HomeMy WebLinkAboutPlanning 2018-11-08 Item 4 - Attachments - Critical Areas Code Updateexu
hat isbest available science?
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Best available science or BAS is the most current science relative to the functions and values of
the C[bC@| @[8@S, including the n3|e Of buffers in prOLgCiiDg VV8d8Dd and StRe8rD fUDCUODS and
fish and wildlife. Under the GMA(RCVV30.7Oa.175).best available science must beused tu
designate and protect critical areas and to take measures to preserve and enhance
anadromous fisheries, such as salmon (fish born in fresh water and spends most of its life in the
salt water and return to fresh water to spawn).
0J
hat are wetlands and what is their importance?
"Wetland" means those areas that are inundated or saturated by groundwater or surface water
at a frequency and duration sufficient to support, and that under normal circumstances do
support, a prevalence of vegetation typically adapted for life in saturated soil conditions.
Wetlands generally include bogs, swamps, marshes, ponds, lakes and similar areas.
Wetlands do not include those artificial wetlands intentionally created from nonwetland sites,
including but not limited to irrigation and drainage ditches, grass -lined swales, canals, detention
fani|idea, wastewater treatment facilities, farm ponds. landscape amenities orthose wetlands
created after July 1, 1990 that were unintentionally created as a result of the construction of a
road, street orhighway. Hovvever, those artificial wetlands intentionally created from non -
wetland areas to mitigate conversion of wetlands as permitted by the City shall be considered
wetlands.
Wetlands and their 8SSOCi@ted buffers are important in that they help maintain water quality;
store and convey storm and flood water; recharge ground water; provide fish and wildlife
habitat; and serve as areas for recreation, education, scientific study and aesthetic
appreciation.
hat are streams and what is their importance?
"Watercourse" means a course or route formed by nature or modified by man, generally
consisting of a channel with a bed and banks or sides substantially throughout its length along
which SUrf8C8 water flows O8tUF8||y, including the G[8eD/E]UVV8[OiSh Rime[. The Ch8OO8| or bed
need not contain water yH8F-rOUDd.Watercourses dOnot include irrigation ditches, StO[0VV8L8[
runoff channels or devices, or other entirely artificial watercourses unless they are used by
salmonids or to convey or pass through stream flows naturally occurring prior to construction of
such devices.
Streams and their associated buffers are important in that they provide important fish and
wildlife habitat and travel corridors; help maintain water quality; Store and convey storm and
flood water; recharge groundwater; and serve as areas for recreation, education, scientific study
and aesthetic appreciation.
27
hat are geologically hazardous areas?
Geologically hazardous areas include areas susceptible to erosion, sliding, earthquake, or other
geological events. They pose a threat to the health and safety of citizens, fish, and wildlife,
when incompatible commercial, residential, or industrial development is sited in areas of
significant hazard.
Some geological hazards can be reduced or mitigated by engineering, design, or modified
construction practices so that risks to health and safety are acceptable. When engineering
technology cannot reduce risks to acceptable levels, building in geologically hazardous areas is
best avoided.
at are fish and wildlife conservation areas?
Fish and wildlife habitat conservation is the management of land for maintaining species in
suitable habitats within their natural geographic distribution so that isolated subpopulations are
not created.
hat are frequently flooded areas?
Floodplains and other areas subject to flooding perform important hydrologic functions and may
present a risk to persons and property. Classifications of frequently flooded areas should
include, at a minimum, the 100-year floodplain designations of the Federal Emergency
Management Agency and the National Flood Insurance Program. Historic losses to salmon
habitat have occurred as a result of development encroaching into floodplains. In addition to
minimizing adverse effects to human health, safety and infrastructure, floodplains are ideal
locations for salmon habitat restoration.
hat is itigation sequencing and compensatory itigation?
If a project proponent is proposing to impact a critical area, the critical areas regulations should
require them to show that they have first avoided and minimized impacts wherever practicable.
Mitigation sequencing should be applied to show avoidance and minimization of impacts. The
following are the steps in the mitigation sequence:
1. Avoiding the impact altogether by not taking a certain action or parts of an action;
2. Minimizing 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.
28
gend
Wetland Area:
Current Buffer (200,4)
Buffer with Ecology Guidance (2014)
Waterc u u rses
Wetland # 31
• Category Ill Wetland (2004)
• Current buffer of 80 feet
• Category II Wetland (2014) with habitat score of 6
(moderate)
• Buffer of 110 feet with minimization measures
per Ecology guidance
29
30
gend
Wetland Area.
Current Buffer (2004)
Buffer with Ecology Guidance (2014)
,atercourses,
Wetland # 37
• Category Ill Wetland (2004)
• Current buffer of 80 feet
• Category Ill Wetland (2014) with habitat score of 5
(moderate)
• Buffer of 60 feet with minimization measures per
Ecology guidance
31
32
TITLE 18 — ZONING
Sections:
18.45.010
18.45.020
18.45.030
18.45.040
18.45.050
18.45.060
18.45.070
18.45.080
18.45.090
18.45.100
18.45.110
18.45.120
18.45.130
18.45.140
18.45.150
18.45.160
18.45.170
18.45.180
18.45.190
18.45.195
18.45.200
18.45.210
18.45.220
T LLY T
Purpose
Best Available Science
Sensitive Area Applicability, Maps and Inventories
Sensitive Areas Special Studies
Interpretation
Procedures
Sensitive Area Permitted Uses
Wetlands Designations, Ratings and Buffers
Wetland Alterations and Mitigation
Watercourse Designations, Ratings and Buffers
Watercourse Alterations and Mitigation
Areas of Potential Geologic Instability Designations,
Ratings and Buffers
Areas of Potential Geologic Instability Uses,
Exemptions, Alterations and Mitigation
Abandoned Mine Areas
Fish and Wildlife Habitat Conservation Areas —
Designation, Mapping, Uses and Standards
Sensitive Area Master Plan Overlay
Sensitive Areas Tracts and Easements
Exceptions
Appeals
Enforcement and Penalties
Recording Required
Assurance Device
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.
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 environmentally 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 ana-
dromous 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.
(turd, 2301 §1 (part), 2010)
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.
(Ord, 2301 §1 (part), 2010)
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
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Chapter 16.52, Flood Zone Management. Areas of seismic
instability are defined and regulated through the Washington State
Building Code.
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.
(Ord. 2301 §1 (part), 2010)
18.45.040 Sensitive Areas 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.
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
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TITLE 18 — ZONING
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 approved
federal wetland delineation manual and applicable regional
supplements. 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.
b. Characterization of the watercourses on site or
adjacent to the site must include:
(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 wa-
tercourse (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 report.
5. A statement specifying the accuracy of the study and
assumptions used in the study.
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.
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
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TUKWILA MUNICIPAL CODE
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 - 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.
(Ord. 2368 , 2012; Ord, 230161(part)) 2010)
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.
(Ord. 2301 §1 (part), 2010)
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 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."
(Ord. 2301 §1 (part), 2010)
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TITLE 18 — ZONING
1.45.070 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 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,
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 wet-
land/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 stepping stones, for access to
contiguous property. Crossings 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).
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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;
(4) Natural system interpretation, education
or research when undertaken by, or in cooperation with, the City;
(5) Flood control or water quality en-
hancement 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 hazardous
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.
(Ord. 2301 §1(prt), 2010)
18.45.080 etlands Designations, Ratings and
Buffers
A. WETLAND DESIGNATIONS.
1. For the purposes of TMC Chapter 18.45, "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 approved federal wetland delineation
manual and applicable regional supplements.
