HomeMy WebLinkAboutAllentown Truck Reroute - Appendix C - Wetlands and Streams Technical Memorandum
Wetlands and Streams Technical Memorandum
City of Tukwila Allentown Truck Reroute
Environmental Impact Statement
City of Tukwila, Washington
February 24, 2025
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Wetlands and Streams Technical Memorandum City of Tukwila Allentown Truck Reroute Environmental Impact Statement
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Contents
1.0 Introduction .....................................................................................................................1
1.1 Project Location.........................................................................................................1
1.2 Data Gathered...........................................................................................................3
1.3 Study Areas ..............................................................................................................3
1.3.1 Wetlands .......................................................................................................3 1.3.2 Streams ........................................................................................................3
2.0 Study Methods .................................................................................................................3
2.1 Review of Existing Information .....................................................................................4
2.2 Field Reconnaissance ................................................................................................5
2.2.1 Wetlands .......................................................................................................5 2.2.2 Streams ........................................................................................................9
3.0 Results .......................................................................................................................... 10
3.1 No Action Alternative ................................................................................................ 12
3.2 Alternative 2 ............................................................................................................ 12
3.2.1 Wetlands ..................................................................................................... 12 3.2.2 Streams ...................................................................................................... 14
3.3 Alternative 3B.......................................................................................................... 15
3.3.1 Wetlands ..................................................................................................... 15 3.3.2 Streams ...................................................................................................... 16
3.4 Alternative 4 ............................................................................................................ 17
3.4.1 Wetlands ..................................................................................................... 24 3.4.2 Streams ...................................................................................................... 25
4.0 References ..................................................................................................................... 25
Tables
Table 1. Summary of Wetland Rating System Categories for Washington State Department of Ecology, City of Tukwila, City of Seattle, and King County .................................................7
Table 2. Summary of Standard Wetland Buffers for City of Tukwila .....................................................7
Table 3. Summary of Wetland Buffers for City of Seattle ...................................................................8
Table 4. Summary of Wetland Buffers for King County......................................................................8
Table 5. Summary of Stream Buffers for City of Tukwila and King County.......................................... 10
Table 6. Summary of Wetlands within the Project Study Areas......................................................... 11
Table 7. Summary of Streams within the Study Area ...................................................................... 12
Figures
Figure 1. Project Location.............................................................................................................2
Figure 2. Wetland and Stream Overview Map................................................................................ 18
Figure 3. No Action Alternative.................................................................................................... 19
Figure 4. Alternative 2 Wetlands and Streams ............................................................................... 20
Figure 5. Alternative 3B Wetlands and Streams ............................................................................. 21
Figure 6. Alternative 4 Wetlands and Streams (Southern Portion)..................................................... 22
Wetlands and Streams Technical Memorandum City of Tukwila Allentown Truck Reroute Environmental Impact Statement
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Figure 7. Alternative 4 Wetlands and Streams (Northern Portion) ..................................................... 23
Appendices
Attachment A. Preliminary Wetland Rating Form and Figures
Attachment B. Site Photos
Abbreviations
BNSF BNSF Railway
County King County
DNR Washington Department of Natural Resources
Ecology Washington State Department of Ecology
EEM estuarine emergent
FGDC Federal Geographic Data Committee
FWHCA fish and wildlife habitat conservation area
GIS geographic information system
GPS Global Positioning System
HDR HDR Engineering, Inc.
