AC.
UNIT 8
McMICKEN HEIGHTS
SINGLE FAMILY 56.3 AC.
MULTI FAMILY 19.5 AC.
UNIT 5
SOUTHCENTER
SINGLE FAMILY 27.2 A,
RETAIL COMM. 278.3 A
OFFICE 213.7 AO. 35
LIGHT INDUSTRIAL 234.5 AC.
34
3 .7
UNIT 1 EARLINGTON
SINGLE FAMILY 1.0 AC.
AGRICULTURE 3.6 AC.
UNIT 2 FOSTORIA
LIGHT INDUSTRIAL 84.6 AC.
OFFICE 40.0 AC.
U_I2
13
35 36
FIGURE 2 -7
SCENARIO III
REDEVELOPMENTI
•
•
SINGLE FAMILY RESIDENTIAL
MULTI FAMILY RESIDENTIAL
COMMERCIAL SERVICES
RETAIL
WHOLESALE DISTRIBUTION
PROCESS MANUFACTURING
. PARKS AND PUBLIC SERVICES
UNDEVELOPED
UNIT 3 INTERURBAN
j
AGRICULTURE
SINGLE FAMILY
MULTI FAMILY
RETAIL COMMERCIAL
OFFICE
LIGHT INDUSTRIAL
127.0 AC.
264.8 AC.
82.0 AC.
62.6 AC.
15.3 AC,
69.8 AC,
UNIT 6
BURLINGTON
AGRICULTURE 16.2 AC.
LIGHT INDUSTRIAL 160.4 AC.
UNIT 7
TUKWILA gOUTH
SINGLE FAMILY 43.2 AC.
RETAIL 52,3 AC.
OFFICE 119.7 AC,
LIGHT IND. 51.2 AC.
PROCESS MANUF. 25.7 AC.
R
J\ " /ZZndl,' �S`
UNIT 4
TUKWILA WEST
MULTI FAMILY 2.8 AC,
OFFICE 8.7 AC,
RETAIL COMM, 9,5 AC.
UNIT 8
McMICKEN HEIGHT`S
SINGLE FAMILY 75.8 AC.
,77
UNIT 5
SOUTHCENTER
SINGLE FAMILY 27.2 AC:
OFFICE 41.3 AC.
34 35
1
/,79#7 thJ
UNIT 1 EARLINGTON
SINGLE FAMILY 1.0 AC.
AGRICULTURE 3.6 AC,
UNIT 2 FOSTORIA
LIGHT INDUSTRIAL 124,6 AC,
FIGURE 2 -6
SCENARIO IL
VACANT LAND BUIL1DOUT
SINGLE FAMILY RESIDENTIAL
■ MULTI FAMILY RESIDENTIAL
• COMMERCIAL SERVICES
j, RETAIL
WHOLESALE DISTRIBUTION
PROCESS MANUFACTURING
111 PARKS ANO PUBLIC SERVICES
UNDEVELOPED
UNIT 3 INTERURBAN
AGRICULTURE
SINGLE FAMILY
MULTI FAMILY
RETAIL COMMERCIAL
OFFICE
LIGHT INDUSTRIAL
UNIT 6
BURLINGTON
AGRICULTURE
LIGHT INDUSTRIAL
127,0 AC,
264,8 AC.
82.0 AC
39,7 AC,
32,6 AC,
69.8 AC,
16.2 AC,
160.4 AC,
UNIT 7 TUKWILA SOUTH
SINGLE FAMILY
48.3 AC.
LIGHT INDUSTRIAL 133.6 AC.
PROCESS MANUF, 121.4 AC.
- {ETIED
TUKWILA WEST
MULTI FAMILY 2.8 AC,
OFFICE 8.7 AC,
RETAIL COMM, 9,5 AC,
UNIT 8
McMICKEN HEIGHT`S
SINGLE FAMILY 75.8 AC,
UNIT 5 # 35
SOUTHCENTER
SINGLE FAMILY 27.2 AC..
OFFICE d.3 AC.
RETAIL 278,3 AC.
LIGHT INDUSTRIAL 441.9 AC.
UNIT 1 EARLINGTON
SINGLE FAMILY 1.0 AC.
AGRICULTURE 3.6 AC,
UNIT 2 FOSTORIA
LIGHT INDUSTRIAL 124,6 AC.
SCENARIO
VACANT LAND BUILIDOUT
SINGLE FAMILY RESIDENTIAL
MULTI FAMILY RESIDENTIAL
COMMERCIAL SERVICES
RETAIL
WHOLESALE DISTRIBUTION
PROCESS MANUFACTURING
• PARKS AND PUBLIC SERVICES
UNDEVELOPED
UNIT 3 INTERURBAN
AGRICULTURE
SINGLE FAMILY
MULTI FAMILY
RETAIL COMMERCIAL
OFFICE
LIGHT INDUSTRIAL
UNIT 6
BURLINGTON
AGRICULTURE
LIGHT INDUSTRIAL
127,0 AC.
264,8 AC.
82,0 AC
39.7 AC,
32.6 AC,
69.8 AC,
16.2 AC,
160.4 AC.
UNIT 7 TUKWILA SOUTH
SINGLE FAMILY " 48,3 AC,
LIGHT INDUSTRIAL 133.6 AC,
PROCESS MANUF, 121.4 AC.
UNIT 4
TUKWILA
MULTI FAMILY
OFFICE
RETAIL COMM,
trY
UNIT 8
Mc MICKEN
SINGLE FAMILY
MULTI FAMILY
-J
WEST
2,8 AC,
8.7 AC,
9,5 AC.
J
HEIGHTS
56.3 AC,
19.5 AC.
UNIT 5
SOUTHCENTER
SINGLE FAMILY 27,2 ,G
RETAIL COMM. 278.3
OFFICE 213.7 Alil<. 35
LIGHT INDUSTRIAL 234,5 AC,'
UNIT 1 EARLINGTON
SINGLE FAMILY 1,0 AC.
AGRICULTURE 3.6 AC,
UNIT 2 FOSTORIA
LIGHT INDUSTRIAL 84.6 AC,
OFFICE 40.0 AC,
\m_i_Jhst
FIGURE 2 -7
SCENARIO III
REDEVELOPMENT! BUILDOUT
a
U
SINGLE FAMILY RESIDENTIAL
MULTI FAMILY RESIDENTIAL
COMMERCIAL SERVICES
RETAIL
WHOLESALE DISTRIBUTION
PROCESS MANUFACTURING
IN PARKS AND PUBLIC SERVICES
UNDEVELOPED
UNIT 3 INTERURBAN
AGRICULTURE
SINGLE FAMILY
MULTI FAMILY
RETAIL COMMERCIAL
OFFICE
LIGHT INDUSTRIAL
127.0 AC,
264,8 AC.
82.0 AC,
62,6 AC.
15,3 AC,
69,8 AC.
UNIT 6
BURLINGTON
AGRICULTURE 16.2 AC.
LIGHT INDUSTRIAL 160.4 AC.
UNIT 7
TUKWILA SOUTH
SINGLE FAMILY 43,2 AC,
RETAIL 52,3 AC.
OFFICE 119.7 AC,
LIGHT IND, 51.2 AC.
PROCESS MANUF, 25.7 AC.
DIE DIUM\
UNIT 4
TUKWILA
MULTI FAMILY
OFFICE
RETAIL COMM,
try
WEST
2.8 AC.
8,7 AC,
9.5 AC.
UNIT 8
McMICKEN HEIGHTS
SINGLE FAMILY 56.3 AC.
MULTI FAMILY 19.5 AC.
UNIT 5
SOUTHCENTER
SINGLE FAMILY
RETAIL COMM.
OFFICE
LIGHT INDUSTRIAL
27.2 .?G
278.3
213.7 1
234.5 AC
84�,
3 .7
UNIT 1 EARLINGTON
SINGLE FAMILY 1.0 AC.
AGRICULTURE 3.6 AC.
UNIT 2 FOSTORIA
LIGHT INDUSTRIAL 84.6 AC,
OFFICE 40.0 AC,
\-- \\0,J*st
12
13
35 ` 36
2
/
FIGURE 2-7
SCENARIO III
REDEVELOPMENTI BUILDOUT
U
'//
SINGLE FAMILY RESIDENTIAL
MULTI FAMILY RESIDENTIAL
COMMERCIAL SERVICES
RETAIL
WHOLESALE DISTRIBUTION
PROCESS MANUFACTURING
• PARKS AND PUBLIC SERVICES
UNDEVELOPED
UNIT 3 INTERURBAN
AGRICULTURE 127,0 AC,
SINGLE FAMILY 264,8 AC,
MULTI FAMILY 82.0 AC,
RETAIL COMMERCIAL 62,6 AC.
OFFICE 15,3 AC.
LIGHT INDUSTRIAL 69.8 AC,
UNIT 6
BURLINGTON
AGRICULTURE 16.2 AC.
LIGHT INDUSTRIAL 160.4 AC.
UNIT 7
TUKWILA SOUTH
SINGLE FAMILY 43.2 AC.
52,3 AC.
119.7 AC.
51.2 AC.
25.7 AC.
RETAIL
OFFICE
LIGHT IND,
PROCESS MANUF.
CHAPTER 3
EXISTING SANITARY SEWER SYSTEM
CHAPTER 3
EXISTING SANITARY SEWER SYSTEM
Sewer System History
The City of Tukwila operated a sewage lagoon system located in the Southcenter area until 1965. When
Metro opened the Renton Wastewater Treatment Plant in 1965 the lagoon system was abandoned and the
sewer system was connected to the Metro system for treatment at the Renton Treatment Plant.
Beginning in 1961 the Tukwila Sewer System experienced rapid expansion by the use of Local
Improvement District's (LID's) and developer extension agreements. The system has since expanded to
include over 140,000 lineal feet of 6, 8, 10, 12, 15, 16, 18, 20, 21 and 24 -inch diameter sewer pipe with
over 470 manholes and eight lift stations.
Existing Collection System
The existing sewer system serves approximately 1700 acres. Over 70 percent of the collection system
consists of concrete pipe with the remainder constructed of asbestos cement, cast iron and ductile iron
pipe.
Some maintenance problems plague the existing sewer system. Grease from most of the restaurants in
the City continually collects in the sewer lines and lift stations. This grease accumulation requires a
regular sewer cleaning program in trouble spots. The cleaning program commands funds and manpower
that could be better used in other areas of the City sewer system.
Settlement of several sewer lines also causes maintenance problems by allowing sediment and grease to
collect in these areas. The settlement also damages pipe joints and increases infiltration of groundwater
into the sewer system. Increased infiltration puts an additional load on the treatment facilities and lift
stations. These problem areas have been identified in the 1984 Comprehensive Sewer Plan and the City
has been correcting the problems when they can. These problems will be discussed in detail in this Plan.
Sewage Lift Stations
The City of Tukwila owns and operates eight (8) sewage lift stations within it's sewage collection system.
The details of each of the lift stations are highlighted in Table 3 -1.
3 -1
Metro Facilities
An 18 -inch diameter interceptor sewer owned by Tukwila and leased by the Municipality of Metropolitan
Seattle (Metro) enters the City of Tukwila from the northwest and flows southeast along Interurban
Avenue to the Metro lift station near 56th Avenue South. The Metro lift station pumps the sewage south
along 53rd Avenue South to South 152nd Street, west under I -5, south to Klickitat Drive, east under I -5
to Southcenter Parkway, south to Strander Boulevard, east along Strander to Metro's secondary treatment
plant located in Renton. See the Sewer Plan Map included in the map pocket at the back of this document
for the location of this interceptor.
The Metro interceptor sewer that crosses the City of Tukwila begins with a 12 -inch force main which
discharges into a 15 -inch gravity sewer. The interceptor increases in size as required to 24, 27 and
finally a 36 -inch diameter sewer that leads to the Renton Treatment Plant. The Tukwila sewer system
flows into this Metro interceptor at seventeen (17) different locations. A sewage disposal agreement
between the City of Tukwila and Metro specifies the charges and conditions of the disposal into the trunk
sewer. The present agreement is included in Appendix A.
The Renton Treatment Plant was recently expanded to accommodate sewage flows of 72 MGD. The
Duwamish River does not have the capacity to receive a sewage effluent discharge of this size, therefore,
the Renton Effluent Transfer System (RETS) outfall was constructed. This outfall consists of a tunnel
nine feet in diameter from the Renton Plant north and west under the City of Tu(cwila and ultimately, to
its outfall into the Puget Sound at Duwamish Head.
Location:
Lift Station No, 1
Basin No. 8
At intersection of
Andover park west &
Strander Blvd.
TABLE 3 -1
LIFT STATION INVENTORY
Lift Station No, 2
Basin No. 13
At intersection of
Andover Park West &
Minkler Blvd.
Date of Construction: 1972
Number of Pumps: 2
Pump Manufacturer: PACO
Pump Model: 81512
Pump Horsepower: 40 HP AT
VARIABLE SPEED
Pump Design Capacity: 2000 GPM AT
46 FEET TOTAL HEAD 25 FEET TOTAL HEAD 21 FEET TOTAL HEAD 20 FEET TOTAL HEAD
Projected Design
Flow: 1285 GPM
1985
3
FAIRBANKS MORSE
5414
10 HP AT
900 RPM
800 GPM AT
PHASE I - 1950 GPM
PHASE II - 4400 GPM
Lift Station No. 3
Basin No. 11
At east end of
Minkler Boulevard
at about 70th.
1972
2
CORNELL
4NWTLH M3 -8
4 HP AT
865 RPM
100 GPM AT
101 GPM
Lift Station No. 4
Basin No. 2
On Interurban Ave.
at about 146th st.
1970
2
CORNELL
4NMDH VCO5.6
5 HP AT
1150 RPM
200 GPM AT
236 GPM
Location:
Lift Station No. 5 Lift Station No. 6
Basin No. 1
Northeast of Inter-
urban Ave. At about
43rd Place S.
Basin No. 3
At southeast corner
of Fort Dent Park
Date of Construction: 1980 1975 1975 1976
Number of Pumps: 2 2 2 2
Pump Manufacturer: Smith & Loveless Cornell Cornell Cornell
Pump Model: 4B2A 4NMTR HUM3 -6 4NMTL HUM3 -6 4NNDH -RH
UM7 -1 /2-6
Pump Horsepower: 5 HP AT 3 HP AT 3 HP AT 7.5 HP AT
1200 RPM 1155 RPM 1155 RPM 1150 RPM
Pump Design Capacity: 400 GPM AT 150 GPM AT
Projected Design
Flow:
28 FEET TOTAL HEAD 30 FEET TOTAL HEAD 26 FEET TOTAL HEAD 42 FEET TOTAL HEAD
70 GPM
TABLE 3 -1 (Continued)
LIFT STATION INVENTORY
100 GPM
3-4
Sanitary Sewer System Drainage Basins
When considering the makeup of a gravity sanitary sewer collection system, the topography of the land
defines the systems drainage basins. These basins are areas that naturally drain to a collection point which
determines the location of trunk lines and lift stations. Using the existing topography allows the system
to flow by gravity and minimizes the depth of construction and the required pumping. The City of
Tukwila has 15 drainage basins identified within the sanitary sewer collection system. These 15 drainage
basins are illustrated on the Sewer Plan Map located in the map pocket at the back of this report.
Descriptions of each basin are as follows:
Drainage Basin No. 1
Drainage Basin No. 1 is located in the northwest corner of the study area and is bounded on the
north, west and east by the 1988 city limits and on the south by 48th Avenue South. Basin No.
1 includes LID 24, the Val Vue Macadam Lift Station and the City's Lift Station No. 5. A
portion of Basin No. 1 on the north side of the West Valley Highway flows directly into the
Metro interceptor. The remainder of Basin No. 1 flows to the City's Lift Station No. 5 and is
pumped to the Metro interceptor. The area within Basin No. 1 on the south side of West Valley
Highway flows to the MacAdam Lift Station and is pumped into the Metro interceptor.
Basin No. 1 consists primarily of commercial development lands and the sewer system is
comprised of 6, 8, 10, 12, 15 and 18 -inch concrete pipe installed in 1969, 1974 and 1980. Part
of the sewer system in Basin No. 1 is owned and operated by Val Vue Sewer District and drains
areas outside the City Limits.
Drainage Basin No. 2
The north central part of Tukwila is designated Drainage Basin No. 2. Basin 2 serves residential
and commercial developments. The drainage basin is bounded in the north and east by the Green
River, on the south by South 153rd Street and on the west by 55th Avenue South, 57th Avenue
South, South 147th Street and 65th Avenue South. The Metro lift station, Lift Station No. 4 and
the City' s trunk sewer on Interurban Avenue (West Valley Highway) are included in this basin.
The south part of Drainage Basin No. 2 conveys wastewater to Lift Station No. 4. Lift Station
No. 4 pumps the wastewater into the Interurban Avenue trunk sewer which flows to the Metro
Lift Station. The remainder of the Basin flows by gravity to the Metro Lift Station. The sewer
system was installed in 1963 and 1967 and consists of 8, 10 and 12 -inch diameter concrete pipe.
3-5
Drainage Basin No. 3
Drainage Basin No. 3 is bounded by I-405 on the south, the Green River on the west, the City
limits on the east and South 139th street on the north. This area covers the low lying green belt
areas along the Green River including Fort Dent Park. Lift Station Nos. 6 and 7 constructed in
1975 as part of LID 25 are located in this Drainage Basin.
The area west of the River drains to Lift Station No. 7, which pumps the wastewater through a
forcemain over the River to a gravity sewer. The gravity sewer serves the area on the east side
of the River and is collected in Lift Station No. 6. Lift Station No. 6 pumps the wastewater to
a Metro forcemain that is located in the railroad right of way on the northeast City limits as it
flows to the Renton Treatment Plant.
Drainage Basin No. 4
This sewer service area is located in the north central part of the City of Tukwila and is bounded
on the south by I-405, on the west by 57th Avenue South, on the north by South 147th Street and
on the east by a line running southeast from South 147th Street and 59th Avenue South to the
West Valley Highway. Included in this basin is the Tukwila City Hall, various office buildings,
restaurants, as well as single family and multi family developments.
Drainage Basin No. 4 utilizes gravity sewers to transport the wastewater to Southcenter Boulevard
and across Interstate 405 where it enters the Drainage Basin No. 8 system. The majority of the
sewer system in this basin consists of 8 and 10 -inch diameter concrete pipe installed from 1963
to 1981.
Drainage Basin No. 5
Located in a residential area in the northwest part of Tukwila, Drainage Basin No. 5 is bounded
on the south by I-405, on the west by I -5, on the north by South 139th Street and South 144th
Street and on the east by 57th Avenue South to 56th Avenue South. Sewer within the Basin
consist of 8, 12 and 15 -inch diameter concrete pipe installed in 1963. The piping is all gravity
flow and conveys the wastewater to the Metro interceptor at four different locations as the
interceptor passes through the Basin.
Drainage Basin No. 6
Drainage Basin No. 6 is a small drainage basin bounded on the east by I -5, on the south by I-405
and on the west and north by the Tukwila City limits. The sewer system in the Basin includes
6, 8, 12, 21, and 24 -inch diameter concrete pipe. The area is a combination of residential and
commercial development. The sewer system drains by gravity directly to the Metro interceptor
as it passes through the Basin.
Drainage Basin No. 7
Drainage Basin No. 7 is located on the west side of I -5 and, therefore, the sewers within the area
are owned and operated by Val Vue Sewer District. This area is located on what is known as
West Hill in the McMicken Heights Area. Basin 7 is bounded by I -5 on the east, South 173rd
Street on the south, the Tukwila city limits on the west and by South 158th Street on the north.
The sewer system consists of 6, 8, 10 and 12 -inch diameter concrete pipe constructed in 1974 as
part of LID 26. The southern portion of the Basin drains by gravity to the Val Vue Lift Station
(McMicken Heights) where it is pumped to the gravity sewer system in the northern part of the
Basin. The north part of the Basin is served by a gravity system that transports the wastewater
to the 24 -inch diameter Metro interceptor that flows under I -5.
Drainage Basin No. 8
Drainage Basin No. 8 covers all of the Southcenter Shopping Area from I -5 to I-405 south to
Strander Boulevard and east to the Green River. The 24, 27 and 36 -inch diameter Metro
interceptor runs along the west and southern boundary of this Basin. The Basin sewer system
operates by gravity as it conveys the wastewater to Lift Station No. 1 which pumps the sewage
into the Metro interceptor. The Tukwila system is composed of 8, 10 and 12 -inch diameter
concrete pipe. Lift Station No. 1 has variable speed pumps and was constructed in 1972.
Drainage Basin No. 9
Drainage Basin No. 9 is located along the eastern City Limits of the City of Tukwila just south
of I-405 and east of the Green River. This Basin includes LID 19 which was constructed in 1972
to serve the light industrial customers in the area. The sewer system is primarily 12 -inch
diameter concrete pipe that drains directly to the Metro 36 -inch diameter interceptor sewer leading
to the Renton Treatment Plant.
3 -7
Drainage Basin No. 10
Drainage Basin No. 10 includes the area of the City of Tukwila east of the Duwamish River
between Strander Boulevard and South 180th Street. The boundaries of this basin have
significantly changed since the 1984 Comprehensive Sewer Plan was drafted. The City of
Tukwila entered into an agreement with the City of Renton to adjust their common boundary to
coincide with the alignment of West Valley Highway. This move eliminated the portion of the
Drainage Basin that was located east of the highway, however it also added a large light industrial
tract of land to the south of the original basin boundaries. The majority of the area is presently
undeveloped and is planned for light industrial type construction. A 12 -inch diameter concrete
pipe is located in the West Valley Highway and drains the area directly to the 36 -inch diameter
Metro interceptor.
Drainage Basin No. 11
Drainage Basin No. 11 is located in the east central part of Tukwila on the west side of the Green
River. The Basin is made up of primarily commercial and light industrial development. The area
is bounded by Strander Boulevard on the north, the Green River on the east, Minider Boulevard
on the south and the western boundary is approximately half way between Andover Park East and
Andover Park West. The southeast corner of the Basin drains to Lift Station No. 3, which is
located at the City Shops. Lift Station No. 3 pumps the sewage to the gravity system on Andover
Park East where it flows north to the Metro interceptor.
Drainage Basin No. 12
Drainage Basin No. 12 is located directly south of the Southcenter Shopping Mall between
Strander and Minkler Boulevards. The area has office buildings, commercial and light industrial
development. Basin No. 12 is bounded by Strander Boulevard on the north, Basin No. 11 on the
east, Minkler Boulevard on the south and on the west the boundary heads north from Minider
Boulevard about 1200 feet west of Andover Park West for a distance of approximately 1400 feet
then it turns due west to I -5. The gravity sewers consist of 8, 12, and 21 -inch diameter concrete
pipe installed in 1973. The wastewater produced by the area flows north to the Metro interceptor
on Strander Boulevard.
3-8
Drainage Basin No. 13
Drainage Basin No. 13 is the largest drainage basin in the system. The Basin serves all of
Tukwila south of Minkler Boulevard from I -5 on the west, to the Green River and the City Limits
on the east. The area is light and heavy industrial and commercial and includes the Shasta
Bottling Plant and Fletcher's Fine Foods, Inc. The southeast corner of Basin 13 flows to Lift
Station No. 8 which pumps the wastewater north to the gravity sewer system on South 180th
Street. The sewer on South 180th St. and the remainder of the area is served by a gravity sewer
system that conveys sewage to Lift Station No. 2 on Andover Park West. Lift Station No. 2
pumps the wastewater into the 21 -inch gravity sewer in Drainage Basin 12 that flows to the Metro
interceptor sewer. The piping system has 8, 10, 12, 15 and 18 -inch diameter concrete pipe that
was constructed in 1964, 1965, 1967 and 1970. Lift Station No. 2 was built in 1967 and Lift
Station No. 8 was constructed in 1976.
South Service Area Basin No. 14
The South Service Area is located outside the present Tukwila City Limits. The Basin is bounded
by I -5, the Green River, South 188th Street and South 204th Street. The Basin is on flat river
bottom land that rises sharply in the west up to I -5. Approximately 315 acres of the Basin is
presently zoned for agriculture and suburban estate, with about 54 acres zoned for heavy industry.
There exists approximately 30 acres of designated wetlands that falls under King County Sensitive
Areas Ordinance No. 4365.
Much of the area remains agricultural and undeveloped in nature. There is no sewer service to
the area at this time. A significant portion of the property Owners in this Basin have applied for
rezone at one time or another for heavy manufacturing and office space. The City of Tukwila
is proposing a trunk sewer to serve the area.
North Service Area Basin No. 15
The 1984 Comprehensive Sewer Plan identified an area in the northern part of Tukwila that is
north and east of the Duwamish River. The area is bounded by the River on the south and west
and on the east by the Beacon Coal Mine Road and the existing Burlington Northern Freight
Depot and consists of approximately 78 acres. The area is contiguous with Fire District No. 1.
The area is assumed to consist of approximately 57 acres of single family residences and 21 acres
of light industrial development.
The majority of the North Service Area is served by septic drain field systems. The Burlington
Northern Depot has a private sewer system that includes gravity sewer, a lift station and a 4 -inch
diameter forcemain that crosses the River to the 48th Avenue South 12 -inch sewer main.
3-9
Industrial Waste Surcharge Program
The following companies located in Tukwila are on Metro's master mailing list and may be subject to
Metro's sewer surcharge if they discharge high strength industrial wastewater into the Metro sewer
system:
N. C. Machinery Company
Petschl's Quality Meats
Shasta Beverages
Ultra Print Photo Lab, Inc.
Seattle Rendering Works (Baker Commodities)
Boeing Support Services
Although exact information about these industrial wastes is confidential, Metro defines high strength
waste as sewage stronger than domestic waste, that is containing more than 300 mg /1 of Biochemical
Oxygen Demand (BOD) and 400 mg /1 of suspended solids concentration (SS).
Since the Tukwila sewer system discharges in the Metro regional sewer system, Tukwila sewer customers
are subject to Tukwila's sewer ordinances as well as Metro's Resolution No. 3374, "Regarding the
Control and Disposal of Industrial Waste into the Metropolitan Sewerage System ", dated February 21,
1980.
National Pollutant Discharge Elimination System (NPDES)
The United States Environmental Protection Agency (USEPA) has established a National Pollutant
Discharge Elimination System (NPDES) program to regulate the discharge of wastewater to surface
waters. The Washington State Department of Ecology (WDOE) administers the NPDES program in this
state for the USEPA to control all wastewater outfalls and overflows.
The City of Tukwila has been issued a permit by WDOE that allows the discharge of wastewater through
overflow structures or low elevation manholes within the sewer system in the event of an emergency.
The permit requires that the City take all reasonable steps to minimize the number of overflows that
occur. This involves the use of standby power and pumps to be used in the event of a power outage.
The City of Tukwila modified several of the lift stations when Lift Station No. 2 was upgraded to allow
the use of their portable sewage pump. The existing lift stations have some detention capacity within the
wetwells that would fill during a power outage. This would allow the City crews time to transport the
pump to the lift station and pump out the wetwell. The WDOE requires that all discharges to surface
waters be reported at the time they occur. The WDOE maintains a 24 -hour emergency telephone number
(206 -649 -7000) for reporting and response purposes.
3 -10
CHAPTER 4
DESIGN CRITERIA AND CONSTRUCTION STANDARDS
General
Design and construction standards are established to guide the City and the Developer for the planning
and construction of new sewer facilities to ensure that the system is adequate to meet projected needs.
Criteria will include: 1) domestic sewage quantities generated by various land use categories; 2) capacities
of sewer interceptors, trunk lines, laterals and lift stations; and 3) infiltration and inflow rates and peaking
factors used to simulate worst case conditions.
Publications used for determining minimum standards are "Criteria for Sewage Works Design" published
by the State of Washington Department of Ecology and the City of Tukwila's "Public Works Sewer
Construction and Development Standards". The proposed sewer system shall meet all Metro
requirements, all Tukwila Municipal Code requirements, any other governmental agency requirements
and shall be consistent with this Comprehensive Sewer Plan.
Minimum Sanitary Sewer Design Requirements
System Design
All proposed sewer lines or lift stations shall be designed in accordance with good engineering
practice by a professional engineer to suit the conditions at the project location. All sewer
extensions shall be designed for the ultimate development of the potential service area in
accordance with current land use plans. The determination of the tributary area for the sewer
shall be based on this plan and any other detailed studies of the areas affected.
All main sewer lines shall be constructed under the jurisdiction of and maintained by the City of
Tukwila Sewer Department. The sewer lines shall be designed for peak flows and free of
infiltration and inflow. No combined sewers will be allowed.
Sewer extensions shall be sized on the basis of projected per capita flows or some other approved
method. Special review will be given to any sanitary sewer extensions within industrial areas.
The Engineer shall consider pre - treatment requirements, excessive sewage flows and any metering
or sampling program that may be required.
4-1
42
Wastewater Flow Rates
The 1984 Comprehensive Sewer Plan established some unit rates for wastewater generation.
These numbers were developed using water meter data within the City of Tukwila and are shown
in Table 4 -1 shown on next page.
Peaking Factors
Due to the great variation in wastewater flow that occurs during the course of a 24 hour day, the
estimation of the peak flow factor is very important for the proper design of sanitary sewer
systems. The maximum flow in a sewer lateral is expected to be 400% over the average flow.
As more and more area is collected by the system and the laterals are joined together to form
trunk or interceptor sewers, the affect of the peaking is reduced. The design peaking factor for
trunk sewers is 250% over the average flow.
The City of Tukwila has a unique set of conditions that influence the peaking within the sewer
system. The makeup of the study area is one of a large industrial commercial area and a small
residential section. This condition results in an unbalanced ratio when considering the usual
operation of a sewer system. The large industrial commercial development produces an increase
in the peaking factor within the system. To investigate this situation for the 1984 Comprehensive
Sewer Plan, water use records were reviewed to determine the actual peaking factor. This may
be due to the fact that the City of Tukwila did not have a water storage reservoir at the time and
the meter readings indicated the daily peak. The peaking factors used in the 1984 Comprehensive
Sewer Plan are used for this report and some are shown in Table 4 -2.
Population Building Area/ Average
Land Use Equivalents Gross Area Daily Flow
Single Family 2.7 /acre 5.6 units /acre 75 gal /cd*
Multi- Family 1.4 /acre 30 units /acre 75 gal /cd
Retail /Comm. N/A 0.3 sf /gsf** 0.15 gal /sf
Office Space N/A 0.45 sf /gsf 0.08 gal /sf
Light Ind. N/A 0.40 sf /gsf 0.015 gal /sf
Heavy Ind. N/A 0.40 sf /gsf 0.50 gal /sf
* Capita per Day
** Square Foot per Gross Square Foot
N/A Not Applicable
Type of Sewer WDOE*
Laterals and Local
Sewers 4.0
Trunks and
Interceptors 2.5
Major Sewer Basins
Heavy Industry
Light Industry
Commercial
Lift Stations
*
**
* **
TABLE 4-1
WASTEWATER GENERATION UNITS
TABLE 4-2
WASTEWATER FLOW PEAKING FACTORS
(AVERAGE FLOW TO PEAK FLOW)
4-3
Me ro **
1.75
Two or More Major
Sewer Basins -- 1.50
2.0
3.0
Tukwila * **
Sewer Plan
4.0
3.0
3.0
3.0
3.0
2.5
Washington Department of Ecology Guidelines
Municipality of Metropolitan Seattle Guidelines
Peaking rates adjusted for the makeup of the Tukwila system and population
distribution.
Collection System Design Criteria
Reference Datum
The reference datum for sewer within the scope of this study are based on King County Aerial
Survey (KCAS) which is equal to NGVD 1929 datum. The exception to this is the Metro sewers,
which are based on a unique reference datum to eliminate negative elevations within the Metro
service area. Metro datum equals KCAS plus one hundred (100) feet.
Sewer Location
Wherever possible the trunk and interceptor sewers shall be located in public right of way. Under
some topographic conditions, the sewers may be located in easements across private property
when approved by the Engineer. Where the sewer line conflicts with other utilities, the sewer
shall be designed to pass under the other utilities and have a minimum vertical separation of 3
feet. If the elevation of the sewer prevents it from passing under the other utilities, special
construction techniques shall be used per the direction of the Engineer.
Materials
Pipe materials shall be polyvinylchloride (PVC) or reinforced cement concrete depending on the
soils conditions for all slopes less than 15 %. Ductile iron pipe is required where scouring
velocities could be a problem or where soils conditions dictate. In highly corrosive soils the
ductile iron pipe shall be polyethylene encased.
Sewer pipe joints shall be water tight, flexible, rubber gasket type capable of passing a standard
pressure test.
Sewer forcemain shall be ductile iron pipe, cement mortar lined or other material approved by
the City Engineer.
Manholes shall be precast, reinforced concrete bases, rings and cones with rubber gaskets per the
Standard Plans of the City of Tukwila.
Pipe Design and Construction
No sewer shall be less than 8 inches in diameter.
4-4
Minimum depth of cover for a sewer in the street shall be six (6) feet and minimum depth shall
be three (3) feet for easement lines. Sewers shall be constructed on a straight alignment between
manholes. Curved sewers will only be allowed with the approval of the Public Works Director
under special circumstances. The "n" value (roughness coefficient) for the pipe for use with
Manning's Equation shall be 0.013. All sewers shall be designed and constructed to give mean
velocities, when flowing full, of not less than 2.0 feet per second. Minimum slopes shall be per
the City of Tukwila requirements based on pipe size. Sewers shall be laid on a uniform slope
between manholes. Any pipe on a 20 percent or greater slope shall be anchored securely with
concrete anchors.
Manhole Design and Construction
Manholes shall be a minimum of 48 inches in diameter. Manhole diameters shall be increased
as required for larger diameter pipe. Manholes shall be installed at the end of each sewer line
of 8 -inch diameter or greater, at all changes in grade, at all changes in pipe size, at all
connections of sewers 8 inches and larger, all changes in direction, all sewer main intersections
and any other location where access to the sewer line is required for cleaning or inspection.
Manholes shall have a maximum spacing of 500 feet.
Outside drop connections shall be provided for all sewers entering a manhole at an elevation 24
inches or more above the invert of the manhole outfall.
Overflows
No overflows or new overflow structures will be permitted.
Grease Traps
Grease traps shall be provided on all new side sewer connections to customers that the City of
Tukwila determines is a potentially heavy grease producer. Typical grease trap requirements shall
be restaurants, food processing installations, auto and truck repair facilities, and all other types
of development that involve grease or oil.
The developer may be required by the City of Tukwila to provide documentation concerning the
quantity of grease that will be discharged to the sewer system.
4-5
Lift Stations
Lift stations within the City of Tukwila shall be designed and constructed to the following
minimum requirements:
Location and Flood Protection: Wastewater lift stations shall be located to provide the
minimum amount of nuisance to local or proposed residential or commercial development.
Lift station design shall take into account noise control, odor control and station
architectural design. Space for future expansion shall be provided as necessary.
If possible, lift stations shall be located at elevations above the 100 year flood. If it is
not feasible to locate above the 100 year flood plain, stations shall be protected such that
a 100 year flood does not damage the facility. All lift stations shall be designed to
operate during the 25 year flood.
Pumping Rate and Number of Units: Each lift station shall have a minimum of two
pumps. Each pump shall have the capability of pumping the design flow. For lift
stations with more than two pumps, the pumps shall be capable of pumping the design
flow with any one of the pumps out of service.
Pumps
Sewage pumps shall have the capability of passing a 3 -inch diameter sphere. Pump suction and
discharge openings shall be a minimum of 4 inches in diameter. All pumps shall operate under
a positive suction head. The pumps shall operate with the use of an approved control system that
senses the water level in the wet well. The pumps shall automatically alternate the pump in use.
Each lift station shall be equipped with either a standby generator or shall have the required
connections to allow the use of a portable generator. For lift stations that utilize portable
generators, an emergency overflow storage vault shall be provided of a capacity required by the
Tukwila Director of Public Works. An alarm system shall be installed for each lift station and
shall sound on a) power failure, b) low water level, c) high water level, and d) pump overload
or failure.
Wet Wells
Sewage Lift Stations shall have a properly sized wet well to minimize wear and tear on the
pumps. The wet well shall have a capacity that will provide a holding time not to exceed 10
46
minutes for the design average flow. The pump controls shall be adjusted such that the pump will
run a minimum of 5 minutes and will be off for a minimum of 2 minutes at peak design flow.
Trash racks and bar screens will be provided as required to protect the pumps.
Infiltration and Inflow
Infiltration and Inflow (I &I) must be considered in the operation and maintenance of a sanitary sewer
system. Infiltration is defined as "the water entering a sewer system from the ground through such means
as but not limited to, defective pipes, pipe connections, joints or manhole walls ". Inflow is defined as
"the water discharged in a sewer system from such sources as roof leaders, sump pumps, foundation
drains, cooling water discharges, manhole covers due to ponding over the manhole and combined sewers ".