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, Ill, 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 human
lifetime; or iv) provide a high level of functions. The following types
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of 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. The wetland is documented as regionally
significant waterfowl or shorebird areas by the State Department
of Fish and Wildlife.
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 — 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:
1. Minimize long-term impacts of development on
properties containing wetlands;
2. Protect wetlands from adverse impacts during
development;
3. Preserve the edge of the wetland and its buffer for
its critical habitat value;
4. 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;
5. Reduce erosion and increased surface water runoff;
6. Reduce loss of or damage to property;
7. Intercept fine sediments from surface water runoff
and serve to minimize water quality impacts; and
8. Protect the sensitive area from human and domestic
animal disturbances.
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.
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 in-
corporating 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
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(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.
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.
(Ord, 2368 848, 2012; Ord. 2301 81(part), 2010)
18.45.90 VVetlands Uses, 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.
B. ALTERATIONS —
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
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 Department of Fish and Wildlife and do not score 20 points
or greater for habitat in the Western Washington Wetland Rating
System.
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, en-
hancing, or providing substitute resources or environments; and/or
6. Monitoring the impact and taking appropriate
corrective measures.
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TITLE 18 — ZONING
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 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 (establishment). 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-establishment 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 Ill 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 ratio of 2:1 for creation or re-establishment, 4:1
for rehabilitation and 8:1 for enhancement alone.
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(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.
e. Habitat features are installed, if habitat is one of
the functions to be improved.
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; and
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
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.
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TITLE 18 — ZONING
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 mi-
tigation 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.
(Ord. 2301 §1(part), 2010)
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.
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.
B. WATERCOURSE BUFFERS — Any land alteration must
be located out of the buffer areas as required by this section.
Watercourse buffers are intended in general to:
1. Minimize long-term impacts of development on
properties containing watercourses;
2. Protect the watercourse from adverse impacts
during development;
3. Preserve the edge of the watercourse and its buffer
for its critical habitat value;
4. Provide shading to maintain stable water tem-
peratures and vegetative cover for additional wildlife habitat;
5. Provide input of organic debris and uptake of
nutrients;
6. 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;
7. Reduce erosion and increased surface water runoff;
8. Reduce loss of, or damage to, property;
9. Intercept fine sediments from surface water runoff
and serve to minimize water quality impacts; and
10. Protect the sensitive area from human and domestic
animal disturbance.
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.
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
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in direct, indirect or long-term 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 in-
creased 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 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.
(Ord, 2301 §1(part), 2 1 )
18.45.110 atercourse Alterations and Mitigation
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 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 de-
signed 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.
(7) 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
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TITLE 18 — ZONING
possible. Long-term solutions such as stormwater retrofits are
preferred over ongoing maintenance dredging.
d. Stormwater runoff shall be detained and
infiltrated to preserve the watercourse channel's dominant
discharge.
e. All construction shall be designed to have the
least adverse impact on the watercourse, buffer and surrounding
environment.
f. 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.
g. 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 water-
course 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 envi-
ronmental 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.
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 shore 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:
a. 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;
b. Bank and buffer configuration restored to an
enhanced state;
c. Channel, bank and buffer areas replanted with
native vegetation that improves the original in species diversity
and density;
d. 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);
e. 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:
Produced by the City of Tukwila, City Clerk's Office Pag18-147
TUKWILA MUNICIPAL CODE
1. To 8UOw planting or to occur during
ooh08 weather conditions; optimal '
2. To avoid disturbance during critical wildlife periods;
or
3. TO account for unique site constraints that dictate
construction timing or phasing.
p]/d 2201§1(part),2010)
18.45.120 Areas of Potential Geologic Instability
Designation, Rating and Buffers
A. DESIGNATION — Areas of potential geologic instability
are classified osfollows:
1. C|8SS 1 area, where landslide potential iSlow, and
which slope is less than 15%;
2. Class 2 arean, where landslide potential is
moderate, which S|Op8 is between 15& and 40%. and which are
underlain byrelatively permeable soils;
3. C|@SS 5 8n38S' vvhSn8 landslide potential is high'
which include areas sloping between 15%and 4O%'and which
are underlain byrelatively impermeable soils Orby bedrock, and
which also include all 8rS8S sloping more steeply than 4O%;
4. Class 4areas, where landslide potential i8very high,
which include sloping Gr88S with mappable z0O8S of groundwater
seepage, and which also include mjnUng mappable landslide
dSpOSi1S nBg8rd|8SS of slope;
B. BUFFERS — The buffers for areas of potential geologic
instability are intended to:
1. Minimize long-term impacts of development On
properties containing sensitive areas;
2. Protect sensitive areas from adverse impacts during
dSv8|UpnlSOt;
l Prevent loading of potentially unstable slope
mnmaoOOS�
'
4. Protect slope stability;
5. Provide erosion control and 8UeOU8U0O Of pre-
cipitation surface water and SNKDw8te[runoff; and
O. Reduce loss OfV[damage 0Jproperty.
AOundisturbed sensitive area O[buffer may substitute for the
yard setback and |8OdGc8p8 requirements OfTK8C Section 18.50
8Od18.52.
C. Each d8v8|Op08Ot p0pOG8| DVDt8iDiOg or threatened by
an area of potential g8O|OgiC instability Class 2 O[higher shall be
subject to 8g8oteChOiC8| report pursuant k)the requirements of
TK8C Chapter 18.45.040 C' and 1845.060. The geoteChOiC@|
report shall 8O8|yZO and 08k8 recommendations on the need for
and width of any S8tb8CkS Or buffers necessary to achieve the
gO8|S and r8qUiv8m8n18 Of TK8C Chapter 1845. Development
proposals shall then include the buffer distances 8Sdefined within
the g0O03chniC8|report.
D. Buffers may be iOC[O@S8d by the Director when an area
is determined to be particularly S8nSiUv8 to the disturbance
Cn98t8d by8development. Such 8deSi8iOn will be based on 8
City n8Yi0w of the report as p[Op8[8d by @ qualified g80t0ChOiC8|
engineer and by8site visit.
(Ord, 2368 §49, 2012; Ord 2301§1/pamV.2010/
18/5.130 Areas of Potential Geologic Instability Uses,
Exemptions, Alterations and Mitigation.
A. GENERAL— The uses permitted inthe underlying zoning
district may be UOdOrt8h0O OO sites that contain areas Ofpotential
geologic instability subject k}the standards 0fthis section and the
recommendations Of8g8OteChOiC8|study.
B. EXEMPTIONS —The following areas are exempt from
regulation 8Sgeologically hazardous areas:
1. Temporary stockpiles Oftopsoil, gravel, beauty bark
Orother similar landscaping O[construction materials;
2. G|OpOS related to 08te[i8|S used as an 8OgiO88n3d
pre -load for 8building pad;
3. Any temporary slope that has been created through
|Ug8| grading activities under an approved permit may be re-
graded without Gpp|iC8hOO Of TK4C Chapter 18.45 under an
approved permit;
4. Roadway embankments within hght-Of-w8y0rroad
easements; and
5. Slopes retained bvapproved engineered structures.
C. ALTERATIONS-
1. Prior to permitting 8|V8[8b0O Of an area Of potential
geologic instability, the applicant must d80OO8t[@tU one Of the
following:
8. There is no Uvid8DC8 of past instability or earth
movement inthe vicinity 0fthe proposed development, and where
8pp0ph8t8' quantitative GD8|yGi8 of S|0p8 stability indicates no
significant risk to the proposed development Or surrounding
properties; or
b. The area of p0tUOd3| g80|0giC iDSC8bi|ib/ CGO be
modified or the project can be designed SOthat any pOt8OU8|
impact 0Dthe project and SUm3VOdiOg properties is 8|i0iO8V8d'
slope stability iSnot decreased, and the increase iOsurface water
discharge 0[sedimentation shall not decrease slope stability.