HGM hydrogeomorphic
I-5 Interstate 5
iMap interactive mapping tool
KCC King County Code
NRCS Natural Resources Conservation Service
OHWM ordinary high water mark
PEM palustrine emergent
PFO palustrine forested
Project City of Tukwila Allentown Truck Reroute Environmental Impact Statement
PSS palustrine scrub-shrub
RCW Revised Code of Washington
ROW right-of-way
SMC Seattle Municipal Code
SPAA Seattle Police Athletic Association
SWIFD Statewide Washington Integrated Fish Distribution
TMC Tukwila Municipal Code
USACE United States Army Corps of Engineers
USDA United States Department of Agriculture
USFWS United States Fish and Wildlife Service
WAC Washington Administrative Code
WDFW Washington Department of Fish and Wildlife
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1.0 Introduction
The BNSF Railway (BNSF) South Seattle Hub in the Allentown neighborhood in the City
of Tukwila, Washington, is an important economic link to the Puget Sound region. It
serves as an inland port, providing domestic intermodal transloading between truck and
rail. Incoming trucks currently access the intermodal facility from the South 129th Street
Bridge to South 50th Place. Outgoing trucks leaving the facility can use either the South
129th Street Bridge or take South 124th Street to the 42nd Avenue South Bridge. After
the planned replacement of the 42nd Avenue South Bridge, truck traffic will also be able
to access the intermodal facility by traveling east on the bridge and reaching the facility
via South 124th Street. In order to improve livability and safety in Allentown without
compromising the operations of the yard, the City of Tukwila is evaluating new potential
truck access routes to the intermodal facility.
This Wetlands and Streams Technical Memorandum identifies existing wetlands and
streams in the Project vicinity and documents the wetland and stream components along
and near the existing truck route, the No Action Alternative, and three proposed route
alternatives for the City of Tukwila Allentown Truck Reroute Environmental Impact
Statement (Project).
1.1 Project Location
Allentown’s boundaries are formed by the right-of-way (ROW) for a Seattle City Light
transmission corridor to the north, Interstate 5 (I-5) and BNSF’s South Seattle Intermodal
Facility to the east, and the Duwamish River to the south and west. The Project is in the
City of Tukwila, City of Seattle, and unincorporated King County (County), Washington
(Figure 1).
Zoned for low-density residential development, land use in Allentown is primarily single-
family housing, along with several neighborhood parks, the Tukwila Community Center,
and the Green River Trail. Natural areas include restored habitat in the Duwamish Hill
Reserve, several small wetlands, and the Duwamish River’s riparian corridor. In addition
to BNSF’s South Seattle facility, nearby land uses include the Gateway Corporate
Center, single-family development in the Riverton neighborhood, and commercial
development along 48th Avenue South, consisting primarily of freight and truck-related
services. Several major transportation routes are in the vicinity of Allentown, including I-5
to the east and south and, to the west, State Route 599, Interurban Avenue, East
Marginal Way, and an elevated section of Sound Transit’s Link Light Rail line.
The Project is in the Duwamish/Green Watershed, Washington Water Resource
Inventory Area 9 in Sections 3, 11, 14 and 15, Township 23N, Range 4E, Willamette
Meridian.
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Figure 1. Project Location
Wetlands and Streams Technical Memorandum City of Tukwila Allentown Truck Reroute Environmental Impact Statement
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1.2 Data Gathered
HDR Engineering, Inc. (HDR), conducted a literature and data review to identify and
characterize potentially affected wetlands and streams in and near the Project vicinity.
Existing documentation and information were compiled and reviewed first, so that the
field reconnaissance effort could focus on filling information gaps. Existing wetland and
stream information was gathered from local, state, and federal agencies. This information
included published reports, maps, websites, and aerial photographs. The data sources
are listed in the following subsections and in Chapter 4.0, References.
1.3 Study Areas
The wetland and stream study areas for Alternatives 2, 3B, and 4 are described below.
The No Action Alternative study area is the existing physical footprint and did not include
additional survey areas.
1.3.1 Wetlands
The study area for wetlands encompasses the area within 300 feet of the edges of the
long-term Project footprint, which is defined as the physical footprint of the truck access
routes that would result in permanent impacts on wetlands. This distance was selected to
match the typical largest applicable potential buffer width for wetlands within the City of
Tukwila, City of Seattle, and unincorporated County. Wetlands evaluated in this technical
memorandum include wetlands that are wholly or partly within the study area.
1.3.2 Streams
The study area for streams, which are referred to as waterbodies and aquatic areas by
the City of Tukwila and County and as fish and wildlife habitat conservation areas
(FWHCAs) by the City of Seattle, encompasses the area within 200 feet of the edges of
the long-term Project footprint. This distance was selected to match the largest
applicable potential buffer width for streams within the City of Seattle and unincorporated
County and shorelines and streams within the City of Tukwila. Streams evaluated in this
technical memorandum include streams that are wholly or partly within the study area.