City ordinances have reduced the number of the sources of inflow and therefore this problem will decrease
as any existing inflow connections are eliminated. Infiltration is primarily the result of poor construction
methods and materials. Improved pipe and joint materials, better control over construction methods,
sewer line TV inspection and sewer line testing have greatly decreased infiltration in new sewers. The
older sewer pipe is the primary source of infiltration and a program of monitoring and repair will
systematically eliminate the bad sections of pipe where excessive infiltration inflow is present.
Infiltration and Inflow (I & I) is expressed in units of gallons per acre per day (gpad). Values used by
Metro for evaluation and /or design of their interceptors have ranged from 1,200 gpad for infiltration and
2000 gpad for inflow for sewers constructed prior to 1960, and 600 gpad for infiltration and 500 gpad
for inflow for a total of 1,100 gpad for sewers constructed after 1960. Generally it is assumed that the
I & I generated from a sewer system increases with age. Soil conditions that result in settlement of the
sewer in areas of high groundwater will experience increased I & I over the life of the sewer.
As a part of the 1984 Comprehensive Sewer Plan, Horton Dennis and Associates (HDA) compiled and
reviewed existing studies and information concerning I & I and made recommendations regarding the need
for additional detailed I & I studies. In areas where information was readily available, HDA conducted
additional I & I studies to supplement the previous studies. The study utilized TV inspection records of
existing sewers and sewage lift station pumping records. By looking at the difference in the pumping
records from dry weather to wet weather conditions, an estimate of total I & I could be made.
The conclusion of the I & I study done for the 1984 Comprehensive Sewer Plan was that the I & I that
4-7
existed in the system was not excessive. No I & I exceeded the set limit of 1100 gallons per day per acre
and therefore no improvements based on excessive I & I were recommended.
A second I & I study was performed on the Tukwila sewer system in 1987 by Horton Dennis and
Associates, Inc. under Project No. 84 -SW08. The study was performed to review TV inspection tapes
of problem areas within the system, to check hydraulic capacities within the system, to check sewers for
reverse grades, to analyze flow data from several lift stations and to develop a schedule of needed repairs.
The repairs would be prioritized based on conditions and cost analysis would be prepared.
This project showed many areas that had reverse grades and showed grease buildup and areas where the
manhole and pipe joints are in need of repair. Using this information plans were developed to repair the
worst areas within the system. The proposed repairs and plans are discussed in greater detail in later
sections.
Additional I & I studies are ongoing in the City of Tukwila and should continue as an overall effort
toward reduction of this problem.
CHAPTER 5
SEWER SYSTEM HYDRAULIC ANALYSIS
Methodology
The purpose of this analysis is to evaluate the capacity of the existing sewer interceptors, laterals and lift
stations with respect to both current estimated wastewater flows and projected ultimate sewage flows that
will develop as a result of future growth. Any deficiencies will be identified and recommendations will
be made for reconstruction, elimination, diversion, zoning restrictions, infiltration inflow rehabilitation,
and /or more extensive study of the problem area. The recommendations will be based on a cost effective
analysis of the defined alternatives.
In areas that do not presently have sewer service, alternatives will be analyzed to ascertain the most viable
means of providing sewer service. The effect of providing these areas sewer service on the downstream
sewer system will also be investigated.
Wastewater flows have been estimated based on the area of the drainage basin that contributes to a trunk
line, then, using this area and the zoning, a projection of the number of units based on redevelopment
growth projections (Scenario III) was made. The projected wastewater flows were then determined based
on the unit flows outlined in Chapter 4 of this Comprehensive Plan and compared to the capacity of the
existing facilities. Areas where a potential problem was indicated were analyzed. The proposed
improvements were developed to rectify the problem areas to provide adequate service for Scenario III.
Sewage Lift Station Considerations
The City of Tukwila presently has eight (8) sewage lift stations operating within their sewage collection
system. Lift stations are usually constructed due to economic factors and /or the topography of the service
area. In some areas, it is not economically feasible to construct interceptor sewers and therefore a lift
station is used to pump the wastewater to a nearby interceptor through a small diameter forcemain. As
an area develops, the construction of an interceptor sewer may become feasible and the City could elect
to eliminate the lift station. In Light of the increasing concern for minimizing energy consumption, and
the problem of sewage overflows and rising operation and maintenance costs of the lift stations, the City
of Tukwila is becoming more and more interested in investigating the possibility of eliminating some of
the existing lift stations. The 1984 Comprehensive Sewer Plan looked at and recommended the
elimination of some of the existing lift stations. This update will revise those recommendations as
necessary to include any changed conditions that may have occurred in the past five years.
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Sanitary Sewer Drainage Basins
Drainage Basin No. 1
Drainage Basin No. 1 is located in the northwest corner of the City of Tukwila, on the north side
of Interstate Highway 5. The majority of the basin is located on the west side of the Green River,
however a small residential agricultural area on the east side of the river is within the Tukwila
City Limits. This area is approximately 5 acres in size and is not sewered. The homes in the
area have private septic tank / drainfield systems.
The City expects the area on the east side of the river will remain residential agricultural
throughout the planning period. If the residents experience drainfield failures and find sewers to
be necessary, the cost will be extremely high unless a larger area including the Allentown area
is sewered. Improvements for this portion of the Allentown area are discussed in Supplement A.
The area on the west side of the river within Basin No. 1 is commercial and light industrial and
is sewered. The Metro Interceptor that passes through the City of Tukwila to the Renton
Treatment Plant goes through the middle of Basin No. 1. The sewers within the basin either flow
directly into the Metro interceptor or they flow to the City's Lift Station No. 5 (Trammel Crow
Lift Station). The sewers are adequate to handle the ultimate wastewater flow from the area.
A new Metro interceptor line along Interurban Avenue South is currently being designed and
anticipated to be complete by 1994. Initially, Metro considered construction of this interceptor
at a depth which would permit abandonment of the Trammel Crow Lift Station. This alternative,
however, is not likely to be achieved because of the relative costs associated with construction.
The new interceptor is anticipated to be at a similar elevation as the existing facility and no
significant changes to the Trammel Crow Lift Station are projected at this time.
Drainage Basin No. 2
Basin No. 2 is located in the north central part of Tukwila and includes residential, commercial
retail and some light industrial development. The area straddles Interurban Avenue and is more
or less developed, limiting the potential for future development and the likelihood of flow
increases. The area drains to the Metro Lift Station on Interurban Avenue that pumps the
wastewater into the Metro interceptor. The City of Tukwila operates Lift Station No. 4 within
this basin.
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Local grease buildup problems exist in the sewer along Interurban Avenue and it is assumed that
the problems are caused by the restaurants along Interurban Avenue. This grease buildup is a
maintenance problem and it is recommended that the City of Tukwila implement a grease trap
ordinance to control the amount of grease that is entering the sewer from these sources.
The 1984 Comprehensive Sewer Plan stated that root infestation was evident within several sewer
laterals in Basin No. 2. A program using copper sulfate to kill the roots entering the sewer
system would help control the problem.
The 8 -inch gravity sewer that is on Interurban Avenue, downstream from Lift Station No. 4, will
be overloaded if the redevelopment buildout scenario were to occur. The wastewater flow to the
lift station will also exceed the capacity of the lift station in the redevelopment buildout scenario.
Two alternatives are proposed to accommodate these projected flows.
The first alternative is to utilize the excess capacity of an existing 12 -inch diameter pipe on the
northeast side of Interurban Avenue by diverting the flow to Lift Station No. 4 across Interurban.
This alternative would also eliminate Lift Station No. 4 by the construction of a 12 -inch diameter
gravity sewer on Interurban Avenue. The elimination of Lift Station No. 4 would have the added
benefit of removing the existing overflow to the Duwamish River. The second alternative is to
upgrade Lift Station No. 4 to handle the projected flows and to construct a ten inch diameter
gravity sewer on Interurban Avenue to alleviate the problem area.
Because the existing system is adequate to handle all projected wastewater flows for the planning
period and for the Vacant Land Buildout Scenario, no improvements are recommended for
Drainage Basin No. 2 at this time. When wastewater flows increase due to a change in zoning
or type of development that is sewered by Lift Station No. 4, the alternatives listed above shall
be reevaluated as to their feasibility.
Drainage Basin No. 3
Drainage Basin No. 3 is located in the eastern portion of the City along the Green River. The
area is used for commercial and light industrial development and includes Fort Dent Park. There
are two areas within the Basin that are not presently served by City sewer. The north end of the
Basin and the south end. The central area drains to Lift Stations 6 and 7 and is pumped to the
Metro interceptor.
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Service to the northern portion of Drainage Basin No. 3, a 27 acre light industrial tract, can be
accomplished by gravity sewer that flows to Lift Station No. 6. This would require
approximately 3000 feet of 8 inch diameter sewer that would be constructed parallel to the
existing Metro - Renton sludge lines. Preliminary investigations indicate that due to the topography
of the area and the elevation of the lift station, the proposed sewers would have to be constructed
at less than the minimum recommended slope. Constructed properly, the sewer would provide
good service to the area.
The southern portion of Drainage Basin No. 3 is "land locked" between the railroad right -of -way,
the Duwamish River and Interstate 405, making the area relatively expensive to provide sewer
service to. The area is planned for light industrial development and consists of just under 13
acres. Service could be provided by jacking a new sewer line under either the freeway or the
railroad right -of -way. Although it believed that these two alternatives would be similar in
construction cost, a thorough analysis of the route options should be performed as development
of this area is considered.
The projected flow to the lift station for the redevelopment buildout scenario indicates that the
wastewater flow will be approaching the full capacity of the lift station. Operating at full capacity
results in the pumps running for extended periods of time and therefore requiring more frequent
maintenance. It is recommended that the flow to the lift station be monitored and maintenance
records kept. It is assumed that the projected redevelopment buildout scenario will not occur
within the expected life of the present pumps in Lift Station No. 6, no recommendations will be
made concerning Lift Station No. 6. At the time the pumps require replacement, it is
recommended that the City reevaluate the wastewater flow to the lift station and increase the size
if necessary or investigate the options available to eliminate the station.
Drainage Basin No. 4
Drainage Basin No. 4 is located in the north central part of the City of Tukwila. Included in this
basin is the Tukwila City Hall, various office buildings, restaurants, as well as single family and
multi family developments. The topography of Drainage Basin No. 4 is rolling.
The capacity of the sewers within the basin are of adequate capacity to handle the estimated
wastewater flows for the redevelopment buildout scenario and are in good condition. The 1984
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Sewer Plan identified the possibility of excessive I & I within this Basin, however, the problem
was not deemed severe enough to warrant further study.
Drainage Basin No. 5
Located in a residential area in the northwest part of Tukwila, Drainage Basin No. 5 has sloping
topography. The area is zoned for single family and multi - family development. The existing
sewers have sufficient capacity to handle the estimated wastewater flows for the redevelopment
buildout scenario. No improvements are projected for this area.
Drainage Basin No. 6
Drainage Basin No. 6 is a small drainage basin having 21 acres located along the western city
limits. The area is a combination of multi - family residential, office and retail development. Due
to the proximity of the Metro interceptor within the Basin, the sewer system is more than
adequate to meet present and future needs.
Drainage Basin No. 7
Drainage Basin No. 7 is located on the west side of I -5 and the sewers within the area are owned
and operated by Val Vue Sewer District. This area is located on what is known as West Hill in
the McMicken Heights Area. The area consists of approximately 80 acres of single family
residential development. The sewer system within the area has sufficient capacity to meet the
needs of the area for the projected development. Due to good velocities in the pipelines,
maintenance problems have not been noted in the system.
Drainage Basin No. 8
Drainage Basin No. 8 covers all of the Southcenter Shopping Area from I -5 to I-405 south to
Strander Boulevard and east to the Green River. The Basin is used for wholesale distribution and
retail sales development. Topography of the area is flat. The 24, 27 and 36 -inch diameter Metro
interceptor runs along the western and southern boundary of this Basin.
Several problems were noted within the Basin No. 8 system due to flat slopes and settlement sags
in the lines. Grease buildup is a problem that requires regular cleaning of the system by high
pressure jetting. The sewer system has sufficient hydraulic capacity to handle the flows for the
redevelopment buildout scenario, with some repair of the settlement areas.
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The 1984 Sewer Plan recommended that the City of Tukwila adopt a grease trap ordinance. Such
an ordinance would help to control the amount of grease that was being discharged to the sewer,
and reduce the costs of maintenance of the sewer system.
During 1988, several small projects were proposed in the Southcenter area to improve the
condition of the sewers. Sewers were identified for replacement and /or repair as needed to
upgrade the system to eliminate a portion of the maintenance problems that have been experienced
in the past. See Project No. 84 -SW08 for more details on the exact location and nature of these
modifications. Presently, due to construction on Southcenter property and other factors, the City
has not established a schedule for the completion of these repairs.
Drainage Basin No. 9
Drainage Basin No. 9 is located along the eastern city limits, just south of I-405 and east of the
Green River. The area is used for wholesale distribution and retail sales. The area is very flat
river bottom land. Eleven acres of this basin are located on the west side of the West Valley
Highway and are undeveloped and therefore unsewered. When the area develops, sewer service
can be provided via an 8 -inch pipe bored and jacked under West Valley Highway.
A grease problem has been identified at the connection of the 12 -inch trunk sewer to the Metro
Interceptor. Due to the high flows in the Metro pipe, the wastewater backs up into the 12 -inch
trunk line. The reduced velocities that result from this condition allow grease to accumulate.
This situation requires regular maintenance of the system to ensure that it operates properly. At
this time no recommendations are made to try to correct the situation.
Drainage Basin No. 10
Drainage Basin No. 10 includes the area east of the Duwamish River between Strander Boulevard
and South 180th Street. The boundaries of Basin No. 10 have been significantly altered from the
boundaries shown in the 1984 Comprehensive Sewer Plan by a change to the eastern Tukwila City
Limits. The City of Tukwila entered into an agreement with the City of Renton to make their
common boundary coincide with the Burlington Northern Railroad right of way. This eliminated
the large area within the City limits west of the highway and added a large area south of the
previous Basin No. 10 boundary. The majority of the area is presently undeveloped and planned
for light industrial development. The area contains approximately 132 acres of flat river bottom
land, but only 100 acres are considered developable due to the highway right of way.
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5 -7
Considering the revised city limits and the expanded nature of the drainage basin, the existing 12-
inch sewer that serves the basin will be overloaded in Scenario No. 3 "Redevelopment Buildout ".
Due to the long narrow configuration of the basin, a single main trunk line connecting to the
Metro interceptor would appear to be the only logical alternative. The capacity of the existing
12 -inch line will have to be increased to accommodate the estimated wastewater flows. Two
alternatives will be proposed to increase the trunk to the required size.
The first alternative would be to provide the full service area with gravity sewer. This would
require the reconstruction of the existing trunk line with 1500 LF of 15 -inch pipe and 1100 LF
of 12 -inch pipe. The 12 -inch pipe would be replaced at a lower elevation to enable sewer service
to the southern area. The remainder of the area would be served by approximately 1500 LF of
12 -inch pipe and 1000 LF of 8 -inch pipe. All of the sewer would be at minimum grade which
could potentially limit development of the south end of the basin.
The second alternative would be to provide a portion of the basin with gravity sewer and then
construct a lift station to serve the south end of the basin. The alternative would require the
construction of approximately 1500 LF of 12 -inch pipe parallel to the existing 12 -inch sewer, a
500 gpm lift station, 1500 LF of 12 -inch pipe and 1000 LF of 8 -inch pipe.
Although these two alternatives will be developed in detail later in this report, it is recommended
that the City investigate the two alternatives to determine the best course of action when sewer
service to this area is requested or required.
Drainage Basin No. 11
Drainage Basin No. 11 is located in the east central part of Tukwila on the west side of the Green
River. The Basin is made up of primarily commercial and light industrial development and
contains flat river bottom lands. The southeast corner of the Basin drains to Lift Station No. 3,
which is located at the City's maintenance facility.
Projected wastewater flows for the Redevelopment Buildout Scenario is estimated to equal the
capacity of the existing pumps in Lift Station No. 3. This loading will put considerable stress on
the pumps and result in frequent maintenance of the pumps. The 1984 Sewer Plan proposed the
elimination of the Lift Station by the construction of a gravity sewer. The City of Tukwila
solicited bids for this project in 1988. The bids were substantially higher than the estimates and
an economic analysis determined that it was not feasible to replace the lift station with gravity
sewers. This Plan, therefore, does not address such an alternative.
The existing pumps are adequate to provide service to the area throughout the pumps anticipated
life of 15 years. It is recommended, however, that the City continue to monitor the loading on
the lift station. If it becomes apparent that proposed development, redevelopment, change in the
type of industry or a change in the zoning in the area will result in the capacity of the lift station
being exceeded, the City will be required to upsize the pumps to meet the demand. When
replacement of the pumps is required, it is recommended that the City consider upsizing the
pumps to a design flow of 150 gpm.
Drainage Basin No. 12
Drainage Basin No. 12 is located directly south of the Southcenter Shopping Mall between
Strander and Minkler Boulevards. The area has office buildings, commercial and light industrial
development. The area contains flat river bottom land that rises sharply to I -5 and McMicken
Heights in the west.
The 1984 Sewer Plan identified two main deficiencies in Basin No. 12, including recurrent grease
buildup within the pipe on Strander Boulevard and in the 21 -inch and 24 -inch diameter pipe near
Lift Station No. 2; and, reappearing maintenance problems associated with private pumping
facilities within the system.
As discussed earlier implementation of a grease trap ordinance could significantly reduce the
problems associated with grease buildup. A second alternative that would control this problem
would be for the City of Tukwila to install grease traps within their sewer system at strategic
locations to reduce the grease loading. A City owned grease trap system would require regular
cleaning by City crews.
The 21 and 24 -inch pipe on Andover Park West and the 12 -inch collector on Strander Boulevard,
have grease problems due to the backwater situation created by flows in the Metro Interceptor on
Strander Boulevard. The high flows in the Metro pipe cause a backwater condition which reduces
the velocities in the collector sewers and allows grease to accumulate. This condition is not
5 -8
readily corrected through construction. To reduce the required maintenance on the system due
to these circumstances, the use of grease traps is again recommended.
Private lift stations exist in the system that were not constructed to the City's design and
construction standards. Many of these were eliminated with the construction of the LID 32
Southcenter Parkway gravity main. However, the remaining lift stations tend to have problems
with wet well capacity, power outages, emergency backup and overflows. To control these
problems, it was recommended that the City of Tukwila adopt a lift station ordinance that would
outline the design, construction and operation of private lift stations.
The South Service Area, described in detail later in this Chapter, will put an additional loading
on the trunk sewer on Andover Park West. The projected wastewater flow from this area will
overload the existing 21 and 24 -inch gravity sewer on Andover Park West. To rectify this, the
"Southcenter Parkway Sewer Extension and Interceptor" study proposed that a parallel 21 -inch
diameter gravity sewer line be constructed along Andover Park West from Minkler Boulevard to
Strander Boulevard and connect to the Metro Interceptor sewer. This proposed pipe will convey
the discharge from Lift Station No. 2 north to the Metro Interceptor.
Drainage Basin No. 13
Drainage Basin No. 13 is the largest drainage basin in the system. The Basin serves all of
Tukwila south of Minkler Boulevard from I -5 on the west, to the Green River and the city limits
on the east. The area is used for light and heavy industrial and commercial type development.
The southeast corner of Basin 13 flows to Lift Station No. 8 which pumps the wastewater north
to the gravity sewer system on South 180th Street. The sewer on S. 180th St. and the remainder
of the area is served by a gravity sewer system that conveys sewage to Lift Station No. 2 on
Andover Park West. Lift Station No. 2 pumps the wastewater into the 21 -inch gravity sewer in
Drainage Basin 12 that flows to the Metro interceptor sewer.
The redevelopment buildout scenario for Basin 13, which calls for nearly one -half million square
feet of heavy industrial development in addition to light industrial and commercial uses, could
produce as much as 1.2 MGD of wastewater flow. It is difficult, at best, to try to predict the
quantity of wastewater from a proposed heavy industrial development area because of highly
variable flows which might occur depending on the type of development and industry that is
5 -9
actually constructed. Some industries discharge relatively small quantities of contaminated
process water and other industries discharge large volumes of wastewater to the sewer. A rate
structure and City ordinances can control this to a certain extent by requiring the industry to use
on -site recycling, flow equalization basins and private treatment systems. It is therefore
recommended that as industry is proposed for the area, the potential effect on the sewer system
be evaluated on a case by case basis. If the effect of construction is an overloaded sewer system,
the industry shall be required to either reduce its wastewater flow or participate with the City in
upgrading the sewer system to accommodate the projected flows.
For the area that drains to Lift Station No. 8, the redevelopment buildout scenario proposes that
the area be converted from light industrial to office space. This situation would overload the
pumps currently operating in Lift Station No. 8. Alternatives include: upgrading the pumps in
Lift Station No. 8 to the required size when needed; or, structuring the zoning of the area such
that development would be limited to acceptable wastewater flow values.
Presently the existing sewer system that drains to Lift Station No. 8 is adequate to meet the needs
of the area. It is recommended that the City monitor the loading on the lift station and reevaluate
the available alternatives as conditions dictate. Limiting the type of development in the area may
not be in the best interests of the City of Tukwila, which would make upgrading the lift station
as the only logical alternative.
Lift Station No. 2, located at the intersection of Minkler Boulevard and Andover Park West, did
not have sufficient capacity for the projected wastewater flows. In 1985 the City of Tukwila
contracted with the Firm of R. W. Beck and Associates to evaluate and upgrade Lift Station No.
2. In the Engineering Report dated February, 1985 the design of the lift station was setup for two
phases, Phase 1: pumping capacity 2.81 MGD and Phase 2: pumping capacity 6.33 MGD.
The proposed lift station considered two alternative types of pump, constant speed pumps and
variable speed pumps. If constant speed pumps were selected, the pumping capacity of the
constant speed pumps could be upgraded to meet Phase 2 conditions by replacing the motors with
higher speed motors, using two speed motors, or sizing the pumps so that the impeller housings
and the motor mounts can accommodate larger impellers and higher horsepower motors to provide
increased pumping capacity.
5 -10
It was decided that constant speed pumps with the capacity to increase the impeller size was the
preferred alternative. The impeller of the proposed pump is initially sized for a capacity of 800
gpm at 25 feet of total head at 10 hp. To accommodate ultimate flows, the pumps will be
modified to pump 2100 gpm at 30 feet of total head at 25 hp.
The existing 8 -inch forcemain was replaced with a 14 -inch diameter forcemain to accommodate
the projected redevelopment buildout scenario wastewater loading. Lift Station No. 2 now has
sufficient capacity with the planned pump changes to provide the City of Tukwila with service
throughout the planning period.
In the 1984 Comprehensive Sewer Plan under the Redevelopment Buildout Scenario it became
apparent that the sewer system in the south end within Basin 13 was undersized. If the area were
to develop as a heavy industrial area, the existing trunk sewers from the south end to the Metro
Interceptor on Strander Boulevard would be overloaded. To study the situation and determine the
best solution to the problem, the south study area must be included in the sizing and routing of
any proposed improvements. To accomplish this task, the City of Tukwila contracted with
Horton Dennis and Associates, Inc. to study the interceptor.
The "Southcenter Parkway Sewer Extension and Interceptor" study (described in detail later in
this Chapter) indicated that the trunk sewer on Andover Park West between Minkler Boulevard
and South 180th Street, and the trunk sewer on Minkler Boulevard from Southcenter Parkway to
Andover Park West, is in need of upgrading. Construction of the proposed interceptor on the
"Minkler Route" would replace the aging deteriorating AC sewer main on Minkler. A 12 -inch
trunk sewer would be required on Andover Park West to provide adequate capacity for the area
along Andover Park West and the Segale Business Park area in the south. The proposed
Southcenter Parkway Sewer Extension and Interceptor will provide the area along Southcenter
Parkway with the required level of sewer service.
South Service Area Basin No. 14
The South Service Area is located outside the present Tukwila City Limits. The Basin is bounded
by I -5, the Green River, South 188th Street and South 204th Street. The Basin contains flat river
bottom land that rises sharply in the west up to I -5. Approximately 315 acres of the Basin is
presently zoned for agriculture and suburban estate, with about 54 acres zoned for heavy industry.
5 -11
There exists approximately 30 acres of designated wetlands which fall under King County
Sensitive Areas Ordinance No. 4365.
The Army Corps of Engineers Flood Mitigation Plans, in conjunction with a document published
by King County and adopted by the surrounding municipalities, entitled "The River of Green"
provides for a substantial construction setback from the Green River • (200 feet). The Soil
Conservation Service is also proposing to designate 70 acres of marsh and agricultural land lying
adjacent to this basin as a part of their construction plans for the Service G- Channel. This
proposal satisfies a cooperative agreement between the surrounding municipalities of Kent,
Auburn, Renton and Tukwila and the S.C.S. to exchange wetland habitats which would be lost
in the construction of the G- Channel Program. The designated wetland areas, comprising a
contiguous 100 acres, delineates a logical basin boundary between areas which could be serviced
by Tukwila and areas which could be serviced by Kent.
Much of the area remains agricultural and undeveloped in nature. A significant portion of the
property owners in this Basin have applied for rezone at one time or another for heavy
manufacturing and office space. For the purposes of the proposed sewer trunk line study, it is
assumed that the area will be rezoned and produce a peak wastewater flow of approximately 1.92
MGD under the redevelopment buildout scenario.
During the course of the HDA study for the "Southcenter Parkway Sewer Extension and
Interceptor" several alternatives were considered for the routing and configuration of the proposed
interceptor. Questions regarding lift station locations and phasing were investigated to determine
the best alternative for the system.
The proposed interceptor originates at the intersection of Orillia Road and South 200th Street then
traverses east to Southcenter Parkway, at Southcenter Parkway the route turns north and follows
Southcenter Parkway to Minider Boulevard, the interceptor then turns east along Minkler
Boulevard to Andover Park West where it enters existing Lift Station No. 2. An alternative route
for the interceptor has it turn east on South 180th Street to it's intersection with Andover Park
West, thence north along Andover Park West to Minkler Boulevard and Lift Station No. 2.
Several different lift station alternatives were studied based on construction phasing, sewer depth
and area of service.
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It is recommended that the City of Tukwila construct a gravity sewer interceptor from Lift Station
#2 to South 200th Street. The interceptor could be located on Minkler Boulevard which would
have the extra advantage of replacing an aging deteriorating 12 -inch AC sewer on Minkler
Boulevard. The trunk main would consist of 18 -inch and 21 -inch diameter ductile iron pipe
constructed at a depth of 6 to 14 feet in depth. This alignment of the trunk sewer would allow
versatility in phasing of the improvement by utilizing existing manholes on South 180th Street and
constructing the interceptor south along Southcenter Parkway to the southern service area as
development dictates.
Advantages of the proposed trunk sewer are: shallow sewer depths to keep the cost of the sewer
down; the proposed interceptor replaces an aging deteriorating 12 -inch AC sewer on Minider
Boulevard; and, the work can be phased to allow it to proceed on an "as- needed" basis.
Disadvantages to this alternative are: new laterals will be required in the South 180th Street and
Andover Park West areas as increased wastewater flows warrant them; and, depending on the
final elevation of Southcenter Parkway /Frager Road South, a 1.0 MGD lift station may be
required.
The addition of the South Service Area to the system affects the sewer systems within Drainage
Basins 12 and 13. The proposed improvements for these areas'are detailed under the descriptions
for those Drainage Basins.
North Service Area Basin No. 15
The 1984 Comprehensive Sewer Plan identified an area in the northern part of Tukwila that is
north and east of the Duwamish River. The area is bounded by the River, on the east by the
Beacon Coal Mine Road, and the existing Burlington Northern Freight Depot. The area is
contiguous with the Fire District No. 1 annexation area. The area is assumed to consist of
approximately 57 acres of single family residence and 21 acres of light industrial development.
This development produces an estimated peak wastewater flow of 0.34 MGD.
The majority of the North Service Area is served by septic drain field systems. The Burlington
Northern Depot has a private sewer system that includes a gravity sewer, a lift station and a fl-
inch diameter forcemain that crosses the Duwamish River to the 48th Avenue South 12 -inch sewer
main.
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It is proposed to abandon the existing septic drain field systems and construct a gravity sewer
system to provide service to the area. Due to the location of the area, the recommendation is for
the area to connect to a sewer system that is proposed for Allentown, which is discussed in
Supplement A.
5 -14
PROPOSED IMPROVEMENTS
CHAPTER 6
PROPOSED IMPROVEMENTS
6-1
General
This chapter itemizes the recommended sewer system improvements for the City of Tukwila based on the
information presented in the preceding chapters. All proposed improvements are based on Scenario III,
Redevelopment Build -out per the approved Land Use Policy Plan and the projected wastewater flows
described in earlier comprehensive sections of this report. Cost estimates of the proposed projects will
be presented and a preliminary scheduling of the improvements will be laid out.
Only major sewer improvements or renovations will be recommended and discussed in this Chapter.
Proposed trunk lines and lift stations will be outlined to provide presently unsewered areas with sewer
service. Lateral or side sewer construction will be assumed to be provided as required by the area and
the specific details will be determined at the time of design of the system. In developed areas that are
presently on septic tank drain field systems, the cost of providing sewer service will be investigated. For
vacant land area where only minor lateral and side sewer construction is necessary, sewer service will
be provided through Developer Extension Agreements with the prospective builders in the area.
Proposed Improvements
For the purposes of this report, the recommended improvements are discussed on a drainage basin by
drainage basin basis. Each project is assigned a descriptive number for identification purposes. Cost
analysis and scheduling will be discussed in a later section. Please refer to Table 6 -1 and 6 -2 located at
the end of this chapter for further information. Project locations are shown on the Comprehensive Sewer
Plan Map included in the map pocket at the back of this document.
Drainage Basin No. 1
The sewer system within the majority of Drainage Basin No. 1 is adequate to provide service to
the area throughout Scenario No. III. No improvements are proposed for this area.
On the east side of the river there is a small area of residential homes that presently have septic
tank drain field systems. These septic tank systems appear to be operating satisfactorily with no
problems. Providing gravity sewer service to the area would be economically unfeasible by itself.
If a sanitary sewer system were constructed for the Allentown area, this area of Drainage Basin
No. 1 would logically be connected to such a system. These improvements are discussed in
Supplement A - Annexation Areas.
Drainage Basin No. 2
Lift Station No. 4, and the 8 -inch diameter gravity sewer on Interurban Avenue South that Lift
Station No. 4 pumps into, will be slightly overloaded under Scenario III. It is assumed that
Scenario III or a significant rezone of the area will not occur within the planning period of this
Comprehensive Sewer Plan. It is recommended that the City monitor the area throughout the
planning period, especially if a rezone is proposed. The amount of wastewater produced by the
area should then be investigated with regards to the loading on Lift Station No. 4.
The sewer on Interurban Avenue South was inspected by TV and several problem areas were
noted that would warrant repair. The specific areas are discussed under the I & I study done
under Project No. 84 -SW08 and Plans and Specifications to repair the more severe areas were
prepared in December, 1987. The City has yet to issue a contract to complete this work.
Grease buildup in the sewer system has been a recurring problem within this drainage basin. The
problem is especially evident in the Interurban area where there are several restaurants
discharging to the sewer. It is the recommendation of this Comprehensive Sewer Plan that the
City of Tukwila adopt a Grease Trap Ordinance that would require the individual industrial or
commercial users to install and maintain the grease traps. This would reduce the maintenance
requirement on the system and allow maintenance crews and equipment to perform other more
productive tasks.
It is recommended that the grease problem along Interurban Ave. S. be specifically monitored.
If grease buildup becomes a severe problem, it has been proposed that the restaurants located on
the north side of Interurban Ave. South be connected to the 12 -inch diameter sewer that is on the
north side of the street. This would serve two functions by reducing the loading on the 8 -inch
diameter sewer downstream from Lift Station No. 4 and by providing more capacity for the heavy
grease loading from these establishments.
Drainage Basin No. 3
Two subareas within Drainage Basin No. 3 are proposed to be served by the Tukwila sanitary
sewer system. The first is located north of Fort Dent Park and is zoned for light industrial
development. The second area is also zoned for light industrial development and is located south
of the river just north of I-405.
6-2
The north area consists of approximately 27 acres that is proposed to be served via a gravity
sewer from Lift Station No. 6. The proposed sewer line would be constructed parallel to the
existing Metro - Renton Sludge line along the railroad right of way. Due to the topography of the
area the pipe will be constructed at minimum slope or less. If the pipe is constructed at less than
minimum slope the velocity of the wastewater in the pipe may be low resulting in maintenance
problems. If the design indicates that this could be a problem, flushing points shall be designed
into the system and regular maintenance performed to keep the sewer clean. The proposed
gravity sewer is Project 1 in this Comprehensive Sewer Plan.
Project 1 - Gravity Sewer to Northern Area of Basin No. 3
Project Description: Construct approximately 3000 LF of 8 -inch diameter gravity sewer
from the undeveloped area to Lift Station No. 6 at minimum grade to serve a 27 acre
light industrial parcel of Drainage Basin No. 3.
The south area within this basin consists of approximately 13 acres of land that is zoned for light
industrial and is presently undeveloped. The area is land locked by I-405 on the south, the river
on the north and the railroad on the east. The area can be served by gravity to either the Tukwila
sewer system or by constructing a direct connection to the Renton Treatment Plant influent line.
The proposed connection would be expensive in that boring would be required in either case.
Two alternatives will be proposed for service to the area and when development pressure develops
for the area, the developer and the City can investigate the most feasible of the two alternatives.
Connection to the Tukwila sewer system will be designated as Project 2A.
Project 2A - Gravity Sewer Under I-405 to Tukwila Sewer System
Project Description: Construct approximately 700 LF of 8 -inch gravity sewer, including
a 450 LF bore under I-405, to tie into the existing Tukwila sewer system.
Connection to the influent line of the Renton Wastewater Treatment Plant will be designated as
Project 2B.
Project No. 2B - Gravity Sewer Under the Railroad to Metro
Project Description: Construct approximately 700 LF of 8 -inch gravity sewer, including
a 200 LF bore under the railroad right of way, to tie into the existing Metro Renton
Wastewater Treatment influent pipe.
The 1 & I study in 1987 through the use of TV inspection of the existing sewer in Drainage Basin
No. 3 identified a broken sewer pipe on Southcenter Boulevard just east of Interurban Avenue.
Project No. 84 -SW08 was completed in 1990 and included grouting and sealing of the pipe. No
other areas in the basin were noted to be in need of repair.
6-3
Drainage Basin No. 4
The sewer system in Drainage Basin No. 4 is adequate to handle the projected wastewater flow
for Scenario III and, therefore, no capital improvement projects are proposed for this basin.
Drainage Basin No. 5
No deficiencies where identified for Drainage Basin No. 5. The sewer system within the basin
is adequate to meet the needs of the area throughout the planning period.
Drainage Basin No. 6
Drainage Basin No. 6 is a very small basin located on the west side of I -5. The Metro interceptor
passes through the basin and provides acceptable sewer service to the area. No capital
improvements are proposed for the basin.
Drainage Basin No. 7
Drainage Basin No. 7 lies within the service area of Val Vue Sewer District and Tukwila has an
agreement for the District to provide sewer service to the area. The topography of the area
provides good velocities in the sewer and the existing system will provide adequate service to the
area throughout the planning period. No capital improvements are proposed for the area.
Drainage Basin No. 8
Drainage Basin No. 8 is in the heart of the commercial district of the City of Tukwila. The area
is flat river bottom land, therefore the sewers are constructed on minimum grades with low flow
velocities. The hydraulic analysis did not indicate a sewer capacity problem with the system,
however, TV inspection of the sewer and continued maintenance problems have noted several
settlement sags in the sewer pipes.
The I & I study done in 1987 identified several areas in the basin that warranted repair work.
The problem areas were assigned a priority rating and plans and specifications were prepared
under Project No. 84 -SW08. The City has not yet contracted for completion of these repairs.
Drainage Basin No. 9
The existing gravity sewer in Basin No. 9 is adequate to provide service to the area throughout
Scenario III. Since the 1984 Sewer Plan was approved, service has been provided to the western
portion of the Basin through a 8 -inch gravity sewer which was installed to serve Nendel's.
64
Grease buildup problems have been noted at the connection to the Metro sewer interceptor due
to the elevation of the interceptor and the elevation of the Tukwila trunk sewer. This problem
results in continued maintenance cleaning of the sewer which is a significant expense to the City.
There is no easy solution to this problem via construction in the trunk sewer system. It is the
recommendation of this Plan for the City to adopt a grease trap ordinance that would control the
amount of grease that enters the sewer, as discussed in other sections of this report.