2. VVhgn8 any portion of an area of pot8OU8| geologic
instability iScleared for development, 8landscaping plan for the
site Gh8U iOdVd8 tnBg nBp|8OtiOg with an 8qV8| mix of evergreen
and dHCidU0US i[8HS, p[8fH[8b|y O8hV8' and approved by the
Director. Replacement vegetation Sh8U be sufficient to provide
erosion and stabilization protection.
D. DISCLOSURES DECLARATIONS AND COVENANTS
1. It Gh8|| be the responsibility Of the applicant 03
SUb0it, consistent with the findings of the g8oteChDiC8| report,
structural p|8OS that were prepared and stamped by 8 structural
engineer. The plans and specifications shall be accompanied by
8 |888[ from the g8O0BChOiCG| eOgiO88[ who prepared the
gROteChniC8|report stating that inhis/her judgment the plans and
Sp8CifiC8tiOOS conform to the [e0000OOd8UOOS in the
g80V@ChniC3| report, the risk Of damage 10 the proposed
development site from soil instability will b8minimal subject h}the
0ODdib0OS set forth in the report, and the proposed development
will not increase the potential for soil movement.
2 Further recommendations signed8OdG88BdhvUl0
g8OteChn|C8|engineer shall b8provided should there b8additions
or exceptions to the original recommendations based on the plans,
Peme18-4V8 Produced by the City of Tukwila, City Clerk's Office
TITLE 18 — ZONING
site conditions or other supporting data. If the geotechnical
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 Co-
venant 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 de-
termines 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
recommendations 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 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 construc-
tion 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.
(Ord. 2301 §1(part), 2010)
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.
(Ord. 2301 §1 (part), 2010)
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TUKWILA MUNICIPAL CODE
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:
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 connectivity.
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 PM) 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.
(Ord, 2201 §1(part), 010)
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
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:
Page 18-1P50
Produced by the City of Tukwila, City Clerk's Office
TITLE 18 — ZONING
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 con-
sideration 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.
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.
(Ord, 2301 §1 (part), 2010)
18.45.170 Sensitive Areas Tracts and Easements
A. In development proposals for planned residential or
mixed use developments, short subdivisions or subdivisions, and
boundary line adjustments 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. 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. A notice shall be placed on the property title or plat map
that sensitive area tracts or easements shall remain undeveloped
in perpetuity.
(Ord, 2301 §1 (part), 2010)
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 3 decision and shall be processed pursuant to TMC
Chapter 18.104.
3. If the applicant demonstrates to the satisfaction of
the Hearing Examiner that application of the provisions of TMC
Chapter 18.45 would deny all reasonable use of the property,
development may be allowed that is consistent with the general
purposes of TMC Chapter 18.45 and the public interest.
4. The Hearing Examiner, 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.
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
Produced by the City of Tukwila, City Clerk's Office Pa: ' 18-151
TUKWILA MUNICIPAL CODE
ordinance provisions that prevents or interferes with the
reasonable use of the property; or
(3) a violation of the sensitive areas
ordinance;
g. The Hearing Examiner, 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 emer-
gency 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.
(Ord. 2368 §50, 2012; Ord. 2301 §1 (part), 2010)
18.45.190 ppeals
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;
2. Technical information and reports considered by the
Community Development Department; and
3. Findings of the Director, which shall be given
substantial weight.
(Ord. 2301 §1 (part), 2010)
18.45.195 Appeals
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 de-
velopment not authorized under a Special Permission, Rea-
sonable 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 permit 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.
Page 18-532 Produced by the City of Tukwila, City Clerk's Office
TITLE 18 — ZONING
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 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.
(Ord. 2301 §1 (part), 2010)
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.
(Ord. 2301 §1 (part), 2010)
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.
(Ord. 2301 §1 (part), 2010)
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.
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.
(Ord, 2301 §1 (part), 2010)
Produced by the City of Tukwila, City Clerk's Office Pag4 18-153
52
City of Tukwila Sensitive Areas Orc
Prepared for:
City of Tukwila
6200 Southcenter Blvd.
Tukwila, WA 98188
Prepared by:
E
WATERSHED
PANY
750 Sixth Street South
Kirkland WA 98033
p 425.822.5242
f 425..827.8136
watershedeo.com
inance
October 2018
Revised November 1, 2018
The Watershed Company Reference Number:
170625
53
City of Tukwila Sensitive Areas Ordinance Update
Best Available Science Review and Gap Analysis
54
T le
fps
The Watershed Company
November 1, 2018
Introduction 1
1 Wetlands 1
1.1 Wetland Designations (TMC 18.45.080.A) 2
1.2 Wetland Ratings (TMC 18.45.080.B) 2
1.3 Wetland Buffer Widths (TMC 18.45.080.D) 3
1.4 Variation of Standard Wetland Buffer Width (TMC 18.45.080.F) 4
1.5 Alterations (TMC 18.45.090.B) 5
1.6 Mitigation Standards (TMC 18.45.090.E) 5
1.7 Wetland and Buffer Mitigation Location (TMC 18.45.090.F) 5
2 Watercourses 6
2.1 Watercourse Ratings (TMC 18.45.100.A) 6
2.2 Watercourse Buffer Widths (TMC 18.45.100.C) 6
2.3 Variation of Standard Watercourse Buffer Width (TMC 18.45.100.E) 7
2.4 Watercourse Alterations and Mitigation (TMC 18.45.110) 7
3 Geologically Hazardous Areas 7
3.1 Designation (TMC 18.45.120.A) 8
3.2 Buffer Widths (TMC 18.45.120.C) 9
3.3 Alterations (TMC 18.45.130.C) 9
4 Fish and Wildlife Habitat Conservation Areas 10
4.1 Designation (TMC 18.45.150.A) 10
4.2 Mapping (TMC 18.45.150.B) 11
4.3 Buffers (TMC 18.45.150.C) 11
4.4 Uses and Standards (TMC 18.45.150.D) 11
5 Frequently Flooded Areas 12
6 General Protective Provisions 13
6.1 Applicability (TMC 18.45.030) 14
6.2 Setbacks (various) 14
6.3 Mitigation sequencing (various) 14
6.4 Definitions (TMC 18.06) 15
References 16
55
City of Tukwila Sensitive Areas Ordinance Update
Best Available Science Review and Gap Analysis
List fT
s
Table 1-1. Recommended revisions to wetlands regulations 1
Table 1-2. Number of sampled wetlands in each category based on their score for functions 2
Table 1-3. Standard wetland buffer widths in TMC and Ecology 2014 3
Table 1-4. Measure to minimize impacts to wetlands (Ecology 2016) 4
Table 2-1. Recommended revisions to watercourses regulations 6
Table 2-2. Buffer ranges by watercourse type per TMC, BAS, and other jurisdictions. 7
Table 3-1. Recommended revisions to geologically hazardous area regulations 8
Table 4-1. Recommended revisions to fish and wildlife habitat conservation area regulations...10
Table 5-1. Recommended revisions to frequently flooded area regulations. 12
Table 6-1. Recommended revisions to general protective provisions. 14
ii
56
The Watershed Company
November 1,znm
| � ^� �
/ � �[Om� � � �i 8[]
The Growth Management Ad mandates that cities develop policies and regulations to
designate and protect critical areas, including vvcdondo, areas with acritical recharging effect nn
aquifers used for potable water, frequently flooded areas, geologically bazacdouaareaa,aodflsb
and wildlife habitat conservation areas (Revised Code of Washington [RCVV] 36.70A.030(5)).