2.0 Study Methods
This section describes the objectives and methods used to study wetlands and streams.
Wetlands and streams were identified through a two-step process. HDR biologists first
reviewed the existing documents listed in Section 2.1. After this review, HDR biologists
completed a field reconnaissance of the study area to ground-truth the locations and
extent of inventoried wetlands and streams. Wetlands and streams within the study area
were identified, mapped, and classified.
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2.1 Review of Existing Information
HDR biologists reviewed the following environmental documents to determine the
presence of wetlands, streams, and FWHCAs in the Project area:
• Washington Department of Natural Resources (DNR) Forest Practices
Application Mapping Tool (DNR 2024a)
• DNR Washington Natural Heritage Program Wetlands of High Conservation
Value Map Viewer (DNR 2024b)
• Washington State Department of Ecology (Ecology) Water Quality Atlas (Ecology
2024a)
• Ecology water quality improvement projects for King County (Ecology 2024b)
• Statewide Washington Integrated Fish Distribution (SWIFD; WDFW 2024a) data
portal
• City of Seattle department of Construction and Inspections GIS (City of Seattle
2024)
• City of Tukwila iMap (City of Tukwila 2024)
• King County iMap (King County 2024)
• United States Department of Agriculture (USDA) Natural Resources
Conservation Service (NRCS) Web Soil Survey (NRCS 2024a)
• United States Fish and Wildlife Service (USFWS) National Wetlands Inventory
(NWI) website (USFWS 2024)
• USDA NRCS Field Office Climate Data for King County, Seattle-Tacoma
International Airport weather station (NRCS 2024b)
• Washington Department of Fish and Wildlife (WDFW) Priority Habitats and
Species on the Web (WDFW 2024b)
• National Oceanic and Atmospheric Administration (NOAA) Tide and Water
Levels for the Seattle gauge (Station 9447130) (NOAA 2024)
• Site-wide Wetland Delineation Report for Seattle Police Athletic Association
(SPAA) (Watershed 2023)
• Village at 47th Project Critical Areas and Habitat Assessment Report & Mitigation
Plan (Wet.land 2022)
• Personal communication with WDFW habitat biologists (WDFW 2023)
These documents provide reference information on the soils, hydrology, wetlands, and
streams in the study area. The City of Tukwila iMap is actively being updated, and the
iMap results in this technical memorandum are based on the mapping available at the
time of this review.
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2.2 Field Reconnaissance
Qualified HDR biologists conducted the wetland and stream field reconnaissance for the
study area on May 22, 2024.
Weather conditions for the site visit were mild with clear skies, which is typical for spring
in the Puget Sound lowlands. Climate data for the Project were determined from the
Seattle-Tacoma International Airport weather station, located approximately 2 miles
southwest of the Project site. During the 3 full months preceding the field investigation
(April to February 2024), a total of 7.09 inches of rainfall were recorded at the Seattle-
Tacoma International Airport weather station (NRCS 2024b). Recorded precipitation
levels were normal for February and below normal for April and March. According to the
Direct Antecedent Rainfall Evaluation Method for determining normal conditions (Sumner
et al. 2009), recorded precipitation for the 3 months prior to the site visit was considered
drier than normal.
2.2.1 Wetlands
After collecting and reviewing existing information, HDR biologists conducted detailed
field reconnaissance surveys within the study area to identify, map, and describe
wetlands that could be affected by the Project. Wetland field reconnaissance surveys
were conducted on May 22, 2024.
Wetlands in the study area are generally located outside of the public ROW and were
visually surveyed from the public ROW; in most cases, from the nearest road or
sidewalk.
Biologists documented and recorded vegetation, soil, and hydrology conditions as
necessary at representative wetland and upland areas using methods outlined in the
Corps of Engineers Wetlands Delineation Manual (Environmental Laboratory 1987) and
the Regional Supplement to the Corps of Engineers Wetland Delineation Manual:
Western Mountains, Valleys, and Coast Region Version 2.0 (USACE 2010). General
observations of existing conditions and characteristics were also recorded for each
wetland and associated buffer. No wetland determination data forms were collected for
wetlands.
