HomeMy WebLinkAboutReg 2010-08-02 Item 6B - Ordinance - Update Sensitive Areas Ordinance (SAO) - Complete Item AgendaCAS NUMBER: 10-084
MTG. DATE
7/26/10
8/2/10
COUNCIL AGENDA .SYNOPSIS
Meeting Date Prepared by
07/26/10 JP
08/02/10 JP
Inttzals
May F evzew
ITEM INFORMATION
1 ounczl review
ORIGINAL AGENDA DATE: JULY 26, 2010
AGENDA ITEM TITLE Revisions to the Sensitive Areas Ordinance (SAO), TMC 18.45
CATEGORY Dzscusszon Motion Resolution Ordinance Bic Award Public Hearing Other
Mtg Date 7/26/10 Mtg Dale Mtg Date Mtg Date 8/2/10 Mtg Date Mtg Date 7/26/10 Mtg Date
SPONSOR Council Mayor El Adm Svcs DCD Finance n Fire Legal P&R Police PW/
SPONSOR'S The ordinance revises the wetland classification system, adds references to the State's
SUMMARY watercourse rating system, clarifies information to be included in sensitive area special
studies and mitigation plans; clarifies where buffer mitigation must be carried out;
removes seven areas from the SAO maps that do not meet the criteria for sensitive areas.
After the close of the public hearing, staff would like direction on the process and level of
review by Council of the SAO revisions.
REVIEWED BY COW Mtg. CA &P Cmte F &S Cmte Transportation Cmte
Utilities Cmte Arts Comm. Parks Comm. Planning Comm.
DATE: 7 -12 -10 CAP; Planning Commission approved revisions on 6 -24 -10
RECOMMENDATIONS:
SPONSOR /ADMIN. Department of Community Development
COMMITTEE unanimous approval; Forward to Committee of the Whole
COST IMPACT FUND SOURCE
EXPENDITURE REQUIRED AMOUNT BUDGETED
$NA $NA
Fund Source: NA
Comments:
MTG. 'DATE 1 RECORD 'OF COUNCIL ACTION
1 7/26/10 (Forward to next Regular Meeting
ITEM No.
APPROPRIATION REQUIRED
$NA
ATTACHMENTS
Informational Memorandum dated 7/21/10
Draft Ordinance
Annotated proposed SAO revisions
Proposed SAO Map Removals (7)
Addendum to SAO departures Memo for Wetland and Watercourse Buffer Widths
Minutes from Community Affairs and Parks Committee meeting of 7/12/10
Attachment E Legislative History Folder (red)
*Community Affairs Parks members Please bring red folder from 7/12
Informational Memorandum dated /48 /1U and ordinance in rinai corm
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TO:
BACKGROUND
DISCUSSION
RECOMMENDATION
ATTACHMENTS*
City of Tukwila
INFORMATIONAL MEMORANDUM
Mayor Haggerton
Tukwila City Council
FROM: Jack Pace, Director, Department of Community Development
DATE: July 28, 2010
SUBJECT: 2010 Sensitive Areas Ordinance and Map Amendments
ISSUE
A. Draft Ordinance
B. Sites to be Removed from Sensitive Areas Map
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07/27/2010 12.17 PM
Jim Haggerton, Mayor
The City Council adopted new sensitive area regulations in 2004. After implementing these regulations for
six years, there are minor revisions that are needed to improve the ordinance as well as housekeeping
changes to maintain consistency with the Shoreline Master Program changes. In addition, there are some
sensitive areas identified on the SAO map that are incorrect the current regulations require Council review
and approval before any areas can be removed from the sensitive areas map.
At its meeting on July 26, 2010, the Committee of the Whole conducted and closed a public hearing on the
proposed revisions to the sensitive area regulations and provided direction to staff on two revisions to the
regulations as discussed below.
Two revisions are proposed to the draft ordinance in the Council's packet for the July 26, 2010 meeting.
The first revision is found on page 10 of the ordinance, TMC 18.45.070 B. 7.a. The proposed revision
clarifies what is meant by a "minor crossing After re- reading the language of that section, staff determined
that all crossings, whether minor or otherwise should be designed to avoid adverse impacts to sensitive
areas, but that requiring an assessment of impacts prepared by a biologist would be a hardship to property
owners for a minor crossing. So the "minor crossing" language is proposed to be removed from that
sentence and instead inserted in the preceding sentence.
The second revision addresses the concern that was raised at Community Affairs and Parks Committee
meeting about providing notice on the removal of trees from a sensitive area. New language is proposed on
page 11 of the ordinance to make clear that only hazardous trees that meet the definition specified in Title
18 of the Municipal Code may be removed from a sensitive area. Staff is not proposing a provision
requiring notice.
If the proposed language addresses the changes requested by the Council on July 26, 2010, adopt the
proposed revisions to the sensitive area regulations and remove seven sites from the Sensitive Areas Map
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pity of Tukwila
Washington
Ordinance No.
AN ORDINANCE OF THE CITY COUNCIL OF THE CITY OF
TUKWILA, WASHINGTON, UPDATING CERTAIN REQUIREMENTS
FOR REGULATING DEVELOPMENT ON SENSITIVE AREAS AND
BUFFERS, AS CODIFIED AT TUKWILA MUNICIPAL CODE
CHAPTER 18.45; REPEALING ORDINANCE NOS. 2074 AND 2174;
PROVIDING FOR SEVERABILITY; AND ESTABLISHING AN
EFFECTIVE DATE.
WHEREAS, the City adopted new regulations governing development on sensitive
areas and buffers in 2004 based on State Growth Management Act (GMA) requirements
to adopt development regulations that protect the functions of sensitive areas, including
wetlands, watercourses, fish and wildlife habitat conservation areas, and areas of
potential geological instability; and
WHEREAS, the City's sensitive area regulations should be consistent with the
Washington State Department of Ecology wetland classification system, which is based
on best available science; and
WHEREAS, the City's sensitive area regulations should be consistent with the
Washington State Department of Natural Resources' stream classification system, and
WHEREAS, after administering the ordinance for six years the City has determined
there are certain clarifications and refinements needed to improve the effectiveness of
the ordinance; and
WHEREAS, TMC Section 18.45.030 F. 3 requires that removal of any information on
the sensitive areas maps be approved by the City Council and Exhibit B illustrates seven
map corrections requiring Council approval, and
WHEREAS, the proposed revisions to TMC Chapter 18 45 are based on best
available science; and
WHEREAS, the City is a party to the Water Resource Inventory Area 9 adopted
salmon habitat plan "Making Our Watershed Fit for A King" that identifies specific
priorities for habitat investments, monitoring and adaptive management needs at a
watershed scale, and guides future habitat protection actions in the urban area; and
WHEREAS, State agencies, including the Department of Community, Trade and
Economic Development; Department of Ecology; and Department of Fish and Wildlife,
received notification and copies of the draft regulations for review at Least 60 days prior
to adoption; and
WHEREAS, the City has prepared a memo, Exhibit A, that describes departures
from best available science in the following areas: 1) buffer widths in urban areas, and
2) wetland or watercourse buffer reduction of up to 50% with mitigation in urban areas;
and
WHEREAS, the Planning Commission held a public hearing on May 27, 2010 to
obtain public input, and reviewed the sensitive area regulations at public meetings on
May 20, 2010 and June 24, 2010; and
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WHEREAS, the City Council held a public hearing on July 26, 2010 to obtain public
input on the sensitive area regulations as recommended by the Planning Corrunission,
and,
WHEREAS, the City received comments from the Department of Community, Trade
and Economic Development and the Department of Ecology and addressed these
comments in the ordinance or as departures;
NOW, THEREFORE, THE CITY COUNCIL OF THE CITY OF TUKWILA,
WASHINGTON, HEREBY ORDAINS AS FOLLOWS:
Section 1. Regulations established. Tukwila Municipal Code Chapter 18.45,
"Environmentally Sensitive Areas," is hereby established to read as follows:
Chapter 18.45
ENVIRONMENTALLY SENSITIVE AREAS
Sections:
18.45.010 Purpose
18.45.020 Best Available Science
18.45.030 Sensitive Area Applicability, Maps and Inventories
18.45.040 Sensitive Area Special Studies
18.45.050 Interpretation
18.45.060 Procedures
18.45 070 Sensitive Area Permitted Uses
18.45.080 Wetland Designations, Ratings and Buffers
18 45.090 Wetland Alterations and Mitigation
18.45 100 Watercourse Designations, Ratings and Buffers
18.45 110 Watercourse Alterations and Mitigation
18.45.120 Areas of Potential Geologic Instability Designations, Ratings and Buffers
18.45.130 Areas of Potential Geologic Instability Uses, Exemptions, Alterations and
Mitigation
18.45.140 Abandoned Mine Areas
18.45 150 Fish and Wildlife Habitat Conservation Areas Designation, Mapping, Uses
and Standards
18.45.160 Sensitive Area Master Plan Overlay
18.45.170 Sensitive Areas Tracts and Easements
18.45.180 Exceptions
18 45.190 Appeals
18.45.195 Enforcement and Penalties
18.45.200 Recording Required
18.45.210 Assurance Device
18.45.220 Assessment Relief
18.45.010 Purpose
A. The purpose of TMC Chapter 18.45 is to protect the environment, human life and
property, designate and classify ecologically sensitive areas such as regulated wetlands
and watercourses and geologically hazardous areas and to protect these areas and their
functions while also allowing for reasonable use of public and private property. These
regulations are prepared to comply with the Growth Management Act, RCW 36.70A, to
apply best available science according to WAC 365 195 -900 through 925 and to protect
critical areas as defined by WAC 365 190 -080.
B. Standards are hereby established to meet the following goals of protecting
environmentally sensitive areas:
1 Minimize developmental impacts on the natural functions of these areas.
2. Protect quantity and quality of water resources.
3 Minimize turbidity and pollution of wetlands and fish bearing waters and
maintain wildlife habitat.
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4. Prevent erosion and the loss of slope and soil stability caused by the removal
of trees, shrubs, and root systems of vegetative cover.
5. Protect the public against avoidable losses, public emergency rescue and
relief operations cost, and subsidy cost of public mitigation from landslide, subsidence,
erosion and flooding.
6. Protect the community's aesthetic resources and distinctive features of
natural lands and wooded hillsides.
7. Balance the private rights of individual property owners with the
preservation of enviromnentally sensitive areas.
8. Prevent the loss of wetland and watercourse function and acreage, and strive
for a gain over present conditions.
9. Give special consideration to conservation or protection measures necessary
to protect or enhance anadromous fisheries.
10. Incorporate the use of best available science in the regulation and protection
of sensitive areas as required by the State Growth Management Act, according to WAC
365- 195 -900 through 365 195 -925 and WAC 365- 190 -080.
18.45.020 Best Available Science
A. Policies, regulations and decisions concerning sensitive areas shall rely on best
available science to protect the functions of these areas and must give special
consideration to conservation or protection measures necessary to preserve or enhance
anadromous fish and their habitats.
B. Nonscientific information may supplement scientific information, but is not an
adequate substitution for valid and available scientific information.
C. Incomplete or unavailable scientific information leading to uncertainty for
permitting sensitive area impacts may require application of effective adaptive
management on a case by case basis. Adaptive management relies on scientific
methods to evaluate how well regulatory or non regulatory actions protect sensitive
areas or replace their functions.
18.45.030 Sensitive Area Applicability, Maps, and Inventories
A. Applicability. The provisions of TMC Chapter 18.45 shall apply to all land uses
and all development activities in a sensitive area or a sensitive area buffer as defined in
the "Definitions" chapter of this title. The provisions of TMC Chapter 18 45 apply
whether or not a permit or authorization is required within the City of Tukwila. No
person, company, agency, or applicant shall alter a sensitive area or buffer except as
consistent with the purposes and requirements of TMC Chapter 18 45 The following
are sensitive areas regulated by TMC Chapter 18 45•
1. Abandoned coal mines;
2. Areas of potential geologic instability Class 2, 3, 4 areas (as defined in the
Definitions chapter of this title and TMC 18 45.120.A),
3. Wetlands;
4. Watercourses;
5. Fish and Wildlife Habitat Conservation Areas.
B. The Growth Management Act also identifies frequently flooded areas and areas
of seismic instability as critical areas. Regulations governing frequently flooded areas
are found in TMC Chapter 16.52, Flood Zone Management. Areas of seismic instability
are defined and regulated through the Washington State Building Code.
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C. The City shall not approve any permit or otherwise issue any authorization to
alter the condition of sensitive area land, water or vegetation or to construct or alter any
structure or improvement in, over, or on a sensitive area or its buffer, without first
ensuring compliance with the requirements of TMC Chapter 18.45.
D Approval of a permit or development proposal pursuant to the provisions of
TMC Chapter 18.45 does not release the applicant from any obligation to comply with
the provisions of TMC Chapter 18.45.
E. When TMC Chapter 18.45 imposes greater restrictions or higher standards upon
the development or use of land than other laws, ordinances or restrictive covenants, the
provisions of TMC Chapter 18.45 shall prevail.
F. It is the obligation of the property owner to comply with all relevant provisions
of this Code.
G. Sensitive Areas Maps and Inventories
1. The distribution of many sensitive areas in Tukwila is displayed on the
Sensitive Areas Maps, on file with the Department of Community Development (DCD).
These maps are based on site assessment of current conditions and review of the best
available scientific data and are hereby adopted by reference.
2. Studies, preliminary inventories and ratings of potential sensitive areas are on
file with the Department of Community Development.
3. As new environmental information related to sensitive areas becomes
available, the Director is hereby designated to periodically add new information to the
Sensitive Areas Maps. Removal of any information from the sensitive area maps is a
Type 1 decision.
4. Regardless of whether a sensitive area is shown on the sensitive areas map,
the actual presence or absence of the features defined in the code as sensitive areas shall
govern. The Director may require the applicant to submit technical information to
indicate whether sensitive areas actually exist on or adjacent to the applicant's site,
based on the definitions of sensitive areas in this code.
5. All revisions, updates and reprinting of sensitive areas maps, inventories,
ratings and buffers shall conform to TMC Chapter 18.45.
18.45.040 Sensitive Area Special Studies
A. Application Required. An applicant for a development proposal that may
include a sensitive area and /or its buffer shall submit those studies as required by the
City and specified below to adequately identify and evaluate the sensitive area and its
buffers.
1. A required sensitive area study shall be prepared by a person with experience
and training in the scientific discipline appropriate for the relevant sensitive area in
accordance with WAC 365 195 905(4). A qualified professional must have obtained a
B.S. or B.A. or equivalent degree in ecology or related science, engineering,
environmental studies, fisheries, geotechnical or related field, and two years of related
work experience.
a. A qualified professional for Fish and Wildlife Habitat Conservation Areas
must have a degree in ecology or related sciences and professional experience related to
the subject species.
b. A qualified professional for wetland sensitive area studies must be a
certified Professional Wetland Scientist or a non certified Professional Wetland Scientist
with at least two years of full -time work experience as a wetlands professional,
including delineating wetlands using the state or federal manuals, preparing wetland
reports, conducting functional assessments, and developing and implementing
mitigation plans.