The GMA further requires that cities periodically review and evaluate their adopted critical
areas policies and regulations, and that this review and update process consider and include
best available science (BAS). Any deviations from science -based recommendations should be
identified, assessed, and explained (Washington Administrative Code |VV/\C| 365-]95-9]5). In
addition, cities are to give special consideration to conservation or protection measures
necessary topreserve orenhance onadronnousfisheries.
In accordance with the GMA, the City of Tukwila (City) last completed a comprehensive update
of its critical areas policies and regulations in 2010. The City's critical areas regulations are
codified in Title 18, Zoning, of Tukwila Municipal Code JMC Chapter 18.45). This code section
includes the text from the adopted Sensitive Areas Ordinance (SAO), Ordinance No. 2301.
The purpose of this memorandum is to provide a review of the City's current SAO, noting gaps
where existing regulations may not be consistent with D/\S, the GMA, and/or its implementing
rules. This document does not attempt to identify every instancevbece the exi existing S\{might
be amended, but instead focuses on identifying more significant potential amendments. The
primary intention of this gap analysis is to help guide the update of the City's SAO.
Sections I through 4 of this report provide a summary of the review and recommended changes
Lnthe four main subject areas inthe Citv'e5A(l. Section addresses frequently flooded areas,
which are defined as critical areas under the GMA but regulated by the City's flood damage
prevention ordinance outside nftb S\[. Finally, Section 6 �zovideerecnnneud recommendations fo
r
general protective provisions. To highlight the findings of the gap analysis, a anonnuary table is
provided otthe beginning ofeach section.
���|�|an'
uv�s
To better incorporate BASinto the wetlands code section, several code revisions are
recommended (Table 1-1).
Table 1-1. Recommended revisions to wetlands regulations.
Code Section Title Review Comment / Recommendations*
18.45.080.13
Wetland Designations
Wetland Ratings
* Remove reference toState delineation manual
* Replace with identification and delineation language
from VVA[173'22-)3S
* Consider defining period ofvalidity for wetland
delineations
* Reference latest version ofState rating system
1
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City of Tukwila Sensitive Areas Ordinance Update
Best Available Science Review and Gap Analysis
18.45.080.D
Wetland Buffer Widths
• Update buffer width requirements to align with BAS
18.45.080.F
Variation of Standard Wetland
Buffer Width
• Revise buffer averaging/reduction scheme to align
with BAS
18.45.090.B
Alterations
• Update small wetland exemptions per BAS
18.45.090.E
Mitigation Standards
• Consider specifying mitigation ratio for buffer
impacts
• Consider adding a requirement for mitigation site
protection
18.45.090.F
Wetland and Buffer
Mitigation Location
• Consider integrating mitigation bank provisions into
hierarchy defined in this section
* See discussion of comments/recommendations in the subsections below this table.
2.1 Wetland Designations (TMC 18.45.080.A)
TMC 18.45.080.A refers to the "Washington State Wetland and Delineation Manual [sic], as
required by RCW 36.70A.175 (Ecology Publication #96-94) and consistent with the 1987 Corps of
Engineers Wetland Delineation Manual." This section should be updated to include the
language from WAC 173-22-035, which states that "Identification of wetlands and delineation of
their boundaries... shall be done in accordance with the approved federal wetland delineation
manual and applicable regional supplements."
The Washington State Department of Ecology (Ecology) model wetlands chapter (Ecology 2016)
also recommends the following language: "Wetland delineations are valid for five years; after
such date the City shall determine whether a revision or additional assessment is necessary."
2.2 Wetland Ratings (TMC 18.45.080.B)
TMC 18.45.080.B refers to the "Washington State Wetlands Rating System for Western
Washington, (Washington State Department of Ecology, August 2004, Publication #04-06-025)."
Ecology updated this rating system in June of 2014. The current BAS-based wetland rating
system is the Washington State Wetland Rating System for Western Washington (Hruby 2014,
Ecology publication No. 14-06-029). Using reference wetlands, Ecology calibrated the updated
2014 wetland rating system to maintain roughly the same distribution of wetland categories
that were present under the prior 2004 rating system. A comparison sample of the distribution
of wetland categories under the old and new rating systems is provided in Table 1-2 below
(Hruby 2014).
Table 1-2. Number of sampled wetlands in each category based on their score for functions.
Category
2004 Rating System
2014 Rating System
I
13
11
II
52
44
III
39
49
IV
7
7
The substantive changes to the wetland rating system are: 1) a High, Medium, or Low ranking
for each function instead of numeric scores; and 2) the opportunity section was replaced with
two new sections: landscape potential and value. The shift to a High, Medium, Low ranking
2
58
The Watershed Company
November 1, 2018
scheme was prompted by a statistical analysis of wetland rating data, which indicated that the
rapid -assessment wetland rating tool is not scientifically accurate beyond a qualitative ranking.
As a result of this change, the total point range changed from 0-100 to 9-27 (Hruby 2014), with
nine possible points each for water quality, hydrologic, and habitat functions.
In addition to updating the reference to the rating system itself, the City should update the
individual point score references for each wetland category throughout TMC 18.45.080.B.
If the City wishes to avoid the need for future updates related to rating system versions, it
should consider amending this section to refer to the 2014 rating system, "...or as revised and
approved by Ecology," and removing references to specific point values.
2.3 Wetland Buffer Widths (TMC 18.45.080.D)
The City's existing wetland buffer widths are based on a departure from BAS supported by an
analysis completed as part of the City's 2010 SAO update. The analysis evaluated existing buffer
conditions and effective widths for "a representative sample of its wetlands" (City of Tukwila
2010). The departure memorandum states, "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" (City of Tukwila 2010).
Accordingly, the standard buffer widths included in the City's regulations match Ecology's
recommended standard buffers for wetlands with low habitat scores (fewer than six points
under the 2014 rating system) adjacent to a proposed land use with high -intensity impacts
(Table 1-3). The Watershed Company conducted an updated evaluation of the City's mapped
wetlands in 2018 under the 2014 Western Washington Rating System. The updated analysis
confirmed that the majority of wetlands within the City do have low habitat scores, and the
remaining wetlands appear to have moderate habitat scores of six or seven under the 2014
Rating System.
Table 1-3. Standard wetland buffer widths in TMC and Ecology 2014.
Category
Wetland buffer
width (ft), TMC
Wetland buffer width (ft), Ecology 2014, high -
intensity land use impact
Habitat score
<6
Habitat score
6-7
Habitat score
8-9
I
100
100
150
300
II
100
100
150
300
III
80
80
150
300
IV
60
50
50
50
For those projects that can mitigate the impacts and disturbances associated with surrounding
land use, required buffer widths may be reduced. Table 1-4 lists impact -minimization measures
which, when implemented in combination with a wildlife corridor to adjacent priority habitats
where applicable, allow an applicant to reduce the standard buffer widths by up to 25 percent
(Ecology 2016). The resulting standard buffer widths range according to habitat score from 75 to
225 feet for Category I and II wetlands and from 60 to 225 feet for Category III wetlands, and are
40 feet for Category IV wetlands.