Potential wetlands in areas not directly accessible during field reconnaissance surveys
were assessed to the extent possible based on visual observations from public areas;
current local, state, and federal habitat maps and reports; and the examination of aerial
photographs. Areas outside of the public ROW that appeared to possess wetland
indicators for vegetation, soil, and hydrology were included in the analysis to provide a
conservative estimate of each alternative’s impacts.
Mapping
Each wetland identified in the study area received a unique identifier that was tracked in
a geographic information system (GIS) database. Estimated wetland boundaries that
were documented at sites accessed during the field reconnaissance were mapped in the
field using a global positioning system (GPS). Wetlands that were not accessible during
field reconnaissance surveys were mapped based on documentation and surveys from
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other projects or sources, field observation, aerial imagery, and best professional
judgement. All wetlands within the study area for the Preferred Alternative will be
delineated during the Final EIS and/or permitting phase of this Project.
Wetland Rating, Classification, and Buffers
Following the field reconnaissance, all wetlands identified in the study area were rated and
the hydrogeomorphic (HGM) (Brinson 1993) classification was determined using the
Washington State Wetland Rating System for Western Washington – 2014 Update Version
2.0 (Hruby and Yahnke 2023). The Ecology wetland rating system defines three main
wetland functions: water quality treatment, hydrologic support, and habitat. The degree to
which several functions are performed by a wetland (e.g., enhancing water quality,
reducing floods, and providing fish and wildlife habitat) results in category assignment, with
Category I offering the highest function and Category IV offering the lowest. A summary of
the rating categories and criteria is provided in Table 1, and preliminary rating forms are
provided in Attachment A.
Wetland habitats in the study area were classified using the system outlined by the
USFWS in Classification of Wetlands and Deepwater Habitats of the United States
(Cowardin et al. 1979; FGDC 2013), typically referred to as the Cowardin system. The
Cowardin system classifies wetlands based on the dominant vegetation structure and
water regime.
Biologists assigned preliminary wetland buffers to the identified wetlands in the study
area based on the local wetland rating systems. The City of Tukwila buffers were based
on Tukwila Municipal Code (TMC) 18.45.80.D, and a variation of standard wetland buffer
widths were applied for interrupted buffers in accordance with TMC 18.45.80.F.2.
Wetlands within the City of Tukwila Shoreline Jurisdiction were regulated in accordance
with TMC 18.45A. Within the shoreline jurisdiction, the regulations of TMC 18.45 shall be
liberally construed together with the Shoreline Master Program to give full effect to the
objectives and purposes of the provisions of the Shoreline Master Program. If there is a
conflict or inconsistency between any of the adopted provisions below and the Shoreline
Master Program, the most restrictive provisions shall prevail.
The City of Seattle’s buffers were based on Seattle Municipal Code (SMC) 25.09.160,
Table A. No wetlands were located within the City of Seattle’s shoreline jurisdiction.
The County buffers were based on King County Code (KCC) 21A.24.325.A.1, and the
wetland buffers were clipped where a legally established roadway transects a wetland
buffer as described in KCC 21A.24.325C.4. No wetlands were located within the County
shoreline jurisdiction.
Summaries of the buffer width requirements for the City of Tukwila, City of Seattle, and
County are provided in Table 2, Table 3, and Table 4, respectively.