Drainage Basin No. 10
The boundaries of Drainage Basin No. 10 have changed significantly since the completion of the
1984 Comprehensive Sewer Plan. The City, through an exchange with the City of Renton
realigned the eastern city limits which resulted in an addition to the south end of Basin No. 10.
The result of this is that the existing sewer in the basin will be overloaded for Scenario III. To
alleviate this problem we are recommending two alternatives to increase the capacity of the sewer
within the basin. The first alternative will provide the entire basin with gravity sewer service and
is designated Project 3A.
Project 3A - Gravity Sewer Service to Basin No. 10
Project Description: Construct approximately 1500 LF of 15 -inch and 1100 LF of 12-
inch gravity sewer from the existing Metro Interceptor to replace the existing trunk
sewer, lower the pipe to serve the south end of the basin and provide the necessary sewer
capacity to the basin. To serve the southern half of the basin it is proposed to construct
approximately 1500 LF of 12 -inch pipe and 1000 LF of 8 -inch pipe which would provide
the trunk sewer for the basin.
The advantage of this alternative would be the gravity sewer within the full basin. The
disadvantage would be the requirement that the existing sewer would have to be abandoned to
lower the full line to provide service to the southern area.
The second alternative would be to include a lift station in the system at the approximate
intersection of the West Valley Highway and Minkler Boulevard extended. This project is
designated as Project 3B.
Project 3B - Service to Basin No. 10 via a Lift Station
Project Description: Construct approximately 1500 LF of 15 -inch gravity sewer to
increase the capacity of the trunk sewer, utilize 1100 LF of the existing 12 -inch trunk
sewer, construct a 500 gpm lift station and construct approximately 1500 LF of 12 -inch
pipe and 1000 LF of 8 -inch pipe to serve the southern half of the drainage basin.
6-5
The advantage of this alternative is that it would make full use of the existing pipe and allow
phasing of the improvement. Using this alternative the pipe can be extended south without
constructing the trunk line. The disadvantage for having a lift station is the ongoing maintenance
and operational requirements.
Drainage Basin No. 11
The sewer system within Drainage Basin No. 11 has sufficient capacity to handle the projected
wastewater loading throughout the planning period. Lift Station 3 will be at design flows for
Scenario III and it is the recommendation of this plan that the City monitor the flow to the lift
station and when it comes time to replace the existing pumps, the City might consider upsizing
the pumps to 150 gpm.
Drainage Basin No. 12
Drainage Basin No. 12 has recurring grease buildup problems in the 12 -inch sewer on Strander
Boulevard and in the 21 -inch and 24 -inch trunk sewer on Andover Park West. High grease
concentrations in the wastewater are not readily handled without major construction or
reconstruction within the sewer system. Grease traps that would function properly located in the
main sewer line would have to be very large structures that would be expensive to construct and
maintain. Sewer main grease traps will be considered to be unfeasible due to economic reasons.
This Comprehensive Sewer Plan has recommended that the City of Tukwila adopt a grease trap
ordinance that would control the grease at the source and reduce the concentration in the sewer.
Generally the existing sewer system within the drainage basin has sufficient capacity for Scenario
III. A deficiency has been identified in the trunk sewer on Andover Park West from Minkler
Boulevard to Lift Station No. 1 on Strander Boulevard when the southern service area is
connected to the system and built out. The Southern Drainage Basin study recommended that a
parallel 21 -inch pipe be constructed on Andover Park West to provide the necessary capacity.
This project is identified as Project 4.
Project 4 - 21 -inch Trunk Line on Andover Park West
Project Description: Construct approximately 2600 LF of 21 -inch ductile iron pipe
gravity sewer parallel to the existing 21 -inch and 24 -inch trunk sewer on Andover Park
West from Lift Station No. 2 on Minkler Boulevard to Strander Boulevard and the Metro
Interceptor. This pipe will be required to increase the capacity of the trunk line due to
the addition of the South Drainage Basin.
6.6
Drainage Basin No. 13
Drainage Basin No. 13 is the largest basin in the sewer system and is the area that the majority
of the development will occur. Basin No. 13 and the South Service Area Basin are projected to
see light industrial and office park growth throughout the planning period. To accommodate this
growth several sewer projects will be required to provide the necessary capacity in the sewer
system. There are a total of five projects recommended for the basin to increase the capacity of
the trunk sewer system in Basin No. 13, which are described as follows:.
Project 5 - Increase Lift Station No. 2 Capacity
Project Description: Refit the pumps in Lift Station No. 2 to increase their capacity from
800 gpm to 2100 gpm. This upgrade is required to provide the necessary capacity that
is required under Scenario III for both Basin 13 and the South Service Area Basin.
Project 6 - 12 -inch Gravity Trunk Sewer on Andover Park West
Project Description: Construct approximately 1900 LF of 12 -inch gravity sewer on
Andover Park West from South 180th Street to Minkler Boulevard to increase the trunk
sewer capacity to the Segale Business Park area.
Project 7 - 8 -inch Lateral Sewers on Andover Park West
Project Description: Reconstruct approximately 600 LF of 8 -inch sewer laterals on
Andover Park West in the Lift Station No. 2 area to increase the lateral sewer capacities
due to changes in the development characteristics of the area.
Project 8 - 18 -inch Gravity Sewer on Minkler Boulevard
Project Description: Construct approximately 2000 LF of 18 -inch gravity sewer on
Minkler Boulevard from Southcenter Parkway to Lift Station No. 2 to increase capacity
and replace a deteriorating 12 -inch AC sewer with grease buildup problems.
Project 9 - Gravity Sewer to South 178th Street
Project Description: Construct approximately 1000 LF of 8 -inch gravity sewer on South
178th Street west from Southcenter Parkway to provide an undeveloped area with sanitary
sewer service.
Projects 5 and 8 are part of the trunk sewer proposed to serve the South Service Area Basin. The
full project will be detailed in the description of the proposed improvements for the South Service
Area Basin.
6-7
South Service Area Basin No. 14
The South Service Area Basin lies outside of the present Tukwila City limits, however, there is
some pressure to develop the area into light industrial or office space. The area would require
sewer service in order to be developed and the City of Tukwila has planned to provide sewers to
the area. The recommended method of service is to construct a gravity sewer trunk line from Lift
Station No. 2 south to the area. For the purposes of this Comprehensive Sewer Plan the proposed
trunk line has been divided into 5 separate projects.
Project 10 - 18 -inch Gravity Sewer on Southcenter Parkway
Project Description: Construct approximately 2600 LF of 18 -inch ductile iron pipe
gravity sewer on Southcenter Parkway from Minider Boulevard to South 180th Street to
provide the 2nd leg of the trunk main and to correct an area of sewer that has experienced
recurring maintenance problems due to sags in the existing sewer pipe.
Project 11 - 21 -inch Gravity Sewer on Southcenter Parkway
Project Description: Construct approximately 3600 LF of 21 -inch ductile iron pipe
gravity sewer on Southcenter Parkway from South 180th Street to the southern Tukwila
City limits to provide the 3rd leg of the sewer trunk main with a capacity of 3.23 MGD.
Project 12 - 21 -inch Gravity Sewer on 57th Avenue South
Project Description: Construct approximately 3700 LF of 21 -inch ductile iron pipe
gravity sewer on 57th Avenue South from the southern Tukwila City limits to South 200th
Street to provide the 4th leg of the sewer trunk main and the first leg outside the City.
The next project in the southern sewer trunk main will consider two alternatives. The alternative
will be dependent upon the final configuration of the road and whether or not gravity sewer
service will be feasible to the area. The alternatives for Project 13 are as follows:
Project 13A - 21 -inch Gravity Sewer on South 200th Street
Project Description: Construct approximately 1300 LF of 21 -inch ductile iron pipe
gravity sewer on South 200th Street west from 57th Avenue South to provide the 5th leg
of the sewer trunk main. This alternative will only be feasible if South 200th Street is
filled to the FEMA flood elevation of 32 prior to sewer construction.
The advantage of this alternative would be gravity sewer and no need for a lift station. The
disadvantage is that the road may not be filled or be allowed to be filled when the sewer main is
proposed and needed, therefore making the alternative unfeasible.
6-8
Project 13B - 1.0 MGD Lift Station at 57th and 200th
Project Description: Construct a 1.0 MGD lift station and approximately 1200 LF of 15-
inch gravity sewer from 57th Avenue South west on South 200th Street to provide the 5th
leg of the sewer trunk main. This alternative would be required to provide sewer service
if the roadway is not filled to elevation 32 when the sewer is constructed.
The advantage of this alternative is that it is not dependent upon the filling of the roadway. When
sewer service is required for the area, the lift station and piping can be built. The disadvantage
is that the lift station will require operation and maintenance care that is a cost to the City.
Project 14 - 10 -inch Gravity Sewer on South 200th Street
Project Description: Construct approximately 1300 LF of 10 -inch gravity sewer along
South 200th Street up to Orilla Road to provide the last leg of the south sewer trunk line.
North Service Area Basin No. 15
The North Service Area is an area located northeast of the Duwamish River that is presently
unsewered. Sewer service is provided by individual septic tank drain field systems. The small
lots in the area and the high groundwater conditions, especially during flooding of the river,
makes the operation of the drain fields questionable. If a large number of the septic tank drain
field systems are shown to be failing, the Health Department will require that the area be
provided with sanitary sewer service. An item of note concerning the North Service Area Basin
is that the Seattle Rendering Works had a failing septic tank system and was trucking
approximately 46,000 gallons of raw sewage per day to the Tukwila sewer system. Now the
Rendering Works effluent is pumped directly to a Metro manhole on Interurban through a private
force main.
It is assumed that the area will require sewer service in the near future. When the sewer is
constructed will be determined by economic factors and the condition of the existing septic
systems. The City of Tukwila has initiated a study and provided funds to the Green River
Community College laboratory for students to gather and test surface water in the area for
coliforms, BOD, phosphates and heavy metals. Two alternatives are proposed to provide sewer
service to the area:
Project 15A - 8 -inch Gravity Sewer to Allentown
Project Description: Construct approximately 2800 LF of 8 -inch gravity sewer in the
North Service Area to connect to the proposed Allentown gravity sewer.
Schedule
The advantages of this alternative is that it would require less construction to provide service to
the area and therefore would be less costly. The big disadvantage is that it is dependent upon
construction of the Allentown sewer. It is not known when the Allentown sewer system will be
feasible to construct.
Project 15B - Sewer Service to the Existing Tukwila System
Project Description: Construct approximately 1600 LF of 8 -inch pipe, 3000 LF of 10-
inch pipe, a 0.5 MGD lift station and 400 LF of 6 -inch forcemain complete with a
crossing of the Duwamish River.
The advantages of this alternative is that it is not dependent upon the construction of gravity sewer
to Allentown to be feasible. The alternative has the disadvantage of added cost and a river
crossing.
The schedules for the proposed improvements are shown on Table 6 -1.
Cost Estimates
The estimated costs for the proposed improvements are shown on Table 6 -1.
6-10
5
Pro
City
PROJECT BASIN DESCRIPTION
1 3 Construct approx. 3000 LF of 8" gravity
sewer from Lift Station 6 along the east side
of Ft. Dent Park
2A 3 Alternate No. 1 - Construct approx. 700 LF
of 8" gravity sewer, with bore under In-
terstate Highway 405.
2B 3 Alternate No. 2 - Construct approx. 700 LF
of 8" gravity sewer, with bore under the
Railroad Right of Way.
3A 10 Construct approx. 1500 LF of 15 ", 2600 LF
of 12 ", and 1000 LF of 8" gravity sewer to
upgrade and provide service to the basin.
3B 10 Construct approx. 1500 LF of 15 ", 1500 LF
of 12" and 1000 LF of 8" gravity sewer and
a 500 gpm lift station to upgrade and pro-
vide service to the basin.
4 12 Construct approx. 2600 LF of 21" ductile
iron pipe gravity sewer paralleling the exist-
ing sewer on Andover Park West from
Minkler to Strander.
13 Refit Lift Station 2 to upgrade pumping
capacity from 800 gpm to 2100 gpm to
handle increased estimated flows.
Table 6 - 1
posed Capital Improvements
of Tukwila Sewer System
* All costs are in 1991 dollars and include Engineering, Admin., Legal and Contingencies.
FUNCTION
Provide sewer service to a 27 acre parcel in
the north part of the basin on the east side of
the Duwamish River.
Provide sewer service to the 13 acre unde-
veloped area in the southern part of the
drainage basin.
Provide sewer service to the 13 acre unde-
veloped area in the southern part of the
drainage basin.
Provide sewer service to a 130 acre partially
developed light industrial area east of the
Duwamish River in the drainage basin.
(Existing 12" pipe will be overloaded in
Scenario 3.)
Provide sewer service to a 130 acre partially
developed light industrial area east of the
Duwamish River in the drainage basin.
Work to be phased and utilize existing pipe
where available.
EST. COST*
$ 300.000
$ 151,000
$ 140,000
Provide additional capacity required to $ 507,000
provide sewer service to the southern area
trunk sewer main from Lift Station No. 2
Under Scenario 3 conditions and the con- $ 66,000
struction of the sewer trunk line to serve the
southern drainage basin, capacity of the lift
station requires upgrading.
6-11
$ 225,000 (15" sewer)
$ 338,000 (12" sewer)
$ 100,000 (8" sewer)
$ 663,000 Total
$ 225,000 (15" sewer)
$ 138,000 (Lift Sta.)
$ 195,000 (12" sewer)
$ 100,000 (8" sewer)
$ 658,000 Total
SCHEDULE
Developer
Dependent
Developer
Dependent
Developer
Dependent
Developer
Dependent
Developer
Dependent
Determined
by sewer
loading
Determined
by sewage
flows
PROJECT BASIN DESCRIPTION
6 13 Construct approx. 1900 LF of 12" gravity
sewer on Andover Park West from S. 180th
St. to Minkler Blvd.
7
8
9
11
13 Reconstruct approx. 600 LF of 8" gravity
sewer laterals on Andover Park West up
from Minkler Blvd. and Lift Station 2.
13 Construct approx. 2000 LF of 18" gravity
sewer on Minkler Blvd. from Southcenter
Pkwy to Andover Park West and Lift Station
2).
Propo
City
13 Construct approx. 1000 LF of 8" gravity
sewer on S. 178th St. west from Southcenter
Pkwy.
10 14 Construct approx. 2600 LF of 18" Ductile
Iron Pipe gravity sewer on Southcenter
Pkwy. from Minkler Blvd. to S. 180th St.
14 Construct approx. 3600 LF of 21" ductile
iron pipe gravity sewer on Southcenter
Pkwy. from S. 180th St. to southern Tuk-
wila city limits, pipe capacity 3.23 MGD
12 14 Construct approx. 3700 LF of 21" ductile
iron pipe gravity sewer on 57th Ave. S.
from the Tukwila city limits to S. 200th St.
Capacity of the pipe 3.23 MGD
Table 6 - 1
sed Capital Improvements
of Tukwila Sewer System
* All costs are in 1991 dollars and include Engineering, Admin., Legal and Contingencies.
FUNCTION EST. COST*
Increase capacity of the sewer serving the $ 250,000
Segale Business Park area to handle pro-
jected flows for the Scenario 3.
Increase lateral sewer capacity as required
due to the change in the development char-
acteristics of the area.
Provide 1st leg of South Drainage Basin $ 360,000
trunk sewer and replace deteriorating 12"
AC sewer on Minkler Blvd. Sewer capacity
set at 3.4 MGD. Relieve maintenance prob-
lem due to sags and excessive grease.
Provide undeveloped area with sanitary $ 100,000
sewer service to Southcenter Pkwy.
Provide 2nd leg of the South Drainage Area
trunk sewer line and alleviate problems due
to sags and grease in the sewer. Note, this
sewer has been downsized to 18" with in-
creased slope to provide a capacity of 3.4
MGD.
Provide the 3rd leg of the South Drainage $ 702,000
Basin trunk sewer line.
Provide the 4th leg of the South Drainage $ 722,000
Basin trunk sewer line.
6-12
City
PROJECT BASIN DESCRIPTION
13A 14 Alternate No. 1 - Construct approx. 1300
LF of 21" ductile iron pipe sewer on S.
180th St. west from 57th Ave. S.
13B 14 Alternate No. 2 - Construct a 1.0 MGD Lift
Station and approx. 1200 LF of 15" gravity
sewer from 57th Ave. S. westward on S.
200th St.
14 14 Construct approx. 1300 LF of 10" gravity
sewer along S. 200th St. up to Orillia Road
15A 15 Construct approx. 5700 LF of 8" gravity
sewer in the area to connect to the future
Allentown gravity sewer
15B 15 Construct approximately 5200 LF of 8"
gravity sewer, a 0.5 MGD lift station and
400 LF of 6" forcemain complete with a
crossing of the River
Table 6 - 1
Pro posed Capital Improvements
of Tukwila Sewer System
FUNCTION
Provide the 5th leg of the South Drainage
Basin trunk sewer line, this alternative is
only feasible if the roadway is filled to the
FEMA flood elevation of 32.
Provide the 5th leg of the South Drainage
Basin trunk sewer line, this alternative
would be required if the roadway is not
filled to elevation 32.
Provide the last leg of the South Drainage $ 170,000
Basin trunk sewer line.
Provide sewer service to the area and allow $ 570,000
the abandoning of the existing septic tank
drain fields in the area. This alternative is
only feasible if the sewer in Allentown is
constructed. See Supplement A.
Provide sewer service to the area on its own
to the existing Tukwila sewer system in the
event that the septic tanks fail.
6-13
* All costs are in 1991 dollars and include Engineering, Admin., Legal and Contingencies.
EST. COST*
$ 254,000
$ 143,000 (Lift Station)
$ 180,000 (15" sewer)
$ 323,000 Total
$ 520,000 (8" sewer)
$ 100,000 (Lift Sta.)
$ 73,000 (Forcemain)
$ 693,000 Total
SCHEDULE
Dependent
on sewage
flows
Dependent
on sewage
flows
Dependent
on sewage
flows
See Supple-
ment A.
See Supple-
ment A.
Listed below in order of priority of recommended improvements to reduce I/I and /or reduce existing or potential maintenance costs. As part of these improvements, it
is recommended that an effective grease control ordinance program be immediately implemented and enforced by the City.
Priority
H1
H2
H3
H4
H5
H6
Location
Adjacent to Pump Sta. 1 on Andover Park West.
MH 150118 (east side of Interurban)
372' south of Metro Pump Station
Along Minkler from Pump Sta. 2
to Southcenter Parkway.
Along west side of Southcenter Pkwy.
including Boeing loop.
Andover Park West at Mazda.
Along Minider Blvd. and Southcenter Pkwy.
including Boeing loop.
H7 17' to 19' South of MH 13047
(West side of Interurban Ave.)
H8
H9
H10
94' to 96' North of MH 13047
(West side of Interurban Ave.)
305'to 313' South of MH 13047
(West side of Interurban Ave.)
Along Southcenter Blvd. (South of
62nd Ave. South), across I-405 to
Andover Park West.
.
IIIMI m Ism am . . M agog Est
CHAPTER 7
IMPLEMENTATION
General
This chapter considers the financial status of the City of Tukwila Sewer Utility. What impact the
proposed improvement schedule on the Sewer Utility finances will be considered. Past operating revenues
and expenses are documented and evaluated. Methods of funding the proposed projects are investigated
and discussed.
Authority
The City of Tukwila is authorized by the State of Washington in RCW 35.67 "Sewerage Systems - Refuse
Collection and Disposal" to establish and collect fees for the operation and maintenance of the sewer
system. The City has the right to review and adjust the charges as they see fit to cover the operation
provided that the rates charged are uniform for the same class of customers or service.
The City of Tukwila is required to produce an Annual Report concerning the financial status of the Sewer
Utility under the RCW 43.09.230. This report details the total expenses and income for the year for the
Sewer Utility.
Sewer System Expenses
The major expense categories for the operation of a sewer utility which must be addressed are as follows:
1) Financing capital improvements that are necessary to provide adequate service and
extension to new service areas.
2) Replacement and updating of existing facilities that require renewal because they are
obsolete or no longer serviceable or undersized.
3) Administration, operation, maintenance and the expenses to cover day to day costs of
operating and maintaining the sewer system.
4) Debt service requirements to provide repayment of interest and principal for all
outstanding bonds for previous system improvements.
5) The single largest expense to the sewer utility is the treatment cost of the wastewater
which is paid to Metro. This would include any surcharge for industrial wastewater
treatment.
Sewer System Revenue
The major income categories for the operation of a sewer utility are as follows:
1) The single largest income item for the Sewer Utility is the Sewer Rates charged to users
of the system.
2) Minor revenues are received from Interdepartmental Sales, Forfeited Discounts and other
misc. items.
Sewer Rates
The City of Tukwila has established sewer user rates to cover the operation and maintenance of
the existing sewer system. The present sewer charges are as follows in Table 7 -1. The goal of
the City of Tukwila when setting the monthly sewer charge is to provide adequate revenues to
cover all operation and maintenance expenses for the sewer system. The charges shall be
equitable and shall be based on the benefit that the property is receiving. The rates shall include
the cost of the replacement and repair of sewer mains, trunk lines, general facilities and any other
reasonable costs associated with the sewer.
Monthly Rates
Residential
TABLE 7 -1
EXISTING SEWER RATES
Each dwelling unit will be charged a flat rate of $4.00 with no
additional charge for volume.
Multiple Dwelling Each Condo or Apartment unit will be charged a flat rate of $4.00
Unit Permanent Type with no additional charge for volume.
Commercial /Industrial A minimum charge of $9.50 per meter for up to 900 cubic feet
plus $9.50 per each additional 900 cubic feet or fraction thereof.
Metro Rates
The City Metro charges as required by the Agreement for Sewage Disposal between the
Municipality of Metropolitan Seattle (Metro) and the City of Tukwila are set at the sum of $13.20
per residential customer and $13.20 per residential customer equivalent (900 cubic feet equals one
residential customer equivalent) for multiple dwelling and commercial /industrial accounts.
Other Charges
Penalty Charge:
A charge of $2.00 per month on sewer accounts more than 30 days in
arrears (40 days after billing date). .
Qualifying Seniors are eligible for reduced rates on one -half sewer and Metro regular rates.
Source: Tukwila Finance Department
7-2
Sewer Connection Fees
It is the goal of the City of Tukwila in establishing the sewer connection fee schedule that all
property owners seeking to connect to the City sewer system and all property benefiting from a
sewer main and any general sewer facilities including but not limited to, interceptors, lift stations,
forcemains and treatment facilities shall share equitably in the cost of these improvements. As
a condition of connection to the City sewer system the costs of the general facilities shall be borne
directly by the property owners or developer through actual installation of these improvements,
by assessment levied against the property, by cost agreement with the property owner or by
connection fee or other appropriate method determined by the City. The side sewer connection
cost shall be borne directly by the property owner.
Annual Financial Report
The City of Tukwila is required by the State of Washington to prepare an annual report regarding the
finances of their Sewer Utility. The 1987 and 1988 reports are summarized in Tables 7 -2, 7 -3, and 7-4
on the following pages.
7-3
1. Sales of Sewer Services
Unmetered Sales to General Customers
Metered Sales to General Customers
Private Fire Protection Service
Public Fire Protection Service
Other Sales to Public Authorities
Sales to Irrigation Customers
Sales for Resale
Interdepartmental Sales
2. Other Operation Revenues
TABLE 7 -2
CITY OF TUKWILA
WATER UTILITY
OPERATING REVENUE DETAIL
Year 1990
Detail
$ -0-
1,396,404.61
-0-
-0-
- 0-
-0-
- 0-
6,353.41
TOTAL SALES OF SEWER SERVICES $1.402.758.02
Forfeited Discounts $ 1,402.00
Miscellaneous Service Revenues -0-
Rents from Sewer Property -0-
Interdepartmental Rents -0-
Other Sewer Revenues 915.00
TOTAL OTHER OPERATING REVENUES
Total
$ 2.317.00
TOTAL OPERATING REVENUES $1.405.075.02
1. Source of Supply Expenses
2. Pumping Expenses
3. Sewer Treatment Expenses
4. (a) Transmission Expenses
(b) Distribution Expenses
5. Customer Accounts Expenses
6. Sales Expenses
7. Administrative & General Expenses
TOTAL OPERATION &
MAINTENANCE EXPENSE
OPERATING EXPENSE DETAIL
Year 1990
7-4
Operation Maintenance
$ -0-
31,291.62
776,199.93
24,264.00
-0-
4,514.63
-0-
266,632.77
$1,102.902.95
$ -0-
16,283.58
- 0-
34,218.62
- 0-
-0-
-0-
- 0-
Total
$ -0-
47,575.20
776,199.93
58,482.62
-0-
4,514.63
-0-
266,632.77
$ 50.502.20 $1 ..153A05.15
1. Sales of Sewer Services
Unmetered Sales to General Customers
Metered Sales to General Customers
Private Fire Protection Service
Public Fire Protection Service
Other Sales to Public Authorities
Sales to Irrigation Customers
Sales for Resale
Interdepartmental Sales
2. Other Operation Revenues
TOTAL OPERATING REVENUES
1. Source of Supply Expenses
2. Pumping Expenses
3. Sewer Treatment Expenses
4. (a) Transmission Expenses
(b) Distribution Expenses
5. Customer Accounts Expenses
6. Sales Expenses
7. Administrative & General Expenses
TOTAL OPERATION &
MAINTENANCE EXPENSE
TABLE 7 -3
CITY OF TUKWILA
SEWER UTILITY
OPERATING REVENUE DETAIL
Year 1989
TOTAL SALES OF SEWER SERVICES
Forfeited Discounts $ 1,524.00
Miscellaneous Service Revenues -0-
Rents from Sewer Property -0-
Interdepartmental Rents -0-
Other Sewer Revenues 535.00
TOTAL OTHER OPERATING REVENUES
OPERATING EXPENSE DETAIL
Year 1989
Operation Maintenance
$ -0-
31,639.65
648,999.85
54,818.77
-0-
5,507.93
-0-
212,568.00
$ 953,534.20
7 -5
Detail
$ -0-
1,271,929.12
-0-
- 0-
-0-
- 0-
-0-
6,124.66
$ -0-
17,289.24
- 0-
22,967.49
-0-
-0-
- 0-
- 0-
Total
$1.278.053.78
$ 2.059.00
$1.280.112.78
Total
$ -0-
48,928.89
648,999.85
77,786.26
- 0-
5,507.93
- 0-
212,568.00
$ 40.256.73 $ 993390.93
1. Utility Operation Income
Operating Revenues
Operating Expenses:
Operating Expenses
Maintenance Expense
Depreciation Expense
Amortization Expense
Taxes Other Than Income Taxes
SUBTOTAL OPERATING EXPENSES
Net Operating Revenues
Income from Utility Plant Leased to Others
UTILITY OPERATING INCOME
2. Other Income
Revenues from Repairs & Merchandising
Income from Nonutility Operations
Nonoperating Rental Income
Interest and Dividend Income
Allowance for Funds Used During Construction
Gains (Losses) from Disposition of Property
SUBTOTAL OTHER INCOME
TOTAL INCOME
3. Miscellaneous Income Deductions
Costs & Expenses of Repairs & Merchandising
Miscellaneous Amortization
Other Income Deductions
SUBTOTAL MISC. INCOME DEDUCTIONS
INCOME BEFORE INTEREST CHARGES
4. Interest Charges
Interest on Long -term Debt
Amortization Debt Discount Expense
Amortization Premium on Debt -Cr.
Miscellaneous Interest Expense
Interest Charged to Construction -Cr.
SUBTOTAL INTEREST CHARGES
Extraordinary Income and Deductions
NET INCOME - YEARS 1990 AND 1989
Source: Tukwila Finance Department
TABLE 7-4
CITY OF TUKWILA
SEWER UTILITY
COMPARATIVE STATEMENT OF INCOME
For Years Ending December 31, 1989 and 1990
7-6
1990
$1,405,075.02
1,102,902.95
50,502.20
152,897.68
-0-
17.436.67
1 ,323,739.50
81,335.52
-0-
81,335.52
96.35
-0-
-0-
72,485.47
45,022.00
-0-
117.603.82
198.939.34
82.35
- 0-
2,205.25
2,287.60
196,651.74
15,079.93
457.77
-0-
-0-
- 0-
15,534,70
-0-
$ 181.117.04
1989
$1,280,112.78
953,534.20
40,256.73
141,960.37
- 0-
15.791.68
1.151.542.98
128,569.80
- 0-
128.569.80
2,858.73
5,928.63
-0-
75,291.49
- 0-
-0-
84.078.85
212.648.65
2,162.36
- 0-
8.710.00
10.872.36
201.776,29
16,150.05
516.21
-0-
- 0-
-0-
16.666,26
-0-
$ 185,110,03
Classes of Capital Improvements
The preferred method of financing capital improvements varies with the type of project. The projects fall
into the three general categories of 1) General Facilities, 2) Local Facilities and 3) Individual Service
Lines. Financing for each of these type of improvements is discussed in detail below:
General Facilities
The most difficult improvements to finance are the general facilities within the sewer system.
General facilities include treatment plants, sewer interceptors, forcemains, lift stations, standby
power or pumping units and any other appurtenances that are required by the total system to
function properly. These facilities benefit large portions of the sewer system and often times
require a significant capital outlay for construction. Determining how to equitably distribute the
cost of these facilities is not easy. The accepted methodology for funding these improvements
is usually handled by one of the following methods.
1) Passing a General Obligation Bond issued by the voters.
2) Forming a Local Improvement District (LID) and assessing the costs of the
construction to the benefiting area on an equitable basis. This method requires
a minimum of 50% of the benefiting property owners to sign the LID petition.
3) The initial developers of the area will finance the improvement and future
developers will be required to pay a "late comers" fee in order to be allowed to
connect to the system and thus obtain building permits.
4) The City can fund the improvement and assess all of the sewer users a general
facilities charge. This charge would become part of the sewer rate and the City
would maintain a general facility account with this money to cover costs of any
proposed projects. This general facilities charge would be based on the estimated
costs of the projects and would include the City's interest charges, Engineering
and any other costs to complete the facilities.
5) The City can apply for any available grant money or low interest loans from State
or Federal government agencies as it comes available. At the present time there
is very limited grant money available.
The City of Tukwila has an established general facilities fund to draw on for improvement of the
sewer system. The City utilized this fund to finance replacement of Lift Station No. 2 in 1987.
Local Facilities
The financing of local facilities is usually easier to define than the general facilities and customers
can easily see their direct benefit. It can be as simple as the property owners who receive service
from the sewer line must pay for all costs associated with the design and construction of the line.
7 -7
Acceptable methods of financing local facilities are summarized below:
1) Formation of a Local Improvement District.
2) Developer extension agreements, future areas can participate in this type of
arrangement through a late comer agreement.
3) State and Federal Grants.
4) A combination of the above.
Individual Service Lines
Individual service lines are constructed by and paid for by the individual property owners. This
would include the City inspection fee and any design fee.
Methods of Financing Improvements
General Obligation or Revenue Bonds
If the City decides to finance the proposed improvement out of the general sewer fund, it may be
in their best interests to issue General Obligation or Revenue Bonds to cover the costs of the
project. Improvements that are typically funded by the sale of bonds are, major sewer
interceptors, lift stations, forcemains, standby power generators or pumping units, any treatment
facility improvement and any other major improvement that is considered as an improvement to
the system as a whole.
General Obligation Bonds require the approval of the voters within the project service area prior
to sale. The cost of these bonds is then assessed against the benefiting property and the revenue
is added to the property taxes. This method of financing is usually used in the formation of a
Local Improvement District.
Revenue Bonds are bonds sold by the City usually on the basis that the money will be repaid by
collection through the sewer rates. Revenue bonds do not require a vote of the benefiting
customers. The City may at their option elect to use other sources to retire these bonds. It is
typical to apply all late comers monies toward the retirement of the revenue bonds for a project.
Local Improvement District
Local Improvement District's (LID's) are formed by local property owners to finance public
utility projects. LID formation is governed by the laws of the State of Washington. Funds are
7 -8
Developer Extension Agreements
The majority of the new facilities constructed to serve undeveloped or
City of Tukwila are financed by Developers Extension Agreements.
required for service to the property within new plats or commercial an
will be designed and constructed in accordance with the City of Tukwil
conditions, late comers agreements may be executed for any sewe
facilities that serve property other than the property owned by the devel
City Financed Projects
The City may deem it necessary in some cases to pay the costs of cons
to serve either an existing area or an undeveloped area. The size of th
the improvement can be financed by available funds. This may be a
to replace an undersized and overloaded line. In the course of making
7 -9
raised through the LID equitable assessment to the property owners in
completed by LID are sewer extensions to existing developed are
stations, etc.
pay a late comers charge for the cost of the project. This methodology
may be used in combination with the developers extension agreement
developer to upsize the proposed sewer line to enable it to serve a lar
Government Grants
From time to time money becomes available for sewer improvement
or Federal Government agencies. This money may be used to fund pr
guidelines established by the granting agency. Examples are low inco
to be a liability to the environment. Presently the availability of grant
project financing for sanitary sewer projects which are completed i
quality could receive up to 50% funding from the State Cente
administered by the Department of Ecology. This type of funding is d
water quality problems with specific enhancement goals identified.
works projects is available from the State Public Works Trust Fund
basis. Receiving low interest funding from this program is based o
e LID. Projects that are
, area trunk sewers, lift
redeveloping areas in the
All of the improvements
industrial developments
standards. Under certain
mains or other general
per financing the project.
ruction of a sewer project
project may be such that
epair project or a project
e improvement the sewer
may become available to new areas, in that case the City would requ're any new connection to
of financing trunk sewers
hen the City requires the
er area.
rojects from either State
jects as they apply to the
e areas and areas shown
oney is limited although
order to enhance water
ial Clean Water Fund
pendent on demonstrated
an financing for public
ually on a competitive
demonstrated need for a
particular project. Consideration of utilizing these types of funding options for financing future
public works is recommended.
Rates, Fees, Policies and Ordinances
Application for Sewer Service
Any property owner requesting sewer service shall complete an application for sewer service.
Receipt of payment by the City as set forth in this section will validate the application for sewer
service. Upon receipt of application for sewer service, the Public Works Department will prepare
a preliminary report consisting of the following:
1) A field inspection and research of the City files.
2) The City will determine any assessments and other charges involved for the
service as set for in this Plan and by City Ordinance.
3) . The City will determine any and all additional offsite improvements that will be
required to provide the property with sewer service. The estimated cost of these
improvements will be conveyed to the applicant.
4) The customer will then be notified of all permit costs for connection to the City
sewer system.
The applicant will then hire an approved contractor to make the required connection to the City
system. If the owner elects to proceed with the project, no work will be done by the City until
the costs or the estimated costs have been paid or an acceptable agreement for payment has been
made with the City.
Individual Sewer Service Connections
Installation of the Sewer Connection
An individual side sewer connection may be accomplished only after a side sewer permit
has been issued and is in compliance with all existing City ordinances. It shall be the
policy of the City of Tukwila that all side sewer work in the public right of way shall be
completed by an approved licensed contractor.
Side Sewer Permit Fee
The fee for a side sewer permit shall be as established by the City of Tukwila Public
Works Department. The fee shall include the issuance of the Side Sewer Permit, one (1)
inspection trip to the site at the time of construction, a side sewer as-built for the City
records and the billing set up fee.
7 -10
If it becomes necessary to relocate any portion of an existing side sewer line for any
reason, a charge for a new side sewer permit will be required.
If for any reason return visits or inspections of a side sewer installation are required by
' City personnel or the City's agent, due to faulty construction, owner or contractor
actions, owner request, or for any other reason, the additional expense incurred shall be
paid by the owner on a time and material basis at the City's standard rates. If the City
incurs any other extraordinary expenses in the completion of the side sewer, the owner
will bare the full cost of these expenses. The City will not accept the side sewer until
which time these additional costs are paid to the City.
Sewer Stub Charges
For new construction, it shall be the policy of the City of Tukwila that sewer service
stubs will be provided to all lots. The cost of installing the sewer stubs will be included
in the cost of construction and financed in the same manner as the construction.
In areas that have sewer service and no sewer stub exists, the property owner requesting
sewer service shall bear the full cost of installing the stub as required by the City of
Tukwila.
General Facility Charges and Local Lateral Charges
For the purposes of this section the terms "General Facility Charge and "Local Lateral Charge"
will be defined as follows:
General Facility Charge: shall include any costs associated with the construction, repair,
upgrading and enlarging of any portions of the sewer system that are considered to
provide benefit to the full system. This shall include but not be limited to sewer trunk
interceptors, lift stations and forcemains and treatment facilities.
Local Lateral Charge: shall include any costs associated with the construction, repair,
upgrading and enlarging of any portions of the sewer system that provides direct sewer
service to the property. This shall include but not be limited to lateral sewer mains,
collector sewers, manholes and cleanouts.