3
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City of Tukwila Sensitive Areas Ordinance Update
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Table 1-4. Measure to minimize impacts to wetlands (Ecology 2016)
Disturbance
Required Measures to Minimize Impacts
Lights
•
Direct lights away from wetland
Noise
•
Locate activity that generates noise away from wetland
•
If warranted, enhance existing buffer with native vegetation plantings
adjacent to noise source
•
For activities that generate relatively continuous, potentially disruptive
noise, such as certain heavy industry or mining, establish an additional 10'
heavily vegetated buffer strip immediately adjacent to the outer wetland
buffer
Toxic runoff
•
Route all new, untreated runoff away from wetland while ensuring
wetland is not dewatered
•
Establish covenants limiting use of pesticides within 150 feet of wetland
•
Apply integrated pest management
Stormwater runoff
•
Retrofit stormwater detention and treatment for roads and existing
adjacent development
•
Prevent channelized flow from lawns that directly enters the buffer
•
Use Low Intensity Development (LID) techniques where appropriate (for
more information refer to the drainage ordinance and manual)
Change in water regime
•
Infiltrate or treat, detain, and disperse into buffer new runoff from
impervious surfaces and new lawns
Pets and human disturbance
•
Use privacy fencing OR plant dense vegetation to delineate buffer edge
and to discourage disturbance using vegetation appropriate for the
ecoregion
•
Place wetland and its buffer in a separate tract or protect with a
conservation easement
Dust
•
Use best management practices to control dust
While the City's current approach results in a simpler set of standard buffers for the City to
implement, it does not reflect the range of existing and potential wetland conditions present in
Tukwila. Specifically, it does not account for any wetlands that provide greater than the lowest
habitat function, despite the 2010 and 2018 analyses identifying several such wetlands. As a
result, any opportunity to protect rare wetland habitat functions where they do exist, and/or
where larger buffers are currently present (e.g. wetland complex near the intersection of 65th
Avenue and Military Road wetland), is lost.
We recommend that the City update its buffer provisions to adopt the BAS-based approach
developed for small cities. This approach provides flexibility for applicants while resulting in
higher -functioning buffers that are sensitive to existing wetland functions. Standard buffer
widths for wetlands with low habitat scores will not increase. Applicants are already required
to submit a delineation and rating study prepared by a professional wetland scientist; this
approach enables the City to use that information to make more prescriptive, site -specific
decisions.
2.4 Variation of Standard Wetland Buffer Width (TMC 18.45.080.F)
TMC 18.45.080.F allows for reduction of the standard buffer width up to 50 percent where
existing conditions are degraded and where the applicant proposes to enhance the degraded
4
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The Watershed Company
November 1, 2018
buffer. However, per Ecology guidance, the BAS-based buffer widths described above "assume
that the buffer is vegetated with a native plant community appropriate for the ecoregion. If the
existing buffer is unvegetated, sparsely vegetated, or vegetated with invasive species that do
not perform needed functions, the buffer should either be planted to create the appropriate
plant community or the buffer should be widened to ensure that adequate functions of the
buffer are provided" (Ecology 2016). In other words, functioning buffers of the widths listed
above are the minimum necessary, per BAS, to protect wetland functions.
Rather than buffer reduction, Ecology guidance recommends buffer averaging to provide
flexibility to applicants and accommodate site constraints. Buffer averaging may also be used to
improve wetland protection when wetland functions vary spatially. Averaging should be
limited to 75 percent of the standard buffer width and should not reduce the total buffer area.
To align with BAS and better protect Tukwila's wetlands, we recommend that the City revise
this section to allow buffer averaging rather than reduction, and to limit that averaging to 75
percent of the standard buffer width.
2.5 Alterations (TMC 18.45.090.B)
TMC 18.45.090.B.5 provides an exemption for wetlands under 1,000 square feet with a habitat
score under five where they are not associated with a riparian corridor or part of a wetland
mosaic, and where they do not contain priority habitat. Per Ecology guidance, this exemption
may be extended to isolated Category IV wetlands under 4,000 square feet. Neither exemption
should apply to wetlands associated with shorelines of the state.
2.6 Mitigation Standards (TMC 18.45.090,E)
The mitigation standards and ratios presented in TMC 18.45.090.E generally align with BAS. To
improve code usability, we recommend that the City add a provision defining the required
mitigation ratio for wetland buffer impacts (1:1). To ensure effective mitigation, Ecology further
recommends that mitigation areas and associated buffers be located in a sensitive areas tract or
conservation easement consistent with TMC 18.45.170.
2.7 Wetland and Buffer Mitigation Location (TMC 18.45.090.F)
The provisions in TMC 18.45.090.F generally align with BAS in establishing preferences for
mitigation location, with on -site mitigation as a first preference. While most local jurisdictions
prefer that off -site mitigation be located within city boundaries, State and federal resource
agencies advocate use of alternative mitigation methods such as mitigation banks, in -lieu -fee
programs, or advance mitigation. The City's mitigation bank standards are found in the
preceding section, .090.E. We recommend that the City integrate these standards into the
preference hierarchy presented in section .090.F to clarify under what circumstances alternative
mitigation methods should be used.
5
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City of Tukwila Sensitive Areas Ordinance Update
Best Available Science Review and Gap Analysis
3 a
ercourses
The City's watercourse regulations should be updated to improve protection and align with
current BAS. A summary of code revisions for consideration is provided below (Table 2-1).
Table 2-1. Recommended revisions to watercourses regulations.
Code Section
Title
Review Comment / Recommendations*
18.45.100.A
Watercourse Ratings
• Consider removing reference to Types 1-4 to avoid
confusion
• Consider defining a process to verify stream
conditions
18.45.100.0
Watercourse Buffer Widths
• Update buffer width requirements
18.45.100.E
Variation of Standard
Watercourse Buffer Width
• Limit buffer reduction to ensure adequate
minimum buffer widths
• Consider adding allowance for buffer averaging
18.45.110
Watercourse Alterations and
Mitigation
• Consider revising for usability
* See discussion of comments/recommendations in the subsections below this table.
3.1 Watercourse Ratings
TMC 18.45.100.A)
TMC 18.45.100.A defines watercourses according to the Washington State Department of
Natural Resources (WDNR) Forest Practices water typing system, consistent with BAS. For each
of the four watercourse classes (Types S, F, Np, and Ns), the code assigns a numerical class
(Types 1, 2, 3, 4). This numerical system looks similar to, but does not align with, the former
WDNR water classification system, which also used numerical classes (Types 1, 2, 3, 4, 5). To
avoid confusion, we recommend removing the numerical classification system and either
relying directly on WDNR terminology or utilizing a lettering system (e.g. Types A, B, C, D).
Critical area rules in the WAC were amended in January 2017 to recommend that, "Counties
and cities that use the stream typing system developed by the department of natural resources
should develop a process to verify actual stream conditions, identify flow alterations, and locate
fish passage barriers by conducting a field visit. Field verification of all intermittent or nonfish
bearing streams should occur during the wet season months of October to March or as
determined locally" (WAC 365-190-130(4)(f)(ii)). This requirement could be added to the
specific requirements for watercourse sensitive area studies in TMC 18.45.040.B. In
incorporating this requirement, other jurisdictions have added a qualifying clause such as "as
practicable" to minimize impacts on project applicants.