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Table 1. Summary of Wetland Rating System Categories for Washington State Department of Ecology, City of Tukwila, City of Seattle, and King County
Regulatory Agency
Category
I II III IV
Ecologya
City of Tukwilab
City of Seattlec
King Countyd
Category I wetlands include wetlands that are rare, particularly sensitive to disturbance, relatively undisturbed (as described in Hruby and Yahnke 2023) with ecological attributes that are
impossible to replace within a human lifetim or provide a high level of functions. They include:
• Relatively undisturbed estuarine wetlands more than 1 acre in size
• Wetlands of High Conservation Value (formerly call national Heritage Wetlands), specifically
• Wetlands identified by the
Washington Natural Heritage Program/DNR as important ecosystems for maintaining plant diversity in our state
• Bogs
• Mature and old-growth forested wetlands more than 1 acre in size
• Wetlands in coastal lagoons
• Wetlands scoring 23 points or more (out of 27) on the
wetland rating form
Category II wetlands provide high levels of some functions and are difficult, though not impossible, to replace. They include:
• Estuarine wetlands smaller than 1 acre in size, or disturbed
estuarine wetlands larger than 1 acre
• Wetlands identified by the DNR Natural
Heritage Program as containing “sensitive” plant species
• Wetlands scoring between 20 and 22
points (out of 27) on the wetland rating form
Category III wetlands have functions scoring between 16 and 19 points under Ecology's Wetland Rating System for Western Washington. Typically, they have
been disturbed and contain less diverse wildlife habitat or are more isolated from other
habitat than Category II wetlands.
Category IV wetlands have levels of functions scoring between 9 and 15 points under Ecology's Wetland Rating
System for Western Washington. Typically, they are
extensively altered.
a Hruby and Yahnke 2023
b TMC 18.45.80.B
c SMC 25.09.160.A
d KCC 21A.24.318.B
Table 2. Summary of Standard Wetland Buffers for City of Tukwila
Wetland Categorya Standard Wetland Buffer Width (feet)
Habitat Score <6 Habitat Score 6–7 Habitat Score 8–9
I 100 150 300
II 100 150 300
III 80 150 300
IV 50 50 50
Source: TMC 18.45.80.D
a Hruby and Yahnke 2023.
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Table 3. Summary of Wetland Buffers for City of Seattle
Wetland Wetland Buffer Requirements for Non-Degraded Buffers
Category I Bogs and Wetlands of High Conservation Value over 100 square feet in total size or of any size that abut any Type S, F, Np, or Ns water per WAC
222-16-030 and 222-16-031
200 feet for all levels of habitat functions
Category I and II wetlands over 100 square feet in total size or of any size that abut any Type S, F, Np, or Ns water per WAC 222-16-030 and 222-16-031
200 feet for wetlands with high level of habitat function
110 feet for wetlands with moderate level of habitat function
100 feet for wetlands with low level of habitat function
Category III wetlands over 100 square feet in total size or of any size that abut any Type S, F, Np, or Ns water per WAC 222-16-030 and 222-16-031
200 feet for wetlands with high level of habitat function
110 feet for wetlands with moderate or greater level of habitat function
60 feet for wetlands with low level of habitat function
Category IV wetlands 1,000 square feet or more in total size or of any size that abut any Type S, F, Np, or Ns water per WAC 222-16-030 and 222-16-031 50 feet for all wetlands
Category IV wetlands under 1,000 square feet in total size that do not abut any Type S, F, Np, or Ns water per WAC 222-16-030 and 222-16-031 No buffer. Use mitigation under SMC 25.09.160 and 25.09.065
Source: SMC 25.09.160, Table A
Note: Per SMC 25.09.160.B, wetland habitat function is as follows: (1) high level equals a habitat function score of 8 or 9; (2) moderate level equals a habitat function score of 5, 6 or 7; and (3) low level equals a habitat function score of 3 or 4.