It is recommended that the City levy a General Facility Charge against all property requesting
sewer service. This charge shall apply to all new construction and to any property that is
7 -11
redeveloping that either has not previously paid a general facility charge or that in the
redevelopment of the property the wastewater flow characteristics from the property are
substantially changed as determined by the City Engineer. The method of paying the charge shall
be approved by the Tukwila Department of Public Works and will generally be according to one
of the following methods:
Connection Charge: The State of Washington passed a law (RCW 35.38) in 1989 which
allows cities like Tukwila to engage in the transmission, treatment and disposal of sewage
to impose a capacity charge on users of the sewage facilities when the user connects,
reconnects or establishes new service. The capacity charge must be approved by the City
Council and reviewed and reapproved annually.
Tukwila has a policy of charging all properties applying for sewer service a connection
fee and a trunk sewer fee. It is recommended that the City combine these charges into
a single connection fee that would cover the total cost. The connection fee would be
established based on the estimated cost of the proposed general facilities that are
necessary to provide for the projected development.
Developer Financing: In some installations the developer will construct all of the general
facilities as proposed in this Comprehensive Sewer Plan that are required to provide the
sewer service for the property. This would occur when the developer constructs the
sewer line from the property being served to an existing Metro interceptor. These
facilities would include but not be limited to: trunk sewers, lift stations and forcemains.
Under this type of construction the developer would only pay the City for approval of the
plans and inspection and testing of the construction.
City /Developer Combined Financing: In many instances the developer will be required
to complete a portion of the general facilities as established in this Comprehensive Sewer
Plan in order to provide sewer service to the property. In these cases the City will give
the developer a credit toward the Connection Charge detailed above for the increased cost
of constructing the oversized facilities.
In some cases, the requested sewer service will require a substantial upgrade of the
7 -12
general facilities or trunk sewer line construction. The City has the option, if the project
is seen to be in their best interests, to join with the developer in completing the general
facilities. The developer would finance the portion of the project that applies to his
development and the City would finance the balance of the project according to guidelines
established above in this Comprehensive Sewer Plan.
Local Improvement District: All of the facilities directly required by the LID to provide
sewer service to the area will be included in the assessed cost of the LID. The City may
or may not include the full general facility charge in the assessed cost in the formation
of a LID. As an alternative for new construction areas, the City may elect to charge the
individual property owners a connection fee at the time they hook up to the sewer to
cover a portion of the general facilities charge. In areas that are presently developed and
the LID is formed for the purposes of repair, upgrade or the elimination of septic tank
systems, the assessment would most likely include the full general facility charge.
Local Lateral Charges: The City of Tukwila shall assess each property a local lateral
charge for sewer service when application is made for connection to the sewer. This
shall apply to all properties benefiting from the construction of the lateral or any property
that is requesting service that has not previously paid for the lateral service. The method
that the local lateral charge is levied shall be approved by the City Engineer and usually
falls under one of the following methodologies.
Laterals Constructed Prior to January 1, 1970: For any properties abutting a sewer line
constructed prior to January 1, 1970, the local lateral charge shall be as set forth below
as it is adjusted for inflation using the ENR factor as shown in Table 7 -5.
TABLE 7-5
LOCAL LATERAL CHARGES
Sewer Charge
Year per Front Foot ENR
1955 -1959 $ 5.26 797
1960 -1964 8.11 936
1965 -1969 10.97 1269
7 -13
Laterals Constructed by the City after January 1, 1970: For any properties abutting a
sewer line constructed by the City after January 1, 1970, the local lateral charge shall
be the actual cost per front foot of the sewer line plus 12% per year interest on the City's
investment. The interest shall be calculated from the date of completion and acceptance
by the City of the construction of the lateral sewer to the date of connection.
Developer Financed Construction: In all areas where the sewer is constructed by a
developer in accordance with the City's standards and this Comprehensive Sewer Plan,
no local lateral charge will be assessed. The developer will be responsible for the City
for all fees for review, approval, inspection and testing of the proposed sewer system.
Local Improvement District: The full cost of the lateral sewer service shall be included
in the assessed cost of the sewer in the formation of a LID. This cost shall include but
not be limited to all costs for design, review, approval, inspection and testing of the
sewer line so that it meets City Standards and the requirements of this Comprehensive
Sewer Plan.
Charges for City Labor, Materials, Equipment and Overhead
City Rates
In all cases where the City is required to perform services to construct, maintain, repair
or perform any other task related to the sewer system, the charge for such services shall
be according to a published rate sheet as determined by the Director of Public Works.
These rates shall be based on the actual costs of providing the service and shall be
regularly reviewed and updated to ensure their validity.
Definitions
Actual Costs shall include the hourly rate for labor, equipment use, tools and the cost of
materials. A percentage of the costs associated with labor, materials and equipment usage
shall be charged in addition to actual costs to cover overhead costs.
Permits and Inspections
The individual requesting or causing the work to be done shall be required to obtain and
pay all costs for any required street opening permits and any other permits, approvals or
inspections required by other government agencies in order to complete the work. If the
7 -14
work is performed by City crews, the City will obtain the necessary permits and services
and charge the customer for the cost of the permits and service fees. City charges shall
be according to the rate sheet published and outlined above.
Special Charges for Wastewater Dumping or Discharge
Industrial Wastewater Discharge
The City in conjunction with Metro shall assess special charges for all industrial
customers that are determined to be discharging a concentrated or high volume of
wastewater to the system. This rate shall be according to accepted engineering guidelines
as established by the Tukwila Department of Public Works and Metro. The rate will be
based on concentrations of Total Suspended Solids (TSS), 5 -Day Biochemical Oxygen
Demand (BOD,) and volume of wastewater. The Industrial Wastewater rate will be
reviewed on a regular based to ensure that it remain equitable to sewer customers.
Wastewater Batch Dumping
The City will charge a special user fee to all customers that are classified as batch
dumpers. Batch dumpers will be any individuals who dump sewage into the system by
the truck load at designated locations. These customers shall apply to the City for a
permit to dump the sewage. This permit charge is presently $20.00 and must be renewed
annually. The City will review this charge and adjust it's cost as necessary due to
inflation. The batch dump customers shall also pay the commercial rate for the volume
of sewage discharged. Volume of sewage discharged shall be measured by truck volume
as established at the time of permitting. Misrepresentation of the volume of wastewater
discharged by the user results in automatic permit revocation and a fine of $50.00.
Unauthorized batch dumping into the sewer system currently results in a fine of $50.00
plus the cost of a permit plus the cost at the commercial rate of disposal of the volume
of wastewater discharged. If the City determines that the wastewater batch dumping was
due to an emergency condition, this fine may be waived.
It is recommended that the City consider the penalty charges associated with
misrepresentation of discharge volumes and unauthorized batch dumping to evaluate the
effectiveness of the penalties.
7 -15
7 -16
Oil and Grease Separators
The City's sewer system has been experiencing oil and grease buildup problems and it
is therefore recommended that the City adopt a Oil and Grease Separator Ordinance to
require all establishments that are producing excessive amounts of grease and oil to install
grease and oil traps or to pay a surcharge to finance the regular cleaning of the sewers.
It is recommended that the City of Tukwila establish a sewer user surcharge to apply to
all sewer customers that produce a significant amount of oil or grease if they are
discharging without the benefit of an approved oil and grease trap. This surcharge would
encourage these customers to install and maintain oil and grease traps on their premises
and thus reduce the loading and maintenance requirement on the sewer system.
CHAPTER 8
OPERATIONS AND MAINTENANCE
CHAPTER 8
OPERATIONS AND MAINTENANCE
Sewer System Responsibility and Authority
At the present time the City of Tukwila does not have an approved detailed Operations and Maintenance
program for the sewer system. During the development of the sewer system standard procedures have
developed with regards to the maintenance and repair of the system. For the purposes of this
Comprehensive Sewer Plan, a cursory review of the current operation and maintenance program will be
outlined. It is recommended that the City of Tukwila consider the drafting of a formal operation and
maintenance plan for the sewer system to detail the standard procedures for the operation of the system.
The City of Tukwila owns and operates the sewer system under the authority granted by Chapter 35.67
of the Revised Code of Washington, "Sewerage Systems - Refuse Collection and Disposal ". The City
has entered into an agreement with the Municipality of Metropolitan Seattle (Metro) for the treatment and
disposal of the wastewater collected in the City sewer system.
The City of Tukwila operates under a Mayor and Council type of government with the utilities
administered by the Department of Public Works. The duties of various positions with respect to the
sewer system operation and maintenance are summarized as follows:
Mayor and City Council ... Set City policy, approve the budget, approve all improvement
projects, appoint key personnel.
Public Works Director Performs administrative tasks, formulates budget, formulates
Department policy, proposes and prioritizes repair, upgrade and
improvement projects, oversees daily operations and emergency
response and responds to customer complaints as necessary.
Engineering Staff Performs design work as requested, prepares engineering
feasibility studies, investigates and assesses problem areas and
performance of the system, recommends improvement projects,
makes future facility requirement projections and assists in all
other areas as required.
Office Staff Performs administrative duties and tasks, billing and collection
of customer accounts, records customer complaints and performs
all other day to day tasks as necessary.
Field Staff Performs all scheduled and routine maintenance and repair of the
system, monitors the operation of the system's lift stations,
inspects and tests new construction, responds to complaints and
emergencies and performs all other tasks as required to keep the
system operational.
8 -1
System Operation and Control
System Components
Due to the City's agreement with Metro for the treatment and disposal of the wastewater collected
in the sewer system, the City does not own or maintain any treatment facilities within their
system. The City pays Metro for treatment of the wastewater under the rates established under
the present agreement that is included in the Appendix of this Comprehensive Sewer Plan for
information purposes.
The facilities included within the City owned and operated system are the collection system and
eight (8) lift stations. The City operates and maintains approximately 17 direct connections to the
Metro interceptor as it passes through the City. A more detailed description of the existing sewer
system is given in earlier sections of this Comprehensive Sewer Plan.
Records
The City of Tukwila maintains the following records for efficient management of the sewer
system:
Customer Accounts: The City maintains records of each sewer account detailing sewer
use and record of any problems.
Metro Records: All reports on wastewater treatment charges and status from Metro are
kept on file.
Maps: A Comprehensive Sewer Plan Map of the full system is maintained by the City
for informational purposes. This map shows all proposed improvements and upgrades
required, all piping, manholes, clean outs, lift stations, forcemains and sewer trunk lines.
As -Built Drawings: The City maintains a comprehensive file of all As -Built Drawings
of the system improvements as they occur. These drawings show the location of side
sewers in many cases and locate all other piping as constructed.
Pump Maintenance Records: The City keeps all lift station pump manufacturer
maintenance and technical information on file to include but not be limited to: pump run
time records, maintenance schedules, maintenance performed, repairs performed,
problems encountered and any other information noted during the regular maintenance
checks of the lift stations.
Preventative Maintenance Program
The City of Tukwila has an adopted preventative maintenance program for the sewer system.
Due to the makeup of the system an exhaustive preventative maintenance program is not required.
8 -2
.
The main component that requires regular servicing is the lift stations. Maintenance guidelines
and procedures for preventative maintenance are generally as follows:
Lift Stations: A regular inspection is made of the lift stations within the system. Running
times are monitored and recorded to determine pump life. The pumps are regularly
serviced and lubricated per the recommendations of the pump manufacturers.
Sewer Mains and Forcemains: Sewer mains are regularly flushed and jet cleaned to
ensure satisfactory service and reduce plugging problems.
Problem Areas
Oil and Grease Accumulation: Over the years the Tukwila sewer system has experience recurring
grease accumulation in side sewers, collector sewers, trunk sewers, manholes, wet wells and
forcemains. Grease problems require a significant portion of the City's maintenance budget and
equipment that could be put to better use on an ongoing system wide preventative maintenance
flushing and cleaning program. Excessive grease entering the Metro interceptor system is also
in violation of the agreement between the City and Metro and needs to be corrected.
The most cost efficient method of correcting the grease and oil problem would be through the
adoption of a oil and grease separator ordinance. This ordinance would require that any sewer
customer that has a potential of discharging high concentrations of oil or grease would be required
to construct and maintain a grease trap on their property. Such accounts would include
restaurants, food processing plants, service stations or any other commercial or industrial account
that uses oil or grease in their production process.
A second alternative that could be used to control the grease that enters the system would be
through the use of oil and grease separators in the sewer system. These facilities would be
located near the problem areas where the flow velocities in the sewers are low and there are a
high incident of grease accumulation due to restaurants or other users in the area.
Sewer Sags: A second problem that requires a significant amount of maintenance time and budget
is due to sags in the existing sewers. These sags are due to settlement in the sewer lines as a
result of poor soil conditions. The sags in the sewer line allow the wastewater to pond and solid
will settle out in the sag. This reduces the capacity of the sewer in these areas. In areas where
oil and grease are a problem, a sag in the sewer line compounds the problem.
8 -3
The City of Tukwila has an ongoing TV inspection program to identify the problem areas in the
system. In recent years approximately 20,000 linear feet have been inspected annually. In areas
with significant problems identified, the City has repaired the sewer by removal of the existing
sewer and construction of a new sewer to serve the area.
Emergency Procedures
Emergency Telephone Numbers
The City maintains a sewer emergency response crew on 24 hour call. This crew is available to
answer any emergency that may occur within the system and has immediate response
responsibility. This would include but not be limited to lift station alarms, sewer backups and
forcemain blockages. The City maintains the following telephone numbers to allow the public
to notify the repair crews:
During Business Hours: 433 -1860
_
pump and control operation resulting in the conditions described above. Historically the
City has not experienced regular or extended power outages. The City maintains a
backup generator in the event of a power failure.
Personnel: Sewer system personnel are available to respond to emergency calls and are
have the capability to perform minor repairs and emergency operations as required to
sustain sewer service.
Supplies and Spare Parts: The City maintains a small inventory of spare parts that are
normal for operations and emergency repairs. In the event of a major catastrophe, the
City would have to procure necessary spares from suppliers and reduce the level of
service to consumers.
Communications: The City maintains a base radio station to keep in contact with the field
crews during normal working hours. After hours there are maintenance crews on call
that can be contacted by the Police Department Dispatcher.
8 -5
Horton Dennis & Associates
Consulting Engineers, Planners & Surveyors
320 Second Avenue South
lirkland Washington
COMPREHENSIVE SEWER SYSTEM PLAN
CITY OF TUICWILA
: SUPPLEMENT A - ANNEXATION AREAS
1991
PREPARED BY:
Horton Dennis & Associates
Consulting Engineers, Planners & Surveyors
320 Second Avenue South
Kirkland Washington
CITY OF TUKWILA
COMPREHENSIVE SEWER SYSTEM PLAN
SUPPLEMENT A - ANNEXATION AREAS
CHAPTER 1- INTRODUCTION
Authorization A1-1
Location A1-1
Authority A1-2
Planning Goals and Objectives A1-2
CHAPTER 2 - PLANNING CONSIDERATIONS AND
SERVICE AREA CHARACTERISTICS
Background A2 -1
Planning Area A2 -1
Sewer Service Areas and Agreements A2 -1
Physical Features of the Sewer Service Area A2 -2
Topography A2 -2
Geology and Soils A2 -2
Surface Water Resources A2 -7
Human Environment A2 -8
Land Use Calculations A2 -8
Population A242
Land Development Potential A243
Growth Management Scenarios A2 -15
Scenario I - Existing Conditions A2 -15
Scenario II - Vacant Land Buildout A2 -15
CHAPTER 3 - EXISTING SEWER SYSTEM
General A3 -1
City of Tukwila A3 -1
Drainage Basin No. 18 A3 -1
Val Vue Sewer District A3 -1
Drainage Basin No. 7 A3 -3
Drainage Basin No. 16 A3-4
Drainage Basin No. 17 ..... .... .. .. A34
Drainage Basin No. 19 A3-4
Drainage Basin No. 21 A3-4
City of Seattle A3-6
Drainage Basin No. 22 A3-6
Drainage Basin No. 23 A3-6
Drainage Basin No. 24 A3-6
Rainier Vista Sewer District A3-6
METRO A3 -7
Industrial Waste Surcharge Program A3 -8
National Pollutant Discharge Elimination System (NPDES) A3 -8
Non Sewered Areas A3 -8
Drainage Basin No. 20 A3 -9
Drainage Basin No. 21 A3 -9
CHAPTER 5 - RECOMMENDED SERVICE AREAS AND IMPROVEMENTS
Introduction A5 -1
City of Tukwila A5 -1
Drainage Basin No. 18 A5 -1
Drainage Basin No. 20 A5 -1
Project No. 27S. - Allentown Sewers A5 -2
Val Vue Sewer District A5 -2
Overall Improvements A5 -2
Project No. 18S - Val Vue Pump Station Monitoring A5 -3
Drainage Basin No. 7 A5 -3
Project 23S. - South 158th Street ULID A5 -3
Drainage Basin No. 16 A5 -3
Project 20S - 42nd Avenue South ULID A5 -3
Project 21S. - 51st Avenue South ULID A5 -3
Project 24S. - South 158th Street ULID A5 -3
Project 25S. - McMicken ULID A5 -3
Drainage Basin No. 17 A5-4
Project No. 22S. - Riverton Crest ULID A5-4
Project 26S. - Original District Rehabilitation A5-4
Project 17S - McAdam Road Pump Station Rehabilitation A5-4
Drainage Basin No. 19 A5-4
Project 16S. - Inco Pump Station Rehabilitation A5-4
Drainage Basin No. 21 A5 -5
Project 19S. - Riverside - Interurban ULID A5 -5
Rainier Vista Sewer District A5-6
City of Seattle A5-6
Drainage Basin No. 22 A5-6
Project No. 28S. - Empire Hill A5-6
Drainage Basin Nos. 23 and 24 A5-6
Metro Facilities . A5 -7
CHAPTER 6 - IMPLEMENTATION
Service Areas and Interlocal Agreements A6-1
City of Seattle Service Area A6 -1
Allentown Sewers A6 -1
Metro Facilities A6 -2
Val Vue Sewer District Area A6 -2
Existing Sewer Rates A6 -2
CHAPTER 1
INTRODUCTION
Authorization
This report compiles and summarize the results and conclusions of planning and engineering studies
performed by Horton Dennis & Associates in developing a comprehensive sewer plan for the recently
annexed areas to the City including Fire District Number 1, Foster, Thorndyke, Riverton and Cascade
View. This update addresses the study area boundaries, population and employment statistics, the
provider of existing sewer service, development plans and zoning, minimum design criteria, and the
existing sewer system. It also assesses the adequacy of existing sewer, recommends improvements and
considers the feasibility and desire for the City to take over service to the annexed areas.
This report is authorized as a supplement to the City's 1991 Comprehensive Sewer Plan. Maintaining
a separate supplement provides the City the ability to separate the requirements for the various areas. It
also provides a more focused approach to defining and evaluation the existing systems and needs of the
newly annexed areas. This document is intended to be used in conjunction with the City's 1991
Comprehensive Sewer Plan. Information contained in the base plan will be referenced as such and not
repeated herein.
Location
The City of Tukwila recently experienced five major annexations, including Fire District No. 1; Riverton;
Foster; Thorndyke; and, Cascade View. This supplement specifically addresses these five areas. The
annexed area pushed the corporate boundaries of the City to the north and the west. The City now
extends to State Route 99 (Pacific Highway South) from South 160th Street to about South 153rd Street,
where the western boundary follows Military Road and Pacific Highway South again to the Duwamish
River and continues north to Boeing Field. The new northeastern boundary follows the Seattle City
Limits south to about South 120th Street.
Specifically, the geographic areas of each of the five annexations are as follows. Fire District Number
1 is generally bounded on the west by the Duwamish River, on the north by the City of Seattle, on the
east by the City of Seattle and Martin Luther King Way South, and on the south by the City of Renton.
The Riverton area extends from the Duwamish River to South 138th Street and is east of Pacific Highway
A1-1
Al2
South. Foster is between South 138th Street and South 144th Street and is east of Pacific Highway South.
Thorndyke includes the southern portion of the annexation area and extends from South 144th Street to
South 160th Street between I -5 and Pacific Highway South. Finally, the Cascade View area is between
Pacific Highway South and Military Road, from approximately South 152nd Street north to south 128th
Street, then along Pacific Highway South to the Duwamish River. Figures 1 -1 and 1 -2 indicate the
annexed areas and their relationship to previous City boundaries.
Authority
Under RCW 35.13A.070 a City may either choose or not choose to assume sewer district responsibilities
for areas it annexes. The City's primary objective is to insure adequate sewer service is being provided
for the annexed areas. The work associated with preparing this document was authorized by a contract
between the City of Tukwila and Horton Dennis & Associates, Inc.
Planning Goals and Objectives
The purpose of this report is to meet the goals and objectives of the Comprehensive Land Use Policy Plan
cited in the main body of the 1991 Comprehensive Sewer Plan. Again, the primary focus of this report
is to define the level of sewer service in the annexed areas and insure adequate service is being provided.
The City may or may not actually assume sewer responsibilities for the newly annexed area in the near
future. Assumption of existing facilities may not be in the best interest of the customers, the City, or
existing purveyors for a number of years. In this case a phased, or gradual assumption of facilities may
be most feasible.
1HDR1
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P1 I(T
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HORTON DENNIS & ASSOCIATES, INC.
CONSULTING ENGINEBS, PLANNERS
& SURVEYORS
Kirkland, WA 98033.6687 (206) 822.2525
Pro). No.5030 Drwn. MAA I Date 5
TUKWILA
• KENT
KING CO.
PIERCE CO.
REN TON
• AUBURN
LK. SAMMAMISH
•
LK. YOUNGS
ISSAQUAH
PRE-ANNEXATION TUKWILA
CITY LIMITS
FIGURE 1-1
VICINITY MAP
NTS
ANNEXATION STUDY
AREA BOUNDARY
FIRE DISTRICT 1 ANNEXATION
RIVERTON ANNEXATION
FOSTER ANNEXATION
THORNDYKE ANNEXATION
1
1
2000 1000
tis
70
0
SCALE IN FEET
t
0 9
TUKWILA
CITY
LIMITS
8. 128TH 8T.
CITY OF SEA —TAC
8. 188TH 8T
2000
0
O
TUKWILA
CITY
LIMITS
fma SR 518
CITY OF
SEATTLE
8. 180TH 8T.
J
FIGURE 1- 2
LOCATION MAP
%//
CITY OF SEATTLE
KING COUNTY
Legend
ANNEXATION STUDY
AREA BOUNDARY
FIRE DISTRICT 1 ANNEXATION
RIVERTON ANNEXATION
FOSTER ANNEXATION
THORNDYKE ANNEXATION
CASCADE VIEW ANNEXATION
K/Ne 1
VA 8.
KING COUNTY
RENTON
City of Tukwila
COMPREHENSIVE WATER PLAN: SUPPLEMENT A — ANNEXATION AREAS
CHAPTER 2
PLANNING CONSIDERATIONS AND
SERVICE AREA CHARACTERISTICS
CHAPTER 2
A2 -1
PLANNING CONSIDERATIONS AND SERVICE AREA CHARACTERISTICS
Background
This supplemental report addresses only the areas recently annexed area to the City. These areas were
swept by a strong wave of annexations that took place in 1989 and nearly doubled the land area of
Tukwila from 2,880 acres to 5,546 acres. In conjunction with these major annexations, the population
significantly increased from 4,760 to 14,631 persons.
Planning Area
The planning area for this study includes the five recently annexed area to the City of Tukwila: Fire
District Number 1; Foster; Thorndyke; Riverton; and, Cascade View. The locations of these areas are
described in Chapter 1 of this report and are shown in Figure 1 -2.
Sewer Service Areas and Agreements
As indicated in Figure 2 -1, the study area is presently served by five separate entities, including: the City
of Tukwila; the City of Seattle; Val Vue Sewer District; Rainier Vista Sewer District; and, Metro. The
City of Tukwila serves a small portion of the annexation area which is east of I -5 and west of the original
city limits, in the vicinity of 53rd Avenue South. The City of Seattle owns and maintains Sewer lines in
the Empire Hill area east of the I -5 right -of -way and, indirectly, provides service to the northernmost
portion of the annexation area, along East Marginal Way South. This area is actually served by direct
connection to Metro lines along East Marginal Way.
Val Vue Sewer District owns and maintains sewers in the annexed areas lying south of the Duwamish
River. In addition, Val Vue Sewer District owns and maintains a collection system lying north and east
of the Duwamish River along Pacific Highway South. Rainier Vista Sewer District provides sewer
service to the area northwest of the Annexation area. In addition, customers west of SR 99 in the
northwesternmost portion of the Cascade View annexation area are within the Rainier Vista service area.
Metro owns a number of large sewer pipe lines that run through and sewer a portion of the annexed area.
These lines include the Renton Effluent Transfer System pipeline; twin 12 -inch effluent forcemains; and,
a 42 -inch diameter interceptor which runs north along East Marginal Way. Local service to the industrial
property along East Marginal Way is provided by direct connection to the Metro facilities although the
City of Seattle bills these customers.
Physical Features of the Sewer Service Area
Topography, geology and soils, and surface and ground water resources are important for consideration
when determining the future development of the area and its sewer system. These factors are discussed
in the following sections.
Topography
Topography of the annexation area is shown on the Sewer Plan Map included in the main body
of the 1991 Comprehensive Sewer Plan and general physiographic areas are indicated on Figure
2 -2. The area can generally be classified as hilly, with some steep slopes leading to the
Duwamish River Valley floor. Steep slopes have been identified on the City's Sensitive Areas
Maps and occur in the Empire Hill area; north of the Duwamish River in the northern portion of
Allentown; along both sides of Pacific Highway South; and, along the Interstate 5 and Highway
518 corridors.
Geology and Soils
The geology of the Duwamish River Basin consists of sedimentary and volcanic bedrock, glacial
deposits of various ages and types, and alluvium in the valley bottoms. Till is found along most
of the highlands and generally caps the drumlin hills. Recessional outwash sand is interspersed
throughout the till and is commonly found along shallow stream valleys and other depressional
areas. Landslide deposits exist within steep - walled tributary valleys. Recent alluvium, composed
of gravel, sand and silt fills the Duwamish Valley and the bottom of the tributary valleys.
The majority of the annexation area is composed of alluvial and till soil types similar to the soil
types found in the remaining Tukwila planning area, as indicated on Figure 2 -3 and described in
Table 2 -1. Alluvial soils are primarily found adjacent to the Duwamish River north to Boeing
Field (Fire District No. 1). Alluvial soils are mostly unconsolidated silt, sand and gravel valley
fill, with some clay. It also includes artificial fill and peat. These soils have two severe
developmental constraints: 1) low bearing capacity; and, 2) high water table. These soil types
are generally suited to light weight buildings or piles.
Till soils are principally found in uplands west of the Duwamish River and north of I-405
(Riverton, Foster and Thorndyke areas). Till soils are hard, blue -gray to gray concrete -like
mixture of clay, silt, sand, and gravel. These soils are generally excellent for large - building
construction and are considered to have foundation, seismic and slope stability.
A2-2
2000 1000
0
SCALE IN FEET
CITY OF SEA —TAC
TUKWILA
CITY
LIMITS
CITY OF
SEATTLE
FIGURE 2 -1
SEWER SER VI CE
AREAS
Legend
ANNEXATION STUDY
AREA BOUNDARY
UNSEWERED AREA
11111111
CITY OF SEATTLE
VAL VUE SEWER DISTRICT
RAINIER VISTA SEWER DISTRICT
SEATTLE UUNCIPAL SEWER
CITY OF TUKWILA
City of Tukwila
COMPREHENSIVE SEWER PLAN: SUPPLEMENT A — ANNEXATION AREAS
`i
2
2000 000
11-ID111
0
SCALE IN FEET
TUKWILA
CITY
LIMITS
CITY OF SEA
2000
TUKWILA
CITY
LIMITS
CITY OF
SEATTLE
if S. 1110TH ST.
FIGURE 2-2
PHYSIO GRAPHIC AREAS
11■• • Ma•••
CITY OF SEATTLE
KING COUNTY
Legend
ANNEXATION STUDY
AREA BOUNDARY
LOWLAND
VALLEY WALL
PLATEAU
City of Tukwila
COMPREHENSIVE SEWER PLAN: SUPPLEMENT A - ANNEXATION AREAS
2000 1000
jiDI11
0
SCALE IN FEET
TUKWILA
CITY
LIMITS
CITY OF SEA -TAC
2000
TUKWILA
CITY
LIMITS
CITY OF
SEATTLE
of I. 1110TH IT.
FIGURE 2 -3
SOIL GROUPS
Legend
CITY OF SEATTLE
-,>,, KING COUNTY
j �\
ji?
ANNEXATION STUDY
AREA BOUNDARY
ALLUVIALS SOILS
OUTWASN SOILS
TILL SOILS
BEDROCK ROCK
OUTCROPPINGS
KINC COUNTY
City of Tukwila
COMPREHENSIVE SEWER PLAN: SUPPLEMENT A - ANNEXATION AREAS
2000 1000
CITY OF SEA -TAC
SCALE IN FEET
I. 11ITH IT.
2000
TUKWILA
CITY
OMITS
4
TUKWILA
CITY
LIMITS
CITY OF
SEATTLE
FIGURE 2-1
SEWER SERVICE
AREAS
IIIIIIII
CITY OF SEATTLE
KING CO UNTY
Legend
ANNEXATION STUDY
AREA BOUNDARY
UNSEWERED AREA
VAL VUE SEWER DISTRICT
RAINIER VISTA SEWER DISTRICT
SEATTLE MUNCIPAL SEWER
CITY OF TUKWILA
r
KING CO UNTY
RENTON
tzi
4
CITY OP SEA-TAC
2000 1000
2000
SCALE IN FEET
1. Ilem ST.
O. 1.111TH
TUKWILA
CITY
LIMITS
TUKWILA
CITY
UM1TS
imx• 811
fi
CITY OP
SEATTLE
4
1
SEWER SERVICE
AREAS
Legend
ANNEXATION STUDY
AREA BOUNDARY
UNSEWERED AREA
VAL VUE SEWER DISTRICT
RAINIER VISTA SEWER DISTRICT
SEATTLE MUNCIPAL SEWER
CITY OF TUKWILA
M.O.= • ••••••■
111111
CITY OP SEATTLE
ICING COUNTY
KING COUNTY
RENTON
02-0:325
City of Tukwila
COMPREHENSIVE SEWER PLAN: SUPPLEMENT A - ANNEXATION AREAS
9
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, A
2000 000
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1
SCALE IN FEET
4. Legend
CITY OF
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tes
-1
TUKWILA
CITY
LIMITS
8. 128TH 8T.
CITY OF SEA-TAC
3. 138111 ST
2000
8 .
0
TUKWILA
CITY
LIMITS
J SR 518
a
a
0
FIGURE 2-2
PHYSIO GRAPHIC AREAS
z
•••••••• •
CITY OF SEATTLE
KING COUNTY
ANNEXATION STUDY
AREA BOUNDARY
LOWLAND
VALLEY WALL
PLATEAU
KING COUNTY
RENTON
0
0
ta
tes
4.
TUKWILA
CITY
LIMITS
S. 121TH ST.
CITY OF SEA—TAC
•
0
3. 133TH ST
13. 144TH ST.
TUKWILA
CITY
LIMITS
SR 518
2000 I 000 0 2000
of
SCALE IN FEET i
V
Z
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FIGURE 2-2
PHYSIOGRAPHIC AREAS
■••••••• • inimmo
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Legend
CITY OF SEATTLE
KING COUNTY
ANNEXATION STUDY
AREA BOUNDARY
LOWLAND
VALLEY WALL
PLATEAU
flN
t *Ay S.
KING COUNTY
RENTON
IA24902
City of Tukwila
COMPREHENSIVE SEWER PLAN: SUPPLEMENT A — ANNEXATION AREAS
-•• "ed•
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01,11111
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FIGURE 2-3
4
•
•
CITY OF SEA
2000 I 000 0 2000
SCALE IN FEET
0
4.
TUKWILA
CITY
LIMITS
•
•
S. 126TH et
5 13. 136TH ST
S. 140TH ST.
TUKWILA
CITY
LIMITS
sR ale
•
0
CITY OF
SEATTLE
S. 160TH ST.
0
z
J
SOIL GROUPS
••••••■•I • ••••••••
•
CITY OF SEATTLE
KING COUNTY
Legend
ANNEXATION STUDY
AREA BOUNDARY
ALLUVIALS SOILS
OUTWASH SOILS
TILL SOILS
BEDROCK ROCK
OUTCROPPINGS
;iv
Ap
8.
KING COUNTY
RENTON
•
•
SCALE IN FEET
TUKWILA
CITY
LIMITS
2000 1000 0 2000
CITY OF SEA -TAC
TUKWILA
CITY
LIMITS
CITY OF
SEATTLE
FIGURE 2-3
SOIL GROUPS
CITY OF SEATTLE
KING COUNTY
Legend
ANNEXATION STUDY
AREA BOUNDARY
ALLUVIALS SOILS
OUTWASH SOILS
TILL SOILS
BEDROCK ROCK
OUTCROPPINGS
KING COUNTY
L.q2 cca5
City of Tukwila
COMPREHENSIVE SEWER PLAN: SUPPLEMENT A - ANNEXATION AREAS
Bedrock, Rock
Outcroppings
Ti, Tp, Tr, Tt
Thin to no soil layer.
High
Slight
Poor
Poor
Good
Excellent Foundation
stability but subject
to limitation of slope.
Good runoff, slow infil-
tration, few springs.
Surface Water Resources
The annexation area is bisected by the Duwamish River flowing north through the area and is
within the Fire District No. 1, Fostoria, and Gillium Creek Drainage Basins identified by the City
of Tukwila. Separate studies have been prepared for each of these drainage basins and are
available from the City of Tukwila, Department of Public Works, Surface Water Utility. The
following summary of each basin was prepared from these studies and is intended only to give
the reader a general understanding of the limits and characteristics of each basin. Additional
drainage sub - basins, as applicable to sanitary sewer system operation, have been identified on the
Comprehensive Sewer Plan Map included with the main body of this report.
The Fire District No. 1 Drainage Basin includes that portion of the annexation area which is east
of the Duwamish River and north of the and easterly projection of South 144th Street.
Approximately one -half of the basin's 2900 acres are within the Tukwila city limits. This basin
actually consists of several independent sub -basins which are drained by a combination of natural
and man-made conveyance systems to the Duwamish River and eventually, the Puget Sound.
Because the basin is bisected by Interstate 5, a significant amount of surface water from the area
is drained by State Highway Department systems. Private drainage systems drain the largely
impervious surface area near Boeing Field.
The portion of the Fostoria Drainage Basin which is within the annexation area is bounded on the
south by South 144th Street, on the west by Military Road, and on the north and east by the
Duwamish River. Approximately 1,000 of the basin's 1,600 total acres are within the annexation
area. Topography in the Fostoria basin directs drainage to the northeast and the Duwamish River.
Several unnamed, year round drainage courses flow through the Fostoria basin and the
downstream portions of these features have been routed downstream portions of features have
been routed through a series of man-made ditches and culverts.
The Gillium Creek Drainage Basin includes the southern portion of the annexation area and is
generally bounded by South 160th Street and Highway 518 on the south, Pacific Highway South
and Military Road on the west, South 144th Street on the north and Interstate 5 on the east. Of
the basin's total 1,855 total acres, approximately 500 are within the annexation area. Surface
Water facilities in the Gillium Creek basin consist of storm sewers and ditches that drain the area
east of the Sea Tac Airport Access freeway; areas north and south of the Highways 405 and 518;
A2 -7
and, area west of the Green (Duwamish) River. All runoff from the basin is routed to discharge
into the Green River through a 108 -inch diameter pipe with flap gate.
Wetlands identified in the annexation area occur near the Boeing Access Road; at the Pacific
Highway South and Highway 518 interchange; at the southeastern corner of Allentown; and,
directly east of the Foster Golf Course on the east side of the Duwamish River. Specific
information on wetlands can be obtained from the City of Tukwila, Department of Community
Development, Sensitive Areas Maps.
Human Environment
This section addresses the human elements of the annexation area including land use, zoning, population,
housing, and employment. Two growth management scenarios are presented in order to project a range
of sewer system demands and needs. The Tukwila Planning Department has studied the annexed area in
terms of population, housing units, total acreage, vacant land by zoning classification, and sensitive land
areas. The following information is based on their studies.
Land Use Calculations
The following describes the comprehensive land use policy plan, zoning and existing land uses for the
annexed areas. The Comprehensive Land Use Policy Plan for the annexed areas indicates the area should
develop in the land use patterns shown on Figure 2-4. In general, the Fire District No. 1 area is
designated as Heavy Industrial for all of the north industrial section; Light Industrial and Low Density
Residential for the east I -5 area: Heavy Industrial, Light Industrial, Commercial and High Density
Residential for the Martin Luther King South area; and, Heavy Industrial, Light Industrial, and Low
Density Residential for the Allentown area. The Comprehensive Plan also indicates Parks and Open
Space along the Duwamish River and for the Allentown Park.