3.2 Watercourse Buffer Widths (TMC 18.45.100.C)
A wide range of stream buffer widths are recommended by BAS, depending on the target
functions and buffer condition. Buffer continuity and vegetative quality are important factors in
determining effective buffer widths. Stream buffer requirements under current code are within
the range, at the low end of the recommended scale for Type F and Type Ns watercourses.
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Table 2-2 below provides a summary of buffer width ranges derived from BAS and other local
jurisdictions.
Table 2-2. Buffer ranges by watercourse type per TMC, BAS, and other jurisdictions.
Stream Type
Watercourse Buffer (ft), TMC
Sample Buffer Ranges (ft)
S
Regulated under SMP
115-165
F
100
100-165
Np
80
50-65
Ns
50
50-65
The City completed an analysis of existing watercourse buffers as part of its 2010 SAO update.
This analysis found that many buffers are in a degraded condition, with little native vegetation
and/or constrained by surrounding infrastructure and development. Where redevelopment
occurs in these areas, vegetative enhancement of the buffer can provide an important tool to
improving buffer function within an urban environment.
3.3 Variation of Standard Watercourse Buffer Width (TMC 18.45,100.E)
TMC 18.45.100.E currently allows buffer reduction up to 50 percent with buffer enhancement.
Based on the functions that different widths of buffers provide, fish bearing streams should
remain as close to 100 feet as possible; however, reductions of up to 25 percent with
enhancement are likely to provide adequate protection for most small stream channels. Buffers
narrower than 33 feet (i.e. a reduced buffer on a Type Ns watercourse) are generally not
considered functionally effective (The Watershed Company 2011), and these should not be
permitted.
The City could continue to allow flexibility through buffer reduction with enhancement.
However, for consistency with the wetland regulations, the City may consider utilizing buffer
averaging only. Given that most existing watercourse buffers are degraded, the City should
consider requiring buffer enhancement when buffer averaging is allowed.
3.4 Watercourse Alterations and Mitigation (TMC 18.45.110)
The provisions of this section are generally consistent with BAS. We recommend a review of
this section for organization, redundancy, and clarity of language. For example, subsection D,
Mitigation Standards, uses restoration terminology inconsistent with other sections in the SAO,
and there are several duplicative provisions in subsection B, Alterations, addressing fish
passable watercourse crossings. The City should also consider updating the reference to the
2003 WDFW culvert design manual to refer instead to the 2013 WDFW "Water Crossing Design
Guidelines" manual.
4 eolo
Ica
ly Hazardous Areas
TMC 18.45.120-.130 and 18.45.140 address areas of potential geologic instability (landslides) and
abandoned coal mines, respectively. Review of these two sections is presented together under
the umbrella of geologically hazardous areas; we recommend that the City consolidate these
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two sections under a single section to improve clarity and usability and align with GMA
terminology. Our review of the SAO did not include an in-depth review of BAS related to
geologically hazardous areas. As such, recommendations are focused on code usability and best
practices. Table 3-1 provides a summary of these recommendations for the City's consideration.
Table 3-1. Recommended revisions to geologically hazardous area regulations.
Code Section
Title
Review Comment / Recommendations*
18.45.120-.140
All
• Consider consolidating landslide hazard and
abandoned coal mine hazard provisions into a
single "geologically hazardous area" section
18.45.120.A
Designation
• Consider adding specific information on mapping
sources
• Consider designating seismic hazard areas and
developing associated protective provisions
18.45.120.0
Buffer Widths
• Consider defining a default buffer in the absence of
a geotechnical report
18.45.130.0
Alterations
• Consider adding specific protective provisions
* See discussion of comments/recommendations in the subsections below this table.
4.1 Designation (TMC 18.45.120.A)
TMC 18.45.120.A designates four classes of potential geologic instability, with increasing hazard
from classes one to four. Classes are defined by slope, soil characteristics, historic landslides,
and/or hydrology. While the City's Sensitive Areas Map depicts these areas, neither the map
nor the code refer to public sources of mapping information. We recommend that the City
revise the designation section or add a mapping section (similar to the approach for fish and
wildlife habitat conservation areas) to include this information. Potential sources of mapping
information include:
• For historic landslides, areas designated as quaternary slumps, earthflows, mudflows, or
landslides on maps published by the U.S. Geological Survey or the WDNR Division of
Geology and Earth Resources;
• For potential or historic landslides, those areas mapped by the WDNR (slope stability
mapping) as unstable (U or class 3), unstable old slides (UOS or class 4), or unstable
recent slides (URS or class 5);
• For soil characteristics, the U.S. Department of Agriculture's Natural Resources
Conservation Service (NRCS) Official Soil Survey Data; and
• For general instability, those areas mapped by the NRCS as having a significant
limitation for building site development.
The City does not currently designate areas of erosion hazard or seismic hazard. Per WAC 365-
190-120(5), "Erosion hazard areas include areas likely to become unstable, such as bluffs, steep
slopes, and areas with unconsolidated soils." Erosion hazard areas also include channel
migration zones. The City's existing designation of areas of potential geologic instability
partially overlap with the WAC definition. We recommend that the City expand this
designation to include erosion hazard areas, identifying such areas using the NRCS Official Soil
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Survey Data where soils are characterized as having a "severe" or "very severe" erosion hazard
based on slope and soil erosion factor K. A preliminary review of the NRCS data shows areas of
severe erosion hazard occurring in the city between Southcenter and Interstate 5.
TMC 18.45.030.B states, "Areas of seismic instability are defined and regulated through the
Washington State Building Code." While the City may wish to continue deferring to the State
for regulation of these areas, we recommend clarifying how and where such areas are
designated in the City. Per WAC 365-190-120(7), "Seismic hazard areas must include areas
subject to severe risk of damage as a result of earthquake induced ground shaking, slope failure,
settlement or subsidence, soil liquefaction, surface faulting, or tsunamis." WDNR maps the risk
of damage as a result of soil -amplified earthquake -induced ground shaking, or site class, on a
countywide basis. It also maps liquefaction susceptibility. Within the city, the WDNR maps
show broad areas of moderate to high liquefaction susceptibility on either side of the
Duwamish/Green and throughout Southcenter. These areas generally coincide with areas of
moderate to severe amplification of ground shaking. Both of these factors are derived from
underlying soil characteristics (Palmer et al. 2004). The City should consider evaluating these
resources for relevance to new sensitive area designations in Tukwila.
4.2 Buffer Widths (TMC 18.45.120.C)
TMC 18.45.130.0 requires that a geotechnical support be submitted, in which the need for and
width of any buffers or setbacks be specified. Consistent with BAS and in accordance with the
precautionary principle, we recommend that the City define a default or standard buffer of 50
feet from all sides of Class 2 or higher areas of potential geologic instability. Reduction or
elimination of this buffer may be justified through the required geotechnical report. This
approach clearly conveys the City's intent to protect these sensitive areas as well as property
and human safety, and ensures a default level of protection while enabling the applicant's hired
geotechnical engineer to justify relief from this requirement on behalf of his or her client.