Table 4. Summary of Wetland Buffers for King County
Wetland Category and Characteristicsa Intensity of Impact of Adjacent Land Use
High Impact Moderate Impact Low Impact
Category I
Wetlands of High Conservation Value 250 feet 190 feet 125 feet
Bog 250 feet 190 feet 125 feet
Estuarine 200 feet 150 feet 100 feet
Coastal Lagoon 200 feet 150 feet 100 feet
Forested Buffer width to be based on score for habitat functions or water quality functions
Habitat score from 8 to 9 points (high level of function) 300 feet 225 feet 150 feet
Habitat score from 6 to 7 points (moderate level of function) 150 feet 110 feet 75 feet
Category I wetlands not meeting any of the criteria above 100 feet 75 feet 50 feet
Category II
Estuarine 150 feet 110 feet 75 feet
Habitat score from 8 to 9 points (high level of function) 300 feet 225 feet 150 feet
Habitat score from 6 to 7 points (moderate level of function) 150 feet 110 feet 75 feet
Category II wetlands not meeting any of the criteria above 100 feet 75 feet 50 feet
Category III
Habitat score from 8 to 9 points (high level of function) 300 feet 225 feet 150 feet
Habitat score from 6 to 7 points (moderate level of function) 150 feet 110 feet 75 feet
Category III wetlands not meeting any of the criteria above 80 feet 60 feet 40 feet
Category IV 50 feet 40 feet 25 feet
Source: KCC 21A.24.325.A.1
a Hruby and Yahnke 2023
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2.2.2 Streams
A field reconnaissance survey was conducted to identify, map, and describe streams
within the study area. The ordinary high water marks (OHWM) of all streams that may be
affected by Project construction will be delineated during the Final Environmental Impact
Statement or permitting phase of this Project. Final stream classification determinations,
in accordance with WAC 222-16-030 and local jurisdictions’ critical areas ordinances, will
also be made at that time.
HDR biologists identified the OHWMs of streams in the study area using Ecology’s
guidance for OHWM identification (Anderson et al. 2016), which is based on the
Shoreline Management Act (Revised Code of Washington [RCW] 90.58.030(2)(b) and
Washington Administrative Code [WAC] 173-22-030(11)). HDR biologists looked for
physical indicators, including but not limited to a natural scour line impressed on the
bank, distribution of upland and water-tolerant vegetation, and drift deposits.
Per 33 CFR 328.3(c)(4), the HTL is defined as “the line of intersection of the land with
the water’s surface at the maximum height reached by a rising tide.” The HTL of the
Duwamish River was evaluated using gauge data. A method used by the USACE to
obtain the HTL uses the Highest Astronomical Tide (HAT) referenced to North American
Vertical Datum of 1988 (NAVD88; 0.0 feet) as reported by NOAA station data for water
surface elevations. The HAT refers to the highest predicted astronomical tide expected to
occur at a specific station over the National Tidal Datum Epoch. The defined HAT (10.96
feet) relative to NAVD88 Epoch 1983-2001 at the Seattle gauge (Station 9447130) was
used to evaluate the HTL/OHWM of the Duwamish River. The USGS station located in
the Duwamish River at E Marginal Way Bridge (Station 12113415), which is located
approximately 1.5 miles downstream of Allentown, was also used to evaluate the
HTL/OHWM of the Duwamish River.
The OHWMs for identified streams within the study area were estimated in the field. The
resulting data were incorporated into Project base maps.
Mapping
The OHWMs of streams identified during the field reconnaissance were estimated using
GPS. Each stream received a unique identifier that was tracked in a GIS database.
Streams that extend beyond the field reconnaissance survey area and other previously
mapped streams outside of the public ROWs were also incorporated into the GIS
database.
Classification
Stream classification determinations will be completed in accordance with WAC 222-16-
030 and local jurisdictions’ critical areas ordinances. Biologists assigned preliminary
stream buffers to the identified streams in the study area based on the local code. Within
the City of Tukwila, watercourses inventoried as Shorelines of the State under RCW
90.58 would be regulated under TMC 18.44, Shoreline Overlay. There were no
shorelines within the City of Seattle and County jurisdiction. Other watercourse buffers
within the City of Tukwila were determined in compliance with TMC 18.45.100.C.
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Riparian corridors in the City of Seattle were determined in compliance with SMC
25.09.12.D.5.a. Watercourse buffers within the County were determined in compliance
with KCC 21A.24.358.B.
A summary of the buffer width requirements for the City of Tukwila and King County is
provided in Table 5. In the City of Seattle, the riparian management area is the area
within 100 feet of the riparian watercourse measured horizontally landward from the
OHWM of the watercourse as surveyed in the field, or from the top of the bank if the
OHWM cannot be determined.