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c. A qualified professional for a geological hazard study must be a
professional geotechnical engineer as defined in the Definitions chapter of this title,
licensed in the state of Washington.
d. A qualified professional for watercourses means a hydrologist, geologist,
engineer or other scientist with experience in preparing watercourse assessments.
2. The sensitive area study shall use scientifically valid methods and studies in
the analysis of sensitive area data and shall use field reconnaissance and reference the
source of science used. The sensitive area study shall evaluate the proposal and all
probable impacts to sensitive areas in accordance with the provisions of TMC Chapter
18.45.
B. Wetland and Watercourse Sensitive Area Studies. The sensitive area study
shall contain the following information, as applicable:
1. The name and contact information of the applicant, a description of the
proposal, and identification of the permit requested.
2. A copy of the site plan for the development proposal showing: sensitive
areas and buffers and the development proposal with dimensions, clearing limits,
proposed storm water management plan, and mitigation plan for impacts due to
drainage alterations.
3. The dates, names and qualifications of the persons preparing the study and
documentation of any fieldwork performed on the site.
4. Identification and characterization of all sensitive areas, water bodies, and
buffers adjacent to the proposed project area or potentially impacted by the proposed
project as described in the following sections.
a. Characterization of wetlands must include:
(1) A wetland delineation report that includes methods used, field
indicators evaluated and the results. Wetland delineation must be performed in
accordance with the Washington State Wetlands Identification and Delineation Manual,
Washington Department of Ecology, March 1997 (or as revised). Field data forms are to
be included in the report. Data collection points are to be shown on the site plan with
their corresponding numbers indicated. After the City of Tukwila confirms the
boundaries, they are to be professionally surveyed to the nearest square foot and the
site plan modified as necessary to incorporate the survey data. Exact wetland acreage
will be calculated after the boundaries have been surveyed.
(2) Cowardin (Classification of Wetlands and Deepwater Habitats of
the U.S. U.S. Department of Interior) classification of the wetland(s).
(3) Hydrogeomorphic classification of the wetland(s).
(4) Hydroperiod.
(5) Brief landscape assessment of the wetland (identify hydrologic
basin/ sub-basin; inlets, outlets; surrounding land use; habitat quality and connectivity;
ultimate point of discharge; presence of culverts or other constraints to flow;
relationship to other wetlands /watercourses adjacent to or potentially impacted by the
proposed project).
(6) Description of buffer size per this chapter, conditions (topographic
considerations, existing vegetation types and density, habitat features, watercourse
edges, presence of invasive species, etc.) and functions.
(7) Functional assessment. For proposed wetland filling or proposed
projects that will impact buffers the Washington Wetland Classification System shall be
used as a functional assessment.
(8) Classification of the wetland under Tukwila's rating system.
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include:
report.
study
b. Characterization of the watercourses on site or adjacent to the site must
(1) Description of: flow regime, physical characteristics of streambed,
banks, dimensions and bank -full width, stream gradient, stream and buffer vegetation
conditions, habitat conditions, and existing modifications.
(2) Brief landscape assessment of the watercourse (identify hydrologic
basin /sub- basin, and contributing basin area acreage, outlets, surrounding land use,
habitat quality and connectivity, ultimate point of discharge, presence of culverts or
other constraints to flow, presence of man -made or natural barriers to fish passage,
relationship to wetlands or other watercourses adjacent to or potentially impacted by
the proposed project, flow regime).
(3) Classification of the watercourse under Tukwila's rating system.
(4) Description of buffer size per this chapter, conditions (topographic
considerations, existing vegetation types and density, habitat features, watercourse
edges, presence of invasive species, etc.) and functions.
(5) Description of habitat conditions, wildlife /fish use of the
watercourse, including sensitive, threatened or endangered species.
c. Citation of any literature or other resources utilized in preparation of the
5. A statement specifying the accuracy of the study and assumptions used in the
6. Determination of the degree of hazard and risk from the proposal both on the
site and on adjacent properties.
7 An assessment of the probable cumulative impacts to sensitive areas, their
buffers and other properties resulting from the proposal.
8. A description of reasonable efforts made to apply mitigation sequencing to
avoid, minimize and mitigate impacts to sensitive areas.
9. Plans for adequate mitigation to offset any impacts.
10. Recommendations for maintenance, short -term and long -term monitoring,
contingency plans and bonding measures.
11. Any technical information required by the Director to assist in determining
compliance with TMC Chapter 18.45.
C. Geotechnical Report.
1. A geotechnical report appropriate both to the site conditions and the
proposed development shall be required for development in Class 2, Class 3, Class 4
areas, and any areas identified as Coal Mine Hazard Areas unless waived pursuant to
TMC Section 18.45.040 E.
2. Geotechnical reports for Class 2 areas shall include at a minimum a site
evaluation review of available information regarding the site and a surface
reconnaissance of the site and adjacent areas. Subsurface exploration of site conditions
is at the discretion of the geotechnical consultant.
3. Geotechnical reports for Class 3, Class 4 and Coal Mine Hazard Areas shall
include a site evaluation review of available information about the site, a surface
reconnaissance of the site and adjacent areas, a feasibility analysis for the use of
infiltration on -site and a subsurface exploration of soils and hydrology conditions.
Detailed slope stability analysis shall be done if the geotechnical engineer recommends
it in Class 3 or Coal Mine Hazard Areas, and must be done in Class 4 areas.
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4. Applicants shall retain a geotechnical engineer to prepare the reports and
evaluations required in this subsection, The geotechnical report and completed site
evaluation checklist shall be prepared in accordance with the generally accepted
geotechnical practices, under the supervision of and signed and stamped by the
geotechnical engineer The report shall be prepared in consultation with the
Community Development and Public Works Departments.
5. The opinions and recommendations contained in the report shall be
supported by field observations and, where appropriate or applicable, by literature
review conducted by the geotechnical engineer which shall include appropriate
explorations, such as borings or test pits, and an analysis of soil characteristics
conducted by or under the supervision of the engineer in accordance with standards of
the American Society of Testing and Materials or other applicable standards. If the
evaluation involves geologic evaluations or interpretations, the report shall be reviewed
and approved by a geotechnical engineer
D Sensitive Area Study and Modifications to Requirements.
1. The Director may limit the required geographic area of the sensitive area
study as appropriate if:
a. The applicant, with assistance from the City, cannot obtain permission to
access properties adjacent to the project area, or
b. The proposed activity will affect only a limited part of the site.
2. The Director may allow modifications to the required contents of the study
where, in the judgment of a qualified professional, more or less information is required
to adequately address the potential sensitive area impacts and required mitigation.
E. Waiver. A waiver to the sensitive area study may be granted by the Director if
the following conditions have been met:
1 A wetland has been classified and delineated, or the Ordinary High Water
Mark (OHWM) has been determined in watercourses and confirmed by the City within
the last two years, in accordance with the requirements of this chapter.
2. The classification and location of wetland boundaries or OHWM have been
confirmed by the City, and the proposed development or action will avoid all impacts
to the sensitive area(s).
3. There is substantial evidence there will be no detrimental impact to the
sensitive areas or buffers, and that the goals, purposes, objectives and requirements of
TMC Chapter 18.45 will be followed.
F. Review of Studies. The Department of Community Development will review
the information submitted in the sensitive area study to verify the information, confirm
the nature and type of the sensitive area, and ensure the study is consistent with TMC
Chapter 18.45. At the discretion of the Director, sensitive area studies may undergo
peer review, at the expense of the applicant.
18.45.050 Interpretation
The provisions of TMC Chapter 18.45 shall be held to be minimum requirements in
their interpretation and application and shall be liberally construed to serve the
purposes of TMC Chapter 18.45
18.45.060 Procedures
When an applicant submits an application for any building permit, subdivision,
short subdivision or any other land use review which approves a use, development or
future construction, the location and dimensions of all sensitive areas and buffers on the
site shall be indicated on the plans submitted. When a sensitive area is identified, the
following procedures apply. The Director may waive item numbers 1, 2, 4 and 5 of the
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following if the size and complexity of the project does not warrant that step in the
procedures and the Director grants a waiver pursuant to TMC Section 18.45.040 E.
Approval by the Department of a sensitive area alteration is contingent upon the
applicant granting the City the right of continuous entry upon proper notice to observe
sensitive area conditions.
1. Sensitive areas study and geotechnical report.
a. The applicant shall submit the relevant study as required in TMC Section
21.04.140 and TMC Chapter 18.45.
b. It is intended that sensitive areas studies and information be utilized by
applicants in preparation of their proposals and therefore shall be undertaken early in
the design stages of a project.
2. Planned residential development permit: Any new residential subdivision or
multiple family residential proposal that includes a wetland or watercourse or its buffer
on the site may apply for a planned residential development permit and meet the
requirements of the Planned Residential Development District chapter of this title.
3. Denial of use or development: A use or development will be denied if the
Director determines the applicant cannot ensure that potential dangers and costs to
future inhabitants of the development, adjacent properties, and Tukwila are minimized
and mitigated to an acceptable level.
4. Preconstruction meeting: The applicant, specialist(s) of record, contractor, and
department representatives will be required to attend pre construction meetings prior
to any work on the site.
5. Construction monitoring: The specialist(s) of record shall be retained to
monitor the site during construction.
6. On -site identification: The Director may require the boundary between a
sensitive area and its buffer and any development or use to be permanently identified
with fencing, and /or with a wood, plastic or metal sign mounted on a treated wood,
concrete or metal post. Sign size will be determined at the time of permitting; however,
the minimum size shall be 10 x 12 inches. It shall be permanently affixed to the post by
bolts and the wording shall be as follows:
"Protection of this natural area is in your care. Alteration, dumping or
disturbance is prohibited pursuant to TMC Chapter 18.45. Please call the City of
Tukwila at 206 431 -3670 for more information."
18.45.070 Sensitive Area Permitted Uses
A. General Uses. The uses set forth in this entire section, including subsections A.
through D, and the following general uses, may be located within a sensitive area or
buffer, subject to the provisions of TMC Chapter 21.04 and of the mitigation
requirements of TMC Chapter 18.45:
1. Maintenance and repair of existing uses and facilities provided no alteration
or additional fill materials will be placed or heavy construction equipment used in the
sensitive area or buffer.
2. Nondestructive education and research.
3. Passive recreation and open space.
4. Maintenance and repair of essential streets, roads, rights -of -way, or utilities.
5. Actions to remedy the effects of emergencies that threaten the public health,
safety or welfare.
6. Maintenance activities of existing landscaping and gardens in a sensitive area
buffer including, but not limited, to mowing lawns, weeding, harvesting and replanting
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of garden crops and pruning and planting of vegetation. The removal of established
native trees and shrubs is not permitted.
B Permitted Uses Subject To Administrative Review. The following uses may be
permitted only after administrative review and approval by the Director
1. Maintenance and repair of existing uses and facilities where alteration or
additional fill materials will be placed or heavy construction equipment used.
2. New surface water discharges to sensitive areas or their buffers from
detention facilities, pre settlement ponds or other surface water management structures
may be allowed provided that the discharge meets the clean water standards of RCW
90 48 and WAC 173.200 and 173.201 as amended, and does not adversely affect water
level fluctuations in the wetland or adversely affect watercourse habitat and
watercourse flow conditions relative to the existing rate. Water quality monitoring may
be required as a condition of use.
3. Bioswales and dispersion outfalls are the only storm water facilities allowed
in wetland or watercourse buffers. Water quality monitoring may be required as a
condition of use.
4. Enhancement or other mitigation including landscaping with native plants.
5. Essential Utilities.
a. Essential utilities must be constructed to minimize, or where possible
avoid, disturbance of the sensitive area and its buffer
b. All construction must be designed to protect the sensitive area and its
buffer against erosion, uncontrolled storm water, restriction of groundwater movement,
slides, pollution, habitat disturbance, any loss of flood carrying capacity and storage
capacity, and excavation or fill detrimental to the environment.
c. Upon completion of installation of essential utilities, sensitive areas and
their buffers must be restored to pre project configuration, replanted as required and
provided with maintenance care until newly planted vegetation is established. In
addition, mitigation to offset impacts to sensitive areas or their buffers must be carried
out in accordance with the standards and mitigation ratios of this chapter
d. All crossings must be designed for shared facilities in order to minimize
adverse impacts and reduce the number of crossings.
6. Essential Public Streets, Roads and Rights -of -Way.
a. For construction of new essential public streets, roads and rights -of -way,
as defined by TMC Section 18.06.285, where avoidance of sensitive areas is not possible,
impacts to the sensitive area and its buffer must be kept to the absolute minimum.
b Essential public streets, roads and rights -of -way, as defined by TMC
Section 18.06.285, must be designed and maintained to prevent erosion and avoid
restricting the natural movement of groundwater.
c. Essential public streets, roads and rights -of -way, as defined by TMC
Section 18.06.285, must be located to conform to the topography so that minimum
alteration of natural conditions is necessary. The number of crossings shall be limited to
those necessary to provide essential access.
d. Essential public streets, roads and rights -of -way, as defined by TMC
Section 18.06.285, must be constructed in a way that does not adversely affect the
hydrologic quality of the wetland or watercourse and/ or its buffer. Where feasible,
crossings must allow for combination with other essential utilities.
e. Upon completion of construction, the area affected must be restored to an
appropriate grade, replanted according to a plan approved by the Director, and
provided with care until newly planted vegetation is established. In addition,
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mitigation to offset impacts to sensitive areas or their buffers must be carried out in
accordance with the standards and mitigation ratios set forth in this chapter
7 Public/Private Use and Access.
a. Public and private access shall be limited to trails, boardwalks, covered or
uncovered viewing and seating areas, footbridges only if necessary for access to other
areas of the property, and displays (such as interpretive signage or kiosks), and must be
located in areas that have the lowest sensitivity to human disturbance or alteration.
Access features shall be the minimum dimensions necessary to avoid adverse impacts
to the sensitive area. Trails shall be no wider than 5 feet and are only allowed in the
outer half of the buffer, except for allowed wetland or stream crossings. For proposed
wetland or watercourse crossings or trails, an assessment of impacts to
wetland /watercourse and buffer function (especially where the sensitive area provides
habitat function for wildlife) will be required and must be prepared by a qualified
biologist. except for minor crossings. such as foot bridges or steuuing stones. for access
to contiguous nrouerty. Crossings {except for minor crosrings for acct c to contiguous
property and trails must be designed to avoid adverse impacts to sensitive area
functions. The Director may require mechanisms to limit or control public access when
environmental conditions warrant (such as temporary trail closures during wildlife
breeding season or migration season).
b. Public access must be specifically developed for interpretive, educational
or research purposes by, or in cooperation with, the City or as part of the adopted
Tukwila Parks and Open Space Plan. Private footbridges are allowed only for access
across a sensitive area that bisects the property
c. No motorized vehicle is allowed within a sensitive area or its buffer
except as required for necessary maintenance, agricultural management or security
d. Any public access or interpretive displays developed along a sensitive
area and its buffer must, to the extent possible, be connected with a park, recreation or
open -space area.
e. Vegetative edges, structural barriers, signs or other measures must be
provided wherever necessary to protect sensitive areas and their buffers by limiting
access to designated public use or interpretive areas.
f. Access trails and footbridges must incorporate design features and
materials that protect water quality and allow adequate surface water and groundwater
movement. Trails must be built of permeable materials.
g. Access trails and footbridges must be located where they do not disturb
nesting, breeding and rearing areas and must be designed so that sensitive plant and
critical wildlife species are protected. Trails and footbridges must be placed so as to not
cause erosion or sedimentation, destabilization of watercourse banks, interference with
fish passage or significant removal of native vegetation. Footbridges must be anchored
to prevent their movement due to water level or flow fluctuations. Any work in the
wetland or stream below the OHWM will require additional federal and state permits.