The Comprehensive Land Use Policy Plan for the Foster, Riverton and Thorndyke areas generally shows
Low Density Residential with the exception of some Commercial and Medium Density Residential along
Pacific Highway South; Public Facilities, Parks and Open Space near Foster High School on South 144th
Street; and, commercial along East Marginal Way South for several blocks south of South 126th Street.
A2 -8
1
-- ..
2000 1000
CITY OF SEA -TAC
0
SCALE IN FEET
�HDR�
2000
TUKWILA
CITY
UMITB
TUKWILA
CITY
UMITB
CITY OF
SEATTLE
•
J
FIGURE 2 -4
COMPREHENSIVE
LAND USE POLICY
ANNEXATION STUDY
_ - AREA BOUNDARY
Q SINGLE FAMILY RESIDENTIAL
MULTI FAMILY RESIDENTIAL
■ OFFICE
COMMERCIAL
LIGHT INDUSTRIAL
® HEAVY INDUSTRIAL
PUBLIC FACILITIES
® PARKS & OPEN SPACE
SPECIAL DEVELOPMENT
CONSIDERATIONS
CITY OF SEATTLE
Legend
City of Tukwila
COMPREHENSIVE SEWER PLAN: SUPPLEMENT A — ANNEXATION AREAS
2000 1000
MDR)
0
SCALE IN FEET
CITY OF SEA —TAC
2000
TUKWILA
CITY
LIMITS
! a. 144TN ST
TUKWILA
CITY
LIMITS
CITY OF
SEATTLE
FIGURE 2 -5
ZONING MAP
Legend
ANNEXATION STUDY
AREA BOUNDARY
SINGLE FAMILY RESIDENTIAL
MULTI FAMILY RESIDENTIAL
■ OFFICE
. COMMERCIAL
. LIGHT INDUSTRIAL
HEAVY INDUSTRIAL
® PARKS & OPEN SPACE
CITY OF SEATTLE
KING COUNTY
City of Tukwila
COMPREHENSIVE SEWER PLAN: SUPPLEMENT A — ANNEXATION AREAS
•
SCALE IN FEET
o �
a 12STM
CITY OF SEA -TAC
2000 1000 0 2000
TUKWILA
CITY
LIMITS
5. 13111TH
! S. 144Th 5T.
TUKWILA
CITY
LIMITS
SR 618
Q
S. 1MoTH 1T.
CITY OF
SEATTLE
FIGURE 2 -4
COMPREHENSIVE
LAND USE POLICY
11
CITY OF SEATTLE
KING COUNTY
Legend
ANNEXATION STUDY
AREA BOUNDARY
SINGLE FAMILY RESIDENTIAL
MULTI FAMILY RESIDENTIAL
OFFICE
COMMERCIAL
® LIGHT INDUSTRIAL
HEAVY INDUSTRIAL
PUBLIC FACILITIES
PARKS & OPEN SPACE
SPECIAL DEVELOPMENT
CONSIDERATIONS
Ay
KING COUNTY
RENTON
�HDRj
CITY OF SEA -TAC
2000 1000 0 2000
SCALE IN FEET
TUKWILA
CITY
LIMITS
!�. 13ITH
•. 140TH ST.
TUKWILA
CITY
UMITS
•. 10OTH ST.
CITY OF
SEATTLE
FIGURE 2 -4
COMPREHENSIVE
LAND USE POLICY
ANNEXATION STUDY
AREA BOUNDARY
SINGLE FAMILY RESIDENTIAL
MULTI FAMILY RESIDENTIAL
OFFICE
COMMERCIAL
LIGHT INDUSTRIAL
1111 HEAVY INDUSTRIAL
PUBLIC FACILITIES
PARKS & OPEN SPACE
CITY OF SEATTLE
Legend
SPECIAL DEVELOPMENT
CONSIDERATIONS
02 -(O25
City of Tukwila
COMPREHENSIVE SEWER PLAN: SUPPLEMENT A - ANNEXATION AREAS
• • •
2000 1000
SCALE IN FEET
TUKWILA
CITY
LIMITS
8. 128TH ST.
CITY OF SEA -TAC
8. 138TH 8T
8. 140TH ST
144TH 81
TUKWILA
CITY
LIMITS
CITY OF
SEATTLE
FIGURE 2 -5
ZONING MAP
Legend
CITY OF SEATTLE
KING COUNTY
ANNEXATION' STUDY
AREA BOUNDARY
SINGLE FAMILY RESIDENTIAL
MULTI FAMILY RESIDENTIAL
OFFICE
COMMERCIAL.
LIGHT INDUSTRIAL
HEAVY INDUSTRIAL
PARKS & OPEN SPACE
KING COUNTY
RENTON
LHDD1
SCALE IN FEET
TUKWILA
CITY
LIMITS
8. 128TH IT
CITY OF SEA —TAC
2000 1000 0 2000
8. 188TH
8. 140Th er
TUKWILA
CITY
UMITB
two 8R 518
CITY OF
SEATTLE
8. 180TH 8
0
J
FIGURE 2 -5
ZONING MAP
■
m
•
•
CITY OF SEATTLE
KING COUNTY
Legend
ANNEXATION' STUDY
AREA BOUNDARY
SINGLE FAMILY RESIDENTIAL
MULTI FAMILY RESIDENTIAL
OFFICE
COMMERCIAL
UGHT INDUSTRIAL
HEAVY INDUSTRIAL
PARKS & OPEN SPACE
0
KING COUNTY
RENTON
Lq z 2'
City of Tukwila
COMPREHENSIVE SEWER PLAN: SUPPLEMENT A — ANNEXATION AREAS
RESIDENTIAL
OFFICE
COMMERCIAL
INDUSTRIAL
PUBLIC FACILITIES
Y.
TABLE 2 -2
LAND USE CATEGORIES
Low - density residential: These areas are characterized by single - family residential uses; 0 - 5
units per gross acre.
Medium - density residential: These areas are multiple - family in nature and are characterized by
duplexes, triplexes, and fourplexes; 6 - 16 units per gross acre.
High - density residential: These areas are multiple - family in nature and are characterized by
apartment buildings; 17+ units per gross acre.
Office areas are characterized by professional and commercial office uses with certain
complementary retail uses.
Commercial areas include commercial services, retail commercial activities with associated
warehousing, and compatible and complementary uses including offices.
Light industrial: Industrial areas characterized by distributive and light manufacturing uses,
commercial and office uses.
Heavy industrial: Industrial areas characterized by heavy or bulk manufacturing uses, distributive
and light manufacturing uses, commercial and office uses.
PARKS AND OPEN SPACE
These areas represent public parks, recreation facilities, school playgrounds, and other public
open spaces, including agricultural lands under open space taxation.
Community facilities include school buildings, churches, government offices, police and fire
stations, and utility facilities.
SPECIAL DEVELOPMENT CONSIDERATIONS
Refers to areas of steep slopes, water surface, and agricultural lands. Along the Green River this
designation refers to that area under shoreline management. This designation does not preclude
development; rather, it depicts areas where urban development must respond sensitively to certain
environmental factors.
A2 -11
The land use character of the area is varied, ranging from intense industrial to the north to rather low
density single family to the south. Industrial development including a portion of the Boeing Field King
County International Airport is in the northern portion of the area. Commercial development exists along
the Highway 99 strip and along East Marginal Way. Land use in the Riverton area is a mix of
commercial /industrial. Residential use is scattered in the remaining portions of the study area. The
community facilities in the annexation area include Southgate Park (which is undeveloped), South Central
Pool, Foster Library, a community pea patch, a King County Park and Fire District No. 1 fire station.
Several major roadways traverse the annexation area. The roadways are Interstate 5, State Route 509,
State Route 599, State Route 518, State Route 99/Pacific Highway, East Marginal Way, and Martin
Luther King Way South. With the combined four annexation areas, the City's total acreage rises from
2880 to 5,546, an area increase of more than 90 percent.
Population
The population in the combined annexation area is greater than the City of Tukwila's population prior to
the annexation. Since 1970, Tukwila's population has remained relatively stable, excluding annexation.
Beginning in 1985 with the McMicken Heights annexation, the population of the City has increased
dramatically. Annexation Fire District No. 1, Foster, Thorndyke, Riverton and Cascade View has
resulted in a population increase from 4,760 to 14,631. These annexations, collectively, are the largest
in the City's history in terms of both population and land area.
In conjunction with the increase in residential population came an increase in employment population.
Strong employment opportunities were reflected in a 1988 employment census of approximately 18,000
employees, which is considerably larger than the residential population. Estimates of the employment
population since the most recent annexation place that figure near 40,000 employees. It is expected by
City planning staff that the residential population will most likely continue to remain considerably less
than the employment population of the City. Table 2 -3 summarizes housing and population data for the
overall study area and each individual annexation area.
A2 -12
TABLE 2 -3
LAND USE AND POPULATION
Fire Dist. Cascade
No. 1 Foster Riverton Thorndyke View Total
Land Area (acres) 1408 196 223 469 370 2666
Population 1308 902 858 2965 2757 8790
Housing Units (total) 663 465 401 1644 1007 4180
Single Family 513 211 282 389 522 1917
Multiple Family 150 254 119 1255 485 2263
Source: City of Tukwila Department of Community Development and Public Works Department.
Land Development Potential
Information on available vacant land was gathered through a drive -by survey conducted by the Tukwila
Planning staff. Table 2-4 shows the amount of vacant land by zoning classification. As indicated, the
largest amount of vacant land available in any one classification is 478 acres and occurs in land zoned R -1
one Family Dwelling classification. Only a limited amount of vacant land is available for multiple family
developments. The R -3 Three and Four Family Dwellings and the R-4 Low Density Apartment
classifications contain 20 and 3 acres of vacant land respectively.
TABLE 2-4
VACANT LAND BY ZONE CLASSIFICATION
Zoning Vacant
Classification Acreage
R -A 14.0
R -1 478.0
R -2 44.0
R -3 20.9
R-4 3.0
P -O 6.6
C -1 1.2
C -2 76.2
C -M 20.8
M -1 27.0
M -2 98.0
TOTAL 789.7
Based on analysis of the foregoing data, the following conclusions were made regarding the development
potential of the study area. These conclusions are inherent to the development of realistic scenarios and
formulation of an effective Comprehensive Sewer Plan.
The Comprehensive Land Use Policy Plan is the official guide to the future development of the annexed
area while the Zoning Ordinance provides the means of realizing the goals listed in the Comprehensive
Land Use Plan. The growth scenarios which have been developed are in conformance with the
Comprehensive Land Use Plan and are discussed later in this Chapter.
Approximately 461 acres of vacant single family zoned land and 14 acres of agricultural zoned land are
available which would permit about 465 additional single family residences. Furthermore, the 23 acres
of vacant multi - family zoned residential land could yield 92 apartment units. Thus, approximately 488
additional dwelling units could be added to the annexed area through complete build -out of the existing
zoning conditions.
Approximately 71 acres of land zoned for commercial use is vacant and 131 acres of land zoned for
industrial use is vacant. The same average gross floor area to employee ratio as used for the employee
density calculations for the 1984 Sewer Plan have been used to estimate the growth scenarios below,
resulting in the following estimated employee densities:
TABLE 2 -5
EMPLOYEE DENSITIES
Employees per Building Factors
Activity Acre (Average) (Average)
Commercial 30 .30
Office 65 .45
Warehousing/Light
Industrial/Wholesale 14.5 .40
A2 -14
Gross Floor Area
per Employee (Average)
435
300
1,200
There is limited available vacant land in the C -1 Neighborhood Retail Business, C -2 Local Retail Business
and C -M Industrial Park zones. Conversely, given the current pace of development, there appears to be
an adequate supply of land zoned for M -1 Light Industry and M -2 Heavy Industry. If land for non-
residential development becomes a problem in the future, redevelopment and intensification of the uses
of commercial /retail buildings may offer one solution. At this time no data has been collected regarding
under - utilized land. Under - utilized land may cause a change in the amount of vacant land listed in the
previous table.
Furthermore it should be noted that some of the available vacant land is within sensitive or marginal
development areas such as steep slopes and wetlands. Given the nature of these lands, lower than
allowable densities may be justified.
Growth Management Scenarios
This section presents two growth scenarios for the purpose of evaluating and planning the sewer systems:
1) existing conditions; and, 2) vacant land buildout. These scenarios are shown on Figures 2-6 and 2 -7,
respectively and Table 2-6 summarizes each scenario. Redevelopment buildout was not considered at this
time due to lack of available information.
Scenario I - Existing Conditions
These scenario is based on the 1989 land use, population, housing and employment data provided
by the Tukwila Planning Department. This scenario is offered for the purpose of evaluating
deficiencies in the existing sewer system by determining the adequacy of present facilities and the
need for immediate improvements.
Scenario II - Vacant Land Buildout
This scenario examines the information provided by the City and projects what the annexed area
would be like if all undeveloped areas were developed in accordance with the Zoning Ordinance.
Table 2-6 summarizes the projected development scenarios.
HU = Housing Unit
GFA = Gross Floor Area
A2 -16
TABLE 2-6
PROJECTED DEVELOPMENT SCENARIOS
Scenario 1 Scenario
Existing Vacant Land
Land Use Conditions Build -out
Single Family 1,917 HU 3,830 HU
Multi - Family 2,263 HU 3,625 HU
Office 293,085 GFA 351,000 GFA
Commercial 401,679 GFA 704,700 GFA
Light Industry 1,059,312 GFA 1,392,000 GFA
Heavy Industry 6,625,920 GFA 7,308,000 GFA
Sub -Total Housing Units 4,180 HU 7,455 HU
Sub -Total Commercial/
Industrial 8,379,496 GFA 9,755,700 GFA
2000 1000
m
9
12111TH ST.
C11'Y OF SEA —TAC
0
SCALE IN FEET
TUKWILA
CITY
LIMITS
r
s. 1$ITH ST
2000
TUKWILA '
CITY
LIMITS
1 an ale
BOEING FIELD
(Heavy Industrial/
CITY OF
SEATTLE
ai
FIGURE 2 -6
EXISTING CONDITIONS
r
Legend
BURLINGTON NORTHERN RAILROAD
(Heavy Industrial)
CITY OF SEATTLE
KING COUNTY
ANNEXATION STUDY
AREA BOUNDARY
SINGLE FAMILY RESIDENTIAL
MULTI FAMILY RESIDENTIAL
OFFICE
COMMERCIAL
UGHT INDUSTRIAL
HEAVY INDUSTRIAL
PUBUC FACIUTIES
PARKS & OPEN SPACE
4.
KINQ Jat w4
BURLINOTON NORTHERN RAILROAD
(Heavy Industrial)
KING COUNTY
RENTON
City of Tukwila
COMPREHENSIVE SEWER PLAN: SUPPLEMENT A — ANNEXATION AREAS
'
•
2000 1000
�HDR�
•
0
■=1
1 11
CITY OF SEA -TAC
SCALE IN FEET
e. 118TH sr.
2000
TUKWILA
CITY
LIMITS
8. 138TH
0
j 8. 140TH IT
j 8. 144TH 8T.
TUKWILA
CITY
LIMITS
j"' SR ma
CITY OF
SEATTLE
8T.
i
FIGURE 2 -7
VACANT LAND
B UILDO UT
ANNEXATION STUDY
• - - AREA BOUNDARY
SINGLE FAMILY RESIDENTIAL
MULTI FAMILY RESIDENTIAL
■ OFFICE
® COMMERCIAL
UGHT INDUSTRIAL
HEAVY INDUSTRIAL
CITY OF SEATTLE
KING COUNTY
Legend
NY it
KING COUNTY
RENTON
City of Tukwila
COMPREHENSIVE WATER PLAN: SUPPLEMENT A — ANNEXATION AREAS
IP-
uJ
a
2000 1000 0
SCALE IN FEET
0
s 8. 128TH ST.
CITY OF SEA —TAC
8. 138TH ST
2000
TUKWILA
CITY
LIMITS
TUKWILA
CITY
LIMITS
f "" SR 618
0
BOEING FIELD
(Heavy Industrial)
CITY OF
SEATTLE
FIGURE 2 -6
EXISTING CONDITIONS
va
111111111
Legend
ANNEXATION STUDY
AREA BOUNDARY
SINGLE FAMILY RESIDENTIAL
MULTI FAMILY RESIDENTIAL
OFFICE
COMMERCIAL
UGHT INDUSTRIAL
HEAVY INDUSTRIAL
PUBLIC FACIUTIES
PARKS & OPEN SPACE
BURLINGTON NORTHERN RAILROAD
(Heavy Industrial)
CITY OF SEATTLE
KING COUNTY
Z
• W4 r a.
BURLINGTON NORTHERN RAILROAD
(Heavy Industrial)
KING COUNTY
RENTON
M VP
IHDD1
d
i
2000 1000 0
SCALE IN FEET
TUKWILA
CITY
LIMITS
a. 12STN ST.
CITY OF SEA -TAC
; S. 1MSTN ST.
a. 140TH ST
2000
4
TUKWILA
CITY
LIMITS
SR 518
BOEING FIELD
IHsavy Industrial)
CITY OF
SEATTLE
v
z
2
J
FIGURE 2 -6
EXISTING CONDITIONS
a
- • -
BURLINGTON NORTHERN RAILROAD
IHsavy Industrial/
CITY OF SEATTLE
KING COUNTY
ANNEXATION STUDY
AREA BOUNDARY
SINGLE FAMILY RESIDENTIAL
MULTI FAMILY RESIDENTIAL
OFFICE
COMMERCIAL
UGHT INDUSTRIAL
HEAVY INDUSTRIAL
PUBUC FACIUTIES
PARKS & OPEN SPACE
JR.
%I Y a.
BURLINGTON NORTHERN RAILROAD
(Heavy Industrial)
KING COUNTY
RENTON
Lq2cO26
1
City of Tukwila
COMPREHENSIVE SEWER PLAN: SUPPLEMENT A - ANNEXATION AREAS
'
2000 1000 0 2000
SCALE IN FEET
CITY OF SEA -TAC
$ 8. 128TH 8T.
TUKWILA
CITY
LIMITS
8. 138TH 8T
8. 140TH 8T.
j 8. 144TH 8T.
TUKWILA
CITY
LIMITS
CITY OF
SEATTLE
FIGURE 2 -7
VACANT LAND
BUILDOUT
III OFFICE
Legend
CITY OF SEATTLE
KING COUNTY
ANNEXATION STUDY
AREA BOUNDARY
SINGLE FAMILY RESIDENTIAL
MULTI FAMILY RESIDENTIAL
COMMERCIAL
LIGHT INDUSTRIAL
HEAVY INDUSTRIAL
KING COUNTY
RENTON
ti
2000 1000 0 2000
SCALE IN FEET
TUKWILA
CITY
LIMITS
8. 128TH 8T.
.4
0
8. 138TH 8T.
a. 140TH 8T.
8. 144TH 8T.
TUKWILA
CITY
LIMITS
CITY OF SEA —TAC
i■a SR 518
CITY OF
SEATTLE
0
z
J
FIGURE 2-7
VACANT LAND
B UILDO UT
CITY OF SEATTLE
KING COUNTY
Legend
ANNEXATION STUDY
AREA BOUNDARY
SINGLE FAMILY RESIDENTIAL
MULTI FAMILY RESIDENTIAL
OFFICE
COMMERCIAL
LIGHT INDUSTRIAL
HEAVY INDUSTRIAL
K/N �� wAr a
KING COUNTY
RENTON
LM
City of Tukwila
COMPREHENSIVE WATER PLAN: SUPPLEMENT A — ANNEXATION AREAS
EXISTING SEWER SYSTEM
CHAPTER 3
EXISTING SANITARY SEWER SYSTEM
General
Sanitary sewer service is provided to the recently annexed areas by the following entities: the City of
Tukwila; the City of Seattle; Val Vue Sewer District; Rainier Vista Sewer District; and, Metro. The
existing service areas of these providers was presented in Chapter 2. Approximately 36 miles of 4 to 24-
inch gravity and pressure sewer line conveys sewage from the area to Metro's regional sewerage system
for treatment and disposal. Detailed discussions regarding the existing sanitary sewer system facilities
serving the study area are presented in this Chapter. The Sewer Plan Map provided with the main body
of this report indicates all existing sanitary sewer system facilities within the City of Tukwila.
There are also areas of the annexation area which utilize septic tank /drainfield systems for on -site sewage
disposal. This Chapter identifies the general location and documented problems of such systems.
City of Tukwila
A small portion of the Annexation area is currently provided sewer service by the City of Tukwila. This
area is indicated on the Sewer Plan Map and described below as Drainage Basin No. 18.
Drainage Basin No. 18
Drainage Basin No. 18 is bounded on the west by Interstate 5; on the north by Interurban Avenue
South; and, on the east by the pre- annexation city limits. Sewer service to this area is provided
by 8 -inch lines which carry flows to the northeast and Metro facilities along Interurban Avenue.
Val Vue Sewer District
The Val Vue Sewer District (Val Vue) provides sanitary sewer service to portions of the Fire District No.
1, Riverton, Foster, Thorndyke, and Cascade View annexation areas. Val Vue, one of the first sewer
districts in King County, was established in 1946 for the purpose of serving the Cascade Homes Addition
and the businesses along Pacific Highway South. The original District was quite small, covering an area
of only 0.37 square miles. Effluent was treated at a primary type treatment plant, located just east of
Pacific Highway South near South 135th, chlorinated and discharged to the Duwamish River. This
treatment plant was later abandoned due to freeway construction and the District subsequently contracted
with Metro for sewage treatment in 1966. Presently Val Vue and Tukwila have several agreements
allowing Val Vue to operate and maintain sewer facilities within the City of Tukwila.
A3 -1
Gradually, the District has expanded and now serves a current total of 3,442 residential and 362 business
accounts. The District presently covers 4.05 square miles of which 2.53 square miles lies with the
annexed areas. With approximately .24 square miles of the District within the pre - annexation city limits,
a total of approximately 2.77 square miles of Val Vue presently lies within the City of Tukwila. By
agreement, Val Vue serves approximately .15 square miles of area which is inside the City of Tukwila
and outside of the District limits.
The Val Vue service area consists of predominantly residential connections but services is also provided
to industrial and semi -rural customers. There is a growing industrial belt in the north section and a
thriving business corridor along Pacific Highway South that is served by Val Vue.
Authority and procedure which govern sewer districts operations is provided in Chapter 56, R.C.W. The
District is governed by three elected officials constituting its Board of Commissioners. Meetings open
to the public are held on the first and third Tuesday of every month.
The primary objective of Val Vue is to provide efficient, low cost sewer service to present and future
accounts. Val Vue operates much the same as a city in that they must comply with the following:
o Develop and maintains a comprehensive sewerage plan to be used as a guide to facilitate
planning and construction of additional sanitary sewer facilities.
o Comply with environmental policies that will provide guidelines for preservation of water
quality as set forth in Federal and State regulations PL 92 -500 and RCW 90-48.
o Comply with the objectives and criteria set forth in the Comprehensive Plan for King
County for areas within King County and City of Tukwila for areas within the city.
o Maintain a financial income level sufficient to retire all bonded indebtedness and other
operation and maintenance costs as they come due.
The relationship between Val Vue's existing and proposed systems and regional sewer planning documents
is summarized as follows:
Water Quality Management Plan 303(e). Ribco, September, 1975. The segment of the
Duwamish River within the annexed Val Vue service area is presently classified as water quality
limited, due to point and non -point sources with violations of coliform, dissolved oxygen and
temperature. Effects of sewage effluent upon receiving waters become an increasing concern.
Val Vue comprehensive planning is in full and complete compliance with the water quality
A3-2
objectives set forth in this study in planning the extension of systems designed to remove sources
of pollution in the Upper Duwamish drainage basin.
Municipality of Metropolitan Seattle Pre- Design Report on Second Stage Construction of
Comprehensive Sewerage Plan, August, 1990. This study recommends the construction of a
trunk system to intercept sewage flows from the Val Vue planning area. The proposed Val Vue
Connection would be a portion of the West Point Treatment System and connect to the north
flowing Elliott Bay Interceptor. It is assumed that this Metro sponsored improvement will be
accomplished at no cost to Val Vue.
Additionally Val Vue has been in contact with Metro regarding the interface of Val Vue's
Comprehensive Sewer Plan with Metro planning process. The sewerage plan adopted by Val Vue
is flexible in terms of the District's connection to Metro and may be amended to conform to the
final method of interception proposed by Metro. Additional information concerning Metro's
proposed Interurban Avenue South interceptor and its effect on the Val Vue System is presented
in Chapter 5.
King County Comprehensive Sewerage General Plan. The Val Vue Comprehensive Plan is in
conformance with King County's Sewerage General Plan. Val Vue has not updated this plan
since annexation of the various areas to the City of Tukwila to identify any changes needed to
comply with the City's sewer requirements. The City of Tukwila did have the opportunity to
review the District's Comprehensive Planning.
Val Vue Sewer District serves areas within the below described drainage basins identified for the purpose
of this Plan. Although these basins generally depict hose presented in the 1985 Val Vue Comprehensive
Sewer Plan, some modifications have been made to further delineate future service to unsewered areas.
Drainage basin boundaries are indicated on the Sewer Plan Map.
Drainage Basin No. 7
Drainage Basin No. 7 includes that area of the City which is west of I -5; south of State Route
518; and, east of 42nd Avenue South. A small portion of this basin is within the pre - annexation
city limits and is discussed in the main body of this document. That portion of the basin which
has sanitary sewer service is served by a network of 8 and 12 -inch lines connecting to Metro
facilities near the I -5 - I-405 interchange. Unsewered areas are discussed later in this Chapter.
A3 -3
Drainage Basin No. 16
Drainage Basin No. 16 includes the Val Vue service area which is south of South 144th Street
and west of Interstate 5. Flows from this area are directed toward 18, 21 and 24 -inch interceptor
which runs easterly along South 154th Street to a connection with Metro facilities near the
intersection of 52nd Avenue South and South 154th Street.
Drainage Basin No. 17
Drainage Basin No. 17 is generally bounded by South 133rd and South 131st Streets on the north;
Interstate 5 on the east south 144th Street on the south; and Military Road (city limits) on the
east. This basin actually operates as two separate basins, although flows from all areas ultimately
drain to the northwest. Flows from the westerly portion of Basin No. 17 drain to the north and
ultimately, Val Vue's connection to Metro near South 126th Street and Interurban Avenue South.
Flows from the easterly portion of Basin No. 17 drain to the McAdam Road Pump Station and
are pumped into Metro's interceptor running along Interurban.
Drainage Basin No. 19
Drainage Basin No. 19 is generally bounded on the north and east by SR 599; on the south by
South 133rd and South 131st Streets; and, on the west by the city limits. Val Vue flows from
this area drain south to the Metro connection near South 126th Street on Interurban Avenue
South. A small area in the northwestern corner of Drainage Basin No. 19 is served by the
Rainier Vista Sewer District, as described later in this Chapter.
Drainage Basin No. 21
Drainage Basin No. 21 covers that portion of Val Vue Sewer District which is north of State
Route 599. Flows from this area drain to the north and the District's connection to Metro near
the intersection of East Marginal Way and the Boeing Access Road. A pump station facilitates
flows to the north from that portion of the Basin which is south of the Duwamish River.
Val Vue owns eleven (11) sewage pump stations of which eight (8) lie within the present city limits of
the City of Tukwila. Two lie inside City of Sea -Tac and one the Boeing Recreational Center Pump
Station lies in King County. A summary of these stations is presented in Table 3 -1.
A3-4
Number
1.
Name /Address
McMicken
17036 S. 53rd Ave.
2. 24th Avenue
2400 S. 142nd St.
3. 142nd Street
2860 S. 142nd St
4. McAdam
13300 Interurban Ave.
5. Inco
3700 S. 124th St.
6. Metro
11911 East Marginal Way
7. East Marginal
11200 E. Marginal Way
8. Duwamish
11201 Pacific Hwy. S.
9. Towing Co.
10712 E. Marginal Way
10. Boeing Rec. Center
10500 W. Marginal Way
11. Seagate
11601 Interurban Ave.
Manufacturer
Smith & Loveless
Peabody Barnes
Submersible Duplex
Cornell Duplex
Wet Well Mounted
Smith & Loveless
Duplex Wet Well
TABLE 3 -1
VAL VUE SEWER DISTRICT
SEWAGE PUMP STATION SUMMARY
Cornell /Ideal Duplex
Wet Well Mounted
Dakota Pump Duplex Paco
Wet Well Mounted
Cascade /Cornell Ideal
Duplex Wet Well Mounted
Cascade Ideal - Duplex
ABS Submersible
Ideal Pump - Duplex Cornell
Vacuum Lift
Cascade Ideal - Duplex Cornell
Wet Well Mounted
Cascade - Ideal Duplex ABS
Submersible
Capacity
650 GPM
2 -25 HP
100 GPM
2 -15 HP
130 GPM
2 -2 HP
425 GPM
2 -7.5 HP
400 GPM
2 -7.5 HP
200 GPM
2 -5 Hp
200 GPM
2 -5 Hp
520 GPM
2 -8 HP
400 GPM
2 -3 HP
300 GPM
2 -5 HP
140 GPM
2 -3 HP
Electrical
480V/3 Phase
480V/3 Phase
240V/ 3 Phase
480V/ 3 Phase
480 V/3 Phase
480V/3 Phase
480V/3 Phase
230V/3 Phase
240V /3Phase
480V/3 Phase
230V/3 Phase
Emergency
Overflow
Full Time
Portable Unit
Location
City of
Tukwila
Emergency Plug City of
Sea -Tac
Emergency Plug City of
Sea -Tac
Emergency Plug City of
Tukwila
Emergency Plug City of
Tukwila
Emergency Plug City of
Tukwila
Emergency Plug City of
Tukwila
Emergency Plug City of
Tukwila
Emergency Plug City of
Tukwila
Emergency Plug City of
Tukwila
Emergency Plug City of
Tukwila
City of Seattle
The City of Seattle operates sewer lines in the Empire Hill area east of Interstate 5, and in the area of
Tukwila which is north of the Boeing Access Road. These areas are included in Drainage Basin Nos.
22, 23 and 24 as indicated on the Sewer Plan Map and described below.
Drainage Basin No. 22
Drainage Basin No. 22 includes the Ryan Way area of Empire Hill and is generally bounded on
the west and south by Interstate 5 and on the north and east by the city limits. The lines in this
area were installed approximately 20 years ago and as indicated on the Sewer Plan Map, feed to
an interceptor along Martin Luther King Jr. Way South (M.L. King Jr. Way South). There is
a pump station north of Ryan Way and M.L. King Jr. Way South which discharges to the Metro
mains that run along East Marginal Way South and eventually, the West Point Treatment Plant.
Drainage Basin No. 23
Drainage Basin No. 23 is east of East Marginal Way South and north of the Boeing Access Road.
Customers in this area are limited to commercial /industrial type facilities. Sewer service is
provided by direct connection to Metro lines running north along East Marginal Way South.
Drainage Basin No. 24
Drainage Basin No. 24 is west of East Marginal Way South and north of the Boeing Access Road.
Connections in this Basin are commercial /industrial type businesses and sewage from these
facilities flows directly int Metro facilities along East Marginal Way.
Rainier Vista Sewer District
The majority of Rainier Vista Sewer District's service area is northwest and west of the Annexation Area,
although several of its service connections are within the northwesternmost portion of the Cascade View
annexation area. Customers in this area include the Riverton General Hospital and other medical related
facilities in the vicinity of South 128th Street and Military Road as well as connections along the west side
of Pacific Highway South (north of South 128th Street).
Sewage from the hospital flows into the Rainier Vista Lift Station No. 11, then westerly through a force
main which discharges into the District's gravity sewer system at the intersection of South 128th Street
and Military Road. Flows from other facilities along South 128th and those along the west side of
Pacific Highway South are transported to the north through 8 -inch lines. The Rainier Vista Lift Station
A3-6
No. 5 then pumps flows from this area through a 6 -inch forcemain to discharge into the Districts gravity
lines near the intersection of 26th Avenue South and South 126th Street.
The following excerpt from Rainier Vista's 1990 Comprehensive Sewer Plan identifies the characteristics
of the two Lift stations serving the small portion of the District which is within the City of Tukwila:
Pump Station No. 5
Location: 12001 Pacific Highway South
Type: Wet -Dry
Horsepower: 30 and 15
Pumping Rate GPM: 150
Pump Station No. 11
Location: South 128th Street & 30th Avenue South
Type: Submersible
Horsepower: 2 ® 15 HP
Pumping Rate: 300 GPM
METRO
Metro has twin 12 -inch force mains that leave the Renton Treatment Plant and travel north along the
railroad alignment to I -5, then through Allentown to the vicinity of S. 112th where it feeds into a 42 -inch
gravity line. The 42 -inch gravity line continues north along East Marginal Way S. to West Point
Treatment Plant. Another 42 -inch gravity sewer begins in the vicinity of S. Norfolk St. and E. Marginal
Way S. to the West Point Treatment Plant.
Sewer customers along E. Marginal Way So., between S. 112th St. and the Seattle City limits, hook -up
direct to one of the 2 - 42 -inch gravity sewers.
The Renton Effluent Transfer System leaves the Renton Treatment Plant and travels along the railroad
track to Foster Golf Course then it crosses to Interurban Avenue So., then it goes north and follows SR
599 leaving the Tukwila area. The RETS line terminus is in Elliott Bay after entering a outfall at
Duwamish head.
A 18 -inch Metro transfer line picks up sewage from the Trammel Crow Lift Station and Val Vue Sewer
District at S. 126th St. and Interurban Avenue S.; then travels south along Interurban Avenue S. to
approximately S. 138th St. at which point there is a lift station; the sewage leaves in a 12 -inch force main
west to 53rd Avenue S.; then along 53rd Avenue S. to S. 144th St. where it changes to 15 -inch gravity
A3 -7
sewer, then along Macadam Road S. to S. 152nd St.; then west under I -5 to 52nd Avenue S. where it
changes to 24 -inch; then south along 52nd Avenue S. to SR 518; then Southeast under I -5 to Southcenter;
then south along Southcenter Blvd. to Strander Blvd., then to 36 -inch at Strander Blvd. and Andover Park
West; then east leaving the Tukwila area and traveling to the Renton Treatment Plant.
In addition to picking up sewage at the beginning of the 18 -inch transfer line, sewage is also intercepted
at the Macadam Lift Station near S. 131st St. and Interurban Avenue S.; Metro Lift Station near S. 138th
St. and Interurban Avenue S.; at 53rd Avenue S. and S. 144th St.; S. 150th St. and Macadam Road S.;
S. 152nd St. and Macadam Roads; 52nd Ave. So. and S. 152nd St.; 52nd Ave. S. and S. 154th St.;
Strander Blvd. and Andover Park West, Andover Park East, and West Valley Highway.
Industrial Waste Surcharge Program
Metro has a sewer surcharge program for discharge of high strength industrial wastewater. Details of
the program can be found in Chapter 3 of the main text of this Comprehensive Sewer Plan.
The only customers within the annexed areas that qualify for the industrial waste surcharge program are:
1. M & M Finishers
2. Metro South Base
3. Metro 12200 E. Marginal Way S. Facility
National Pollutant Discharge Elimination System ( NPDES)
The City of Seattle has a NPDES permit for overflow from a lift station in the vicinity of Empire Way
South, north of the Boeing Access Road. The overflow is at a Metro regulator pump station that feeds
to the Duwamish River via a storm drain. The location of the discharge is in the vicinity of Norfolk
Street and the Duwamish River. The permit is number 1, Serial No. 178, issued by WDOE. The
average daily flow through the Metro regulatory to Metro's West Point Sewage Treatment Plant is 75
mgd. The permit allows a discharge of 1.0 mgd to the Duwamish.
Non Sewered Areas
There are small areas throughout the annexation area which are presently unsewered, as discussed
previously in this Chapter. Those listed below are of primary concern because of documented on -site
sewage disposal system failures and theier close proximity to the Duwamish River. Provisioon of sewer
service to these and other unsewerd areas are discussed in Chapter 5.
A3-8
Drainage Basin No. 20
Drainage Basin No. 20 includes the majority of the Allentown area of the City and is generally
bounded by South 116th Street on the North; Interstate 5 on the east; and, the Duwamish River
on the west and south. As described below, this unsewered area is of significant concern because
of its proximity to the Duwamish River and the documented problems with septic systems within
the Basin.
Drainage Basin No. 21
Drainage Basin No. 21, as described earlier in this Chapter, includes the northernmost portion
of Val Vue Sewer District. The southern portion of the Basin, which is bounded on the north and
east by the Duwamish River, and on the south and west by SR 599, is currently unsewered. A
small area of the Basin which is north of the Duwamish River is also without sewer service.