4.3 Alterations (TMC 18.45.130.C)
The existing provisions in TMC 18.45.130.0 require that an applicant, through submittal of a
geotechnical report, demonstrate that the proposed project is compatible with the areas of
potential geologic instability present on -site. These provisions provide a catch-all and place the
onus on the geotechnical consultant to recommend any project conditions necessary to achieve
that compatibility and ensure the safety of the project. To improve clarity for the applicant and
inform/facilitate permit review for City staff, we recommend expanding this code section to
include more specific protective provisions. Potential provisions include:
• Requiring that critical facilities be sited outside of, and not below, potential areas of
geologic instability unless there is no practical alternative, as demonstrated by the
applicant;
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• Requiring that land disturbing activities provide for stormwater quality and
quantity control, including preparation of a TESC and permanent drainage plan
prepared by a professional engineer;
• Prohibiting removal of vegetation from areas of potential geologic instability and
their buffers unless permitted as part of an approved alteration, in which case it
should be minimized to the extent practicable;
• Requiring that surface drainage, including downspouts, not be directed across the
face of areas of potential geologic instability;
• Requiring that proposed activities minimize the amount of grading and filling to the
amount necessary; and
• Requiring that the proposed alteration not result in greater risk or increased buffers
on neighboring properties.
5 Fish an
fe Habitat Conservation areas
The City's fish and wildlife habitat conservation area regulations should be updated to improve
protection and align with current BAS. To better align with GMA definitions, we recommend
that these regulations be combined with the SAO sections on watercourses, discussed in Section
2, above. A summary of code revisions for consideration is provided below (Table 4-1).
Table 4-1. Recommended revisions to fish and wildlife habitat conservation area regulations.
Code Section
Title
Review Comment / Recommendations*
18.45.150
All
• Consider combining with 18.45.100, Watercourses,
per GMA definition
18.45.150.A
Designation
• Revise to align with GMA list
• Incorporate relevant language from 18.45.150.B,
Mapping
• Consider defining process of designation of habitats
of local importance
18.45.150.E
Mapping
• Consider revising language to be more specific
18.45.150.0
Buffers
• Add requirement for site -specific buffers based on
analysis by qualified professional
18.45.150.D
Uses and Standards
• Add requirement for habitat assessment
* See discussion of comments/recommendations in the subsections below this table.
5.1 Designation (TMC 18.45.150.A)
The GMA list of designated fish and wildlife habitat conservation areas was amended in
January 2017 to include (WAC 365-190-130(2):
(a) Areas where endangered, threatened, and sensitive species have a primary association;
(b) Habitats and species of local importance, as determined locally;
(c) Commercial and recreational shellfish areas;
(d) Kelp and eelgrass beds; herring, smelt, and other forage fish spawning areas;
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(e) Naturally occurring ponds under twenty acres and their submerged aquatic beds that provide fish
or wildlife habitat;
(f) Waters of the state;
(g) Lakes, ponds, streams, and rivers planted with game fish by a governmental or tribal entity; and
(h) State natural area preserves, natural resource conservation areas, and state wildlife areas.
The City's list is generally consistent with the WAC and needs only minimal revisions and
reorganization. We recommend that the City clarify those priority habitats and species that have
been designated locally, including mudflats and marshes and areas critical for habitat
connectivity as well as eagle habitat and heron rookeries (currently TMC 18.45.150.A.2, .5, and
.9).
The subsequent section, Mapping, contains language that provides additional information
about these designated areas, referring to specific features within the city (TMC 18.45.150.B.1
and .2). We recommend that this information be relocated into TMC 18.45.150.A, Designation.
Finally, the City should consider codifying the process used to identify and designate habitats
and species of local importance.
5,2 Mapping (TMC 18.45.150.8)
TMC 18.45.150.B.2 lists sources of maps and data to guide the City with respect to the location
of fish and habitat conservation areas. Additional sources for consideration include:
• Washington Department of Fish and Wildlife (WDFW) Salmonscape maps
• WDNR water type maps
• U.S. Fish and Wildlife Service Information for Planning and Conservation Maps
• U.S. Fish and Wildlife Service and National Marine Fisheries Service Critical Habitat
Maps
5.3 Buffers
TMC 18.45.150.C)
While this section defines a default buffer of 100 feet, it does not identify how an applicant
should determine whether a site -specific buffer width is necessary and what that buffer width
may be. Consistent with the City's approach for geologically hazardous areas, we recommend
that this section be amended to require that buffers be based on site -specific conditions;
management recommendations provided by the WDFW Priority Habitats and Species Program,
if applicable (see below); and the recommendation of a qualified professional in a sensitive area
special study.
5e4 Uses and Standards (TMC 18.45.150.D)
A requirement for a habitat assessment prepared by a qualified professional should be added to
this subsection, or to TMC 18.45.040, Sensitive Area Special Studies, to better reflect BAS. To
align with BAS, the habitat assessment should include a discussion of any federal, state, or local
special management recommendations, including WDFW habitat management
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recommendations, that have been developed for species or habitats located on or adjacent to the
project area, and a description of how the project employs those recommendations. The habitat
assessment should also include a detailed discussion of the direct and indirect potential impacts
on habitat by the project, including both site -specific and landscape -scale impacts as well as
impacts to water quality. At the local scale, factors such as habitat structure and composition,
species features, recruitment opportunity for snags and large woody debris, and water should
be managed for wildlife at present and in the future. Landscape -scale features requiring
consideration in land use planning include patch size and juxtaposition, edge, corridors and
fragmentation, and proximity of other sensitive areas.
Frecuently Flooc
e
reas
Frequently flooded areas in the City of Tukwila are regulated under TMC Chapter 16.52, Flood
Plain Management. The purpose of this chapter is to minimize public and private losses due to
flood conditions; it applies to special flood hazard areas in the city, as identified by the Federal
Emergency Management Agency (FEMA) in Flood Insurance Rate Maps. BAS-recommended
changes to this chapter are discussed below and summarized in Table 5-1.
Table 5-1. Recommended revisions to frequently flooded area regulations.
Code Section
18.45
Applicability
Title
Review Comment / Recommendations*
• Consider adding a subsection to Chapter 18.45 to
address GMA-specific requirements in frequently
flooded areas
• Determine preferred method for compliance with
FEMA BiOp
* See discussion of comments/recommendations in the subsections below this table.
The GMA recognizes that, in addition to flood hazard, frequently flooded areas also provide
important hydrological functions and vital salmon habitat. The 2008 FEMA National Marine
Fisheries Service Biological Opinion (FEMA BiOp) (NMFS 2008) found that implementation of the
National Flood Insurance Program (NFIP) in the Puget Sound region jeopardizes the continued
existence of federally threatened salmonids and resident killer whales. As a result, NMFS
established Reasonable and Prudent Alternatives to ensure that development within special
flood hazard areas (100 year floodplain), floodway, channel migration zone, and riparian buffer
zone do not adversely affect water quality, water quantity, flood volumes, flood velocities,
spawning substrate, or floodplain refugia for listed salmonids. The City's flood regulations
must adhere to the FEMA BiOp through application of these Reasonable and Prudent
Alternatives to prevent and/or minimize the degradation of channel and floodplain habitat
(Ecology 2015). Specifically, the FEMA BiOp requires changes to implementation of the
National Flood Insurance Program (NFIP) in order to meet the requirements of the Endangered
Species Act (ESA) in the Puget Sound watershed. Because the NFIP is implemented by FEMA
through participation by local jurisdictions that adopt and enforce floodplain management
ordinances, FEMA has delegated responsibility to the local jurisdictions to ensure that
development does not adversely affect listed species.