8. Dredging, Digging or Filling.
a. Dredging, digging or filling within a sensitive area or its buffer may occur
only with the permission of the Director and only for the following purposes:
(1) Uses permitted by TMC Sections 18.45.080, 18 45.090, 18.45 110,
18.45.130;
(2) Maintenance of an existing watercourse;
(3) Enhancement or restoration of habitat in conformance with an
approved mitigation plan identified in a sensitive area study;
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(4) Natural system interpretation, education or research when
undertaken by, or in cooperation with, the City;
(5) Flood control or water quality enhancement by the City;
(6) Maintenance of existing water quality controls, for normal
maintenance needs and for any diversion, rerouting, piping or other alteration
permitted by TMC Chapter 18.45;
(7) Filling of abandoned mines.
b. Any dredging, digging or filling shall be performed in a manner that will
minimize sedimentation in the water. Every effort will be made to perform such work
at the time of year when the impact can be lessened.
c. Upon completion of construction, the area affected must be restored to an
appropriate grade, replanted according to a plan approved by the Director, and
provided with care until newly planted vegetation is established.
9. Removal of Hazardous Trees. Only trees, as defined in Chapter
18.06.395, may be removed from a sensitive area. In cases where the hazard is not
obvious, an assessment by an arborist certified by the International Society of Arborists
may be required by the Director. Tree replacement in accordance with TMC Chapter
18.54 is required for any hazardous tree removed from a sensitive area. Dead trees may
not be removed, unless they present a hazard to public safety or structures.
C. Permitted Uses Subject to Exception Approval. Other uses may be permitted
upon receiving a reasonable use exception pursuant to TMC Section 18.45.180. A use
permitted through a reasonable use exception shall conform to the procedures of TMC
Chapter 18.45 and be consistent with the underlying zoning.
D. Uses allowed under a Sensitive Area Master Plan prepared and approved under
the provisions of TMC Section 18.45.160.
18.45.080 Wetland Designations, Ratings and Buffers
A. Wetland Designations.
1. For the purposes of TMC Chapter 18.45, "wetlands" and "regulated
wetlands" are defined in the Definitions chapter of this title. A wetland boundary is the
line delineating the outer edge of a wetland established by using the Washington State
Wetland and Delineation Manual, as required by RCW 36.70A.175 (Ecology Publication
#96 -94) and consistent with the 1987 Corps of Engineers Wetland Delineation Manual.
2. Wetland determinations and delineation of wetland boundaries shall be
made by a qualified professional, as described in TMC Section 18.45.040
3. Wetland areas within the City of Tukwila have certain characteristics and
functions and have been influenced by urbanization and related disturbances. Wetland
functions include, but are not limited to, the following:
a. Improving water quality;
b Maintaining hydrologic functions (reducing peak flows, decreasing
erosion, groundwater recharge, flood storage); and
c. Providing habitat for plants, mammals, fish, birds, and amphibians.
B. Wetland Ratings. Wetlands shall be designated in accordance with the
Washington State Wetlands Rating System for Western Washington, (Washington State
Department of Ecology, August 2004, Publication #04 -06 -025) as Category I, II, III, or IV
as listed below:
1. Category I wetlands are those that: i) represent a unique or rare wetland
type; or ii) are more sensitive to disturbance than most wetlands; or iii) are relatively
undisturbed and contain ecological attributes that are impossible to replace within a
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wetlands listed by Washington Department of Ecology and potentially found in
Tukwila are Category I:
a. Estuarine wetlands (deepwater tidal habitats with a range of fresh
brackish- marine water chemistry and daily tidal cycles, salt and brackish marshes,
intertidal mudflats, bays, sounds, and coastal rivers);
b. Wetlands that perform many functions well and score at least 70 points in
the Western Washington Wetlands Rating System.
2. Category II wetlands are difficult, though not impossible, to replace and
provide high levels of some functions. These wetlands occur more commonly than
Category I wetlands, but still need a relatively high level of protection. The following
types of wetlands listed by Washington Department of Ecology and potentially found
in Tukwila are Category II wetlands:
a. Estuarine wetlands smaller than an acre, or those that are disturbed and
larger than one acre;
b. Wetlands that perform functions well. Wetlands scoring between 51 -69
points (out of 100) on the questions related to the functions present.
3 Category III wetlands have a moderate level of functions (scores between 30
and 50 points). Wetlands scoring between 30 -50 points generally have been disturbed
in some ways and are often less diverse or more isolated from other natural resources in
the landscape than Category II wetlands.
4. Category IV wetlands have the lowest levels of functions (scores less than 30
points) and are often heavily disturbed. While these are wetlands that should be able to
be replaced or improved, they still need protection because they may provide some
important functions. Any disturbance of these wetlands will be considered on a case by
case basis.
C. Wetland Buffers.
1. A buffer area shall be established adjacent to designated wetland areas. The
purpose of the buffer area shall be to protect the integrity and functions of the wetland
area. Any land alteration must be located out of the buffer areas as required by this
section. Wetland buffers are intended in general to.
a. Minimize long -term impacts of development on properties containing
wetlands;
b. Protect wetlands from adverse impacts during development;
c. Preserve the edge of the wetland and its buffer for its critical habitat value;
d. Provide an area to stabilize banks, to absorb overflow during high water
events and to allow for slight variation of aquatic system boundaries over time due to
hydrologic or climatic effects;
e. Reduce erosion and increased surface water runoff;
f. Reduce loss of or damage to property;
g. Intercept fine sediments from surface water runoff and serve to minimize
water quality impacts; and
h. Protect the sensitive area from human and domestic animal disturbances.
2. An undisturbed sensitive area or buffer may substitute for the yard setback and
landscape requirements of the TMC Chapter 18.50 and 18.52.
D. Wetland Buffer Widths. The following standard buffers shall be established
from the wetland edge:
1. Category I and II Wetland. 100 -foot buffer
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2. Category III Wetland: 80 -foot buffer.
3. Category IV Wetland. 50 -foot buffer.
E. Buffer Setbacks.
1 All commercial and industrial buildings shall be set back 15 feet and all other
development shall be set back 10 feet from the buffer's edge. The building setbacks shall
be measured from the foundation to the buffer's edge. Building plans shall also identify
a 20 -foot area beyond the buffer setback within which the impacts of development will
be reviewed.
2. The Director may waive setback requirements when a site plan demonstrates
there will be no impacts to the buffer from construction or occasional maintenance
activities (see TMC Figure 18 -2).
F. Variation of Standard Wetland Buffer Width.
1. The Director may reduce the standard wetland buffers only where the buffer
conditions are currently degraded (due to existing development within the prescribed
buffer width, the presence of significant amount of invasive vegetation that impairs
buffer function, and/ or lack of native vegetation) on a case -by -case basis, provided the
remaining buffer is enhanced and the buffer does not contain slopes 15% or greater.
Where a buffer has a variable topography that includes Class I slopes on the landward
half of the buffer, a buffer reduction may be allowed if the proposed reduction is in the
area with the Class I slopes, and a 10 -foot planted setback from the top of the slope is
maintained. Further, a geotechnical review of the proposed buffer enhancement plan
must determine the buffer enhancement can be implemented without destabilizing the
slope. The approved buffer width shall not result in greater than a 50% reduction in
width.
2. Buffer reduction with enhancement may be allowed by the Director as a Type
2 permit with an approved buffer enhancement plan prepared by a qualified wetland
biologist, if:
a. Additional protection to wetlands will be provided through the
implementation of a buffer enhancement plan,
b. The existing condition of the buffer is degraded; and
c. Buffer enhancement includes, but is not limited to the following:
(1) Planting vegetation that would increase value for fish and wildlife
habitat or improve water quality or hydrology;
(2) Enhancement of wildlife habitat by incorporating structures that are
likely to be used by wildlife, including wood duck boxes, bat boxes, snags, root
wads /stumps, birdhouses and heron nesting areas; or
(3) Removing non- native plant species and noxious weeds from the
buffer area and replanting the area subject to 2.c. (1) above.
3. Buffers for all types of wetlands will be increased when they are determined
to be particularly sensitive to disturbance or the proposed development will create
unusually adverse impacts. Any increase in the width of the buffer shall be required
only after completion of a wetland study by a qualified wetlands specialist or expert
that documents the basis for such increased width. An increase in buffer width may be
appropriate when:
a. The development proposal has the demonstrated potential for significant
adverse impacts upon the wetland that can be mitigated by an increased buffer width;
or;
b. The area serves as a habitat for endangered, threatened, sensitive or
monitor species listed by the federal government or the State.
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4. Every reasonable effort shall be made to maintain the existing viable native
plant life in the buffers. Vegetation may be removed from the buffer as part of an
enhancement plan approved by the Director. Enhancements will ensure that slope
stability and wetland quality will be maintained or improved. Any disturbance of the
buffers for wetlands shall be replanted with a diverse plant community of native
northwest species that are appropriate for the specific site as determined by the
Director. If the vegetation must be removed, or because of the alterations of the
landscape the vegetation becomes damaged or dies, then the applicant for a permit
must replace existing vegetation along wetlands with comparable specimens, approved
by the Director, which will restore buffer functions within five years.
5. The Director shall require subsequent corrective actions and long -term
monitoring of the project if adverse impacts to regulated wetlands or their buffers are
identified.
18.45.090 Wetland Alterations and Mitigation
A. No use or development may occur in a Category I, Category II, Category III or
Category IV wetland or its buffer except as specifically allowed by TMC Chapter 18.45.
Any use or development allowed is subject to review and approval by the Director.
Where required, a mitigation plan must be developed and must comply with the
standards of mitigation required in TMC Chapter 18.45. In addition, federal and /or
state authorization is required for direct impacts to waters of the United States or the
State of Washington.
1. Alterations to wetlands are discouraged and are limited to the minimum
necessary for project feasibility. Requests for alterations must be accompanied by a
mitigation plan, are subject to Director approval, and may be approved only if the
following findings are made:
a. The alteration will not adversely affect water quality;
b. The alteration will not adversely affect fish, wildlife, or their habitat;
c. The alteration will not have an adverse effect on drainage and /or storm
water detention capabilities;
d. The alteration will not lead to unstable earth conditions or create an
erosion hazard or contribute to scouring actions,
e. The alteration will not be materially detrimental to any other property;
and
B Alterations.
f. The alteration will not have adverse effects on any other sensitive areas.
2. Alterations are not permitted to Category I and II wetlands unless specifically
exempted under the provisions of TMC Chapter 18.45.
3. Alterations to Category III wetlands are allowed only where unavoidable and
adequate mitigation is carried out in accordance with the standards of this section.
4. Alterations to Category IV wetlands are allowed, only where unavoidable
and adequate mitigation is carried out in accordance with the standards of TMC Section
18.45.090
5 Wetlands that are less than 1,000 square feet may be exempted where it has
been shown by the applicant that they are not associated with a riparian corridor, they
are not part of a wetland mosaic, do not contain habitat identified as essential for local
populations of priority species identified by the Washington State Deparhnent of Fish
and Wildlife and do not score 20 points or greater for habitat in the Western
Washington Wetland Rating System.
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6. Mitigation plans shall be completed for any proposals for dredging, filling,
alterations and relocation of wetland habitat allowed in TMC Chapter 18.45.
C. Mitigation Sequencing. Applicants shall demonstrate that reasonable efforts
have been examined with the intent to avoid and minimize impacts to wetlands and
wetland buffers. When an alteration to a wetland or its required buffer is proposed,
such alteration shall be avoided, minimized or compensated for in the following order
of preference:
1. Avoiding the impact altogether by not taking a certain action or parts of an
action,
2. Minimizing wetland and wetland buffer impacts by limiting the degree or
magnitude of the action and its implementation, by using appropriate technology, or by
taking affirmative steps to avoid or reduce impacts;
3 Rectifying the impact by repairing, rehabilitating or restoring the affected
environment;
4. Reducing or eliminating the impact over time by preservation and
maintenance operations during the life of the action;
5 Compensating for the impact by replacing, enhancing, or providing
substitute resources or environments; and/ or
6. Monitoring the impact and taking appropriate corrective measures.
D. Wetland Mitigation Plan Content.
1 The mitigation plan shall be developed as part of a sensitive area study by a
specialist approved by the Director. Wetland and/ or buffer alteration or relocation
may be allowed only when a mitigation plan clearly demonstrates that the changes
would be an improvement of wetland and buffer quantitative and qualitative functions.
The plan shall follow the performance standards of TMC Chapter 18 45 and show how
water quality, wildlife and fish habitat, and general wetland quality would be
improved.
2. The scope and content of a mitigation plan shall be decided on a case -by -case
basis taking into account the degree of impact and the extent of the mitigation measures
needed. As the impacts to the sensitive area increase, the mitigation measures to offset
these impacts will increase in number and complexity
3. For wetlands, the format of the mitigation plan should follow that established
in Wetland Mitigation in Washington State. Part 2 Developing Mitigation Plans
(Washington Department of Ecology, Corps of Engineers, EPA, March 2006 or as
amended).
4. The components of a complete mitigation plan are as follows:
a. Baseline information of quantitative data collection or a review and
synthesis of existing data for both the project impact zone and the proposed mitigation
site.
b. Environmental goals and objectives that describe the purposes of the
mitigation measures. This should include a description of site selection criteria,
identification of target evaluation species and resource functions.
c. Performance standards of the specific criteria for fulfilling environmental
goals and for beginning remedial action or contingency measures. They may include
water quality standards, species richness and diversity targets, habitat diversity indices,
or other ecological, geological or hydrological criteria.
d. A detailed construction plan of the written specifications and descriptions
of mitigation techniques. This plan should include the proposed construction sequence
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and construction management, and be accompanied by detailed site diagrams and
blueprints that are an integral requirement of any development proposal.
e. A monitoring and/ or evaluation program that outlines the approach for
assessing a completed project for the specified monitoring period. An outline shall be
included that spells out how the monitoring data will be evaluated by agencies that are
tracking the mitigation project's progress.
f. Contingency plan identifying potential courses of action and any
corrective measures to be taken when monitoring or evaluation indicates project
performance standards have not been met.
g. Performance security or other assurance devices as described in TMC
Section 18.45.210.
E. Mitigation Standards.
1. Types of Wetland Mitigation:
a. Mitigation for wetlands shall follow the mitigation sequencing steps in
this chapter and may include the following types of actions:
(1) Restoration:
a) Re- establishment. The manipulation of the physical, chemical or
biological characteristics of a site with the goal of restoring wetland functions to a
former wetland, resulting in a net increase in wetland acres and functions;
b) Rehabilitation. The manipulation of the physical, chemical or
biological characteristics of a site with the goal of repairing historic functions and
processes of a degraded wetland, resulting in a gain in wetland functions but not
acreage;
(2) Creation (establislunent). The manipulation of the physical, chemical
or biological characteristics to develop a wetland on an upland or deepwater site, where
a biological wetland did not previously exist;
(3) Enhancement. The manipulation of the physical, chemical or
biological characteristics to heighten, intensify, or improve specific functions (such as
vegetation) or to change the growth stage or composition of the vegetation present,
resulting in a change in wetland functions but not in a gain in wetland acreage.