Problems associated with the lack of service in these areas is documented below.
The Duwamish River experiences various water quality problems and is designated as "water quality
limited" in the 303 Water Quality Management Plan, due to an undetermined combination of septic tank
leachate and urban runoff. The City of Tukwila should consider expansion of sanitary sewers into areas
of know septic tank service and enforcement of hookups for residences currently using septic tanks, when
the system fails, if they are living within 330 feet (city code) of a active sewer line. This would place
these areas in compliance with current water quality standards, as well as the King County's General
Sewerage Comprehensive Plan which calls for the abatement of pollution conditions where such conditions
exist.
The unsewered areas of Drainage Basin Nos. 20 and 21 have a history of significant septic tank /drainfield
failures. These failures have resulted in overflows and seepage running in ditches and the ground surface.
Potential contamination of the ground water is also a concern. Known overflow /drainfield failures as
recorded by King County Department of Public Health for these areas are summarized in Table 3 -2. In
some cases public sewers are available but the residence is not connected. In other cases public sewer
is proposed but not yet constructed and for many other residences sewer are not presently planned.
Many of the septic /drainfield systems were constructed at a period where standard are not as stringent as
they are today. Presently King County requires a minimum lot area of 12,500 square feet in order to
install a septic tank / drainfield system. Also standards regarding depth of permeable soil and depth to
A3-9
water to le has increased. Many of the lots for example in Allentown are 9,600 square feet and are either
poorly d ained and /or with a seasonal high water table. The City should pursue the installation of sewers
in the Ali entown area.
Some r idences in the Thorndyke area (Drainage Basin No. 21) which are being sewered by
septic /dr: infield systems where sewers are within 250 feet. Tukwila's municipal code 14.12.030 states
that buil ings within 250 linear feet of a sewer line shall be deemed to be within the area served by said
sewer. owever, a septic system may only be allowed per requirements of King County local Health
Departm nt which do not allow for such where there is a sanitary sewer system within 330 linear feet.
The Cou ty requires existing residents to hookup when the septic tank has to be repaired.
A3 -10
TABLE 3 -2
THE STATUS OF SEPTIC TANKS IN THE TUKWILA AREA
A - -> The house is on a septic tank system; and there is an existing sewer main,
but no side sewer connection.
B —> The house is on a septic tank system, and there is presently a proposed project
for new sewer to serve this area.
C —> The house is on a septic tank system; and there is no existing or proposed
sewer main
Address Number
Street Number
Sewer Status
15222
15230
11532
11612
11600
11412
11702
11705
11729
11807
11809
11816
13212
15225
13039
11630
11822
11838
12010
12258
13013
14110
14855
11659
11662
11806
11828
11831
11835
11837
11846
11853
11863
12056
12064
12084
37th Ave. S.
37th Ave. S.
38th Ave. S.
38th Ave. S.
39th Ave. S.
40th Ave. S.
40th Ave. S.
40th Ave. S.
40th Ave. S.
40th Ave. S.
40th Ave. S.
40th Ave. S.
40th Ave. S.
40th Ave. S.
41st Ave. S.
42nd Ave. S.
42nd Ave. S.
42nd Ave. S.
42nd Ave. S.
42nd Ave. S.
42nd Ave. S.
42nd Ave. S.
42nd Ave. S.
44th Ave. S.
44th Ave. S.
44th Ave. S.
44th Ave. S.
44th Ave. S.
44th Ave. S.
44th Ave. S.
44th Ave. S.
44th Ave. S.
44th Ave. S.
44th Ave. S.
44th Ave. S.
44th Ave. S.
B
B
B
B
B
B
B
B
B
B
B
B
A
A
A
C
C
C
C
C
A
A
B
C
C
C
C
C
C
C
C
C
C
C
C
TABLE 3 -
THE STATUS OF SEPTIC TANKS IN THE TUKWILA AREA
A —> The house is on a septic tank system; and there is an existing sewer main,
but no side sewer connection.
B —> The house is on a septic tank system, and there is presently a proposed project
for new sewer to serve this area.
C —> The house is on a septic tank system; and there is no existing or proposed
sewer main.
Address Number
Street Number
Sewer Status
12202
12218
12228
12236
12242
12084
13600
12005
14631
S. 137th St.
10428
12203
12234
12240
13407
10932
12218
12235
12245
S. 124th St.
S. 124th St.
14414
14440
14445
14809
14809
15005
13546
13607
14241
13042
13319
14215
14251
14257
15070
44th Ave. S.
44th Ave. S.
44th Ave. S.
44th Ave. S.
44th Ave. S.
44th PI. S.
45th PI. S.
46th Ave. S.
46th Ave. S.
46th Ave. S.
47th Ave. S.
47th Ave. S.
47th Ave. S.
47th Ave. S.
48th Ave. S.
49th Ave. S.
49th Ave. S.
49th Ave. S.
50th Ave. S.
50th Ave. S.
50th PI. S.
51st Ave. S.
51st Ave. S.
51st Ave. S.
51st Ave. S.
51st Ave. S.
51st Ave. S.
52nd Ave. S.
52nd Ave. S.
53rd Ave. S.
56th Ave. S.
56th Ave. S.
57th Ave. S.
Macadam Rd.
Macadam Rd.
Macadam Rd.
C
C
C
C
C
C
A
C
A
A
A
C
C
C
A
C
C
C
C
C
C
B
B
B
B
B
B
A
A
A
C
C
C
A
A
B
T1- 1 - -Pn. 2/3
Address Number
Street Number
Sewer Status
4208
S. 115th St.
>> CO 03 03 03 03 03 CO W>>> 0 0 0 C) 0 CI > 03 03 C) 0
4218
S. 116th St.
3916
S. 117th St.
3924
S. 117th St.
5014
S. 118th St.
4206
S. 122nd St.
4406
S. 124th St.
4623
S. 124th St.
4811
S. 124th St.
4815
S. 124th St.
4902
S. 124th St.
4626
S. 134th St.
4363
S. 135th St.
4412
S. 136th St.
4240
S. 146th St.
4406
S. 146th St.
4020
S. 148th St.
4041
S. 148th St.
4261
S. 148th St.
4410
S. 148th St.
4411
S. 148th St.
4427
S. 148th St.
4004
S. 152nd St.
3740
S. 154th St.
SEWER STATUS TOTALS
Condition "A"
21
Condition "B"
30
Condition "C"
45
TABLE 3-2
THE STATUS OF SEPTIC TANKS IN THE TUKWILA AREA
A - - -> The house is on a septic tank system; ; an_ there is an existing sewer main,
but no side sewer connection.
B - -> The house is on a septic tank system, and there is presently a proposed project
for new sewer to serve this area.
C —> The house is on a septic tank system; and there is no existing or proposed
sewer main
T3- 1 - -Pg. 3/3
DESIGN CRITERIA AND SERVICE REQUIREMENTS
CHAPTER 4
DESIGN CRITERIA AND CONSTRUCTION STANDARDS
General Information
Upgrading and extending sewers within the City of Tukwila should be to the City's standards established
in Chapter 4 of the City's 1991 Comprehensive Sewer Plan. In that Metro improvements are regional
facilities and would not be assumed by the City, Tukwila's standards would not apply to those
municipalities. Other entities such as Val Vue and Rainier Vista Sewer Districts and the City of Seattle
are providing direct sewer service throughout annexed area, and these systems may be assumed by the
City in the future. It is therefore important that any future improvements to these systems be constructed
in accordance with the City of Tukwila minimum standards for sewer systems. To insure compliance with
Tukwila standards, each purveyors operating inside the City should obtain a franchise for operation of
utilities. The terms of franchises should clearly define limits of responsibility, minimum criteria for
operation and provide for review of proposed improvement projects by the City. This will insure that the
City's standards are being applied and provide a mechanism to coordinate street and other utility
improvements. Franchise requirements should be developed pursuant to RCW 34A.87.040.
Design Criteria
The City's design criteria is summarized in Table 4 -1. Additional information regarding minimum
standards can be found in Chapter 4 of the main body of this report. Because the Val Vue Sewer District
serves so much of the Annexation Area, the District's minimum design criteria is also presented in Table
4 -2 for comparison purposes. In that both sets of criteria were derived from the from the data available
in the "Criteria for Sewerage Works Design" published by the Department of Ecology in February, 1978,
they are very similar.
Residential Flows
Domestic Sewage
Lateral Peaking Factor
Trunks and Interceptor
Peaking Factor
Infiltration/Inflow
Light Industrial Flows
Industrial Waste
Peaking Factor
Infiltration/Inflow
Heavy Industrial Flows
Industrial Waste
Peaking Factor
Infiltration /Inflow
Table 4-1
DESIGN CRITERIA COMPARISON
Val Vue
100 gpcd (including infiltration)
4.0 times average flow
2.5 times average flow
N/A
Val Vue
2,000 gpad (average flow)
3.0 times average flow
400 gpad (average flow)
Val Vue
4,000 gpad (average flow)
2.0 times average flow
400 gpad
City of Tukwila
70 gpcd (not including
infiltration)
4.0 times average flow
2.5 times average flow
1100 gpad
City of Tukwila
0.015 gal /s.f.
3.0 times average flow
1100 gpad
City of Tukwila
0.50 gal /s.f.
3.0 times average flow
1100 gpad
RECOMMENDED SERVICE AREAS AND IMPROVEMENTS
CHAPTER 5
RECOMMENDED SERVICE AREAS AND IMPROVEMENTS
Introduction
This chapter presents alternatives and recommendations for proposed improvements to the sewer systems
and extension of sewers in the annexed area. In that proposed improvements are dependent on the City
exercising its option for takeover or existing purveyors' planned improvements, various options for service
area expansion are discussed. Service areas, system evaluations and proposed improvements area
discussed according to the purveyors serving the annexation area and further defined according to the
drainage basins described in Chapter 3 and identified on the Sewer Plan Map. Table 5 -1 at the end of
this chapter lists each major improvement proposed for the study area as identified by the Comprehensive
Plans of the serving purveyors. Additional improvements for unsewered areas, as well as cost estimates
and project scheduling are included in Table 5 -1. Chapter 6 presents an implementation program for
achieving the recommendations outlined herein.
City of Tukwila
Drainage Basin No. 18
Drainage Basin No. 18 is presently served by Tukwila with no known system deficiencies. No
improvements for this area are proposed at this time.
Drainage Basin No. 20
The highest priority for sewer improvements in the annexed area is the need for a sewer system
in the Allentown area. As discussed in Chapter 3 and documented in Table 3 -1, there are
numerous documented septic /drainfield failures in this area.
The Sewer Plan Map shows a suggested layout for sewers to serve Allentown and indicates that
the majority of the area drains to the south. Sewer facilities for all but the northwest portion of
Allentown will be constructed such that they will flow into Metro facilities along Interurban
Avenue South. As discussed in the main body of this report, Metro has proposed major revisions
to their Interurban facilities and design of a sewer system for the Allentown area will be
dependant on those revisions. Preliminary Metro engineering studies indicate that although
several options for improvements have been considered, pumping from Allentown across the
Duwamish River will be required.
A5 -1
The northwesternmost portion of Allentown is actually within Drainage Basin No. 21 and
naturally drains toward Val Vue facilities in that basin. Because that area is typically referred
to as part of Allentown, it has been included in the overall project description for provision of
Allentown sewers. Sewer service to the area west of 42 Avenue South requires either pumping
to the south Allentown system or gravity flow into Basin No. 21 and connection to Val Vue
facilities. Connection to the Val Vue system has been selected as the most cost efficient
alternative and included in the cost estimates provided in Table 5 -1. Such a connection would
require and interlocal agreement with Val Vue if it is to be accomplished in lieu of or prior to
takeover of Val Vue facilities in the area.
Project No. 27S. - Allentown Sewers
Provision of sewer service to the Allentown area requires construction of approximately
4300 LF of 12 -inch, 5950 LF of 10 -inch, and 9850 LF of 8 -inch gravity sewer;
construction of a lift station; 950 LF of 6 -inch force main; abandoning septic tanks
construction of side sewer connections for the entire project (363± connections).
Val Vue Sewer District
Operating under the authority of RCW 56, Val Vue has maintained a comprehensive plan in compliance
with King County and State requirements. In that portions of their systems have deteriorated due to root
intrusion and structural decay, Val Vue is presently planning major system replacements. Over the next
few years they plan near $2,000,000 worth of system improvements within the annexed area. These
improvements are summarized in Table 5 -1. Additionally, several extensions are in the planning stages
to sewer areas where sewers do not now exist. Future projects identified by the District are discussed
below.
Overall Improvements
As part of the recent Metro analyses completed as a preliminary design function to the proposed
Metro Interurban Avenue interceptor, an infiltration analysis of portions of the District's system
was completed. This analysis included smoke testing of lines and identified areas where minor
system repairs should be completed. Such repairs are anticipated to be completed on and ongoing
basis as part of the District's routine maintenance program.
Pump station monitoring has been identified as an improvement which will benefit the overall
operation of the District. This project is identified as Project No. 18S and is described below.
A5 -2
Project No. 18S - Val Vue Pump Station Monitoring
Provision of a telemetry /alarm system on several of the District's pump station is
proposed in order to provide better monitoring throughout the system and increase the
effectiveness of emergency response procedures.
Drainage Basin No. 7
A portion of Drainage basin No. 7 is included in the pre - annexation city limits and discussed in
the main body of this report. The only improvements contemplated in this basin, however, are
provision of sanitary sewer service to previously unsewered areas as described below.
Project 23S. - South 158th Street ULID
This proposed ULID will result in sanitary sewer service in the vicinity of South 158th
Street and 42nd Avenue South. Construction of approximately 7320LF of 8 -inch gravity
sewer and 3660 LF of 6 -inch side sewers is contemplated.
Drainage Basin No. 16
The following projects are contemplated or underway for Drainage Basin No. 16:
Project 20S - 42nd Avenue South ULID
Completion of this project will provide sanitary sewer service to the vicinity of 42nd
Avenue South and South 146th Street by installation of approximately 5,200 LF of 8"
gravity sewer and 2500 LF of 6 -inch side sewers. Project completion is anticipated in
1991.
Project 21S. - 51st Avenue South ULID
Provision of sewer service to the area along and west of 51st Avenue South (south of
South 144th Street) requires construction of 1,250 LF of 12 -inch and 6,070 LF of 8 -inch
gravity sewer lines and approximately 3700 LF of side sewers.
Project 24S. - South 158th Street ULID
Construction of 1,120 LF of 8 -inch gravity sewer and 3660 LF of side sewers will
provide sewer service to the area around South 158th Street and Military Road.
Project 25S, - McMicken ULID
This unsewered area of Drainage Basin No. 16 is south of SR 518 and west of 42nd
Avenue South. Provision of service to the area requires construction of approximately
4,430 LF of 8 -inch gravity sewer and 22001f of 6 -inch side sewers.
A5-3
Drainage Basin No. 17
Val Vue projects proposed for Drainage Basin No. 18 include extension of sewers into previously
unsewered areas as well replacement and rehabilitation of aged lines.
Project No. 22S, - Riverton Crest ULID
The total Riverton Crest ULID project contemplates extending sewer service to the area
around Military Road and South 140th Street and extends west of the City of Tukwila.
That portion of Project 22S. which is within Tukwila requires approximately 5810 LF of
8 -inch gravity sewer, 3500 LF of 6 -inch side sewers and 50 LF of bored casing
underneath Military Road.
Project 26S. - Original District Rehabilitation
Rehabilitation of the aged and in some cases deteriorating lines in the "original district
area" includes replacement of approximately 3,270 LF of existing 6 -inch gravity sewer
line with 8 -inch pipe; lining approximately 4890 LF of existing 8 -inch lines; and,
construction of approximately 7000 LF of 6 -inch and 9000 LF of 4 -inch replacement side
sewers. Extremely wet conditions in some areas require special engineering
considerations and restoration allowances.
Project 17S - McAdam Road Pump Station Rehabilitation
Although the McAdam Road Pump Station is located within Drainage Basin No. 2, its
primary function is to pump flows from Drainage Basin No. 17. Rehabilitation of the
pump station is anticipated in order to accommodate the increase flows which will result
from providing service to previously unsewered areas and due to growth within the basin.
Specific increases in capacity have not been determined and will depend on the District's
efforts at reduction of infiltration as well as the rate of growth and timing of expansions
in the area.
Drainage Basin No. 19
Provision of sewerservice to the small area of Drainage Basin No. 21 which is within Allentown
is discussed earlier in this chapter as part of Drainage Basin No. 20 and Project No. 27S. The
other Val Vue project contemplated for Drainage Basin No. 19 is rehabilitation of the Inco Pump
Station as listed below. A portion of Drainage Basin No. 19 is served by Rainier Vista Sewer
District and is discussed later in this chapter.
Project 16S. - Inco Pump Station Rehabilitation
Rehabilitation of the Inco Pump Station is proposed for the purpose of renewing aging
equipment in the station.
A5 -5
Drainage Basin No. 21
The only major system improvement proposed for Drainage Basin No. 21 is provision of sewer
service to the area of Thorndyke which is bounded on the north and east by the Duwamish River
and on the west and south by Interurban Avenue South. This area is of particular concern
because of its close proximity to the River and the potential impacts of failing septic systems in
the area. Project 19S. addresses the issue of providing service to this area.
Project 19S. - Riverside - Interurban ULID
Provision of sewer service to the area of Thorndyke which is west of the Duwamish and
east of East Marginal Way is proposed. Installation of approximately 3060 LF of 8 -inch
gravity sewer and 1530 LF of 6 -inch side sewer is required. In addition, a lift station is
proposed for construction near the intersection of South 1 lth Street and 38th Avenue
South. Approximately 900 LF of 6 -inch force main will be constructed to connect this
new lift station with the existing Seagate Lift Station. The Seagate Lift Station will pump
flows north across the Duwamish River for ultimate discharge into Metro facilities near
on East Marginal Way near the Boeing Access Road.
At some time in the future the City may wish to consider the assumption of Val Vue Sewer District as
allowed under RCW 35.13A. From an operational stand point assumption of portions the facilities would
not be difficult because most of Val Vue drains to the east into Tukwila and /or directly to Metro facilities.
If the City decided to assume Val Vue's assets for those areas presently lying inside the City it would
leave Val Vue with the portion of sewers inside King County and portion inside the newly formed City
of SeaTac. With such a small revenue base remaining it would make Val Vue's operations uneconomical.
It is therefore recommended the City of Tukwila not assume Val Vue Sewer District within the next 5
years. This will also enable Val Vue to implement its improvements without the concerns of assumption
in the near future. At such time as either additional area is annexed to the City or the City of SeaTac
wishes to assume sewer facilities inside that City, Tukwila may wish to reconsider this issue. At that
time, an agreement between Val Vue and cities of Tukwila and Sea -Tac for ultimate sewer service to the
area will be required.
The City of Tukwila should require Val Vue to obtain a sewer franchise to operate within the City right -
of -ways. The franchise would establish requirements whereby the City is informed on all sewer work
performed by Val Vue inside the City. This would serve to coordinate sewer improvements with other
City utility and street improvements. The City should also support and encourage the implementation of
Val Vue's comprehensive plan and planned expansions and improvements to their system within the City.
Rainier Vista Sewer District
As discussed previously, Rainier Vista Sewer District serves a small portion of Drainage No. 19.
Although no major system improvements are proposed for this area, Rainier Vista has indicated the
intention to relocate lines and renew pump station equipment which currently require frequent
maintenance. Specifically, updating Rainier Vista Lift Station No. 5 to replace aging pumps and provide
additional capacity for anticipated development (outside city limits) and relocation of the force main from
the pump station to avoid a high erosion area is proposed. These facilities have not been noted in Table
5 -1 because they are considered maintenance issues and /or are related to improvements which are
primarily for areas outside of the city limits.
City of Seattle
Drainage Basin No. 22
Sewer service to the Ryan Way area of Empire Hill is presently provided by the City of Seattle.
As this area continues to develop, additional sewers will be required. It is recommended the City
of Tukwila takeover sewer service from the City of Seattle for all customers lying within this
area. An interlocal agreement between the two purveyors should be written establishing the basis
of the takeover and allowing Tukwila to sewer the area via the City of Seattle's existing 18 and
24 inch interceptor running along the northeast side of the I -5 right -of -way to Metro's facilities.
Such an agreement should allow for future expansion of service to currently unsewered portionsof
Basin No. 22. Existing lines have been installed within the past 20 years and are suspected to
be in relatively good condition, although ctual condition of existing lines are unknown. The City
of Tukwila may wish to conduct a field survey of the existing system prior to accepting
ownership. Provision of sewer service to unsewered areas of Drainage Basin No. 22 is identified
as Project No. 28S. as described below.
Project No. 28S. - Empire Hill
Construction of approximately 2800 LF of 8 -inch gravity sewer along S. 107th St. and
49th Avenue South is required to provide sanitary sewer service to previously unserved
Empire Hill Area.
Drainage Basin Nos. 23 and 24
Service for the area north of the Boeing access road and west of I -5 is presently provided by the
City of Seattle via City mains or direct connections to Metro's 42 -inch pipelines in East Marginal
Way So. It is recommended that Tukwila take over customers in this area and provide operation
A5-6
Metro Facilities
Metro is presently planning major system improvements and upgrade of their interception and
transportation of sewage generated from the annexed areas. These improvements may also affect
Tukwila's existing system along Interurban Ave. So., north of Metro's Interurban Pump Station. For
these reasons it is recommended the City of Tukwila be involved in the final plan selection for these
improvements. The implementation of these improvements by Metro may eliminate Val Vue's Macadam
Lift Station, provide an additional connection to the Val Vue system near 43rd Ave. S. and Interurban
upgrade Metro's Interurban pump station and provide a point of gravity sewer connection to the Allentown
area.
..«..�.._
and maintenance for any sewers which are not owned by Metro or privately owned sewers. The
extent of the City's responsibility in this area would be sewer lines crossing and lying within the
right -of -way of East Marginal Way So. New extensions and improvements in this area should
be accomplished by the City of Tukwila. There are no known problems with the existing
facilities in this area, however actual documented condition of mains is unknown. The City may
wish to conduct a field survey of these facilities to confirm their condition.
17S. 2
PROJECT BASIN DESCRIPTION
WITHIN VAL VUE SEWER DISTRICT"
16S. 17 Rehabilitation of the Inco Pump Station by
adding two variable speed pumps and a new
control panel.
Rehabilitation of the McAdam Pump Station
by upgrading the piping system and various
other equipment.
18S. Several Add alarm system to existing pump stations.
19S. 19 ULID for Riverside Interurban Area. Con-
struct 3,060 LF of 8" gravity sewer along
the following: S. 116th St., 38th Ave. S., S.
119th St., 40th Ave. S., S. 119th St., 40th
P1. S., and Interurban Place. Construct
1530 LF 6" side sewer for entire project.
Construct a lift station at S. 117th St. &
38th Ave. S. and 900 LF of 6" force main
from new lift station to Seagate Lift Station.
20S. 14 ULID for 42nd Ave. S. & S. 146th St. Con-
struct 5,200 LF of 8" gravity sewer along
the following streets: 42nd Ave S., S. 146th
St., S. 148th St., and easements. Construct
2500 LF 6" side sewer for entire project.
TABLE 6 - 1
PROPOSED CAPITAL IMPROVEMENTS
CITY OF TUKWILA SEWER SYSTEM
FUNCTION
Provide increased capacity to the pump
station.
Provide increased capacity to the pump
station.
Provide better monitoring of the pump sta-
tions.
Provide sanitary sewer service to previously
unserved Riverside Interurban Area
(Duwamish River & E. Marginal).
Provide sanitary sewer service to previously
unserved 42nd Ave. S. & S. 146th St. Area.
EST. COST*
$ 15,000
$ 76,000
$ 183,600 (8" sewer)
$ 50,000 (Lift Sta.)
$ 27,000 (forcemain)
$ 68,850 (side sewer)
$ 33,550 (ULID Cost)
$ 363,000 Total
$ 300,000 (8" sewer)
$ 112,500 (side sewer)
$ 41,500 (ULID Cost)
$ 454,000 Total
$ 30,000 (pumps) 1994
$ 10,000 (control panel)
$ 40,000 Total
SCHEDULE
1997
1991
To be deter-
mined by
VVSD
To be com-
pleted in
1991
23S. 7
24S. 7
PROJECT BASIN DESCRIPTION
WITHIN VAL VUE SEWER DISTRICT`'
21S. 14 ULID for 51st Ave. S. (S.of S. 144th St.)
Area. Construct 1,250 LF of 12" gravity
sewer and 6,070 LF of 8" gravity sewer
along the following streets: 51st Ave S., S.
151st St., S. 148th St., S. 150th St., S.
152nd St.,and easements. Construct 3700
LF 6" side sewer for entire project.
22S. 15 ULID for Riverton Crest Area. Construct
50 LF of Casing for boring across Military
Road and 5,810 LF of 8" gravity sewer
along the following streets: S. 149th St.,
Military Rd., 33rd Ave. S., and easements.
Construct 3500 LF 6" side sewer for entire
project. Note: Only the portions of this Val
Vue Sewer District ULID which fall within
the City of Tukwila is included.
ULID for S. 158th St. E. of 42nd Ave. S.
Construct 7,320 LF of 8" gravity sewer
along the following streets: 44th Ave. S., S.
158th St., S. 156th St., 47th Ave. S., 51st
Ave. S., and easements. Construct 3660 LF
6" side sewer for entire project.
ULID for Military Rd. and S. 158th St.
Construct 60 LF of Casing for boring across
Military Road and 1,120 LF of 8" gravity
sewer along the following streets: S. 158th
St. and Military Rd. Construct 560 LF 6"
side sewer for entire project.
TABLE 5 - 1
PROPOSED CAPITAL IMPROVEMENTS
CITY OF TUKWILA SEWER SYSTEM
FUNCTION
Provide sanitary sewer service to previously
unserved 51st Ave. S. (S. of S. 144th St.)
Area.
Provide sanitary sewer service to previously
unserved Riverton Crest (Military & S.
140th St.) Area.
Provide sanitary sewer service to previously
unserved S. 158th St. E. of 42nd Ave. S.
Area.
* All costs are in 1991 dollars and include Engineering, Admin., Legal and Contingencies.
** Costs for these projects are based upon the Val Vue Sewer District Capital Improvement Plan, June 1990.
EST. COST*
$ 75,000 (12" sewer)
$ 364,200 (8" sewer)
$ 166,500 (side sewer)
$ 60,300 (ULID Cost)
$ 666,000 Total
$ 7,500 (casing)
$ 348,600 (8" sewer)
$ 157,500 (side sewer)
$ 51,400 (ULID Cost)
$ 565,000 Total
$ 439,200 (8" sewer)
$ 164,700 (side sewer)
$ 60,100 (ULID Cost)
$ 664,000 Total
Provide sanitary sewer service to previously $ 9,000 (casing)
unserved Military Rd and S. 158th St. Area. $ 67,200 (8" sewer)
$ 25,200 (side sewer)
$ 10,000 (ULID Cost)
$ 112,000 Total
SCHEDULE
To be deter-
mined by
VVSD
To be deter-
mined by
VVSD
To be deter-
mined by
VVSD
To be deter-
mined by
VVSD
-
PROJECT BASIN DESCRIPTION
WITHIN VAL VUE SEWER DISTRICT"
25S. 7 ULID for NE McMicken Area. Construct
4,430 LF of 8" gravity sewer along the
following streets: 42nd Ave S., S. 160th St.,
40th Pl. S., 43rd Ave. S., and easements.
Construct 2200 LF 6" side sewer for entire
project.
26S. 15 Original District Rehabilitation Project.
Replace 3,270 LF of existing 6" gravity
sewer with new 8" gravity sewer along the
following streets: 35th Ave. S., 38th Ave.
S., S. 136th St., S. 137th St., and S. 138th
St. Also line 4,890 LF of existing 8" gravi-
ty sewer along the following streets: 34th
Ave. S., 37th Ave. S., S. 135th St., and S.
140th St. Construct and replace 7000 LF 6"
side sewer and 9000 LF 4" side sewer for
entire project. Project includes special
sidewalk restoration and an allotment for
extreme wet conditions in the area.
TABLE 5 - 1
PROPOSED CAPITAL IMPROVEMENTS
CITY OF TUKWILA SEWER SYSTEM
FUNCTION
Provide sanitary sewer service to previously
unserved NE McMicken (42nd Ave. S. & S.
160th St.) Area.
Upgrade existing sewer system because of
poor pipe condition and problems with
inflow and infiltration of surface water.
* All costs are in 1991 dollars and include Engineering, Admin., Legal and Contingencies.
** Costs for these projects are based upon the Val Vue Sewer District Capital Improvement Plan. June 1990.
EST. COST*
$ 265,800 (8" sewer)
$ 99,000 (side sewer)
$ 36,200 (ULID Cost)
$ 401,000 Total
$ 196,200 (replace)
$ 244,500 (line pipe)
$ 315,000 (6" side s.)
$ 180,000 (4" side s.)
$ 100,400 (special)
$1,036,100 Total
SCHEDULE
To be deter-
mined by
VVSD
To be deter-
mined by
VVSD
PROJECT BASIN DESCRIPTION
27S. 18 Sewer system for Allentown Area. Con-
struct 4,300 LF of 12" gravity sewer, 5,950
LF of 10" gravity sewer, and 9,850 LF of
8" gravity sewer within the Allentown area.
Construct a lift station and 950 LF of 6"
force main. Abandon existing septic tanks
and construct side sewer connections for the
entire project (363 connections).
28S. 21 Empire Hill sewer system. Construct 2,800
LF of 8" gravity sewer along S. 107th St.
and 49th Ave. S.
CHAPTER 6
IMPLEMENTATION
This chapter presents the required actions for implementation of the service areas and system
improvements discussed and recommended in Chapter 5. Financial considerations, service area and
franchise agreements, operation and maintenance responsibilities, proposed scheduling of improvements
and legal considerations are summarized for the annexation area only. Additional overall system
recommendations, as well as information on the City's financial considerations and developers extension
policies is included in the main body of the 1991 Sewer Comprehensive Plan.
Service Areas and Interlocal Agreements
Achieving the service areas recommended in Chapter 4 of this supplement requires coordination of actions
summarized below.
City of Seattle Service Area
For takeover of facilities and customers in the areas presently served by the City of Seattle,
including the Empire HIll area and the area along East Marginal Way South, the Cities of
Tukwila and Seattle need to draft an agreement allowing this to occur. Negotiations concerning
such a takeover are underway. At the time of takeover, Seattle should furnish Tukwila with
available as-built drawings, billing information, maintenance records and other available
information. The City may wish to conduct a field survey of existing system to document
facilities and their condition.
Allentown Sewers
The City of Tukwila should take the lead in providing sewers for the Allentown area. There is
substantial documentation of failed septic /drainfield systems in the area. Possible sources of
funding include the States 205(3) grants for planning purposes for the needed improvements,
Centennial Clean Water Fund for up to 50% plus 15% for hardship cases. Other possible grant
or loan monies may also be available. A substantial portion of the project's funding would have
to be local money. This funding could be by an L.I.D. whereby the property owner pays for its
improvement over a period of 10 -20 years. The City may also wish to fund a preliminary data
collection and design study to develop a specific project proposal, preliminary engineering and
assess ground and surface water issues as well as health issues. With proper documentation of
surface water quality, a Health Department declaration may be possible and would assist in
securing available grant funding to reduce the cost to the local residences.
A6 -1
Metro Facilities
As stated in Chapter 5 Metro is planning the construction of major improvements that may benefit
sewer service to the annexed area. The City should maintain a key involvement in this planning
process to insure these planning improvements meet the needs of the City.
Val Vue Sewer District Area
Implementation of facilities within the Val Vue Sewer District area consists of supporting and
encouraging Val Vue to implement its planned improvements. In order to track and coordinate
these improvements with other planned City improvements it is recommended Val Vue and the
City negotiate a franchise agreement allowing Val Vue to operate inside the City.
The improvements recommended to be accomplished are those that are contained in the Val Vue
Sewer District Capital Improvement Plan dated 1990. Val Vue Sewer District has a five -year
Capital Improvement Plan beginning with 1990 and ending in 1995. The plan will be reviewed
and updated annually prior to the adoption of the next year's operating budget. Each year the
first year of the program will be considered for incorporation into the preliminary budget for the
next year. Each year will be added to the end of the program to make the capital budget truly
an on -going program. The proposed activities were based on the following criteria:
A. Comprehensive Plan
B., Need
C. Extent of Service
D. Public Health and Safety
E. Efficiency and Service
F. Legal Requirements
G. Economic Input
The Val Vue Sewer District is hopeful of obtaining a Public Works Trust Loan from the
Washington Department of Community Development for about $2 million. Funding for the
remaining projects will be through local improvement districts or by the District.
Existing Sewer Rates
A summary of the City of Seattle and Val Vue Sewer District rates are listed in Table 6 -1. City of
Tukwila sewer rates are indicated in the main body of this report.
A6 -2
2
Residential
Apartments
Commercial
TABLE 6-1
SEWER RATES
Seattle Val Vue
$2.28/100 cu. ft. / $15.35/mo.
plus Metro's cost plus Metro's cost
Same as commercial $10.75 /unit /mo.
plus Metro's cost
$2.28/100 cu. ft. of
waterPmo. plus
Metro's cost
Based on the 4 lowest, consecutive, water usage months. The rate is constant for 1 year except
that during the year a rate increase is normally implemented. Three unit residents or more are
charged as commercial.
Duplexes and multi -unit residents may apply for a reduction in the water usage amount to
calculate the cost based on water usage for irrigation during the months of May, June, July and
August.
A6 -3
$15.35 /mon first 750 cu. ft.
plus 4.09 /add. 100 cu. ft.
plus Metro's cost
„
appendix interlocal agreements
.
•Eis.:•17i)1 r1
Executed in._.k_.cout• parts• of
h this is counterpart
i•:UHICI1'Ai,7'i'Y 07 ;' ;:� i'7:,].'i'•',;i S °•...1'TLE - CI'PY OP TLKt!] I,A
SUPPI.'EI•i :9:'Ai, AOf'.! {E;: •:•rr FOR SEWAGE DISPOSAL
50J8 263
TIIIS ACnE:......::.:T made as of this day of A199)/
196ti, bet:•:ecn the City of - Tukwila, a municipal corporation of the
State of ::'ashinntcn, hereinafter referred to as the "CITY" and the
Municipality of ::etropolitan Seattle, a municipal corporation of
the State of llashinr,ton,'hcreinaftcr referred to as "METRO",
W I T N E S S E T II:
WHEREAS, as of September 1, 1966 the parties entered
into an Agreement for Sewage Disposal, hereinafter referred to as
the "Basic Agreement ", and thereafter embarked upon the performance
of the Basic Arreen;ent : and
WHEREAS, at the time of the execution of the Basic
Agreement it was assumed by both parties as a material factor in
the negotiation of the Basic A4f'eement that the City's Andover
Park Se;,_;e Pumpins Station, hereinafter referred to as the "Station ",
located at the intersection of Andover Park ':ay West and Strand ^_r
Blvd. , Tukwila, :•lashineton, would not be necessary to the operation
of the local see: -era e facilities contemplated by the Basic Agree-
ment; and
WHEREAS, Metro's Tukwila Interceptor is now near comple-
tion and it has now been determined that contrary to the prior
assumption, the operation of the Station '•;ill still he necessary
to the operation of the facilities of the City after Metro's
Tukwila Interceptor is placed into service, and that the Station
will serve a natural drainage area of less than 1,000 acres; and
WHEREAS, the parties desire to settle certain disputes
which nave arisen relative to the responsibility for maintenance
and operation of t _ Andover ?ar:-. Sewa -e Pumping Station and
a]. mistakes c:' :act en the part r•f the parties during the
nC. .oLiation or t.._ F :asic Arree7.ent as to the need to operate the
. UJ3 264
and
•
Andover Pumping Station after er'n str•uct.ion of the !Metro facilities;
WHEREAS, the City desire;, to use the interim force main
constructed by Metro from the Tukwila Lagoon to Strander Blvd.,
and Petro is ::i11in; to convey such
thereof on the conditions set .forth
WHEREAS, the City desires
of Strander Blvd. and is ~milling to
resurfacing upon payment of an
thereof; and
WHEREAS, the parties
Val Vue Connection Trunk Sewer
conditions set forth herein;
WOW THEREFORE, in consideration of the mutual
contained herein, it is hereby agreed as follows:
1. At the time Metro's Tu!•::•:i1a Interceptor as specified
in its Sewage Disposal Project Contract !Jo. 67 -6 is accepted by
the Municipality and placed
City written notice of such
notice, Metro shall prepare
amount
desire
•
vain and to relocate a portion
in this ar,reement; and
to defer the final resurfacing
assume responsibility for such
equal to the estimated cost
that an extension of Metro's
be made by Metro on the terms and
covenants
into operation, Metro will give the
event. Prior to the giving of such
the Andover Park Sewage Pumping Station
for the pumping of the decreased volume of sewage occasioned by
the placement into service of the Tukwila Interceptor. Such pre-
paration shall consist of cha_n -ins the impellers on the pumps in
said station.