Table 5. Summary of Stream Buffers for City of Tukwila and King County
Water Type City of Tukwila Buffer Width (feet) King County Buffer Width (feet)a
Type S
Shoreline Residential – 50b
115 Urban Conservancy (without Levees) – 100b
Urban Conservancy (with Levees) – 125b
High Intensity – 100b
Type F 100c 115
Type Np 80c 65
Type Ns 50c 65
Type O Not applicable 25
a KCC 21.A.24.358.B for streams within the Urban Growth Area and outside of a basin or shoreline designated as "high" on the Basin and Shoreline Conditions Map.
b TMC 18.44.040
c TMC 18.45.100.B
3.0 Results
Twelve wetlands and two streams were identified within the 300-foot study areas of the
Project design alternatives (see Figure 2). Of these, three wetlands (Wetlands 1, 2, and
5) were accessed during the field reconnaissance. The remaining nine wetlands and two
streams were evaluated using observations from public access points, aerial imagery,
and existing documentation. The identified wetlands vary in overall size and were
generally depressional wetlands located in low spots or tidal fringe wetlands located on
the banks of the Duwamish River. Details for each of these wetlands are summarized in
Table 6. Summaries of wetlands and streams in the study area for each alternative are
provided in Table 6 and Table 7, respectively.
Wetland rating forms are provided in Attachment A, and site photographs are provided in
Attachment B.
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Table 6. Summary of Wetlands within the Project Study Areas
Wetland Name HGM Classificationa Cowardin Classificationb Wetland Ratingc Jurisdiction
Buffer width (feet)
Design Alternative with Potential Direct or Buffer Impacts
Accessed During Field
Reconnaissance Surveys
1 Tidal Fringe PSS/EEM
II (based on estuarine special
characteristic); habitat score of 6
City of Tukwila 150d 3B, 4 Yes
2 Tidal Fringe PFO/PSS/EEM
I (based on estuarine special
characteristic); habitat score of 6
City of Tukwila 150d 3B, 4 Yes
3 Depressional PFO/PSS II; habitat score of 5 City of Tukwila 100d 3B, 4 No
4a Depressional PFO/PSS/PEM II; habitat score of 5 City of Tukwila 100d 2 No
4b Depressional PFO/PSS/PEM III; habitat score of 5 City of Tukwila 80d 2 No
5 Depressional PFO/PSS/PEM II; habitat score of 5 City of Tukwila 100d 2 Yes
6 Depressional PEM III; habitat score of 3 City of Tukwila 80d 2 No
7 Depressional PFO/PSS/PEM II; habitat score of 5 City of Tukwila 100d 2 No
8 Tidal Fringe PSS/EEM
II (based on estuarine special characteristic); habitat score of 6
City of Tukwila 150d 3B, 4 No
9 Depressional PSS/PEM II; habitat score of 5
City of Tukwila and City of Seattle
75d / 110e 2 No
10 Depressional / Slope / Riverine PFO / PSS / PEM III; habitat score of 6 City of Tukwila 150d 4 No
11 Slope PFO / PSS/ PEM III; habitat score of 6 City of Tukwila 150d 4 No
12a Riverine / Slope PFO / PSS II; habitat score of 6 City of Tukwila 150d 4 No
12b Riverine / Slope PFO II; habitat Score of 6 City of Tukwila 150d 4 No
a Cowardin et al. 1979; FGDC 2013; EEM = estuarine emergent; PEM = palustrine emergent; PFO = palustrine forested; PSS = palustrine scrub-shrub.
b Brinson 1993
c Hruby and Yahnke 2023
d TMC 18.45.80.D.
e SMC 25.09.160, Table A, and SMC 25.09.160.B.
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Table 7. Summary of Streams within the Study Area
Stream Name Water Typea Jurisdiction Buffer width (feet)
Design Alternative with Potential Direct or Buffer Impacts
Duwamish River Type S City of Tukwila 50b (Shoreline Residential)/ 100b (Urban Conservancy without Levees) 3B, 4
Stream 1 Type F City of Tukwila 100c 4
a WAC 222-16-030
b TMC 18.44.040.
c TMC 18.45.100.C.