(4) A combination of the three types.
b. Required mitigation ratios are described in TMC Section 18.45.090.E.b.(1).
Alternate mitigation ratios may be accepted by the Director upon presentation of
justification based on best available science that shows the proposed compensation
represents a roughly proportional exchange for the proposed impacts.
(1) Alterations are not permitted to Category I or II wetlands unless
specifically exempted under the provisions of this program. When alterations are
allowed, mitigation ratios for Category I wetlands shall be at a 4.1 for creation or re-
establishment, 8:1 for rehabilitation, and 16:1 for enhancement. Mitigation ratios for
Category II wetlands shall be at 3:1 for creation or re- establishment, 6:1 for
rehabilitation and 12:1 for enhancement. Creation or re- establislunent shall be
contiguous to the wetland, unless an exception is authorized by the Director. For
Category II estuarine wetlands, re- establishment, creation and enhancement ratios will
be decided on a case -by -case basis.
(2) Alterations to Category III wetlands are prohibited except where
unavoidable and mitigation sequencing in accordance with this chapter has been
utilized and where mitigation is carried out in accordance with the standards in the
section. Mitigation for any alteration to a Category III wetland must be provided at a
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ratio of 2:1 for creation or re- establishment, 4.1 for rehabilitation and 8 1 for
enhancement alone.
(3) Mitigation for alteration to a Category IV wetland will be 1.5:1 for
creation or re- establishment, 3:1 for rehabilitation or 6:1 for enhancement. Where only a
portion of a Category IV wetland is filled, the potential functionality of the remaining
reduced wetland must be considered in mitigation planning.
2. The following shall be considered the minimum performance standards for
approved wetland alterations:
a. Wetland functions improved over those of the original conditions.
b Hydrologic conditions and hydroperiods are improved over existing
conditions and the specific hydrologic performance standards specified in the approved
mitigation plan are achieved.
c. Acreage requirements for creation, re- establishment, rehabilitation or
enhancement and for proposed wetland classes are met.
d. Vegetation native to the Pacific Northwest is installed and vegetation
survival and coverage standards over time are met and maintained.
improved.
and
e. Habitat features are installed, if habitat is one of the functions to be
f. Buffer and bank conditions and functions exceed the original state.
3 Maintenance and monitoring of mitigation shall be done by the property
owner for a period of no less than five years and for ten years when the mitigation plan
includes establishing forested wetland and /or buffers. Maintenance shall be carried
out in accordance with the approved mitigation plan. Monitoring reports must be
submitted to the City for review with the frequency specified in the approved
mitigation plan.
4. The Community Development Director may approve, through a Type 2
decision, the transfer of wetland mitigation to a wetland mitigation bank using the
criteria in 4.a. through 4.f. below. The Director must determine the number of wetland
mitigation bank credits required to meet the mitigation ratios established in TMC
Chapter 18.45.
a. Off -site mitigation is proposed in a wetland mitigation bank that has been
approved by all appropriate agencies, including the Department of Ecology, Corps of
Engineers, EPA and certified under state rules, and
b The proposed wetland alteration is within the designated service area of
the wetland bank; and
c. The applicant provides a justification for the number of credits proposed;
d. The mitigation achieved through the number of credits required meets the
intent of TMC Chapter 18.45; and
e. The Director bases the decision on a written staff report, evaluating the
equivalence of the lost wetland functions with the number of wetland credits required;
and
f. The applicant provides a copy of the wetland bank ledger demonstrating
that the approved number of credits has been removed from the bank.
F Wetland and Buffer Mitigation Location.
1. In instances where portions of a wetland or wetland buffer impacted by
development remain, mitigation for buffer impacts shall be provided on -site. Where an
essential public road, street or right -of -way or essential public utility cannot avoid
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reducing a buffer by more than 50 additional buffer enhancement must be carried out
at other locations around the impacted wetland.
2. On -site mitigation for wetland impacts shall be provided, except where the
applicant can demonstrate that:
a. On -site wetland mitigation is not scientifically feasible due to problems
with hydrology, soils, waves or other factors; or
b. Mitigation is not practical due to potentially adverse impact from
surrounding land uses, or
c. Existing functions created at the site of the proposed restoration are
significantly greater than lost wetland functions or
d. Regional goals for flood storage, flood conveyance, habitat or other
wetland functions have been established and strongly justify location of mitigation at
another site.
3. Off -site mitigation shall occur within the same watershed where the wetland
loss occurred.
4. Mitigation sites located within the Tukwila City limits are preferred.
However, the Director may approve mitigation sites outside the city upon finding that:
a. Adequate measures have been taken to ensure the non development and
long -term viability of the mitigation site; and
b. Adequate coordination with the other affected local jurisdiction has
occurred.
5. In selecting mitigation sites, applicants shall select a site in a location where
the targeted functions can reasonably be performed and sustained and shall pursue
sites in the following order of preference:
a. Sites within the immediate drainage sub basin,
b. Sites within the next higher drainage sub basin; and
c. Sites within Green/ Duwamish River basin.
G. Mitigation Timing. Mitigation projects shall be completed prior to activities that
will permanently disturb wetlands and either prior to or immediately after activities
that will temporarily disturb wetlands. Construction of mitigation projects shall be
timed to reduce impacts to existing wildlife, flora and water quality, and shall be
completed prior to use or occupancy of the activity or development. The Director may
allow activities that permanently disturb wetlands prior to implementation of the
mitigation plan under the following circumstances:
1. To allow planting or re- vegetation to occur during optimal weather
conditions;
2. To avoid disturbance during critical wildlife periods; or
3. To account for unique site constraints that dictate construction timing or
phasing.
18.45.100 Watercourse Designations, Ratings and Buffers
A. Watercourse Ratings. Watercourse ratings are consistent with the Washington
Department of Natural Resources water typing categories (noted in parentheses after
each category), which are based on the existing habitat functions and are rated as
follows:
1. Type 1 (S) Watercourse: Watercourses inventoried as Shorelines of the State,
under RCW 90.58 These watercourses shall be regulated under TMC Chapter 18.44,
Shoreline Overlay.
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2. Type 2 (F) Watercourse: Those watercourses that are known to be used by
fish or meet the physical criteria to be potentially used by fish and that have perennial
(year round) or seasonal flows
3. Type 3 (Np) Watercourse: Those watercourses that have perennial flows and
do not meet the criteria of a Type F stream or have been proven not to contain fish using
methods described in the Forest Practices Board Manual Section 13
4. Type 4 (Ns) Watercourse: Those watercourses that have intermittent flows
(do not have surface flow during at least some portion of the year) and do not meet the
physical criteria of a Type F watercourse.
value;
B. Watercourse Buffers.
1. Any land alteration must be located out of the buffer areas as required by this
section. Watercourse buffers are intended in general to:
a. Minimize long -term impacts of development on properties containing
watercourses;
b. Protect the watercourse from adverse impacts during development;
c. Preserve the edge of the watercourse and its buffer for its critical habitat
d. Provide shading to maintain stable water temperatures and vegetative cover
for additional wildlife habitat;
e. Provide input of organic debris and uptake of nutrients;
f. Provide an area to stabilize banks, to absorb overflow during high water
events and to allow for slight variation of aquatic system boundaries over time due to
hydrologic or climatic effects;
g. Reduce erosion and increased surface water runoff;
h. Reduce loss of, or damage to, property;
i. Intercept fine sediments from surface water runoff and serve to minimize
water quality impacts; and
j. Protect the sensitive area from human and domestic animal disturbance.
2. An undisturbed sensitive area or buffer may substitute for the yard setback and
landscape requirements of TMC Chapter 18.50 and 18.52.
C. Watercourse Buffer Widths. The following buffer widths, measured from the
Ordinary High Water Mark (OHWM), apply to each side of a watercourse. If the
OHWM cannot be determined, then the buffer will be measured from the top of bank:
1. Type 1 (S) Watercourse: Regulated under TMC Chapter 18.44, Shoreline
Overlay
2. Type 2 (F) Watercourse: 100 foot -wide buffer.
3. Type 3 (Np) Watercourse: 80- foot -wide buffer
4. Type 4 (Ns) Watercourse: 50- foot -wide buffer
D. Buffer Setbacks.
1. All commercial and industrial buildings shall be set back 15 feet and all other
development shall be set back 10 feet. Building setbacks shall be measured from the
foundation to the buffer's edge. Building plans shall also identify a 20 -foot area beyond
the buffer setback within which the impacts of development will be reviewed.
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2. The Director may waive setback requirements when a site plan demonstrates
there will be no impacts to the buffer from construction or occasional maintenance
activities (see TMC Figure 18 -2).
E. Variation of Standard Watercourse Buffer Width.
1. The Director may reduce the standard watercourse buffers on a case -by -case
basis, only where the buffer is significantly degraded (due to existing development
within the prescribed buffer width, the presence of significant amount of invasive
vegetation that impairs buffer function, and/ or lack of native vegetation), provided the
remaining buffer is enhanced in accordance with an approved buffer enhancement
plan, prepared by a qualified professional, and does not contain slopes 15% or greater.
Where a buffer has a variable topography that includes Class I slopes on the landward
portion of the buffer, a buffer reduction may be allowed if the proposed reduction is in
the area with the Class I slopes, and a 10 foot planted setback from the top of the slope
is maintained. Further, a geotechnical review of the proposed buffer enhancement plan
must determine that the buffer enhancement can be implemented without destabilizing
the slope. The approved buffer width shall not result in greater than a 50% reduction in
width. Any buffer reduction proposal must demonstrate to the satisfaction of the
Director that it will not result in direct, indirect or long -tern adverse impacts to
watercourses, and that:
(a) The buffer is vegetated and includes an on -site buffer enhancement plan
prepared by a qualified professional, to retain existing native vegetation and install
additional native vegetation in order to improve the buffer function; or
(b) If there is no significant vegetation in the buffer, a buffer may be reduced
only if an on -site buffer enhancement plan is provided. The plan must include using a
variety of native vegetation that improves the functional attributes of the buffer and
provides additional protection for the watercourse functions.
2. Buffers for all types of watercourses will be increased when they are deter-
mined to be particularly sensitive to disturbance or the proposed development will
create unusually adverse impacts. Any increase in the width of the buffer shall be
required only after completion of a watercourse study by a qualified specialist or expert
that documents the basis for such increased width. An increase in buffer width may be
appropriate when:
(a) The development proposal has the demonstrated potential for significant
adverse impacts upon the watercourse that can be mitigated by an increased buffer
width; or
(b) The area serves as habitat for endangered, threatened, sensitive or monitor
species listed by the federal government or the State.
3. Every reasonable effort shall be made to maintain the existing viable native
plant life and non- invasive significant trees in the buffers. Vegetation may be removed
from the buffer as part of an enhancement plan approved by the Director
Enhancements will ensure that slope stability and watercourse quality will be
maintained or improved. Any disturbance of the buffers for watercourses shall be
replanted with a diverse plant community of native northwest species that are
appropriate for the specific site as determined by the Director. If the vegetation must be
removed, or because of the alterations of the landscape the vegetation becomes
damaged or dies, then the applicant for a permit must replace existing vegetation along
watercourses with comparable specimens, approved by the Director, that will restore
buffer functions within five years.
4. The Director shall require subsequent corrective actions and long -term
monitoring of the project if adverse impacts to regulated watercourses or their buffers
are identified.
18.45.110 Watercourse Alterations and Mitigation
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A. Watercourse Alterations. No use or development may occur in a watercourse or
its buffer except as specifically allowed by TMC Chapter 18.45. Any use or
development allowed is subject to the standards of TMC Chapter 18.45
B. Alterations.
1. Diverting or rerouting may only occur with the permission of the Director
and an approved mitigation plan.
2. Any watercourse that has critical wildlife habitat, or is necessary for the life
cycle or spawning of salmonids, shall not be rerouted unless it can be shown that the
habitat will be improved for the benefit of the species.
3. A watercourse may be rerouted or day lighted as a mitigation measure to
improve watercourse function.
4. As a condition of approval, the Director may require water quality
monitoring for stormwater discharges to streams, and additional treatment of
stormwater if water quality standards are not being met.
5. Piping. Piping of any watercourse should be avoided. Relocation of a
watercourse or installation of a bridge is preferred to piping. If piping occurs in a
watercourse sensitive area, it shall be limited to requirements for stream crossings for
access and shall require approval of the Director.
a. Piping of Type 1 watercourses shall not be permitted.
b Piping may be allowed in watercourses if it is necessary for access
purposes. In all watercourses, it must be demonstrated that the piping will not cause
adverse impacts to fish, confine the channel or floodplain, create an entry point for road
run -off, create downstream scouring, cause erosion or sedimentation, or adversely
impact riparian habitat (including downstream habitat).
c. Piping projects shall be performed pursuant to the following applicable
standards:
(1) The conveyance system shall be designed to comply with the
standards in current use and recommended by the Department of Public Works and the
standards of the Washington Department of Fish and Wildlife in the "Design of Road
Culverts for Fish Passage" manual (2003 or as amended).
(2) Where allowed, piping shall be limited to the shortest length possible
as determined by the Director to allow access onto a property
(3) Where water is piped for an access point, those driveways or
entrances shall be consolidated to serve multiple properties where possible, and to
minimize the length of piping.
(4) When required by the Director, watercourses under drivable surfaces
shall be contained in an arch culvert using oversize or super span culverts for
rebuilding of a streambed. These shall be provided with check dams to reduce flows,
and shall be replanted and enhanced according to a plan approved by the Director
(5) All watercourse crossings shall be designed to accommodate fish
passage, unless technically not feasible.
(6) Water quality must be as good or better for any water exiting the pipe
as for the water entering the pipe, and flow must be comparable.
6. Maintenance dredging of watercourses shall be allowed only when necessary
to protect public safety, structures and fish passage and shall be done as infrequently as
possible. Long -term solutions such as stormwater retrofits are preferred over ongoing
maintenance dredging.
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7. Stormwater runoff shall be detained and infiltrated to preserve the
watercourse channel's dominant discharge.
8. All construction shall be designed to have the least adverse impact on the
watercourse, buffer and surrounding environment.
9. All piping or other alterations shall be carried out or constructed during
periods of low flow, or as specified by the State Department of Fish and Wildlife in
accordance with an approved Hydraulics Permit.
10. On properties being developed or re- developed, or when stream crossings in
public or private rights -of -way are being replaced, existing culverts that carry fish
bearing watercourses or those that could bear fish (based on the criteria in WAC 222 -16-
031, Washington Forest Practices Rules and Regulations), shall be upgraded to meet the
standards in the WDFW manual "Design of Road Culverts for Fish Passage" (2003 or as
updated) if technically feasible.