2. Immediately upon the receipt of said notice the City
shall resume complete responsibility for the maintenance and oper-
ation of the station. Petro snall have, thereafter, no obligation
or rc:pensibilit :: whatsoever fogy the operation, maintenance, repair
or replacement of the station and any s °_t• :erase_ faciliti -5 tribu:ar :.
thereto.
3. Metro shall, within t'' :ent y days of giv1r. the afore-
said no:_ce,.pay to the City total :J-cunt or X15,117.70.
4. I :r.Lro shell I>rora't.1y rclor-tc on the cxistinr,
City of Tukwila casement the portion of 10 inch force rain pre-
sently located on temporary r.ir!tt- of -; :ny and Metro shall convey
to the City the entire 10 In force main as so relocated extending
from the Lagoon to Strander ! lvd. It is reco-nised by both parties
this force main is not a permanent sewerage facility and Metro
races no warranty as to its useful life or serviceability. Upon
the relocation and conveyance of said force main to the City, the
City shall have full responsibility for the maintenance, operation
and eventual replacement of said force main. The City shall there-
after have sole and complete responsibility for the construction
and operation of sewerage facilities adequate to deliver City
sewage to Metro's Tukwila Interceptor as now constructed on Strander
Blvd. Metro shall continue to operate the Tukwila Sewage Lagoon
facilities through May 31, 1968.
5. Pacific Mechanical Constructors Inc., the contractor
presently completinG construction of the Tukwila Interceptor
under contract No. 67 -6 with Metro and 'ruder separate contract
with Val Vue Sewer District, is required under said contracts to
complete the restoration and final resurfacing of Strander Blvd.
and is now prepared to accomplish such restoration. To accomodate
the City's request that such final rer.urfacing be deferred to
such time as the City may desire, Pietro shall within forty -five days
from the date of this ar,recment cause Pacific Mechanical Con-
structors Inc. to pay the sum of $9,540 to the City, representing
the estimated cost of completin- such pav1nE under both contracts.
The City does hereby, effective upon receipt of such funds,
release Pacific i'echanical Constructors Inc., ! Metro and Val Vue
Sewer District from their responsibility for the co :-pleti.on of.
euch navin^.
6. Metro shall pro-ot1:' construct the portion of the
V_) /uc Connection Trunk mac: r . _c•crihcc on Exhibit A attached
•
5068 265
hereto and by this ro former me is h.Irt hereof. Such portion
shall he so connt•rncted as to permit loc.'.l service connections
to be made thereto and in consideration thereof the City shall
pay to Metro the cost of constructing an S -inch local on
such alignment. Within 20 days following the first local connec-
tion, the City shall pay to Metro the surd of $23,075 representing
the cost of an S -inch sewer from Point A on Exhibit "A" to the
connection with the 24 -inch Precway Crossing Serer. Within 30
days following the first local connection made to the Val Vue
Connection Trunk, between Point A and Point D the City will pay
to Metro the sum of $5,652. Metro will have and reserve the right
to use the Val Vue Connection Sewer to transport sewage to the
Metropolitan Sewerage System from tributary areas outside the
present boundaries of the City. The City shall own, operate and
maintain said se:•:er hut in the event Metro shall use such sewer,
Metro shall pay to the City a proportionate share of the cost of
operation, maintenance or replacement of such sewer. Metro's
share of such costs shall be in the same proportion which the
area served by such sewer located - outside the City bears to the
total area served by such sewer. At such time as Metro notifies
the City in writing that the use of the Val Vue Connection is no
longer required by Metro to transport sewage collected from areas
outside of the City, 1•letro shall thereby relinquish its rights of
use and the City shall thereupon pay to Metro that portion of the
total cost of construction of the Val Vue Connection sewer which
shall have been borne by t•letro. The City shall promptly issue a
street use permit for such construction on the same terms and
conditions as the street use permit issued to !Metro by the City
'under date of August 21, 1967.
7. In consideration of the payments and the mutual
covenants hereof the parties hereto do hereby mutually release
one another from any and all clairs at law or in equity arising out
-4-
of any mistakes of fact, allege' rcprc•r:ent.:tions or understandings
of the parties relative to the Andover. Station and the effect of
the Basic Agreement upon the operation of the Station.
8. Except as herein specifically provided, the Basic
Agreement is in no way affected or modified by this Supplemental
Agreement and shall be ;ind remain in full force and effect in
accordance with the terms thereof.
9. This Supplemental Agreement merges and supersedes
all prior negotiations, representations and agreements between
the parties hereto relating to the subject matter hereof and con-
stitutes the entire agreement as to the said subject matter between
the parties.
IN WITNESS WHEREOF the parties hereto have executed this
• agreement as of the day and year first above written.
"
ATTE,
� 9= ,,
uu,i�
ATTEST:
' 1 •
i ll it.4...1. ie at / _et' CGa_i
M 3 . alyn Sullivan
Clerk of the Council
CITY OF TUKWILA
-5-
MUNICIPALITY OF MMETROPOLImN SEATTLE
eltwed ou-Ze
C. Care bonworth
Chairman of the Council
SEWAGE DISPOSAL AGREEMENT
THIS AGREEMENT, made and entered into this 07a2 s
day of Ju Iii , 1977, by and between VAL VUE SEWER
DISTRICT, a municipal corporation of the State of Washington,
hereinafter referred to as "District" and the CITY OF TUKWILA,
a municipal corporation of the State of Washington, hereinafter
referred to as "Tukwila ";
W I T N E S S E T H :
WHEREAS, the public health, welfare and safety of
the residents of Tukwila and the residents of the District
require the development of adequate systems of sewage collection
and disposal; and
WHEREAS, the District is developing a sanitary sewage
disposal system and anticipates establishing a sewer collection
system within its boundaries immediately adjacent to the Tukwila
areas hereinafter described; and
WHEREAS, Tukwila has constructed facilities of adequate
capacity and anticipated connection to said facilities by the
District under Tukwila Local Improvement District No. 24,
C
hereinafter referred to as "LID 24 ", of those areas herein
described on Exhibit A, attached hereto; and
WHEREAS, the District is desirous to connect to said
Tukwila facilities from the areas hereinafter described; and
WHEREAS, the District and the residents of the herein-
after described areas desire that sewer collection service be
provided for those areas, and the location of LID 24 and other
topographic conditions make it difficult and expensive for the
District to serve the requirements of the areas to be served; and
C C.
WHEREAS, said conditions make it feasible for the
District to meet the sewage drainage requirements of said areas
to LID 24; and
WHEREAS, the District is desirous of delivering to
Tukwila the sewage collected in said areas for disposal through
its system; and
WHEREAS, to provide for the disposal by the District
of sewage collected in the District areas to be serviced and
hereinafter described, it is necessary that a contract for
these services be entered into now establishing certain rights
and duties of the parties incident thereto,
NOW, THEREFORE, for and in consideration of the mutual
premises and the covenants contained herein, it is agreed as
follows:
1. The area of land described in Exhibit A, all of
which is contained within the District, consists of approximately
1,808,800 square feet. Of this area, Utility Local Improvement
District No. 9, within the District, contains 785,389 square
feet of land and the land remaining exclusive of Utility Local
Improvement District No..9, hereinafter referred to as 'ULID 10 ",
contains 1,023,411 square feet.
2. At such time as any owner of real property within
the area described in Exhibit A, or any portion thereof, elects
to receive sewer service, the District shall pay to Tukwila the
amount of $0.03550786 per square foot of land. The total to be
paid by the District to Tukwila for land within the boundaries
of ULID 9 shall be $27,887.48. The total moneys to be paid by
the District to Tukwila for the balance of the land covered by
this Agreement, exclusive of the area within ULID 9, shall be
• 2
$36,339.07.
3. The District contemplates construction of the
Macadam Road Interceptor as more fully described and set forth
in the document entitled. "Sanitary Sewers Facilities Plan"
• which is dated November, 1976 and which has been partially
funded under the State of Washington, Department of Ecology,
Environmental Protection Agency, Grant No. C- 530806 -01 -0.
Portions of said plan are attached to this Agreement as
Exhibits B and C.
4. As a part of its construction of the sanitary
sewers facilities described in the above paragraph, the
District agrees to: •
A. Construct the Macadam Road Interceptor as near
as practicable to the time schedule contained in Exhibit C, but
no later than three from the date of this Agreement; and
B. Construct the Macadam Road Interceptor at a
proper elevation to accept flow from the Tukwila Pump Station
from gravity thus allowing abandonment of said Pump Station; and
C. Not charge Tukwila any fees for the connection
of the Tukwila Pump Station to the Macadam Road Interceptor as
described on Exhibit B; and
D. Not charge Tukwila operation and maintenance
costs for said Macadam Road Interceptor; and
E. Return to Tukwila all salvagable portions of
the personal property contained within the limits of Tukwila
LID 24 as the sole property of Tukwila; and
F. Pay Tukwila an additional fee to those as
described in Paragraph 1 of this Agreement of $0.02649566 per
square foot of land as described in Exhibit A if the items
c c
3
C
contained in Paragraph 4(A), (B) and (C), or any one of them, are
not fulfilled, completed or performed by District, in whole or in
part.
5. If and only if the District performs all of its
'obligations as set forth in Paragraph 4(A), (B) and (C), the
District will not be charged periodic operation and maintenance
costs for use of Tukwila's LID 24 facilities. lt eke- r!•cn -the. -
4)1 stoic 41- does•awl-0orato4W lliu -f €iiA4- i s- 4c1t0A a ions w -taka-
GU.L.lom; -4 E - &aragrap21- 4(A.. (S} --and. (47} --44 ad-s.4 w4osa m t
- e-- Iliatzlot— shall--p ay- -t,o— Tulv.4 1a•- aa-- acicy]rt,lonaj.— fr6A- .0- thosa-
-a -- descra.bed an Paragzap11- 3. -4 €-t ,is- A,greemer tr-O €48.-416.49.5
.pe .-aquai8�.ciOt�-0,�r• -1a7K3 QCs es4Tr�bec� iii -S i]r�i}fir�rr
6. The District shall have the right and authority
to enter upon the streets, avenues, alleys, roads and public
places of Tukwila, for the purpose of construction work,
making extensions of mains and laterals, connecting same with
service pipes from abutting property, repair equipment and
maintain and operate said lines in Tukwila.
7. The District shall leave all Tukwila streets,
avenues, alleys, roads or public places after laying and install-
ing mains and doing construction work, making repairs to equipment,
etc., in as good and safe a condition in all respects as they
were in before the commencement of such work by the District, its
agents or contractors and to the satisfaction of Tukwila.
In case of any damage to said Tukwila streets, avenues,
alleys, roads or public places, paved roadways, turnouts, gutters,
ditches, sidewalks, drain pipes, hand or embankment rails or
bridges by the District, the District agrees to immediately
repair said damage at its sole cost and expense.
4
•
8. The District hereby agrees for itself, its
successors or assigns, to indemnify, protect, save and hold
harmless Tukwila from all claims, actions or damages of every
kind and description which may accrue to or be suffered by any
.person or persons, corporation or property by reason of any faulty
construction, defective material or equipment or maintenance, or
by the improper occupation of said Tukwila right -of -way, by the
District or by reason of the neglect, improper or faulty manner
of safeguarding any excavations, temporary turnouts, or
inefficient operations by the District of sewer pipe over said
streets, avenues, alleys, roads and public places as herein -
before designated, and in case that suit or action is brought
against Tukwila for damages arising out of or by reason of the
above - mentioned cause, the District, its successors or assigns,
will, upon notice to it or them of the commencment of said
action, defend the same at its sole cost and expense and in
case judgment shall be rendered against Tukwila in suit or
actions, will fully satisfy said judgment within ninety (90)
days after said suit or action shall have finally been deter-
mined, if determined adversely to Tukwila.
The District hereby agrees for itself, its successors
and assigns, to repair any damage to the roads over which it
holds a franchise in Tukwila and all other improvements caused
by the failure of the District's work during the life of this
Agreement.
Failure on the part of the District to promptly
repair the damaged work in Tukwila upon notice to do so shall
be warrant for Tukwila to make necessary repairs and charge
the same to the District at the reasonable cost thereof.
5
•
Acceptance of the work by Tukwila at the time of
completion shall be no defense for avoidance of this covenant.
Provided that the District, its successors or assigns, shall
have the right to• employ its or their own counsel in any cause
or action and by given the exclusive management of the defense
thereof.
9. The' District shall collect all of the sewage in
said areas in the same manner as the sewage is collected for
disposal in other areas of the District.
The additions, improvements, repairs and maintenance
made to the sewage collection facilities provided for said
areas shall be at the,sole discretion and determination of
the District as to the kind, type, manner and time except as
specifically covered by this Agreement.
10. The laying, construction, maintenance and opera-
tion of the District's system of sewer pipe, laterals, service
pipe, etc., granted under this Agreement shall not preclude
Tukwila, its accredited agents or contractors, from blastings,
grading or doing other necessary road work contiguous to the
said District's pipe lines, provided that the District shall
have twenty -four (24) hours' notice of said blasting or excava-
ting in order that the District may protect its lines of pipe
and property. Tukwila shall be liable to the District for any
negligent acts damaging said system in the performance of the
aforesaid road work, or any costs necessitated by the relocation
of sewer lines due to said road work.
11. Property owners within the areas of Tukwila who
have met the requirements of the District shall be entitled to
connect to the lines of the District at such time as they are
6
completed and are approved to receive sewage within said area.
Said connections shall be accomplished at the expense of the
property owner and in accordance with the rules and regulations
of the District and the ordinances of Tukwila, with points of
connection being determined by the District.
12. Property owners connecting to said lines shall
be required to obtain from the District and Tukwila such
permits or licenses for connection as are generally required
throughout the District and Tukwila.
13. Upon completion of the facilities for the areas
of Tukwila to be serviced, the District shall have the sole
duty and obligation to operate, maintain, repair and replace
such facilities.
14. Neither party shall have the right to assign
this Agreement or any of its rights and obligations hereunder
either by operation of law or by voluntary agreement without the
written consen', of either party and neither party may terminate
its obligations hereunder by dissolution or otherwise without
first securing the written consent of the other party and this
Agreement shall be binding upon and inure to the benefit of the
respective successors and assigns of the parties hereto.
15. This Agreement shall be in full force and effect
and binding upon the parties hereto, their successors and
assigns, agents, employees, subcontractors, sublessors, inde-
pendent contractors, and any and all other parties working for
or under the direction of said parties, upon the execution of
this Agreement and shall continue in full force and effect
until such time as this Agreement is terminated by mutual
assent.
7
16. Whenever, in this Agreement notice is required
to be given, the same shall be given by certified mail addressed
to the respective parties at an address hereafter designated in
writing by either of the parties. The date of giving such notice
.shall be deemed to be the date of mailing thereof.
17. This Agreement may be executed in six counterparts,
any of which shall be regarded for all purposes as one original.
DATED the day and year first above written.
CITY OF TUKWILA
By 4• giead By
Edgar r lb. Bauch, Mayor Andy mkus, Commissioner
ATTEST:
By
axine Anderson
City Clerk
APPROVED AS TO FORM:
By
Lawrence E. Hard
Deputy City Attorney
VAL VUE SEWER DISTRICT
By % /5E ,
Betty , Cow sinner
By.
B. W. Butters, Commissioner
ATTEST:
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exhibit b
macadam road interceptor
•
PHASING
9 -1
rnu.v.�aaa� Ytr+c.:+a�neri•'erraK .Mf'tttrYti `,:FYYV:. {in ?
The component projects will be committed to separate time schedules.
All scheduling of Steps . 2 $ 3 is dependent upon the individual
projects receiving sufficiently high pr-iord.ty- rating- from -the
DOE- far -F -Y -197 -and upon funds being available for continuation
of the Wastewater Treatment. Works Grant Program. Grant appli-
c2*_ions..for Steps 2 f, 3 will be submitted separately for each of
the four coral, :: Jnt rr ^5e.Ctz • T.h.e following cons cl i-a r-pia &in•g..
is anticipated:
Phase 1 - Macadam Road Interceptor. Construction of
the Macadam Road Interceptor should be possible during
the 2nd half of 1977. This project has highest priority
due to the severity of septic tank overflows within
its service area. $.500-,004-in-HUD-grant-funding
being- reserved_to- construct sewage- co•1•lection- systems
wi•t•kin- Sub-Bassi - 2'. The commitment of $300,000 of this
funding is contingent upon construction of the Macadam
Road Interceptor. Table 9 -1 is the anticipated time schedule
for the interceptor assuming Step 2 prioritization
by December, 1976.
E.,;.M'U►t 1�4
h;4 c,(_:
Although. Step One of the Wastewater Treatment, Construction Grants
Program for the entire scope of work contained in this document has
been the responsibility of the.Val Vue Sewer District, Steps Two
and Three for the component projects will he divided between
METRO and Val Vue. NE-TRO -. has- assumed -the- responsibility-- for__the
Val-Vue- Gonneetron- as the area_for this- project_exceeds
1000 -- acres. Val Vue will complete Steps' Two and Three for the Macadam
Road, Rainier Vista and Riverton Interceptor Projects.
• 1
..1
-_j
JUN
JUL1AUGISEP 13CT (NOV IDEC JAN
STEP 1 FACILITY PLAN
1976
FEB
TABLE 9-1
'1AR
APR
STEP 2
PLANS &
SPECS
9-2
MAY
JUN
1977
JUL
REVIEW
PLANS&
SPECS
AUG
BID
PROCESS
%Gt
PAGe 2-
SEP
z
0.
0
C4
OCT
NOV
DEC
• STEP 3 '
CONSTRUCTION
PHASE 1
Prior to the construction of the Val Vue Connection, the
Macadam Road Interceptor will be connected to the Interurban
Interceptor.
Phase II --Cont-ingent-upon -
rating-
and
FY-19781
SEPA DOCUMENTATION
ENVIRONMENTAL CHECKLIST
A. BACKGROUND
1. Name of proposed project, if applicable:
City of Tukwila
1991 Comprehensive Sewer System Plan, including Supplement A - Annexation Areas.
2. Name of applicant:
City of Tukwila.
3. Address and phone number of applicant and contact person:
Ross Earnst, Director of Public Works
6300 Southcenter Blvd.
Tukwila, Washington 98188
(206) 433 -0179
4. Date checklist prepared:
November 15, 1991.
5. Agency requesting checklist:
City of Tukwila.
6. Proposed timing or schedule (including phasing, if applicable):
A suggested Capital Improvement Schedule is included in Chapter 6 of the Base Sewer System
Plan and Chapter 5 of Supplement A - Annexation Areas. Specific timing of improvements will
depend on the availability of funding, scheduling of developer extensions and sewer system
demands.
7. Do you have any plans for future additions, expansion, or further activity related to or
connected with this proposal? If yes, explain.
Please refer to Chapter 6 of the base plan and Chapter 5 of the supplement for detailed
information on future improvements contemplated for the Tukwila sewer system. The sewer system
plan does not propose any land use expansions or changes and only considers the system
improvements which are required to meet existing and projected sewer system flows.
8. List any environmental information you know about that has been prepared, or will be
prepared, directly related to this proposal.
None Known.
9. Do you know whether applications are pending for governmental approvals of other proposals
directly affecting the property covered by your proposal? If yes, explain:
None Known.
10. List any government approvals or permits that will be needed for your proposal, if known.
Tukwila City Council Approval.
State of Washington Department of Ecology review.
11. Give brief, complete description of your proposal, including the proposed uses and the size
of the project and site. There are several questions later in this checklist that ask you to describe
certain aspects of your proposal. You do not need to repeat those answers on this page. (Lead
agencies may modify this form to include additional specific information on project description.)
This proposal contemplates the adoption of the City of Tukwila 1991 Comprehensive Sewer System
Plan, with Supplement A - Annexation Areas. These documents address future sewer service to
all areas of the existing Tukwila city limits and propose a capital improvements schedule for
system improvements in accordance with sewer system flow projections developed as part of the
Plan.
12. Location of the proposal. Give sufficient information for a person to understand the precise
location of your proposed project, including a street address, if any, and section, township, and
range, if known. If a proposal would occur over a range of area, provide the range or boundaries
of the site(s). Provide a legal description, site plan, vicinity map, and topographic map, if
reasonably available. While you should submit any plans required by the agency, you are not
required to duplicate maps or detailed plans submitted with any permit applications related to this
checklist.
The Ciry of Tukwila is generally located south of the Ciry of Seattle, east of the City of Sea Tac
and west of the Ciry of Renton as indicated on Figure 1 -1 of the Plan. The City is within all or
part of the following Sections: Section 33, Township 24 North; and, Sections 3, 4, 9, 10, 14, 15,
22, 23, 24, 25, 26, 35, and 36, Township 23 North, Range 4 East.
B. ENVIRONMENTAL ELEMENTS
1. Earth
a. General description of the site (circle one): Flat, rolling, hilly, steep slopes,
mountains, other
Topography of the area is characterized by the flat topography of the Duwamish River
Valley floor, with slopes leading up to a plateau in the western portion of the City.
b. What is the steepest slope on the site (approximate percent slope)?
Not Applicable.
c. What general types of soils are found on the site (for example, clay, sand, gravel,
peat, muck)? If you know the classification of agricultural soils, specify them and note
any prime farmland.
The majority of the area consists of alluvial soils composed of silt, clay and some peat
with some bedrock outcroppings.
d. Are there surface indications or history of unstable soils in the immediate vicinity?
If so, describe.
Unstable soils may occur along the banks of the Duwamish River or in steep slopes
leading to the valley floor.
2. Air
e. Describe the purpose, type, and approximate quantities of any filling or grading
proposed. Indicate source of fill.
Not Applicable.
f. Could erosion occur as a result of clearing, construction, or use? If so, generally
describe.
Not Applicable.
g. About what percent of the site will be covered with impervious surfaces after project
construction (for example, asphalt or buildings)?
Not Applicable.
h. Proposed measures to reduce or control erosion, or other impacts to the earth, if any:
Not Applicable.
a. What types of emissions to the air would result from the proposal (i.e., dust,
automobile, odors, industrial wood smoke) during construction and when the project is
completed? If any, generally describe and give approximate quantities if known.
Not Applicable.
b. Are there any off -site sources of emissions or odor that may effect your proposal?
If so, generally describe.
Not Applicable.
c. Proposed measures to reduce or control emissions or other impacts to air, if any:
Not Applicable.
3. WATER
a. Surface:
1) Is there any surface water body on or in the immediate vicinity of the site
(including year -round and seasonal streams, saltwater, lakes, ponds, wetlands)?
If yes, describe type and provide names. If appropriate, state what stream or
river it flows into.
The Green Duwamish River flows through the City of Tukwila as indicated on the
maps included in the Plan. Other small streams and wetland areas are within the
city limits. This proposal does not impact any surface waters.
2) Will the project require any work over, in, or adjacent to (within 200 feet)
Not Applicable.
No.
No.
the described waters? If yes, please describe and attach available plans.
Not Applicable. This proposal contemplates adoption of the Plan only. Specific
project construction documents will address surface water considerations as
required.
3) Estimate the amount of fill and dredge material that would be placed in or
removed from surface water to wetlands and indicate the area of the site that
would be affected. Indicate the source of fill material.
4) Will the proposal require surface water withdrawals or diversions? Give
general description, purpose, and approximate quantities if known.
5) Does the proposal lie within a 100 -year floodplain? If so, note location on
the site plan.
Not Applicable. This proposal does not contemplate any activity relating to
floodplains.
6) Does the proposal involve any discharges of waste materials to surface
waters? If so, describe the type of waste and anticipated volume of discharge.
No.
b. Ground
1) Will ground water be withdrawn, or will water be discharged to ground
water? Give general description, purpose, and approximate quantities if known.
2) . Describe waste material that will be discharged into the ground from septic
tanks or other sources, if any (for example: Domestic sewage; industrial,
containing the following chemicals ... agricultural; etc.). Describe the general
size of the system, the number of such systems, the number of houses to be
served (if applicable), or the number of animals or humans the system(s) are
expected to serve.
None.
c. Water Runoff (including storm water):
1) Describe the source of runoff (including storm water) and method of
collection and disposal, if any (include quantities, if known). Where will this
water flow? Will this water flow into other waters? If so, describe.
Not Applicable.
4. PLANTS
2) Could waste materials enter ground or surface waters? If so, generally
describe.
Not Applicable.
d. Proposed measures to reduce or control surface, ground, and runoff water impacts,
if any:
This Comprehensive Plan has been developed to address the provision of sanitary sewer
service to all areas of the City. Provision of such service will protect surface and ground
water quality by reducing the hazards associated with on -site sewage disposal.
a. Check or circle types of vegetation found on the site:
X deciduous tree: alder, maple, aspen, other
X evergreen tree: fir, cedar, pine, other:
X shrubs,
X grass
X pasture
crop or grain
X wet soil plants: cattail, buttercup, bulrush, skunk cabbage, other
water plants: water lily, eelgrass, milfoil, other
_ other types of vegetation:
b. What kind and amount of vegetation will be removed or altered?
None.
c. List threatened or endangered species known to be on or near the site.
None Known.
d. Proposed landscaping, use of native plants, or other measures to preserve or enhance
vegetation on the site, if any:
Not Applicable.
5. ANIMALS
a. Circle any birds and animals which have been observed on or near the site or are
known to be on or near the site:
birds: hawk, heron, eagle, songbirds, other:
mammals: deer, bear, elk, beaver, other:
fish: bass, salmon, trout, herring, shellfish, other:
b. List any threatened or endangered species known to be on or near the site.
None Known.
c. Is the site part of a migration route? If so, explain.
Puget Sound Flyway.
d. Proposed measures to preserve or enhance wildlife, if any:
Not Applicable.
6. ENERGY AND NATURAL RESOURCES
a. What kinds of energy (electric„ natural gas, oil, wood stove, solar) will be used to
meet the completed project's energy needs? Describe whether it will be used for heating,
manufacturing, etc.
Operation of the Tukwila sewer system requires the use of electricity and water.
b. Would your project affect the potential use of solar energy by adjacent properties?
If so, generally describe.
No.
c. What kinds of energy conservation features are included in the plans of this proposal?
List other proposed measures to reduce or control energy impacts, if any:
Future sewer system projects have been designed to minimize the use of energy for
pumping of sewage flows.
7. ENVIRONMENTAL HEALTH
a. Are there any environmental health hazards, including exposure to toxic chemicals,
risk of fire and explosion, spill, or hazardous waste, that could occur as a result of this
proposal? If so, describe.
There is a minimal hazard associated with the operation of sanitary sewer systems.
1) Describe special emergency services that might be required.
Sewer system monitoring and emergency response procedures are employed by the
City in accordance with the State Department of Ecology requirements.
2) Proposed measures to reduce or control environmental health hazards, if any:
Provision of sanitary sewer service is in itself a mitigation measure for protection
of the environment.
b. Noise
1) What types of noise exist in the area which may affect your project (for
example: traffic, equipment, operation, other)?
Not Applicable.
2) What types of levels of noise would be created by or associated with the
project on a short -term or a long -term basis (for example: traffic, construction,
operation, other)? Indicate what hours noise would come from the site.
None.
3) Proposed measures to reduce or control noise impacts, if any:
None Required.
8. LAND AND SHORELINE USE
a. What is the current use of the site and adjacent properties?
The existing land use of the area is identified in Chapter 2 of the Base Plan and
Supplement A - Annexation Areas. As indicated, land use within the City of Tukwila
ranges from single and multi family residential uses to Boeing Field airfield. Southcenter
Shopping Center is a regional shopping area located in the heart of Tukwila. Other
commercial, industrial and warehouse uses also exist in the Southcenter area.
b. Has the site been used for agriculture? If so, describe.
Not Applicable.
c. Describe any structures on the site.
Not Applicable.
d. Will any structures be demolished? If so, what?
No.
e. What is the current zoning classification of the site?
Zoning is consistent with land use and is identified in Chapter 2 of the Base Plan and
Supplement A.
f. What is the current comprehensive plan designation of the site?
Please refer to Chapter 2 of the Base Plan and Supplement A. Comprehensive Plan
designations reflecting the diverse land uses within the City are appropriately assigned.
g. If applicable, what is the current shoreline master program designation of the site?
Not Applicable.
h. Has any part of the site been classified as an "environmentally sensitive area? If so,
specify.
Sensitive areas are identified by the City of Tukwila Department of Community
Development. This Comprehensive Water System Plan will not impact such areas.
i. Approximately how many people would reside or work in the completed project.
Not Applicable.
j. Approximately how many people would the completed project displace?
None.
9. HOUSING
k. Proposed measures to avoid or reduce displacement impacts, if any:
Not Applicable.
1. Proposed measures to ensure the proposal is compatible with existing and projected
land uses and plans, if any:
This Comprehensive Sewer System Plan was developed to address the future sewer system
needs of the City of Tukwila based on existing and projected land use patterns and
associated sewer system capacity requirements.
a. Approximately how many units would be provided, if any? Indicate whether high,
middle, or low - income housing.
None.
b. Approximately how many units, if any, would be eliminated? Indicate whether high,
middle, or low- income housing.
None.
c. Proposed measures to reduce or control housing impacts, if any:
Not Applicable.
10. AESTHETICS
a. What is the tallest height of any proposed structure(s), not including antennas: what
is the principal exterior building material(s) proposed?
Not Applicable.
b. What views in the immediate vicinity would be altered or obstructed?
None.
c. Proposed measures to reduce or control aesthetic impacts, if any:
Not Applicable.
11. LIGHT AND GLARE
Not Applicable.
a. What type of light or glare will the proposal produce? What time of day would it
mainly occur?
None.
b. Could light or glare from the finished project be a safety hazard or interfere with
views?
c. What existing off-site sources of light or glare may affect your proposal:
Not Applicable.
d. Proposed measures to reduce or control light and glare impacts, if any:
Not Applicable.
12. RECREATION
a. What designated and informal recreational opportunities are in the immediate vicinity.
Not Applicable.
b. Would the proposed project displace any existing recreational uses? If so, describe.
No.
c. Proposed measures to reduce or control impacts on recreation, including recreation
opportunities to be provided by the project or applicant, if any:
Not Applicable.
13. HISTORIC AND CULTURAL PRESERVATION
a. Are there any places or objects listed on, or proposed for, national, state, or local
preservation registers known to be on or next to the site? If so, generally describe.
Not Applicable.
b. Generally describe any landmarks or evidence of historic, archaeological, scientific,
or cultural importance known to be on or next to the site.
Not Applicable.
c. Proposed measures to reduce or control impacts, if any:
Not Applicable.
14. TRANSPORTATION
a. Identify public streets and highways serving the site, and describe proposed access to
the existing street system. Show on site plans, if any.
See Figure 1 -1 and 2 -1 of the Base Plan and Supplement A - Annexation Areas.
Interstate Highways 5 and 405, the Burlington Northern Railroad, and State Route 99
bisect the City.
b. Is site currently served by public transit? If not, what is the approximate distance to
the nearest transit stop?
Not Applicable.
c. How many parking spaces would the completed project have? How many would the
project eliminate?
None.
d. Will the proposal require any new roads or streets, or improvements to existing roads
or streets, not including driveways? If so, generally describe (indicate whether public or
private).
No.
e. Will the project use (or occur in the immediate vicinity of) water, rail, or air
transportation? If so, generally describe.
No.
f. How many vehicular trips per day would be generated by the completed project? If
known, indicate when peak volumes would occur.
None.
g. Proposed measures to reduce or control transportation impacts, if any:
Not Applicable.
15. PUBLIC SERVICES
a. Would the project result in an increased need for public services (for example: fire
protection, police protection, health care, school, other)? If so, generally describe.
No.
b. Proposed measures to reduce or control direct impacts on public services, if any.
Not Applicable.
16. UTILITIES
a. Circle utilities currently available at the site: electricity, natural eas, water, refuse
service, telephone, sanitary sewer, septic system, other.
b. Describe the utilities that are proposed for the project, the utility providing service,
and the general construction activities on the site or in the immediate vicinity which might
be needed.
This proposal establishes a plan for the future development of sewer systems within the
City of Tukwila and assures that adequate facilities are provided to meet projected sewer
system capacity requirements.
C. SIGNATURE
The above answers are true and complete to the best of my knowledge. I understand that the lead
agency is relying on them to make its decision.
Signature:
Date Submitted:
D. SUPPLEMENTAL SHEET FOR NONPROJECT ACTIONS
1. How would the proposal be likely to increase discharge to water; emissions to air; production,
storage, or release of toxic or hazardous substances; or production of noise?
No Increases.
Proposed measures to avoid or reduce such increases are:
Not Applicable.
2. How would the proposal be likely to affect plants, animals, fish or marine life?
No Impacts.
Proposed measures to protect or conserve plants, animals, fish or marine life are:
None Necessary.
3. How would the proposal be likely to deplete energy or natural resources?
Construction of new sewer facilities will require the use of construction materials typical to this
type of construction.
Proposed measures to protect or conserve energy or natural resources are:
Efficient planning and design of utilities and minimizing the use of pump stations will assist in
conservation of energy.
4. How would the proposal be likely to use or affect environmentally sensitive areas or areas
designated (eligible or under study) for governmental protection; such as parks, wilderness, wild
and scenic rivers, threatened or endangered species habitat, historic or cultural sites, wetlands,
floodplains, or primelands?
This proposal will not impact any of the above listed areas.
Proposed measure to protect such resources of to avoid or reduce impacts are:
Any future work done on the Tukwila sewer system will be consistent with the regulations and
policies governing the protection of such resources.
5. How would the proposal be likely to affect land and shoreline use, including whether it would
allow or encourage land or shoreline uses consistent existing plans?
This proposal will not affect, allow or encourage land and shoreline uses.
Proposed measures to avoid or reduce shoreline and land use impacts are:
Not Applicable.
6. How would the proposal be likely to increase demands on transportation or public services
and utilities?
This proposal will not impact demands on transportation or public utilities but will provide a
guideline for future development of the City's sewer system.
Proposed measures to reduce or respond to such demands are:
Not Applicable.
7. Identify, if possible, whether the proposal may conflict with local, state or federal laws
requirements for the protection of the environment.
This proposal is not in conflict with any such laws.
�
SANITARY SEWER SYSTEM CONSTRUCTION STANDARDS
CITY OF TUKWILA
PUBLIC WORKS SEWER CONSTRUCTION
AND DEVELOPMENT STANDARDS
Pat Brodin
Dave Grage
Scott Moore
MAYOR
Gary L. Van Dusen
COUNCIL MEMBERS
Joe H. Duffie Joan Hernandez
Dennis L. Robertson Clarence B. Moriwaki
Allen E. Ekberg Steve Lawrence
John "Wally" Rants
PREPARED BY PUBLIC WORKS DEPARTMENT STAFF
Phil Fraser
Ross Heller
Kee -hoon Pak
Greg Villanueva
Ross Earnst, Director Ron Cameron, City Engineer
Ted Freemire, Superintendent Div. I
Bob Giberson
John Howat
Brian Shelton
August 6, 1990
TABLE OF CONTENTS
DEFINITIONS 1
DEVELOPER EXTENSION AGREEMENTS 3
CONNECTION CHARGES
SANITARY SEWERAGE COLLECTION SYSTEM 4
CONSTRUCTION PERMITS AND AUTHORIZATION 13
PERMITS: DESIGN STANDARDS FOR PLAN SUBMITTALS 14
CONSTRUCTION ON EASEMENTS 15
TESTING OF SANITARY SEWERS 15
AIR TESTING 15
T.V. INSPECTION 15
INDEX OF SANITARY SEWER STANDARD PLANS (S1 THROUGH S11).... 16
3
SANITARY SEWERAGE SYSTEM DESIGN STANDARDS 4
COMPREHENSIVE SEWERAGE PLAN 5
SERVICE AREA CONSIDERATIONS 5
EXTENT OF SEWER IMPROVEMENTS 5
SEWER SEPARATION FROM WATER SYSTEMS 6
SEWER SEPARATION FROM WELLS 6
SEWER DIAMETER REQUIREMENTS 6
SEWER MAIN DEPTH 6
ROUGHNESS COEFFICIENT 6
SANITARY SEWER SLOPES 7
ALIGNMENT 7
SANITARY SEWER MANHOLES 8
STREAM CROSSINGS 9
SANITARY SIDE SEWERS 9
SIDE SEWER DESIGN 9
CONNECTION TO CITY SEWER SYSTEM 10
GREASE TRAPS 10
SANITARY SEWER SYSTEM MATERIALS 12
GRAVITY SEWER PIPE 12
FITTINGS 12
MANHOLES 12
FRAMES AND COVERS 12
LADDERS AND STEPS 12
DROP CONNECTIONS 12
TRENCH EXCAVATION 13
PIPE BEDDING 13
BACKFILL 13
DEFINITIONS
These definitions are a supplement to Section 14.16.010 of the City of
Tukwila Municipal Code.