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To comply with the requirements of the FEMA BiOp, the City has three options, or "doors:"
1. Adopt the model ordinance developed by FEMA (FEMA 2010);
2. Develop floodplain regulations that protect floodplain functions on a programmatic
basis; or
3. Require the completion of a floodplain habitat assessment for any development within
the floodplain. Habitat assessments must evaluate impacts to stormwater, floodplain
capacity, and vegetative habitat.
Unless the City adopts the model ordinance or develops customized floodplain regulations that
are reviewed and approved by FEMA, the third option, "Door 3," is the default requirement.
The first option, the model ordinance, would most likely represent the most conservative
approach to protecting floodplain functions, but it would also be expected to be the most
restrictive option in terms of future development and provide the least flexibility in
implementation. The second option allows local jurisdictions to establish regulations that
recognize local conditions and may incorporate programs that enhance floodplain functions
into the evaluation of how floodplain functions are maintained. However, FEMA must approve
any "Door 2" approach before it is implemented through the submittal and review of a
programmatic checklist. "Door 3" is the most common approach taken by local jurisdictions.
Ecology also recommends applying standards more stringent than the minimum FEMA-
required protections. For example, minimum elevation of new structures should be at least two
or three feet above the Base Flood Elevation (BFE), instead of just one foot.
In incorporating these new requirements, the City should consider adding a section to the SAO
specific to frequently flooded areas. The section would designate these areas pursuant to the
GMA, define requirements associated with the FEMA BiOp, and refer to TMC Chapter 16.52 for
all other regulations in frequently flooded areas.
7 eneral Protective Provisions
Protective provisions broadly applicable to all sensitive areas are found in sections 18.45.020
through 18.45.070 and 18.45.160 through 18.45.170 TMC. General recommendations for
revisions or additions to these sections are discussed below and summarized in Table 6-1.
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Table 6-1. Recommended revisions to general protective provisions.
Code Section
Topic
Review Comment I Recommendations*
18.45.030,
18.45.040,
18.06.018
Applicability
• Consider clarifying applicability by defining
adjacency according to maximum potential buffer
widths
18.45
Setbacks
• Require setbacks from all applicable sensitive areas
18.45
Mitigation sequencing
• Require mitigation sequencing for all sensitive areas
18.06
Definitions
• Review and update per BAS
* See discussion of comments/recommendations in the subsections below this table.
7.1 Applicability (TMC 18.45.030)
Sections 18.45.030 and 18.45.040 TMC indicate that SAO requirements apply where sensitive
areas exist on or adjacent to an applicant's property. The definition of "adjacent" in section
18.06.018 TMC states, "'Adjacent' means lying near or close to; sometimes, contiguous;
neighboring. Adjacent implies that the two objects are not widely separated, though they many
not actually touch."
In implementation, a subjective or non-specific definition of adjacency can lead to uncertainty
regarding SAO applicability. For example, an applicant with knowledge of a wetland on the far
side of a neighboring property may not know whether a project on his or her own property will
be subject to SAO requirements. We recommend that the City revise the current definition of
"adjacent" to clearly define a distance to the edge of each type of sensitive area based on the
maximum potential buffer. For example, under the current wetland buffer regulations, the
aforementioned applicant would not be subject to SAO requirements if the neighbor's wetland
is more than 100 feet away.
7.2 Setbacks (various)
In the existing SAO, setbacks are required from wetland buffers (TMC 18.45.080.E) and
watercourse buffers (TMC 18.45.100.D). Building setbacks provide access for maintenance and
should apply to all sensitive areas, with the possible exception of seismic hazard areas. Setbacks
10 to 15 feet wide are adequate. We recommend that the City add a general requirement for
building setbacks from all sensitive area buffers or, where no buffers are required, from
sensitive area edges.
7.3 Mitigation sequencing (various)
Demonstration of mitigation sequencing is a required component of wetland and watercourse
sensitive area studies (TMC 18.45.040.B). A definition of mitigation sequencing is provided in
the wetlands section (TMC 18.45.090.C). Mitigation sequencing is a critical component of
sensitive areas protection, helping to ensure that adverse impacts permitted under the SAO are
the minimum necessary, and that those impacts will be compensated for. We recommend that
the City develop a general mitigation section, clarifying that mitigation is broadly required in
all sensitive areas and defining the mitigation sequencing process.
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7.4 Definitions (TMC 18.06)
In association with the revisions recommended by this gap analysis, the City should review and
revise the definitions in Chapter 18.06 TMC relevant to the SAO to better align with BAS.
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eferences
City of Tukwila. June 2010. Addendum to SAO Departures Memo for Wetland Watercourse
Buffer Widths. Department of Community Development, City of Tukwila, WA.
Ecology (Washington State Department of Ecology). 2015. Guidance to Local Governments on
Frequently Flooded Area Updates in CAOs. Online at:
http://www.ecy.wa.gov/programs/sea/floods/FloodedAreaGuidance.html.
Ecology (Washington State Department of Ecology). June 2016. Wetland Guidance for CAO
Updates: Western Washington Version. Ecology Publicaion No. 16-06-001.
ESA Adolf son. May 2007. City of Tukwila Shoreline Master Program Update Shoreline
Inventory and Characterization Report. Prepared for the City of Tukwila, Ecology Grant
#G0600234, Tukwila, WA.
FEMA (Federal Emergency Management Agency), Region 10. 2010. Floodplain Management
and the Endangered Species Act: Checklist for Programmatic Compliance. Bothell, WA.
Hruby, T. 2013. Update on Wetland Buffers: The State of the Science, Final Report. Ecology
Publication No. 13-06-11. Washington State Department of Ecology, Olympia, WA.
Hruby, T. 2014. Washington State Wetland Rating System for Western Washington: 2014
Update. Ecology Publication No. 14-06-029. Washington State Department of Ecology,
Olympia, WA.
NMFS (National Marine Fisheries Service). 2008. FEMA Biological Opinion, Puget Sound.
Online at: http://www.fema.gov/media-library-data/20130726-1900-25045-
9907/nfip biological opinion puget sound.pdf.
Palmer, S.P., S.L. Magsino, E.L. Bilderback, J.L. Poelstra, D.S. Folger, and R.A. Niggemann.
September 2004. Liquefaction Susceptibility and Site Class Maps of Washington State, By
County: Maps 17A and 17B. Washington Division of Geology and Earth Resources Open
File Report 2004-20, Sheets 33-34 of 78.
The Watershed Company. October 2011. City of Burien Comprehensive Plan Update, Best
Available Science Review. Prepared for the City of Burien, WA.
The Watershed Company. 2014A. City of Newcastle Comprehensive Plan Update, Best
Available Science Review. Prepared for the City of Newcastle, WA.
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The Watershed Company. 2014B. City of Woodinville Comprehensive Plan Update, Best
Available Science Review. Prepared for the City of Woodinville, WA.
The Watershed Company. July 2015. City of Bremerton Critical Areas Ordinance: Gap Analysis.
Prepared for the City of Bremerton, WA.
The Watershed Company. January 2016. City of Kirkland Critical Areas Regulations Technical
Report. Prepared for the City of Kirkland Planning and Building Department, Kirkland,
WA.
The Watershed Company and Parametrix. January 2014. Best Available Science and Existing
Conditions Report for Island County's Fish and Wildlife Habitat Conservation Areas.
Prepared for the Island County Planning and Community Development Department,
Coupeville, WA.
Washington Administrative Code. 2018. Washington State Legislature. Available online:
http://apps.leg.wa.gov/WAC/default.aspx.
WDFW (Washington Department of Fish and Wildlife). 2018. Washington State Priority
Habitats and Species List.
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