C. Mitigation Plan Content. All impacts to a watercourse that degrade the
functions of the watercourse or its buffer shall be avoided. If alteration to the
watercourse or buffer is unavoidable, all adverse impacts resulting from a development
proposal or alteration shall be mitigated in accordance with an approved mitigation
plan as described below.
1. Mitigation plans shall be completed for any proposals of dredging, filling,
diverting, piping and rerouting of watercourses or buffer impacts and shall be
developed as part of a sensitive area study by a specialist approved by the Director.
The plan must show how water quality, treatment, erosion control, pollution reduction,
wildlife and fish habitat, and general watercourse quality would be improved.
2. The scope and content of a mitigation plan shall be decided on a case -by -case
basis taking into account the degree of impact and extent of mitigation measures
needed. As the impacts to the watercourse or its buffer increase, the mitigation plan to
offset these impacts will increase in extent and complexity.
3. The components of a complete mitigation plan are as follows:
a. Baseline information including existing watercourse conditions such as
hydrologic patterns /flow rates, stream gradient, bank full width, stream bed
conditions, bank conditions, fish and other wildlife use, in- stream structures, riparian
conditions, buffer characteristics, water quality, fish barriers and other relevant
information.
b Environmental goals and objectives that describe the purposes of the
mitigation measures. This should include a description of site selection criteria,
identification of target evaluation species and functions.
c. Performance standards for fulfilling environmental goals and objectives
and for triggering remedial action or contingency measures. Performance standards
may include water quality standards, species richness and diversity targets, habitat
diversity indices, creation of fish habitat, or other ecological, geological or hydrological
criteria.
d. Detailed construction plan of the written specifications and descriptions of
mitigation techniques. This plan should include the proposed construction sequence
and construction management, and be accompanied by detailed site diagrams and
blueprints that are an integral requirement of any development proposal.
e. Monitoring and /or evaluation program that outlines the approach for
assessing a completed project. An outline shall be included that spells out how the
monitoring data will be evaluated by agencies that are tracking the mitigation project's
process. For projects that discharge stormwater to a stream, the Director may require
water quality monitoring.
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f. Contingency plan identifying potential courses of action and any
corrective measures to be taken when monitoring or evaluation indicates project
performance standards have not been met.
g. Performance security or other assurance devices as described in TMC
Section 18.45.210.
D Mitigation Standards.
1. The Washington "Stream Habitat Restoration Guidelines" (Washington State
Aquatic Habitat Guidelines Program, Washington Department of Ecology, US Fish and
Wildlife Service, Washington Department of Fish and Wildlife, 2004 or as amended)
shall be used as Best Available Science for the development of watercourse and buffer
mitigation techniques.
2. The following shall be considered the minimum standards for approved
stream alterations:
(1) Maintenance or improvement of stream channel habitat and
dimensions such that the fisheries habitat functions of the compensatory stream reach
or exceed that of the original stream,
(2) Bank and buffer configuration restored to an enhanced state,
(3) Channel, bank and buffer areas replanted with native vegetation that
improves the original in species diversity and density;
(4) Stream channel bed and biofiltration systems equivalent to (in the
case of public drainage maintenance projects) and better than in the original stream (in
the case of other kinds of projects),
(5) Original fish and wildlife habitat enhanced unless technically not
feasible.
3. Relocation of a watercourse shall not result in the new sensitive area or buffer
extending beyond the development site and onto adjacent property without the written
agreement of the affected property owners.
F. Mitigation Timing. Department of Community Development- approved plans
must have the mitigation construction completed before the existing watercourse can be
modified. The Director may allow activities that permanently disturb a watercourse
prior to implementation of the mitigation plan under the following circumstances:
1. To allow planting or re- vegetation to occur during optimal weather
conditions; or
2. To avoid disturbance during critical wildlife periods; or
3. To account for unique site constraints that dictate construction timing or
phasing.
18.45.120 Areas of Potential Geologic Instability Designations, Ratings and
Buffers
A. Designation. Areas of potential geologic instability are classified as follows:
1. Class 1 area, where landslide potential is low, and which slope is less than
15
2. Class 2 areas, where landslide potential is moderate, which slope is between
15% and 40 and which are underlain by relatively permeable soils;
3 Class 3 areas, where landslide potential is high, which include areas sloping
between 15% and 40 and which are underlain by relatively impermeable soils or by
bedrock, and which also include all areas sloping more steeply than 40
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4. Class 4 areas, where Landslide potential is very high, which include sloping
areas with mappable zones of groundwater seepage, and which also include existing
mappable landslide deposits regardless of slope;
B. Buffers.
1. The buffers for areas of potential geologic instability are intended to:
a. Minimize long -term impacts of development on properties containing
sensitive areas;
b. Protect sensitive areas from adverse impacts during development;
c. Prevent loading of potentially unstable slope formations;
d. Protect slope stability;
e. Provide erosion control and attenuation of precipitation surface water and
stormwater runoff; and
f. Reduce loss of or damage to property.
2. An undisturbed sensitive area or buffer may substitute for the yard setback and
landscape requirements of TMC Section 18.50 and 18.52.
C. Each development proposal containing or threatened by an area of potential
geologic instability Class 2 or higher shall be subject to a geotechnical report pursuant
to the requirements of TMC Chapter 18.45.040 B and 18 45.060. The geotechnical report
shall analyze and make recommendations on the need for and width of any setbacks or
buffers necessary to achieve the goals and requirements of TMC Chapter 18.45.
Development proposals shall then include the buffer distances as defined within the
geotechnical report.
D. Buffers may be increased by the Director when an area is determined to be
particularly sensitive to the disturbance created by a development. Such a decision will
be based on a City review of the report as prepared by a qualified geotechnical engineer
and by a site visit.
18.45.130 Areas of Potential Geologic Instability Uses, Exemptions, Alterations and
Mitigation.
A. General. The uses permitted in the underlying zoning district may be
undertaken on sites that contain areas of potential geologic instability subject to the
standards of this section and the recommendations of a geotechnical study
B. Exemptions. The following areas are exempt from regulation as geologically
hazardous areas:
1. Temporary stockpiles of topsoil, gravel, beauty bark or other similar
landscaping or construct materials;
2. Slopes related to materials used as an engineered pre -load for a building pad,
3. Any temporary slope that has been created through legal grading activities
under an approved permit may be re- graded without application of TMC Chapter 18.45
under an approved permit;
4. Roadway embankments within right -of -way or road easements; and
5. Slopes retained by approved engineered structures.
C. Alterations.
1 Prior to permitting alteration of an area of potential geologic instability, the
applicant must demonstrate one of the following:
a. There is no evidence of past instability or earth movement in the vicinity
of the proposed development, and where appropriate, quantitative analysis of slope
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stability indicates no significant risk to the proposed development or surrounding
properties; or
b. The area of potential geologic instability can be modified or the project can
be designed so that any potential impact to the project and surrounding properties is
eliminated, slope stability is not decreased, and the increase in surface water discharge
or sedimentation shall not decrease slope stability
2. Where any portion of an area of potential geologic instability is cleared for
development, a landscaping plan for the site shall include tree replanting with an equal
mix of evergreen and deciduous trees, preferably native, and approved by the Director.
Replacement vegetation shall be sufficient to provide erosion and stabilization
protection.
D. Disclosures, Declarations and Covenants.
1. It shall be the responsibility of the applicant to submit, consistent with the
findings of the geotechnical report, structural plans that were prepared and stamped by
a structural engineer The plans and specifications shall be accompanied by a letter
from the geotechnical engineer who prepared the geotechnical report stating that in
his /her judgment the plans and specifications conform to the recommendations in the
geotechnical report, the risk of damage to the proposed development site from soil
instability will be minimal subject to the conditions set forth in the report, and the
proposed development will not increase the potential for soil movement.
2. Further recommendations signed and sealed by the geotechnical engineer
shall be provided should there be additions or exceptions to the original
recommendations based on the plans, site conditions or other supporting data. If the
geotecluucal engineer who reviews the plans and specifications is not the same engineer
who prepared the geotechnical report, the new engineer shall, in a letter to the City
accompanying the plans and specifications, express his or her agreement or
disagreement with the recommendations in the geotechnical report and state that the
plans and specifications conform to his or her recommendations.
3. The architect or structural engineer shall submit to the City, with the plans
and specifications, a letter or notation on the design drawings at the time of permit
application stating that he or she has reviewed the geotechnical report, understands its
recommendations, has explained or has had explained to the owner the risks of loss due
to slides on the site, and has incorporated into the design the recommendations of the
report and established measures to reduce the potential risk of injury or damage that
might be caused by any earth movement predicted in the report.
4. The owner shall execute a Sensitive Areas Covenant and Hold Harmless
Agreement running with the land on a form provided by the City The City will file the
completed covenant with the King County Department of Records and Elections at the
expense of the applicant or owner. A copy of the recorded covenant will be forwarded
to the owner.
E. Assurance Devices. Whenever the City determines that the public interest
would not be served by the issuance of a permit in an area of potential geologic
instability without assurance of a means of providing for restoration of areas disturbed
by, and repair of property damage caused by, slides arising out of or occurring during
construction, the Director may require assurance devices pursuant to TMC Section
18.45.210.
F. Construction Monitoring.
1. Where recommended by the geotechnical report, the applicant shall retain a
geotechnical engineer to monitor the site during construction. The applicant shall
preferably retain the geotechnical engineer who prepared the final geotechnical recom-
mendations and reviewed the plans and specifications. If a different geotechnical
engineer is retained by the owner, the new geotechnical engineer shall submit a letter to
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the City stating whether or not he /she agrees with the opinions and recommendations
of the original geotechnical engineer. Further recommendations, signed and sealed by
the geotechnical engineer, and supporting data shall be provided should there be
exceptions to the original recommendations.
2. The geotechnical engineer shall monitor, during construction, compliance
with the recommendations in the geotechnical report, particularly site excavation,
shoring, soil support for foundations including piles, subdrainage installations, soil
compaction and any other geotechnical aspects of the construction. Unless otherwise
approved by the City, the specific recommendations contained in the soils report must
be implemented by the owner The geotechnical engineer shall make written, dated
monitoring reports on the progress of the construction to the City at such timely
intervals as shall be specified. Omissions or deviations from the approved plans and
specifications shall be immediately reported to the City. The final construction
monitoring report shall contain a statement from the geotechnical engineer that based
upon his or her professional opinion, site observations and testing during the
monitoring of the construction, the completed development substantially complies with
the recommendations in the geotechnical report and with all geotechnical- related
permit requirements. Occupancy of the project will not be approved until the report
has been reviewed and accepted by the Director.
G. Conditioning and Denial of Use or Developments.
1. Substantial weight shall be given to ensuring continued slope stability and
the resulting public health, safety and welfare in determining whether a development
should be allowed.
2. The City may impose conditions that address site -work problems which
could include, but are not limited to, limiting all excavation and drainage installation to
the dryer season, or sequencing activities such as installing erosion control and
drainage systems well in advance of construction. A permit will be denied if it is
determined by the Director that the development will increase the potential of soil
movement that results in an unacceptable risk of damage to the proposed development,
its site or adjacent properties.
18.45.140 Abandoned Mine Areas
A. Development of a site containing an abandoned mine area may be permitted
when a geotechnical report shows that significant risks associated with the abandoned
mine workings can be eliminated or mitigated so that the site is safe. Approval shall be
obtained from the Director before any building or land altering permit processes begin.
B. Any building setback or land alteration shall be based on the geotechnical report.
C. The City may impose conditions that address site -work problems which could
include, but are not limited to, limiting all excavation and drainage installation to the
dryer season, or sequencing activities such as installing drainage systems or erosion
controls well in advance of construction. A permit will be denied if it is determined
that the development will increase the potential of soil movement or result in an
unacceptable risk of damage to the proposed development or adjacent properties.
D. The owner shall execute a Sensitive Areas Covenant and Hold Harmless
Agreement running with the land on a form provided by the City. The City will file the
completed covenant with the King County Division of Records and Elections at the
expense of the applicant or owner. A copy of the recorded covenant will be forwarded
to the owner.
18.45.150 Fish and Wildlife Habitat Conservation Areas Designation, Mapping,
Uses and Standards
A. Designation. Fish and wildlife habitat conservation areas include the habitats
listed below:
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1. Areas with which endangered, threatened, and sensitive species have a
primary association;
2. Habitats and species of local importance, including but not limited to bald
eagle habitat, heron rookeries;
3 Commercial and recreational shellfish areas,
4. Kelp and eelgrass beds;
5 Mudflats and marshes;
6. Naturally occurring ponds under 20 acres and their submerged aquatic beds
that provide fish or wildlife habitat;
7. Waters of the State;
8. State natural area preserves and natural resource conservation areas; and
9. Areas critical for habitat colulectivity.
B. Mapping.
1. The approximate location and extent of known fish and wildlife habitat
conservation areas are identified by the City's Sensitive Areas Maps, inventories, open
space zones, and Natural Environment Background Report. The City designates 1, 2, 5,
6, 7, and 9 above as known fish and wildlife habitats within its current limits.
2. Fish and wildlife habitat conservation areas correlate closely with the areas
identified as regulated watercourses and wetlands and their buffers in Tukwila. The
Green /Duwamish River is recognized as the most significant fish and wildlife habitat
corridor, as well as off channel habitat areas created in the river to improve salmon
habitat (shown on the Sensitive Areas Map) in the Shoreline jurisdiction. Gilliam
Creek, Riverton Creek, Southgate Creek, Johnson Creek, and Hamm Creek (in the north
PAA) all provide salmonid habitat. In addition, the Native Growth Protection Area in
the Tukwila South project area provides an important upland wildlife habitat corridor.
Tukwila Pond and its associated wetlands also meet the definition of a fish and wildlife
habitat for waterfowl and other birds during all seasons of the year In addition to the
Sensitive Areas Maps, the following maps are to be used as a guide for the City, but do
not provide a final habitat area designation.
a. Washington State Department of Fish and Wildlife Priority Habitat
Species Maps;
b. Anadromous and resident salmonid distribution maps contained in the
Habitat Limiting Factors reports published by the Washington Conservation
Commission; and
c. Washington State Digital Coastal and Coastal Zone Management
Program.
C. Buffers. Fish and Wildlife Habitat Conservation Areas shall have buffers no less
than 100 feet in width. Buffer reductions approved for an underlying wetland or
watercourse shall also apply to the related Conservation Area.
D Uses and Standards. Fish and wildlife habitat conservation areas will be
regulated through TMC Chapter 18 44, Shoreline Overlay District, and the regulations
in TMC Chapter 18.45 related to wetlands and watercourses. No additional use
regulations apply specifically to Conservation Areas.
18.45.160 Sensitive Area Master Plan Overlay
A. The purpose of this section is to provide an alternative to preservation of existing
individual wetlands, watercourses and their buffers in situations where an area -wide
plan for alteration and mitigation will result in improvements to water quality, fish and
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wildlife habitat and hydrology beyond those that would occur through the strict
application of the provisions of TMC Chapter 18.45.
B. The City Council may designate certain areas as Sensitive Area Master Plan
Overlay Districts for the purpose of allowing and encouraging a comprehensive
approach to sensitive area protection, restoration, enhancement and creation in
appropriate circumstances utilizing best available science. Designation of Sensitive
Area Master Plan Overlay Districts shall occur through the Type 5 decision process
established by TMC Chapter 18.104.