APWA SPECIFICATIONS - shall have reference to standard specifications
for municipal public works construction prepared by the
Washington State Chapter of the American Public Works Association
and the State of Washington for the current edition as adopted by
the City of Tukwila.
ASTM - American Standards for Testing Materials.
COMMERCIAL AND INDUSTRIAL SEWAGE SERVICE - Sewage collection and /or
sewage disposal service furnished, or available to the use or
premises used or engaged in the selling, manufacturing,
processing, and /or dispensing of products or services, or
otherwise catering to the public.
CROSS - CONNECTION - Any physical arrangement whereby a public water
supply is connected, directly or indirectly, with any other water
supply system, sewer, drain, conduit, pool, storage reservoir,
plumbing fixture or other device which contains or may contain
contaminated water, sewage or other wastes or liquids of unknown
or unsafe quality, which may be capable of imparting
contamination to a public water supply as a result of backflow.
DIRECTOR - The Director of Public Works for the City of Tukwila or his
duly authorized representative.
DOE - State Department of Ecology.
DSHS - State Department of Social and Health Services.
HEALTH OFFICER - The Director of Public Health of the Seattle-King
County Department of Public Health or his duly authorized
representative.
METRO - Regional organization responsible for the collection and
treatment of sewage.
MUTCD - Manual on Uniform Traffic Control Devices, latest edition. All
street closures and traffic detours shall be signed, coned and
flagged according to this manual.
OSHA - Occupational Safety and Health Administration.
RECIPIENTS OF SERVICE - All property owners within the City, within
the area served by the sewerage system of the City are hereby
required and shall be compelled to connect their private drains
and sewers with the sewerage system of the City, and it is
• unlawful for any property owner to fail or refuse to make such
connections.'
1
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DEVELOPER EXTENSION AGREEMENTS
A. When extension of the existing sewer system is required for
service, a developer extension agreement shall be entered into
between the owner and the City.
B. Developer's agreements shall be approved by the Public Works
Director and appropriate elected officials prior to issuance of
any permits.
C. To initiate the developer extension process, the owner must
submit an application for utility permits along with property
legal description and six sets of site improvement plans. Upon
completion of design review by the City, approved design plan and
a preconstruction letter of requirements will be sent to the
owner. The owner shall resubmit plans for final approval, if
required. The contractor shall work off of the City approved plan
only. After completion of construction, turnover documents will
be provided to the City along with a request for turnover of the
constructed public facilities. These proposed public facilities
will be accepted through the City council or the Mayor's office
only, and if rejected, will remain the sole property and
maintenance responsibility of the developer. The turnover of
proposed public facilities is not tied to the certificate of
occupancy, and remains the sole responsibility of the developer
to provide the necessary documentation to allow consideration for
such turnover through the City's elected officials.
D. Easements for mainline sewer systems shall be a minimum of 10
feet wide. Easement legal descriptions shall be prepared by a
surveyor or engineer licensed to practice in the State of
Washington. Easement legal descriptions shall be reviewed and
approved by the City prior to acceptance. Only the Mayor or City
council accepts new facilities for the public.
E. Developer extension projects shall be deeded to the City for
maintenance and operations by bill of sale.
CONNECTION CHARGES
All property benefitting from existing sewer facilities shall pay the
following applicable connection charges, at the current rates, as
specified in the Tukwila Municipal Code:
i A. Permit: Plan /Inspection fee charge
I B. Regular connection charge
.
C. Special connection charges for the development's contribution to
the City's mains as specified in the Tukwila Municipal Code.
Refer: T.M.C. 14.16.072, 14.16.074 and 14.16.076.
To determine these fees, an owner is required to supply a legal
the plan submittal.
- 3
D. Latecomer's agreement authorized:
1. The City may enter into agreements with property owners who
have installed sewer mains and appurtenances in order to
provide for the reimbursement to owners of a fair prorated
share of any real estate who have not contributed to the
original cost of such facilities and who subsequently
connect to the sewerage system or use same.
2. Such agreements shall be entered into at the time of or
before the acceptance of the sewerage system by the City.
The Public Works Department shall determine the prorated
share in one payment from the benefitting properties, based
on a cost determined at the time of acceptance of the
facility. Seventeen percent (17 %) charge for administrative
costs at the time of application for service shall be
applied for the handling of this assessment.
F. METRO capacity charge.
To determine these fees, an owner is required to complete the
METRO Sewer Use Certification form, and return copies to METRO
and the local sewer agency.
SANITARY SEWERAGE COLLECTION SYSTEM
These specifications are the minimum criteria and standards for
sanitary sewerage collection systems to be accepted by the City of
Tukwila. The requirements herein apply equally to sewer systems to be
privately owned (side sewer, private main) as well as to public
systems (mainline extensions). Septic systems shall conform to King
County standards and be approved through the King County Health
Department, Environmental Health Division.
SANITARY SEWERAGE SYSTEM DESIGN STANDARDS
In general, all sanitary sewerage systems, whether public or private,
shall conform to the design requirements of the criteria for sewerage
works designed by the State of Washington, D.O.E., D.S.H.S., as well
as all Metro and City of Tukwila design requirements. Criteria for the
sewage works design as published in 1978 (revised 1980) by the State
of Washington State Department of Social and Health Services
(D.S.H.S.) and the Environmental Protection Agency (E.P.A.) sets forth
guidelines and standards of applicable minimum requirements for sewer
systems. All related code requirements of the Tukwila Municipal Code
shall be met in the design and construction of any element of the
sewerage system within the City of Tukwila, including Chapter 14 of
the T.M.C. and standards outlined in this construction manual.
Sewerage waste disposal systems shall conform to King County standards
as adopted under Chapter 14.08 of the T.M.C.
4
SERVICE AREA CONSIDERATIONS
COMPREHENSIVE SEWERAGE PLAN
The City of Tukwila has developed a comprehensive sewerage plan to
allow for the orderly and cost effective development of sewerage
facilities to serve existing and future users of the Tukwila sewer
system. One element of the comprehensive plan is a map of proposed
sewer extensions to service areas presently without sewers. The
comprehensive plan of proposed extensions indicates the general
location of interceptor and trunk sewers, intended to provide the
framework for the collection system for upgrading deficient sewerage
systems and also to allow for final buildout of the City and for the
potential service area. All proposed sewer improvements and extensions
shall be consistent with the comprehensive sewer plan, as well as with
the comprehensive land use plans for the City of Tukwila.
All sewer extensions shall be designed for the ultimate development of
the potential service area in accordance with the current land use
plans and the comprehensive sewer plan. The determination of the
tributary area shall be based on the comprehensive sewer plans adopted
by the City of Tukwila and detailed studies of the areas affected.
New sewer systems shall be designed on the basis of per capita flows
or other methods as approved by the City and D.O.E. Detailed design
calculations and service area maps shall be required for the system
design. Said calculations shall be certified by a professional
engineer.
Special consideration must be given to sanitary sewer extensions for
industrial districts. The potential for pretreatment requirements,
excessive sewage flows or special flow metering or sampling
requirements must be considered prior to industrial sewer collection
system designs.
EXTENT OF SEWER IMPROVEMENTS
In general, a developer shall be required to extend the sanitary sewer
improvements to the extreme boundary of his property in accordance
with the comprehensive plans. The extension shall be of size and grade
to be extended in the future as required by the plan. In cases where
the plan does not require future extension, the sewer shall be
extended as required to service that affected property.
In cases where required extension of the sewer is beyond the needs for
the development, and other benefitting properties can be identified,
the developer may be able to arrange through a developer's agreement
for partial reimbursement at the time of other developments. Any such
arrangement must be agreed to in writing through the City prior to
acceptance of the system as public through the City council and /or
Mayor.
5
SEWER SEPARATION FROM WATER SYSTEMS
A. HORIZONTAL SEPARATION:
All sanitary sewers shall be located at least 10 feet
horizontally from any existing or proposed water main. Said
separation shall be measured from the outside edges of the pipes.
Should local conditions prevent the required separation, the
sewer main shall be located below and no closer than 4 feet
horizontally from the water main. Said sewer shall be constructed
of cast iron or ductile iron pipe with mechanical joint fittings.
B. VERTICAL SEPARATION:
All sanitary sewer crossings under water mains shall be laid at
such an elevation that the top of the sewer pipe in a minimum of
18 inches below the bottom of the water main. In cases where said
clearance cannot be achieved, the water mains shall be relocated
to provide the required clearance, or the sewer shall be
constructed with ductile iron pipe, cast iron pipe, or
prestressed concrete cylinder pipe with mechanical joints, for a
distance of 10 feet on either side of the water main.
SEWER SEPARATION FROM WELLS
No sanitary sewer shall be constructed within 100 feet of a potable
water supply well or other water source.
SEWER DIAMETER REOUIREMENTS
MAINS. The minimum size of sanitary sewer mains to be accepted by the
City of Tukwila shall be eight inches (8 ") in diameter. Larger
diameter sewers shall be required where indicated on the comprehensive
plans or where design studies indicate larger sizes are required to
minimize grades.
SIDE SEWERS. All commercial side sewers shall be a minimum diameter
of six inches (6 "). All residential side sewers shall be a minimum of
four inches (4 ").
SEWER MAIN DEPTH
All sewer mains shall be buried deep enough to provide adequate depth
to service the lowest fixtures in the properties served. In any case,
the minimum depth of cover for a sewer in street right -of -way is four
feet (4').
ROUGHNESS COEFFICIENT
An 'N' value of 0.013 shall be used in Manning's formula for the
design of all sewer facilities.
6
SANITARY SEWER SLOPES
All sanitary mains shall be designed and constructed to give mean
velocities, when flowing at the maximum rated flow per the designed
flow from the service area of not less than 2.0 feet per second. The
following minimum slopes should be provided; however, slopes greater
than these are desirable. Steeper slopes will give higher velocities
which reduce maintenance, especially in sewers not running full.
ALIGNMENT
SEWER SIZE MINIMUM SLOPE
(INCHES) (FEET PER 100 FEET)
4 2.00 Side Sewer Only
6 0.60 Side Sewer Only
8 0.40
10 0.28
12 0.22
14 0.17
15 0.15
16 0.14
18 0.12
21 0.10
24 0.08
27 0.07
30 0.06
36 0.05
Sewers shall be laid with uniform slope between manholes. Sewers of
20% slope or greater shall be anchored securely with concrete anchors,
approved by the City.
All sewers shall be designed with a straight alignment between
manholes. Rates of curvature must be within the manufacturer's
tolerances for the particular pipe used.
7
B. OUTSIDE DROP CONNECTIONS
C. CONNECTIONS
D. STANDARD MANHOLES
E. CHANNELIZATION
SANITARY SEWER MANHOLES
A. LOCATION:
Sanitary sewer manholes are required at the following locations:
1. End of all sewer mains, including end reaches over 150 1.f. in
length (mains less than 150 1.f. in length may be provided with
clean outs in lieu of a manhole at upper end only).
2. All changes in slope.
3. Changes in pipe diameter.
4. All connections of sewers 8" and larger (including side sewers).
5. At all intersections of sewer mains.
6. Changes in sewer alignment.
7. Manholes shall be located at distances not greater than 500 1.f.
for all sewer mains.
An outside drop connection shall be provided for a sewer entering
a manhole at an elevation of 24 inches or more above the invert
of the outfall invert elevation (measured at the wall of the
manhole - see standard drop connection plans)
All manholes shall be provided with stubs to first joints no more
than 24 inches from the outside face of the manhole barrel.
Manholes shall be designed per the criteria in the Sewer Standard
Plans in the Appendix of this manual. The minimum diameter of
sewer manholes shall be 48 inches for sewer lines up to 21 inch
diameter, 54 inch diameter manholes for sewer lines up to 36 inch
diameter, and 72 inch diameter manholes for pipe sizes up to 42
inch diameter.
All City manholes shall have precast concentric cones. The
maximum heights of the riser section shall be 24 inches,
including the frame and cover. The minimum clean opening in the
manhole frame shall be 23 -3/4 inches (see Standard Plans).
All sanitary sewer manholes shall be fully channeled to the crown
of the sewers. The manholes shall be channeled to accomplish
smooth flow through the transition and to minimize turbulence. To
maintain the energy gradient and velocity through grade changes
and changes in diameter at manholes, the invert of the downstream
- 8 -
manhole shall be designed a minimum of 0.1 foot below all
incoming invert elevations.
F. MANHOLE FOUNDATIONS
Care must be taken to insure that pressures exerted on the soils
beneath the manholes and the adjacent mains are approximately
uniform. Unequal soil pressures may result in excessive
settlement at manholes. A spread foundation or other measures
may be required to reduce the unit load imposed by the manhole.
STREAM CROSSINGS
Sewers entering or crossing streams shall be located at least 5 to 7
feet below the elevation of the stream bed. The sewer shall be
designed to withstand all anticipated loading, erosion impacts and
hydraulic forces. Construction methods and materials shall insure that
the sewers remain water tight and free from changes in alignment or
grade. All pipe under streams shall be D.I.P.
Construction activities in waterways require permits and approvals
from outside agencies. All work in stream crossings shall be scheduled
during the summer months and at times which no conflict with fish runs
occurs. All stream crossings shall be approved through the Public
Works Director. Stream crossings for sewer lines will be discouraged
unless no other alternative is available.
SANITARY SIDE SEWER DESIGN
All sanitary side sewers shall be laid on not less than two percent
(2 %) grade, not more than two vertical to one foot horizontal; shall
not be less than 30 inches (30 ") from any building; shall not have
less than twelve inches (12 ") of cover inside the property line and
shall be not less than six inches (6 ") in diameter from the main
sanitary to the property line. Not more than one house shall be
connected with a lateral sanitary sewer except in certain cases
approved by the Public Works Director; except also, where connection
is to an existing sanitary side sewer within a public street.
All side sewers shall be not less than six inches (6 ") in diameter,
except services to single family residences shall not be less than
four inches (4 ") in diameter from the property line to the building.
All side sewers shall have clean outs located at 100 foot intervals,
and at the termination of the sewer at the building, and all vertical
or horizontal bends in the pipe of 90% or greater. The maximum length
of a 6" side sewer shall be 150 feet (150').
Each lot or parcel of real property within the area to be served with
a sanitary sewage disposal system, upon which such lot or parcel of
property there shall be situated any building or structure for human
occupancy or use for any purpose, shall be provided with a connection
to the public sewer system. Each building or structure shall be
provided with its own sanitary side sewer. Buildings within 250 1.f.
of a sanitary sewer line or lateral shall be deemed to be within the
area served by said sewer; however, a septic system may only be
allowed per the requirements of King County which do not allow for
- 9 -
such where there is a sanitary sewer system within 660 1.f..
The sanitary side sewer shall be designed in'such a manner as to be of
sufficient size to carry all sanitary sewage and waste fluids of any
kind from said buildings in said sanitary sewage system, and each
toilet, sink, stationary wash stand, or any other piece of equipment
having waste fluids, shall be connected with said sanitary sewage
system.
Materials allowable for sanitary side sewer construction are plastic
(PVC minimum schedule 35), concrete where soil conditions permit and
slopes are less than 15 %, ductile iron pipe, C.I. or PVC pipe where
its use is justified due to scouring velocities or other special soils
foundation problems exist. Ductile iron pipe placed in peat areas or
areas of potential corrosion shall be polyethylene encased.
Pipe bedding shall per Standard Plan , or better if soils conditions
warrant. Backfill shall be placed at 12" lifts maximum and compacted
to 95% throughout. For testing of side sewer and permit requirements,
see other sections of this manual.
CONNECTION TO CITY SEWER SYSTEM
In general, each legally defined lot adjacent to a City sewer main
shall be serviced with a six inch side sewer stub. The developer shall
design the side sewer system to utilize the stub supplied.
The City maintains as -built records concerning the location and
approximate depth of side sewer stub. These records are for
informational purposes only and it shall be the developer's
responsibility to verify the location and depth of the existing
services.
In cases where a stub has not been supplied, the developer shall
connect directly to the City main. The developer shall assume all
costs for said connection, including, but not limited to, street
repairs, tapping charges, bonds, permits, etc. Cuts into City streets
shall be repaired per the City's Standard Pavement Patch Plan
(available in the Public Works Department).
Side sewer connections into Metro interceptor sewer lines shall be
allowed only by written permission from Metro. The City will be the
agency through which permits will be obtained for such connections.
The permittee is responsible for all coordinations with Metro for
necessary inspections and approvals.
GREASE TRAPS
Grease traps are required on all buildings where food preparation
occurs; or where, in the opinion of the Public Works Director, they
are necessary for the proper handling of liquid wastes. When
required, Grease traps shall comply with the following:
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..........�......�.... ........�....... ■
Location. The vault shall located outside the building, not closer
than 5' nor farther than 25' from the building foundation.
Design. The tank shall be a double baffle type.
Size. Tank sizing shall be per Appendix H of the Uniform Plumbing
Code; with meals per hour being equal to seating capacity of the
restaurant.
Maintenance. It is the owner's responsibility to clean and maintain
the trap on a regularly scheduled basis (typically monthly). The City
may inspect the trap; and, as the result of such inspection, require
the owner to provide more frequent service.
All grey water (sinks, dishwasher, floor drains, drains under garbage
compactor, etc.), and only grey water, shall be routed through the
trap.
In addition, all grease traps shall comply with section 711 of the
Uniform Plumbing Code.
SANITARY SEWER SYSTEM MATERIALS
GENERAL. All materials used for construction of City of Tukwila
sanitary sewers shall be new and undamaged. All materials used on the
project shall be inspected and approved by the City prior to
installation. Acceptance of the materials by the City shall not
relieve the developer /contractor from the responsibility to guarantee
construction and materials.
All materials and methods referenced herein shall conform to the
applicable standards for materials and construction found in the
"Standard Specifications for Municipal Public Works Construction ",
latest edition, published by the Washington State Chapter of the
American Public Works Association, and the Washington State Department
of Transportation, hereinafter referred to as the APWA /WSDOT Standard
Specifications.
GRAVITY SEWER PIPE. Pipe approved by the City for sanitary mains
includes: plain concrete, reinforced concrete, cast iron, ductile iron
and PVC (polyvinyl chloride) pipe. All sanitary sewer pipe shall be
clearly marked by type, class and /or thickness, as applicable. The
lettering shall be legible and permanent under normal handling and
storage conditions. All sewer pipe shall conform to the applicable
APWA /WSDOT standards for pipe and materials. The supplier shall
provide the City with a certificate for materials, as requested.
FITTINGS. All fittings shall be made of the same materials as the
pipe. All open ends shall be capped or plugged with a plug of
material and gasket approved by the City. All fittings shall be able
to withstand test pressures and loading forces for the specific
application, and conform to applicable standards of the APWA /WSDOT
standard specifications.
MANHOLES. All manholes shall be precast and in conformity with City
Standard Plans. Sanitary sewer manholes shall also be constructed in
accordance with APWA /WSDOT standard specifications and details. The
contractor /developer shall provide the City with the certification of
materials and shop drawing for manholes, as requested.
FRAMES AND COVERS. Manhole frames and covers shall be cast iron only
and conform to the City Standard Plan, and applicable APWA /WSDOT
standard specifications. All manhole covers located outside the
street section shall have locking lids.
LADDERS AND STEPS. All manholes shall have ladders and safety steps
designed per City Standard Plans and applicable APWA /WSDOT standard
specifications.
DROP CONNECTIONS. All drop manholes shall conform with City Standard
Plans and applicable APWA /WSDOT standard specifications.
TRENCH EXCAVATION
Trenches shall be provided per the City's Standard Plans and
OSHA /WISHA requirements. The trench shall be kept free from water
until joining is complete. Surface water shall be diverted so as not
to enter the trench. The owner shall maintain sufficient pumping
equipment on the job to insure that these provisions are carried out.
The owner shall perform all excavation of every description and of
whatever substance encountered and boulders, rocks, roots and other
obstructions shall be entirely removed or cut out to the width of the
trench and to a depth 6 inches (6 ") below sewer main grade. Where
material is removed from below sewer main grade, the trench shall be
filled to grade with material satisfactory to the City and thoroughly
compacted.
PIPE BEDDING
All pipe bedding shall be per the City's Standard Pipe Bedding Plan,
with all sanitary sewer pipe having Type 2 bedding as specified by the
APWA /WSDOT standard specifications. Bedding for PVC sewer pipe shall
extend at least six inches (6 ") above the crown of the sewer pipe as
specified in the City's Standard Plan and APWA /WSDOT standard
specifications.
BACRFILL
Backfilling and surface restoration shall closely follow installation
of pipe, so that not more than 100 feet is left exposed without
express approval of the City. Select backfill material shall be placed
and compacted above the bedding material, as outlined in City Standard
Plans, and compacted to 95% of the maximum density as determined by
ASTM Designation D 1557 -66T Method A. When other governmental agencies
other than the City have jurisdiction over roadways within the
construction, the backfill and compaction shall be done to the
satisfaction of the agency having jurisdiction. If suitable backfill
material, as determined by the City, is not available from trenching
operations, the City may order the placing of select backfill or some
other suitable material in the trench profile.
CONSTRUCTION PERMITS AND AUTHORIZATION
All construction on sanitary sewer systems by private development
shall be in accordance with the APWA /WSDOT standard specifications,
current edition adopted by the City. D.O.E. standards, the City of
Tukwila Municipal Codes, the City's Comprehensive Sewer Plan, and the
standards set forth in this document.
PERMITS: DESIGN STANDARDS FOR PLAN SUBMITTALS
All plans and specifications for sewer main extensions and sanitary
side sewer services must be presented to the City Public Works
Department, via the City permits coordinator, for review and approval
prior to beginning of construction.
Permits to install, repair or relocate sewer lines shall be secured
from the City Public Works Department, via the City's permit
coordinator, before carrying out the work. These permits shall be in
accordance with Tukwila Municipal Codes Chapter 14.12.
A street repair bond to assure restoration may be required by the
Public Works Director before the installation of a sewer connection is
made.
The following information shall be shown on all sewer plan submittals
to the City:
1. Size of pipe.
2. Type and class of pipe.
3. Slope of pipe.
4. Invert elevation at all manholes, side sewers or clean outs and
at the inlet and outlet of any manhole where there is a drop
connection or a change in pipe size.
5. Profile of all lines may be required by the Director. A minimum,
existing topography, proposed topography and invert elevations
shown at point sewer leaves structures, connects to the main, and
at all bends and junctions, is required. If a profile is
required, each profile shall be shown on the same sheet as the
plan for the corresponding line.
6. Permanent or proposed street grades.
7. All surface and subsurface utilities and improvement structures,
and all pertinent topography.
8. Stations of all connection bends and tees.
9. Location of existing buildings and services.
10. Existing and proposed street right -of -way and easement limits for
all utilities, including reference to any necessary permission
and release from damages for owners of property through to the
ultimate disposal point or facility.
11. All special structures, appurtenances or other construction.
12. Identify any possible utility conflicts.
13. Identify all clean outs.
- 14 -
CONSTRUCTION ON EASEMENTS
TESTING OF SANITARY SEWERS
All construction on easements shall be performed strictly in
accordance with the easement provisions. The contractor is responsible
to make himself aware of all conditions pertaining to the easement
agreement. No work shall be permitted in easement areas until
specifically authorized by the City.
All sanitary sewer mains shall be air tested and T.V. camera
inspected. Sanitary side sewers may be air or water tested. All
testing shall be accomplished after the trench has been backfilled and
compacted. Manholes shall be channeled prior to testing.
AIR TESTING
All sanitary sewer pipelines shall be air tested in accordance with
APWA /WSDOT standard specifications for air - permeable or non
air - permeable pipe, as applicable. The contractor shall furnish all
materials and equipment necessary for conducting the tests and all
testing shall be performed under the supervision of the Director. The
contractor may desire to make an air test prior to backfilling for his
own purposes. However, the air test for acceptance shall be made
after backfilling has been completed and compacted. Water testing is
allowed for sanitary side sewers only.
T.V. INSPECTION
All new sanitary sewer mains shall be T.V. camera inspected by the
contractor on VHS format and presented to the City's inspector for
review for sign -off of sewer permits. The contractor /developer shall
also be responsible to insure that the sewer mains are in fact ready
for T.V. camera inspection. The contractor shall bear all costs
incurred in correcting any deficiencies found during T.V. inspection,
including the cost of any additional T.V. inspection required to
verify the corrections.
- 15 -
S -1
S -2
S -3
S -4
S -5
S -6
S -7
S -8
S -9
S -10
S -11
S -12
INDEX OF SANITARY SEWER STANDARD PLANS
FOR THE CITY OF TUKWILA
Sanitary Side Sewer
Clean -Out
Access, Channelization, & Step Detail
Sanitary Sewer Manhole - 48" & 54"
Sanitary Sewer Manhole - 72"
Shallow Sanitary Sewer Manhole - 48" & 54"
Shallow Sanitary Sewer Manhole - 72" & 96"
24" Manhole Frame With Cover
Reinforcing Details for Manhole Top Slabs
Drop Connection
Pipe Bedding for Sanitary Sewers
Grease Trap
- 16 -
•
I PROPERTY LINE
1
�
r
w , Long Sweep
6 I Bend
Materials: (All New)
PVC — Mln. schedule 35.
Concrete — When soil conditions permit
and slopes ore less than 15%.
Ductile iron(polyethylene encased) — peat
or potential corrosion areas.
Ductile or Cast Iron — Justified due to
scouring velocities or soil problems.
Coven 12' Min Cover required over all
Slope: Min. 2% Max. 20X
Anchor for >20%
Plugged
Clean Out
(Total 9Q requires
Clean Out)
4' Sewer Pipe
Clean Out
6' Plug
6
6' SEWER PIPE
Plugged
Clean Out
/ (Wye)
10' Min.
STREET
pipe.
Solt Plpe
Adapter
J L �
i
( (Remove or FM Existing Septic Tank)
[_ C INSPECTION TEE
AT CfTY R/W UNE
Show Address
on Plan.
523
BIRCH ST.
8' or LARGER MAIN SEWER
Sanitary Sewer Must
Be 18' Below Water Line
When Crossing.
Test Tee & Clean Out Detail
WOMMIKVIWZ 18' 18' Min.
Cover unless
extended to
Grade.
3cr
CITY R/W
UNE
1 1
Use Saddle for Existing Main.
MI, of MEAWAEC7
SANITARY SIDE SEWER
Not to scale.
Aug 6, 1990
s -1
J
1/8- Raise —
1/2 Wide Border
10 r
"
5/er
9-
8 3/4
1 1/4
7 3/4'
15
Plpe Material M Specified
By The Engineer
Cast Iron Ring And Cover
3/4. Squares Spaced-3/4'
M Indicated—Ht 1/Er
2 7/8*
Fibre Joint
Pocking
4 -- Plug To Be Sealed In Some Manner
As Main Sevier Joints.
Mt" Tvzhoila
8" CLEAN—OUT
Not to scale.
Aug 6, 1990
S-2
STEP DETAIL
ACCESS DETAIL
8' Min. 18" Max.
Precast
Concrete
Rings
Precast Cone Section
CHANNELIZATION DETAIL
Kor —N —Seal
Inside Drop (Min 0.1' Max 1.5';
6' Min.
}
Legs may be parallel or approximately
radial at option of manufacturer
except that all steps in any manhole
shall be similar.
Steps to be located over shelf, not
over channel.
6" Min.
24"
12" Typ.
9 1/2" for Precast M.H.
Step See Detail
•
Note:
cc=
Slope Shelf to Pipe: 4% •
Side Channel
i
,' ." . • •
•
.. ..••••••••••••••••••••••....
Crushed Rock 17 Min.
MH Ring & Cover
See S -8.
Rubber Gasket & Grout at All Joints.
4 Min 1
Construct Channel &
Shelf in Field
Smooth Finish with
5 (1/2) Class Conc.
5 Sack Cement Mix
with 1/2 Aggregate.
Precast Bose
Ci ey ®f Tithwillaz
ACCESS, CHANNELIZATION,
& STEP DETAIL
Not to scale.
Aug 6, 1990
S -3
8* Min. 25 Max.
r
I •-•-
L
••
Notes:
See Access
Detail S-3.
r
L
24"
See Channel.
Detail S-3.
. ...... . ....... . .. ..
J 8 Min at C.L
18" Max. See Note 2.
Step See 5-3.
4"Min.
1. Max. Pipe Diameter may be limited by Pipe
Configuration or as determined by Engineer.
2. The Maximum Dimension from Manhole to Pipe Joint
applies only to Pipe Diameters 24 and less.
3. Rubber Gasket & Grout at All Joints.
Manhole Ring and Cover
See S-8.
J
12 Max.
See Note 2.
Max. 21 for 48" M.H.
Max. 36" for se M.H.
See Note 1.
4"Min.
Meg f Tveku.ojilau
SANITARY SEWER MANHOLE
— 48" & 54"
Not to scale.
Aug 6, 1990
S-4
NOTE:
r
L
RUBBER GASKET & GROUT
AT ALL JOINTS.
72" —48" Reducing
Slab
5'
6" Min. 3--
Max. Pipe Size 42"
72"
24"
6 1/2" —
12" Typ. *
1 See Access
Detail S-3.
J
Precast Bose Section
See Channel.
Detail S-3.
Shelf
_J
Steps
See 5-3.
Is, of TizZiao
72" SANITARY SEWER MANHOLE
TYPES IA4 & 1B4
Not to scale.
Aug 6, 1990
S-5
8' Max.
r
6- Min
8' Max.
Note:
IT Min. & 24 Max.
1
r
6 Min I1.
1
- N • •
It Min. & 24 Max.
1
yriprzeffiriffir,
54"
Precast Base\
#mosostarreell"M
Precast Base
36 Opening required when Crown to Slab Is less than 4.
See Channel.
Detail S-3.
1
See Channel.
Detail S-3.
Casting See S-8.
Adjustment Section
Step See S-3.
54 Top Slab Cover
See S-9.
Max Pipe Size 36
Max Pipe Size May Be Limited
By Pipe Configuration
54" MANHOLE
Casting See S-8.
Adjustment Section
Step See S-3.
48" Top Slab Cover
See S-9.
Max Pipe Size 21"
Max Pipe Size May Be Limited
By Pipe Configuration
48" MANHOLE
Meg of Takuzeiga
SHALLOW SANITARY SEWER MANHOLE
— 48" & 54"
Not to scale.
Aug 6, 1990
S-6
1
i
11'Max.
je
IN
Zerelififfile4E4 r
12" Mln.
1
11' Max.
r
12'
t
12' Min. & 24' Max.
1
.....................
1
96'
12: Min. & 24' Max.
1
6' Mln. .
Precast Bose
24'
Precast Base
J
Not.: For >48' Pipes. Ladder must be provided for access.
1
See Channel.
Detail S -3. ,
Costing See S-8.
Adjustment Section
Step See S -3.
9er Flat Slab Cover
See S -9.
Precast Base Section
See Channel.
Detail S -3.
Max Pip. Size 6Q'
Max Pip. Size May Be
Limited By Pip. Configuration
Not.: Locate Access Hole
Over Channel On All
Type III Manholes
96" MANHOLE
Casting See S -8.
Adjustment Section
Step S.. S -3.
72" Fiat Slab Cover
See S -9.
Precast Manhole Section
Max Pipe Size 48"
Max Pip. Size May Be Limited
By Pip. Configuration
Const. Channel Shelf
72" MANHOLE
Meg Ml'�a,dlla
SHALLOW SANITARY SEWER MANHOLE
—72" & 96"
Not to seals.
Aug 6, 1990
S -7
Covers shall have the •word "SEWER" in 2" raised
letters when used in connection with sanitary
sewer installations, or "STORM" when in connection
with storm drain installation, or "WATER" when
in connection with potable water distribution.
Non —Sldd Pattern
to be cost integral
on top of cover.
L 3 /°r
A { 1
2 1/
Machine Seat
25
Section A —A
Cast Iron —Non Locking Cover
Minimum weight 150 lbs.
Note: Frame to be grouted 3/4'
in place.
Frame Plan
2636'
Top o
web
Section B —B
Cast Iron Frame
Minimum weight 210 Ibs
24" Manhole
Frame With Cover
Not to scale.
Aug 6, 1990
S -8
1
■
#6 Bar
2
2
#5 Bar
96"Slab with 48" Opening
O.D. of 96 Manhole Section
O.D. of 7 Manhole Sec.
T
54"Slab with 24"Opening
96"Slab with 24"Opening
#6 Bars • ?Centers
Both Directions
Bottom Face
Both Directions
#6 Bar
12
72" Slab with 48" Opening 72" Slab with 24" Opening
#5 Bars 0 rCenters
Both Directions
Bottom Face
rClr.
•5 Bar
#4 Bars 0 rCenters
Bottom Face
#4 Bar
Clr.
48"Slab with 24" Opening
Or Manhole Seis,
of Tukwila'
REINFORCING DETAILS FOR
MANHOLE TOP SLABS
Not to scale.
Aug 6, 1990
S-9
6' Min.
n
t
•
Flexible Joint
Backfiil with
compacted material
os directed by
the engineer.
1' Max.
Class 50 Cost Iron
90' Bend.
Note:
Drop piping to be same size
as intercepted sewer.
One Length of Ductile Iron
Pipe (Class 50) To Solid
Bearing When Span is
More Than 4'.
i
6' Min.
Cem Conc Class 5(1 1/2)
Cement 5 Sock Mix with
1 1/2 Aggregate
Ductile Iron Drop Connection
PLAN
See Access
: Data il -
See Channel.
Detail S -3.
Kor —N —Seal
1/2 Blind Flange
As Dam with
Stainless Steel Bolts.
F 12 Typ.
Class C Concrete
Tee
6 Min.
Mortar Dom or Plug as
required by Engineer.
Steps
See S -4.
Flexible Joint
2" Min. Cover
Backfiil with compacted
material as directed
by engineer.
Strap to Manhole
Every 5'.
6 Min.
ti Min Cover
All Pipe Except Ductile
Iron Pipe Shall Be
Concrete Encased.
Cement Concrete
Class C
Poured in Place
Typical Manhole Foundation Construction
Concrete Encased Drop Connection
Me, of Tytheojia
DROP CONNECTION
Not to scale.
Aug 6, 1990
s -10
Sieve Size
X Passing
3/e
100
3/8"
95-100
08
0-10
0200
0-3
Sand equivalent
35 Mln•
Sieve Size
X Passing
3'
100
1/4"
25 Min.
140
40 Max.
0 200
7 1/2 Max.
Sand Equivalent
35 Min.
DIMENSION
CLASS A
CLASS 9
a
4" IAIN
1/4 I.D.
12'MAX
4'MIN. 27
under
er MIN. over
27
b
1/4 0.D.
1/2 0.D.
c
3/4 0.D.
1/2 0.D.
Sldefill Material
(See Note)
Sodding Material,
Type I, Rigid,
See Gradation
Table
Foundation Level
Notes:
w
Limit of Pipe Zone . e
‘- Alternate
Laid—back
6' Trench
Pr ..or
A.
BEDDING FOR RIGID PIPE IN TRENCHES
1. Provide uniform support under barrel.
2. Hand tamp under haunches.
3. Compact bedding material to 95X MAX density
except directly over pipe, hand tamp only.
4. Make surface of bedding level, or slope up away
from pipe.
5. Trench width(W)
—Pipe ID. plus 24'
I.D. or smaller.
—Pipe 1.D. plus 36'
than 24' I.D.
—The pipe zone will be the actual trench vrldth,
except that for Class A bedding. the Min.
concrete width shall be 1 1/2 I.D. + 18".
6. Sidefill material shall conform to bocicfill except
that rocks or lumps larger than 1' per foot of
pipe diameter shall not be used.
Max. for pipe 24'
Max. for pipe larger
Bedding Material
Gradation Table
Backfill Material
Gradation Table
Meg of Tukwila'
PIPE BEDDING FOR SANITARY SEWERS
Not to scale.
Aug 6, 1990
S-1 1
—/
A L
INLET
L
1
PLAN - BASE
CLEAR ACCESS OPNGS
IN TOP COVER
24"
SECTION M
12-
OUTLET
2—DIAMOND PLATE
INSPECTION COVER
PLAN - COVER
NOTE:
ALL BAFFLE/ WEIR PLATE TO BE
GALVANIZED
DIAMOND PLATE
ACCESS COVER
CC of Tukwila
GREASE TRAP
Not to 3 cele.
Aug 6, 1990
S- 1 2
^
%
TUKWILA CITY LIMITS
KING COUNTY
RENTON
F TUKWILA
TEM PLAN MAP
SEATTLE
KING COUNTY
2.
7.;
CITY OF TUKWILA
SEWER SYSTEM PLAN MAP
MATCHLINE SHEET 2 .
•• • ",