C. Criteria for designating a Sensitive Area Master Plan Overlay District shall be as
follows:
1. The overlay area shall be at least 10 acres.
2. The City Council shall find that preparation and implementation of a
Sensitive Area Master Plan is likely to result in net improvements in sensitive area
functions when compared to development under the general provisions of TMC
Chapter 18.45
D. Within a Sensitive Area Master Plan Overlay District, only those uses permitted
under TMC Sections 18.45.070, 18.45.090 and 18.45.110 shall be allowed within a
Category I wetland, a Type 1 (S) watercourse, or their buffers.
E. Within a Sensitive Area Master Plan Overlay district, the uses permitted under
TMC 18.45.070, 18.45.090 and 18.45.110 and other uses as identified by an approved
Sensitive Area Master Plan shall be permitted within Category III and Category IV
wetlands and their buffers; and within Type 2, (F) 3 (Np) and 4 (Ns) watercourses and
their buffers, provided that such uses are allowed by the underlying zoning
designation.
F. A Sensitive Area Master Plan shall be prepared under the direction of the
Director of Community Development. Consistent with subsection A, the Director may
approve development activity within a Sensitive Area Overlay District for the purpose
of allowing and encouraging a comprehensive approach to sensitive areas protection,
creation, and enhancement that results in environmental benefits that may not be
otherwise achieved through the application of the requirements of TMC Chapter 18.45
G. The Director shall consider the following factors when determining whether a
proposed Sensitive Areas Overlay and Master Plan results in an overall net benefit to
the environment and is consistent with best available science:
1. Whether the Master Plan is consistent with the goals and policies of the
Natural Environment Element of the Tukwila Comprehensive Plan.
2. Whether the Master Plan is consistent with the purposes of TMC Chapter
18.45 as stated in TMC Section 18.45.010.
3 Whether the Master Plan includes a Mitigation Plan that incorporates stream
or wetland restoration, enhancement or creation meeting or exceeding the requirements
of TMC Section 18.45.090 and or TMC Section 18.45.110 as appropriate.
4. Whether proposed alterations or modifications to sensitive areas and their
buffers and /or alternative mitigation results in an overall net benefit to the natural
environment and improves sensitive area functions.
5 Whether the Mitigation Plan gives special consideration to conservation and
protection measures necessary to preserve or enhance anadromous fisheries.
6. Mitigation shall occur on -site unless otherwise approved by the Director The
Director may approve off -site mitigation only upon determining that greater protection,
restoration or enhancement of sensitive areas could be achieved at an alternative
location within the same watershed.
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7. Where feasible, mitigation shall occur prior to grading, filling or relocation of
wetlands or watercourses.
8. At the discretion of the Director, a proposed Master Plan may undergo peer
review, at the expense of the applicant. Peer review, if utilized, shall serve as one
source of input to be utilized by the Director in making a final decision on the proposed
action.
H. A Sensitive Area Master Plan shall be subject to approval by the Director of
Community Development. Such approval shall not be granted until the Master Plan
has been evaluated through preparation of an Environmental Impact Statement (EIS)
under the requirements of TMC Chapter 21.04. The EIS shall compare the
environmental impacts of development under the proposed Master Plan relative to the
impacts of development under the standard requirements of TMC Chapter 18.45 The
Director shall approve the Sensitive Area Master Plan only if the evaluation clearly
demonstrates overall environmental benefits, giving special consideration to
conservation or protection measures necessary to preserve or enhance anadromous
fisheries.
18.45.170 Sensitive Areas Tracts and Easements
A. Development. In development proposals for planned residential or mixed use
developments, short subdivisions or subdivisions, and boundary line adjustlnents and
binding site plans, applicants shall create sensitive areas tracts or easements, in lieu of
an open space tract, per the standards of the Planned Residential Development District
chapter of this title.
B Applicant. Applicants proposing development involving uses other than those
listed in TMC Section 18.45.170A, on parcels containing sensitive areas or their buffers,
may elect to establish a sensitive areas tract or easement which shall be:
1. If under one ownership, owned and maintained by the ownership,
2. If held in common ownership by multiple owners, maintained collectively; or
3. Dedicated for public use if acceptable to the City or other appropriate public
agency.
C. Notice. A notice shall be placed on the property title or plat map that sensitive
area tracts or easements shall remain undeveloped in perpetuity
18.45.180 Exceptions
A. Reasonable Use Exceptions.
1. If application of TMC Chapter 18.45 would deny all reasonable use of the
property containing wetlands, watercourses or their buffers, the property owner or the
proponent of a development proposal may apply for a reasonable use exception.
2. Applications for a reasonable use exception shall be a Type 4 decision and
shall be processed pursuant to TMC Chapter 18.104.
3 If the applicant demonstrates to the satisfaction of the Planning Commission
that application of the provisions of TMC Chapter 18.45 would deny all reasonable use
of the property, development may be allowed which is consistent with the general
purposes of TMC Chapter 18.45 and the public interest.
4. The Commission, in granting approval of the reasonable use exception, must
determine that:
a. There is no feasible on -site alternative to the proposed activities, including
reduction in size or density, modifications of setbacks, buffers or other land use
restrictions or requirements, phasing of project implementation, change in timing of
activities, revision of road and lot layout, and/ or related site planning that would allow
a reasonable economic use with fewer adverse impacts to the sensitive area.
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b As a result of the proposed development there will be no unreasonable
threat to the public health, safety or welfare on or off the development proposal site.
c. Alterations permitted shall be the minimum necessary to allow for
reasonable use of the property.
d. The proposed development is compatible in design, scale and use with
other development with similar site constraints in the immediate vicinity of the subject
property if such similar sites exist.
e. Disturbance of sensitive areas has been minimized by locating any
necessary alterations in the buffers to the greatest extent possible.
f. The inability to derive reasonable use of the property is not the result of:
(1) a segregation or division of a larger parcel on which a reasonable use
was permittable after the effective date of Sensitive Areas Ordinance No. 1599, June 10,
1991;
(2) actions by the owner of the property (or the owner's agents,
contractors or others under the owner's control) that occurred after the effective date of
the sensitive areas ordinance provisions that prevents or interferes with the reasonable
use of the property; or
(3) a violation of the sensitive areas ordinance.
g. The Commission, when approving a reasonable use exception, may
impose conditions, including but not limited to a requirement for submission and
implementation of an approved mitigation plan designed to ensure that the
development:
(1) complies with the standards and policies of the sensitive areas
ordinance to the extent feasible; and
(2) does not create a risk of damage to other property or to the public
health, safety and welfare.
h. Approval of a reasonable use exception shall not eliminate the need for
any other permit or approval otherwise required for a project, including but not limited
to design review
B. Emergencies. Alterations in response to an emergency that poses an immediate
threat to public health, safety or welfare, or that poses an immediate risk of damage to
private property may be excepted. Any alteration undertaken as an emergency shall be
reported within one business day to the Community Development Department. The
Director shall confirm that an emergency exists and determine what, if any, mitigation
and conditions shall be required to protect the health, safety, welfare and environment
and to repair any damage to the sensitive area and its required buffers. Emergency
work must be approved by the City. If the Director determines that the action taken, or
any part thereof, was beyond the scope of an allowed emergency action, then the
enforcement provisions of TMC Section 18.45.195 shall apply.
18.45.190 Appeals
A. Any appeal of a final decision made by the Community Development
Department, pursuant to TMC Chapter 18.45, shall be an appeal of the underlying
permit or approval. Any such appeal shall be processed pursuant to TMC Section
18.108.020 and TMC Chapter 18.116.
B In considering appeals of decisions or conditions, the following shall be
considered.
1. The intent and purposes of the sensitive areas ordinance;
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2. Technical information and reports considered by the Community
Development Department; and
3. Findings of the Director, which shall be given substantial weight.
18.45.195 Enforcement and Penalties
A. Violations. The following actions shall be considered a violation of this chapter.
1. To use, construct or demolish a structure or to conduct clearing, earth
moving, construction or other development not authorized under a Special Permission,
Reasonable Use or other permit where such permit is required by this chapter
2. Any work that is not conducted in accordance with the plans, conditions, or
other requirements in a permit approved pursuant to this chapter, provided the terms
or conditions are stated in the permit or the approved plans.
3. To remove or deface any sign, notice, complaint or order required by or
posted in accordance with this chapter.
4. To misrepresent any material fact in any application, plans or other
information submitted to obtain any sensitive area use, buffer reduction or
development authorization.
5. To fail to comply with the requirements of this chapter
B Enforcement. It shall be the duty of the Community Development Director to
enforce this chapter pursuant to the terms and conditions of TMC Chapter 8 45
C. Inspection Access.
1. For the purposes of inspection for compliance with the provisions of a perrnit
or this chapter, authorized representatives of the Community Development Director
may enter all sites for which a permit has been issued.
2. Upon completion of all requirements of a permit, the applicant shall request a
final inspection by contacting the planner of record. The permit process is complete
upon final approval by an authorized representative of the Community Development
Director.
D. Penalties.
1. Any violation of any provision of this chapter, or failure to comply with any
of the requirements of this chapter, shall be subject to the penalties prescribed in TMC
Chapter 8 45, "Enforcement," and shall be imposed pursuant to the procedures and
conditions set forth in that chapter.
2. It shall not be a defense to the prosecution for failure to obtain a permit
required by this chapter that a contractor, subcontractor, person with responsibility on
the site, or person authorizing or directing the work erroneously believed a permit had
been issued to the property owner or any other person.
E. Remedial Measures Required. In addition to penalties provided in TMC
Chapter 8.45, the Director may require any person conducting work in violation of this
chapter to mitigate the impacts of unauthorized work by carrying out remedial
measures.
1. Remedial measures must conform to the policies and guidelines of this
chapter.
2. The cost of any remedial measures necessary to correct violation(s) of this
chapter shall be borne by the property owner and/ or applicant.
F. Injunctive Relief.
1. Whenever the City has reasonable cause to believe that any person is
violating or threatening to violate the sensitive areas regulations or any rule or other
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provisions adopted or issued pursuant to these regulations, it may either before or after
the institution of any other action or proceeding authorized by this ordinance, institute
a civil action in the name of the City for injunctive relief to restrain the violation or
threatened violation. Such action shall be brought in King County Superior Court.
2. The institution of an action for injunctive relief under this section shall not
relieve any party to such proceedings from any civil or criminal penalty prescribed for
violations of these regulations.
G. Abatement. Any use, structure, development or work that occurs in violation of
these regulations, or in violation of any lawful order or requirement of the Director
pursuant to this section, shall be deemed to be a public nuisance and may be abated in
the manner provided by the Tukwila Municipal Code, Section 8 45.105.
18.45.200 Recording Required
The property owner receiving approval of a use or development permit pursuant to
TMC Chapter 18.45 shall record the City- approved site plan, clearly delineating the
wetland, watercourse, areas of potential geologic instability or abandoned mine and
their buffers designated by TMC Sections 18.45.080, 18.45.090, 18.45.100, 18.45.120,
18.45.140 and 18.45.150 with the King County Division of Records and Elections. The
face of the site plan must include a statement that the provisions of TMC Chapter 18.45,
as of the effective date of the ordinance from which TMC Chapter 18.45 derives or is
thereafter amended, control use and development of the subject property, and provide
for any responsibility of the property owner for the maintenance or correction of any
latent defects or deficiencies.
18.45.210 Assurance Device.
A. In appropriate circumstances, such as when mitigation is not completed in
advance of the project, the Director may require a letter of credit or other security
device acceptable to the City to guarantee performance and maintenance requirements
of TMC Chapter 18.45 All assurances shall be on a form approved by the City Attorney
and be equal to 150% of the cost of the labor and materials for implementation of the
approved mitigation plan.
B. When alteration of a sensitive area is approved, the Director may require an
assurance device, on a form approved by the City Attorney, to cover the cost of
monitoring and maintenance costs and correction of possible deficiencies for five years.
In the event that more than five years monitoring and maintenance is required, the
amount of security required will be for the first five years and years 7 and 10 If at the
end of five years performance standards are not being achieved, an increase in the
security device may be required by the Director. When another agency requires
monitoring beyond the City's time period, copies of those monitoring reports shall be
provided to the City.
C. The assurance device shall be released by the Director upon receipt of written
confirmation submitted to the Department from the applicant's qualified professional
that the mitigation or restoration has met its performance standards and is successfully
established. Should the mitigation or restoration meet performance standards and be
successfully established in the third or fourth year of monitoring, the City may release
the assurance device early. The assurance device may be held for a longer period, if at
the end of the monitoring period, the performance standards have not been met or the
mitigation has not been successfully established. In such cases, the monitoring period
will be extended and the bond held until the standards have been met.
D. Release of the security does not absolve the property owner of responsibility for
maintenance or correcting latent defects or deficiencies or other duties under law.
18.45.220 Assessment Relief
A. Fair Market Value. The King County Assessor considers sensitive area
regulations in determining the fair market value of land under RCW 84.34.
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B. Current Use Assessment. Established sensitive area tracts or easements, as
defined in the Definitions chapter of this title and provided for in TMC Section
18.45.170, may be classified as open space and owners thereof may qualify for current
use taxation under RCW 18.34; provided, such landowners have not received density
credits, or setback or lot size adjustments as provided in the Planned Residential
Development District chapter of this title.
C. Special Assessments. Landowners who qualify under TMC Section 18 45.220 B
shall also be exempted from special assessments on the sensitive area tract or easement
to defray the cost of municipal improvements such as sanitary sewers, storm sewers
and water mains.
Section 2. Repealer. Ordinance Nos. 2074 and 2174 are hereby repealed.
Section 3. Severability. If any section, subsection, paragraph, sentence, clause or
phrase of this ordinance or its application to any person or situation should be held to
be invalid or unconstitutional for any reason by a court of competent jurisdiction, such
invalidity or unconstitutionality shall not affect the validity or constitutionality of the
remaining portions of this ordinance or its application to any other person or situation.
Section 4. Effective Date. This ordinance or a summary thereof shall be published
in the official newspaper of the City, and shall take effect and be in full force five days
after passage and publication as provided by law
PASSED BY THE CITY COUNCIL OF THE CITY OF TUKWILA, WASHINGTON,
at a Regular Meeting thereof this day of 2010
ATTEST /AUTHENTICATED
Christy O'Flaherty, CMC, City Clerk
APPROVED AS TO FORM BY:
Office of the City Attorney
Attachment: Exhibit A Memo
Exhibit B Map Corrections
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Jim Haggerton, Mayor
Filed with the City Clerk:
Passed by the City Council:
Published:
Effective Date:
Ordinance Number:
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City of Tukwila
Department of Community Development
ADDENDUM TO SAO DEPARTURES MEMO FOR WETLAND
WATERCOURSE BUFFER WIDTHS
BACKGROUND AND PURPOSE
June 17, 2010
BEST AVAILABLE SCIENCE FOR WETLAND BUFFERS
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EXHIBIT A
Jim Haggerton, Mayor
Jack Pace, Director
The City of Tukwila adopted its Sensitive Areas Ordinance (SAO, codified in TMC 18.45) in 2004, as
required by the State Growth Management Act. As part of the development of the regulations three
technical documents were prepared in 2003 by the City's consultant, ESA Adolfson: 1) Best Available
Science (BAS) Report for Wetlands, 2) Best Available Science Report for Watercourses; and 3) a memo
explaining the reasons for departures from BAS "BAS Departures Memo
The original departures analysis identified three areas where the City's proposed ordinance deviated from
BAS for wetlands: the wetland classification system, wetland buffer widths, and wetland mitigation
ratios. The City is in the process of updating its Sensitive Areas Ordinance and this addendum has been
prepared to document remaining departures from BAS.
One of the proposed modifications to the Sensitive Areas Ordinance is to adopt the Washington State
Wetland Rating System for Western Washington. Another proposed modifications it to adopt the
recommended wetland mitigation ratios in the "Wetland Mitigation in Washington State, Agency Policies
and Guidance thus meeting BAS for these two areas. The continuing departure from BAS in the
Sensitive Areas Ordinance is related to the establishment of wetland and watercourse buffers.
Best Available Science for establishing wetland buffers is documented in "Wetlands in Washington State,
Volume 1: A Synthesis of the Science (March 2005) and in Volume 2, Protecting and Managing
Wetlands April 2005. These are jointly issued documents prepared by the Washington Department of
Ecology, the Seattle District Corps of Engineers, and the US Environmental Protection Agency.
Volume II provides three alternatives for establishing buffers, based on BAS: 1) width based on wetland
category, 2) width based on wetland category and the intensity of impacts from proposed changes in land
use; and 3) buffer width based on wetland category, intensity of impacts and wetland functions or special
characteristics.
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6300 Southcenter Boulevard, Suite #100 Tukwila, Washington 98188 a Phone 206 431 -3670 Fax: 206 431 -3665
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For the first alternative (based on wetland category alone), the wetland buffer widths would be as follows:
Category I 300 feet
Category II 300 feet
Category III 150 feet
Category IV 50 feet
For the second alternative (based on wetland category and extent of impact) the following buffer widths
would apply:
1 Wetland Category 1; Al land iS I Moderat61thid use irripaet Illiti 1and iiiii.46f
1 I 1 150ft 1 225ft 300 ft. 1
1 II 1 150ft 1 225ft 300ft
1 III 1 75ft 110ft 150ft
1 IV 1 25 ft 1 40 ft 50 ft
For the third category (wetland category, impact from land use and wetland functions) the buffer ranges
would vary as follows:
Category I ranging from 50 feet to 250 feet depending on level of functions and forested
wetlands buffers are detennined on a case by case basis)
Category II ranging from 50 to 300 feet depending on level of functions
Category III ranging from 40 to 150 feet, depending on level of functions
Category IV ranging from 25 to 50 feet, depending on level of functions
Tukwila is not proposing to modify its wetland buffers from those that are already in the draft SMP and
which reflect the widths in the current Sensitive Areas Ordinance. Current required buffer widths are:
Category I 100 feet (there are no wetlands in Tukwila that currently score highly
enough to qualify for this category)
Category II 100 feet (roughly equivalent to current Type I wetland)
Category III 80 feet (roughly equivalent to current Type II)
Category IV 50 feet (roughly equivalent to current Type III)
No Category I wetlands exist in Tukwila The City's Category II wetland buffer width, currently in the
Sensitive Areas Ordinance would fall within the low range of BAS -based buffer widths, as defined in
"Wetlands in Washington State, Volume 2, Protecting and Managing Wetlands" if alternative 3 were
used, depending on proposed land uses and wetland functions. The City's Category III wetland buffers
Where wetlands have already been assessed using the Washington State Wetland Rating System, the state system
classifications will be so shown on revisions to the SAO map. Where this classification system has not been applied
to wetlands, they will be provisionally classified as indicated in the text. This approach is based on experience
applying both Tukwila's and the state classification systems. For example where the wetland was rated a Type 2
under Tukwila's existing system, it is scored as a Category III under the state system.
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would fall within the low end of the range if alternatives 2 or 3 were used to set buffer widths, depending
on proposed land use impacts and wetland functions. Finally, the current SAO buffer widths for Category
N wetlands are consistent with the recommended buffer widths based on BAS.
Another alternative approach for establishing wetland buffer widths was adopted by the City of Renton
and approved by the Depai anent of Ecology, and is based on wildlife habitat functions. Buffer widths
would be 50 feet for all Category N wetlands, no matter what the habitat score and would range from 75
150 feet for Category III Wetlands, 100 to 225 feet for Category II wetlands, and 125 225 feet for
Category I wetlands, all depending on habitat scores. In general Tukwila wetlands would score very low
for habitat function due to the urbanized nature of the city and the fact that most of the wetlands are
isolated and surrounded by dense development. If that is assumed to be true, Tukwila buffer widths
already comply with the low end of the buffer widths adopted by Renton (Category N 50 feet,
Category III 75 feet [Tukwila specifies 80 feet], and Category II 100 feet).
Tukwila's SAO further deviates from BAS by allowing buffer reductions of up to 50 percent for degraded
buffers, in exchange for buffer enhancement (enhancement generally involves removal of invasive plants;
soil amendments; installation of native plants, including trees; and mulching). Although this provision
allows for reduction of the buffer to less than BAS based widths, buffer reduction is intended to improve
buffer function over what currently exists in the mostly degraded wetland buffers in Tukwila. The code
does not allow buffer reductions for buffers that are not degraded.
BEST AVAILABLE SCIENCE FOR WATERCOURSE BUFFERS
The Washington Department of Natural Resources under the Forest Practices Rules (WAC 222 -16 -030)
designates water types for watercourses and also specifies buffer widths for each watercourse type. These
prescribed buffer widths are considered to be based on Best Available Science, but it should be noted that
they were developed for forest practices and don't necessarily make sense for urbanized areas, where little
if any forested buffers remain along watercourses.
Under the DNR system, the following buffers (Riparian Management Zones RMZ) would apply to
watercourses in Western Washington:
Watercourse Type Buffer Width (RMZ) (feet)
Type S (Tukwila Type 1) 200
Type F (Tukwila Type 2) 140 -170
Type Np (Tukwila Type 3) 110
Type Ns (Tukwila Type 4) 90
The Washington Department of Fish and Wildlife (WDFW) in its report entitled "Management
Recommendations for Washington Priority Habitats: Riparian provides standard recommended Riparian
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Habitat Area (RHA) widths, based on BAS as shown in the
current WDNR typing system).
Watercourse Type
Type S and F streams
Type Np streams; or other perennial or fish bearing streams
1.5 -6.1 m (5 -20 ft) wide
Type Np streams; or other perennial or fish bearing streams
<1.5 m (5 ft) wide
Type Ns streams; or intermittent streams and washes with low
mass wasting* potential
Type Ns streams; or intermittent streams and washes with
high mass wasting potential
Watercourses
following table (stream typing adapted to
Recotnrnerided:RHA. Widths (feet)
250
200
150
150
225
ANALYSIS OF EXISTING SENSITIVE AREA BUFFERS IN THE SHORELINE
JURISDICTION
The development pattern in Tukwila is typical of an urban area with many sections of watercourses
channelized or piped, wetlands isolated and disconnected from habitat corridors and both watercourses
and wetlands with narrow degraded buffers that have significant invasive vegetation and low buffer
function. This development primarily occurred over a period of years prior to the passage of the Growth
Management Act and the adoption of sensitive area regulations in Tukwila. As a result, development has
encroached in most areas of the city to the point where applying buffer widths complying with those
based on BAS would make many existing sites partially or completely nonconforming and vegetating the
buffer would be unachievable due to existing development.
In order to justify the deviation from BAS for buffer widths, the City has analyzed existing buffer
conditions and effective widths for many sensitive areas. The results of the analysis are provided below.
Tukwila has analyzed the existing buffer conditions for watercourses and evaluated the opportunities for
achieving wider buffers and improved buffer functions. Our findings are presented below for each major
watercourse. The reaches of the major watercourses which are in the Shoreline Jurisdiction are not
addressed in this analysis. There are other short fragments of watercourses (mostly seasonal and not fish-
bearing) that drain wetlands or carry seeps from slopes, which generally have minimal and very disturbed
buffers and are not included in this analysis.
In general, most watercourses have been channelized and left with significantly reduced buffers over
years of development prior to adoption of critical areas legislation. In many cases watercourse segments
flow through roadside ditches that have virtually no buffers except for narrow strips of mowed
grass /weeds. Many stream segments flow through residential properties, where buffers have been
reduced or eliminated for lawn and non native landscaping.
Riverton Creek. This watercourse flows through residential and commercial /industrial areas and, prior to
the establishment of sensitive area protections, was rerouted, channelized, straightened, and culverted
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throughout its length. Many sections of the watercourse have steepened and hardened banks (rip rap,
concrete walls) and little buffer vegetation.
The upper reaches of both the east and west tributaries of Riverton Creek flow mostly through
residentially developed properties, and are characterized by narrow (ranging from 2 to 30 feet on
average), disturbed buffers. Some narrow portions of the buffer are vegetated with native trees, others are
in residential lawn areas and are mowed to the edge of the bank. Others are largely vegetated by invasive
and/or ornamental shrubs.
In the west tributary, the watercourse is mostly open, except where it is culverted to pass underneath SR
599 and associated ramps, under local streets and across existing paved areas of commercial and
industrial development. In this area, the watercourse has been moved to the edges of industrially
developed land between parking lots and the highway. Actual vegetated buffers in these reaches range
from about 90 feet for about 1500 feet of its length on the west, narrowing to 15 -30 feet; and 5 -30 feet on
the east. Across one developed property the watercourse is confined to a concrete walled channel, with
some meanders and vegetated buffers (trees, shrubs, recently planted small trees in some parts) varying
from 5 to 10 feet wide. Due to the constraints presented by existing development and road infrastructure,
minimal to no opportunity is available for increasing the vegetated buffer.
The lower reach of the east tributary is piped for over 2,600 feet, where it then flows in an open ditch in
the right of way of SR 599. In this location it has periodically mowed narrow buffers. It then flows
through a culvert and is united with the west tributary in an open ditch as previously described. Due to
the constraints presented by existing development, there is little opportunity for achieving wider effective
buffers on this watercourse.
Recent riparian restoration work done by property owners on a small segment of this watercourse
illustrate how buffer reduction tends to work in Tukwila. The watercourse reach in question is classified
as a Type 2 watercourse (F) and required a buffer of 100 feet. In the first case, the existing buffer was
already impacted by a single family residence, lawn and a driveway. The buffer was vegetated by
invasive plants with some overstory of small native trees and ranged from 10 to 50 feet in width between
the existing house and the driveway. The property owner applied to short-plat the property, which would
require respecting the regulatory buffer of 100 feet. A buffer reduction was granted and the buffer was
enhanced by removing invasive species and planting a variety of native trees, groundcover and shrubs.
The buffer remains the same width as it was prior to the short-plat, but has much higher function than the
previous situation.
The other case is directly across the watercourse from the buffer restoration site described above. The
buffer on the property was already degraded by existing residential development and was about 15 to 20
feet wide and characterized by significant invasive vegetation. Because the owner proposed to change the
use, a buffer reduction was granted, and the buffer was enhanced by removing invasive vegetation and
planting a variety of native trees, shrubs and groundcover and mulching. As a result of the granted buffer
reduction, the buffer has been widened to between 25 and 40 feet, resulting in a wider effective buffer
than existed previously and a buffer with improved function.
South>?ate Creek. This watercourse has three main tributaries, most of which are open channels, that are
culverted where the tributaries cross streets.
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The northern tributary, which has three main branches (classified as Types 3 and 4 (Np and Ns), flows
mostly through residential areas and has vegetated buffers that vary in width from property to property
(generally from a few feet to 25 feet). The south branch of this tributary, classified as a Type 3
watercourse (Np) flows through Southgate Park, where buffers are disturbed but have a native tree canopy
with an understory of mostly invasive species. Buffers are about 100 feet wide in part of this reach (the
section on publicly owned property), but are much narrower downstream, where the watercourse passes
through residential properties. In these areas the vegetated buffers (not including lawn) range from 15 to
40 feet wide. The middle branch of this tributary, classified as a Type 4 watercourse (Ns) is open in its
upper reach and has wide forested buffers (generally 160 feet on either side, except for one residential
development that encroaches on the buffer). From there, the branch is piped through a residential area,
opening up again into additional residential areas where buffers are generally vegetated but range from 5
to 40 feet wide. The north branch of this tributary, classified as a Type 4 watercourse (Ns), is mostly
open with two sections of piping and flows through residential properties. It has disturbed buffers with
some vegetation that range from 0 to 20 feet wide. These three branches meet where they then enter a
pipe that runs along a street for about 450 feet before opening up again in roadside ditches with poorly
vegetated and very narrow buffers (5 -10 feet wide).
The middle tributary (classified as Type 4 [Ns] in its upper reach and Type 3 [Np] in the lower reach) also
flows through residential areas, where its effective vegetated buffer varies from 15 to 50 feet on either
side. The lower reach flows through a channel between a commercially /industrially development and a
major street. Buffers here are vegetated but range from 10 to 20 feet wide. In its lower reach the
tributary is piped for over 300 feet, discharging into the open channel of the southern tributary. Widening
of buffers in this tributary would be constricted by existing development except in the upper reach.
Buffer reductions in the upper reach would be unlikely due to steep slopes.
The southern tributary of Southgate Creek is mostly open. The upper reach, classified as a Type 3
watercourse (Np), flows in a narrow channel between I -5 and a city street (Macadam). It has disturbed
narrow buffers (5 to 10 feet wide) with mostly invasive vegetation. Some of this reach has recently been
planted as mitigation for impacts from the Sound Transit Light Rail construction. The middle reach of
this watercourse flows along the base of steep slopes just to the west of I -5 and the Light Rail line.
Buffers are variable and are impacted on the west by existing residential development. They are mostly
less than 20 feet wide in this reach. The lower, northern reach of this watercourse is classified as Type 2
(F) and is open except for street crossings (culverts). It flows through a series of roadside ditches with
buffers ranging from a few feet to 20 feet. Buffers are mostly vegetated with invasive species and mowed
grasses in this reach. At the lowest part of the reach, the other tributaries join this one and the
watercourse passes through a recently restored wetland, which forms the watercourse buffer ranging from
25 to 200 feet. It is vegetated (currently with shrubby vegetation, but eventually will be partly forested as
the plants grow). Upon exiting the wetland, the watercourse is piped underneath SR 599 and all the way
to where it discharges into the Duwamish River, except for a short open channel segment in the shoreline
jurisdiction.
Because of existing development, there is little to no opportunity for achieving wider buffers except in the
upper reaches, where no development has occurred due to steep slopes or being located on public
property.
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Gilliam Creek. This watercourse originates on the slopes west of I -5 and north and south of I -518,
eventually flowing eastward in between I -405 and Tukwila Parkway, discharging into the Green River.
The upper reaches of the watercourse tributaries are generally classified as Type 3 (Np). The southwest
tributary of the watercourse was recently partially relocated and restored as mitigation for work on SR
518. It is considered to be fish bearing or have the potential for fish. It has degraded buffers with
invasive vegetation (about 200 feet wide on the west and 20 on the east) for most of its length except for
the recent restoration of buffers along the relocated segment. Buffers in the restored areas are around 25
feet wide and are bordered by the highway on the north and existing development on the other sides.
Other tributaries on the south side of SR 518 have well vegetated buffers in excess of 200 feet wide
(located on WSDOT right of way on steep slopes), except where they are impacted by residential
development. One tributary has recently restored buffers, which do not yet have much areal cover.
The northwest tributary of Gilliam Creek in its upper reaches is open channel in some areas and piped in
others. Where open, buffers generally range from 10 to 25 feet and are surrounded by existing residential
development and paved parking areas. A segment of the watercourse flows along the north side of SR518
with Southcenter Blvd on the other side. Buffers in this reach range from abut 75 to 100 feet and are
vegetated but disturbed (significant presence of invasive vegetation. A north tributary of the watercourse
consists of a segment with seasonal flow that flows through a residentially developed area.. Buffers are
degraded and range from zero to 20 feet. The seasonal watercourse then flows through a steep ravine
(now part of a regional stormwater detention facility) that has forested buffers ranging from 150 to 250
feet wide. Some enhancement of the buffers and riparian edges has been done to remove invasive plants
and install native shrubs and trees under the existing tree canopy. These buffers are in public ownership.
From this area, the stream is piped, flowing easterly to and beneath I -5 until it is again open in a channel
on the east side of I -5. This channel, which is mostly open with some culverted segments, is classified as
a Type 2 watercourse (F) and flows between 1-405 and Tukwila Parkway. Buffers are forested, where the
channel is open, but are narrow, generally 25 feet wide on either side of the watercourse, with some areas
up to 150 feet in width. Few opportunities exist for achieving wider buffers for Gilliam Creek.
Johnson Creek. This watercourse, located in the recently annexed Tukwila South project area, is a
ditched watercourse surrounded by previously mowed agricultural fields. It is classified as a Type 2
watercourse (DNR Type F). The open portion of the stream has a partially vegetated buffer (native and
invasive plants) that ranges from about 5 to 15 feet wide on both sides in the lower reach. In the middle
reach of this stream, it flows in a roadside ditch with narrow, mowed buffers about 5 feet wide on the
south and well over 200 feet wide on the north into an agricultural field /wetland where cattle grazing used
to take place. There is no upper story vegetation along this stretch of the watercourse. The upper part of
the stream is ditched through an emergent wetland (located in unincorporated King County) that is
snowed for hay production. There is no shrub or tree canopy along the watercourse in this location.
A development proposal called the Tukwila South Project plans to relocate and rehabilitate the lower
reach of Johnson Creek. The work will include installation of a fish passable flap gate The proposed
buffer, which will be planted with native trees and shrubs, will extend from 5 to 50 feet on the south side
(bordering S. 204 Street) and 40 to 75 feet on the north side (bordering a new cross valley levee). Part
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of the buffer will be on levee, and the proposal is to plant the levee slope with native shrubs, but it is
uncertain if the Corps of Engineers will allow planting with anything other than grass. The conceptual
design of this watercourse relocation (and accompanying expanded buffer widths) was approved through
the Hydraulics Permit Approval issued by the Washington Department of Fish and Wildlife (WDFW) and
the Department of Ecology 401 Water Quality Certification.
Wetlands
Tukwila has analyzed a representative sample of its wetlands (different categories, relatively disturbed
and non disturbed, varying sizes and locations) to determine actual vegetated buffer widths and evaluate
the potential for providing wider buffers.
There are only 2 wetlands snapped in the urban center of Tukwila (south of 1 -405 and east of I -5). Both
are analyzed below. The newly annexed area of Tukwila, south of S. 180 has numerous wetlands that
are subject to an existing 401 Water Quality Certification, a pending Section 404 permit and a pending
Special Permission from the City for filling of many of the wetlands and permitting of mitigation in the
southern end of the site. The remaining wetlands in the City are found north of I -405 and west of I -5.
The vast majority of the wetlands falls into the lowest category of wetland (currently Tukwila Type 3 and
most likely Category IV under the state system) and are mostly isolated and surrounded by development.
Not including the newly created wetlands in salmon habitat restoration projects in the shoreline of the
Green/Duwamish River, Tukwila has only 3 highly rated wetlands (under the current SAO rating system
they are Type 1 and would likely be Category II or III under the state system), two of which are in City
ownership. There are just over 20 wetlands that are classified as Type 2 under the current SAO and
would likely be Category III or IV under the state system.
Tukwila Pond Wetland. This wetland (see Figure 1) is currently classified as a Type 1 wetland under
Tukwila's existing SAO, with prescribed buffers of 100 feet. It likely would be classified as a Category II
or III wetland under the state classification system. Tukwila has designated the wetland complex as a
Fish and Wildlife Habitat Conservation Area, due to its importance for migratory waterfowl, which
provides the wetland with additional protection. The revisions to the SAO include a proposed buffer of
100 feet for Fish and Wildlife Habitat Conservation Areas to be consistent with the adopted Shoreline
Master Program. It is a 19 acre open water wetland with an emergent and scrub shrub wetland associated
with it. The associated wetland is being enhanced to increase wildlife habitat function and eventually will
have 4 wetland classes. The entire site is owned by the City as a park and is, therefore protected. The
wetland is surrounded by commercial development and has very narrow vegetated buffers. The vegetated
buffer on the east varies from 20 to 100 feet and is adjacent to a 5 lane street with a sidewalk. The
southern a of this buffer has been recently enhanced by removal of blackberries and planting of native
shrubs and trees. The vegetated southern buffer is only a few feet wide for its entire length and is
adjacent to an underground electrical cable, a railroad track, and a warehouse operation on the west side.
The northern buffer is about 15 feet wide and is adjacent to a retaining wall with commercial
development and paved parking beyond the retaining walland a retail building on the northwest end of the
buffer. The western buffer is a developed park with gravel trails, viewing platforms overlooking the
wetland, some native and non- native vegetation and a large gravel area, with a building and picnic tables.
It is about 300 feet in width and is bordered on the west by commercial buildings and paved parking
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areas. There is no opportunity of achieving a wider buffer for this wetland due to the existing
development on all sides. There is opportunity for improving buffer function, however.
Military Road Wetland. This wetland (see Figure 2), is currently classified as Type 1 under Tukwila's
existing system with prescribed 100 foot buffers, and would likely be a Category II or III wetland under
the state system. It is a relatively undisturbed wetland on steep slopes. It has not been delineated, so the
boundaries are approximate. It forms the headwaters for Riverton Creek. The buffers on the north, west
and south sides are also relatively undisturbed and vary from 250 to 350 feet wide. There is no functional
buffer on the east, as the wetland is adjacent to a street that is entirely developed for residential use.
Therefore, no buffer widening would be possible on the east side of the wetland. Wider buffers on the
north, east and south would be possible and could be required by the Director under the existing code due
the steep slopes. No buffer reduction would be allowed, as the proposed buffers are relatively
undisturbed.
Interurban Trail Wetland Complex. This wetland complex (Figure 3), classified as Type 1 under
Tukwila's current SAO (with a required buffer of 100 feet) and likely to be classified as Category II or III
under the state system, consists of linear wetlands along the Interurban Trail, running over 5,000 linear
feet, and between two sets of railroad tracks. There is an additional depressional wetland adjacent to the
wetlands on the north that was created as mitigation for wetland impacts elsewhere. The buffer on the
west side of the westernmost wetland has been reduced by industrial development along West Valley
Highway to an average of 0 to 5 or 10 feet. The southern wetland buffer extends into an existing street
and has very little vegetation between the street and the wetland edge. The buffers along the east and
west sides of the wetlands are also minimal, with the wetland edges running up to the base of the elevated
railroad track and trail berms. The slopes of the berms are snowed grass and rocks. Buffers on the north
of the wetlands average about 50 feet in width. They are bordered by an existing industrial gravel storage
yard with no structures. Due to the presence of existing infrastructure on three sides of the wetland
complex, no increases in buffer width are possible. The northern buffer could possibly be widened.
Wetland East of 32n Avenue South. South of S. 135 This wetland (Figure 4) is classified as Type 2,
with prescribed buffers of 80 feet. It would likely be classified as a Category III or IV wetland under the
state system. As can be seen on the aerial photo, the wetland is surrounded by residential development
and the partially vegetated buffers are part of residential back yards, with some areas of lawn. Buildings
are encountered within 25 feet of the wetland edge in some areas of the buffer. The width of shrub and
tree canopy in the buffers generally range from 0 to about 20 feet in width, with the remaining buffer in
lawn. Due to the existing development pattern, increases in buffer width are not possible, unless through
development, buffer reductions of up to 50% could be granted, resulting in an enhanced, vegetated buffer
that is at least 25 feet or possibly 40 feet, depending on the wetland classification under the state system.
Wetland Complex off 65 Avenue. There are two wetlands in the wetland complex (see Figure 5). One
is classified as a Type 2 and the other as a Type 3 under Tukwila's current SAO. It is likely that both
wetlands would be classified as Category III under the state system. The buffer between the wetlands is
about 200 feet and is forested and relatively undisturbed, with minimal invasive vegetation in the
understory. The southern effective buffer for both wetlands is very narrow, with the western wetland
buffer consisting of residential multi- family buildings and paved parking areas up to the edge of the
wetland and the eastern wetland formed by single family residential back yards. The western wetland
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also has disturbed buffer on the north and northwest, where single family developments encroach almost
to the edge of the wetland. The western buffer for the wester wetland ranges from about 50 to 200 feet
in one location and has a dirt trail through it. The eastern wetland's northern vegetated buffer is about
200 feet in width, with the closest structure within about 150 feet. The eastern buffer is approximately
150 to 200 feet wide and is disturbed on its outer edge from existing residential uses. Because the buffers
on the west and east sides of the wetland complex are on steep slopes and are relatively well vegetated,
buffer reductions would not be allowed.
Fire Station 53 Wetland. This wetland (Figure 6) is classified as a Type 3 under the current SAO with
prescribed buffers of 50 feet, and would likely be a Category IV under the state system. The buffers on
the east, south and west sides are degraded due to the presence of railroad tracks and an existing fire
station, with associated paved parking and landscaping. Effective buffer widths on the east and west sides
are about 25 feet or less. The buffer on the northwest side of the wetland is forested and extends up a
steep slope and across an unused public right -of -way on to platted, undeveloped lots for about 175 feet
before encountering residential structures. The buffer on the south end of the wetland extends about 80
feet before encountering residential structures. Thus, except for the northwestern side of the wetland,
wider buffers are not possible due to existing development.
Wetland North of S. 152n (off 58 Avenue SW). This wetland (Figure 7) is classified as a Type 3
wetland under Tukwila's current SAO (with required 50 foot buffers) and would likely be a Category IV
wetland under the state system. Buffers around the western, eastern and southern sides are vegetated and
are about 50 feet wide. They are bordered by existing residential development. On the northwest the
vegetated portion of the buffer extends another 50 feet to the edge of a mowed area that is part of a school
ground. The northern buffer is vegetated for between 15 and 20 feet in width, has a structure within it and
is bordered by a cleared and graveled area. Buffer increases would not likely be possible on the west or
south sides of the wetland due to existing development. Increased buffers are possible on the north, as the
site is not fully developed.
Wetland South of I -405. This is a Type 3 wetland (see Figure 8) under the existing SAO ordinance and
would probably be classified as a Category IV wetland under the state system. The wetland is adjacent to
a watercourse, Gilliam Creek. It has a vegetated buffer about 20 feet wide on the north, where it lies next
to I -405. To the south the buffer extends about 100 feet to Southcenter Blvd. In this area, the buffer is
partially vegetated with native trees and shrubs, as well as invasive plants, and partially mowed grass and
ornamental trees. The east buffer is about 30 feet wide and extends to a street that crosses over 1 -405).
The buffer on the west extends about 100 feet (except where I -405 intersects the buffer) to another
wetland that is also adjacent to Gilliam Creek. These wetlands may have been created in the past as
mitigation for work on I -405. Due to the constraints presented by the existing transportation
infrastructure, no buffer expansion is possible.
Wetlands near Crystal Snrings Park (formerly called Five Rivers site). This site (Figure 9) contains 5
small, isolated wetlands that are classified under the existing SAO as Type 3 (with required 50 foot
buffers) and would likely be categorized under the state system as Category IV. Buffers are forested but
have been disturbed, as the understory is mostly vegetated with invasive plants. The easternmost wetland
and part of the buffer lies across a public utility right -of way that is periodically mowed. The buffer
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extends some 150 feet, before encountering a street. The buffer along the west side of the western
wetland is nearly nonexistent, as the wetland borders an existing street. The buffers to the north are
forested and extend over 200 feet. Wider regulatory buffers on three sides could be required for these low
function wetlands, but some use of the property would still need to be allowed.
CONCLUSION
As explained in the above analysis, virtually none of the existing buffer areas for the sensitive areas in the
City currently comply with the buffer widths called for by BAS, nor is there much opportunity for
widening the buffers to meet regulatory requirements. Also, all but a few sensitive area buffers are
disturbed. In some cases wider areas of buffer plantings can be achieved when buffer reductions are
granted where existing vegetated areas are already narrower than half of the regulatory buffer. In all
cases if a buffer reduction were granted, buffer enhancement would be required that would help to
improve buffer function for water quality (soil amendments, dense plantings, shade from trees),
hydrology (dense plantings) and wildlife (plantings, habitat features such as logs or snags).
For the reasons cited above, the City of Tukwila does not believe it makes sense to adopt buffers that are
recommended by the Department of Ecology, WDFW or DNR.
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FIGURE 1
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Addendum to SAO Departures Memo for Wetland and Watercourse Buffer Widths
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FIGURE 3
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Addendum to 5A() L)epaitures Memo for Wetland and Watercourse Buffer Widths
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FIGURE 4
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FIGURE 5
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FIGURE 6
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FIGURE 7
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FIGURE 9
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Reasonable Use
L05-010 approval
to fill portion of
Type 2 wetland to
construct a single
family home.
Remove portion
of wetland from
SAO maps.
FIGURE 1
Riverstone Homes Reasonable Use
Exhibit B
71
72
Created
Enhanced Wetland
and relocated Type
2 stream
Wetland area
to be removed
due to approval
of reasonable
use request.
FIGURE 2
NORMED: Removal of Portion of Type 2 Wetland Illustrate Reconfigured
Stream and Additional Type 2 Wetland Area
73
74
Remove Type
4 stream from
map City's
surface water
superinten-
dent
identified this
as drainage
course
FIGURE 3
Remove Drainage Course from Map
75
76
Mapped wetland
and stream are
drainage swale
per recorded
short plat.
FIGURE 4
Remove Type 3 Wetland and Type 4 Watercourse
77
78
Isolated Type 3
wetlands filled for
Southcenter Sq
development-off
site mitigation at
Tukwila Pond.
FIGURE 5
Type 3 Isolated Wetlands Filled for Southcenter Square Development
79
80
FIGURE 6
Remove Type 3 Wetland
81
82
Remove Type 3
wetland this is a
drainage swale
constructed as
part of Claim
Jumper project.
FIGURE 7
Remove Type 3 Wetland
83