3.1 No Action Alternative
There were no wetlands or streams identified within the No Action Alternative study area
(see Figure 3).
3.2 Alternative 2
Wetlands within the Alternative 2 study area are described in Section 3.2.1. The stream
identified within the Alternative 2 study area is described in Section 3.2.2.
3.2.1 Wetlands
Wetlands 4, 5, 6, 7, and 9 were identified within the Alternative 2 study area. These
wetlands are described below and shown in Figure 4. There is one wetland mapped by
NWI as an excavated and permanently flooded palustrine unconsolidated bottom
wetland on the SPAA property. This mapped wetland is an excavated stormwater feature
that was constructed in uplands and does not meet the City of Tukwila’s definition of a
wetland (TMC 18.06.922; Watershed 2023).
Wetland 4a
Wetland 4a is a depressional wetland bordered by road and railroad prisms and a steep
hillslope. This wetland is mapped by NWI, WDFW, and the Cities of Seattle and Tukwila
(City of Seattle 2024; City of Tukwila 2024; USFWS 2024; WDFW 2024b) and was
delineated by Watershed (2023) as Wetland B. The wetland was viewed from the South
Boeing Access Road and was observed to have palustrine forested, scrub-shrub, and
emergent habitats. The forested habitat was dominated by black cottonwood (Populus
balsamifera) and willow (Salix sp.). The scrub-shrub habitat included red osier dogwood
(Cornus sericea), salmonberry (Rubus spectabilis), and willow species. The herbaceous
stratum included reed canarygrass (Phalaris arundinacea), other unidentified grasses,
and climbing nightshade (Solanum dulcamara) occurring as woody vines. The wetland
was observed to be deeply ponded with areas of open water and was assumed to have
no outlet. The wetland extended to the south and out of view. Watershed (2023)
describes a constructed berm, approximately 8 feet tall and 40 feet long, separating
Wetlands 4a and 4b.
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Wetland 4a was determined to be a Category II wetland with high water quality and
hydrologic functions and a moderate level of habitat functions (Attachment A).
Wetland 4b
Wetland 4b is a depressional wetland bordered by road and railroad prisms and a steep
hillslope. This wetland is mapped by NWI, WDFW, and the Cities of Seattle and Tukwila
(City of Seattle 2024; USFWS 2024; WDFW 2024b) and was delineated by Watershed
(2023) as Wetland A. The wetland could not be viewed from the South Boeing Access
Road and was reported to have palustrine forested, scrub-shrub, and emergent habitats.
The forested habitat was dominated by black cottonwood and red alder. The scrub-shrub
habitat included red osier dogwood and Himalayan blackberry. The herbaceous stratum
included climbing nightshade occurring as woody vines. The wetland is supported by a
high water table and saturation. Watershed (2023) describes a constructed berm,
approximately 8 feet tall and 40 feet long, separating Wetlands 4a and 4b.
Wetland 4b was determined to be a Category III wetland with high water quality and
hydrologic functions and a moderate level of habitat functions (Attachment A).
Wetland 5
Wetland 5 is a depressional wetland that is in a topographic depression bordered by
Airport Way South, South Boeing Access Road, and the BNSF rail yard. This wetland is
mapped by NWI, WDFW, and the Cities of Seattle and Tukwila (City of Seattle 2024; City
of Tukwila 2024; USFWS 2024; WDFW 2024b). The wetland was viewed from the
shoulder of Airport Way South at the northern extent of the wetland. The wetland was
observed to have palustrine forested, scrub-shrub, and emergent habitats. The forested
habitat was dominated by black cottonwood, willow, and red alder (Alnus rubra). The
scrub-shrub habitat included red osier dogwood, rose spirea (Spiraea douglasii), and
willow species. The herbaceous stratum included broadleaf cattail (Typha latifolia), reed
canarygrass, and other unidentified grasses. The wetland was observed to be deeply
ponded with areas of open water. No outlet was observed; however, an outlet was
assumed based on the stream mapped by USGS and DNR that drains this wetland area
to the Duwamish River approximately 1,200 feet to the west (DNR 2024a). Despite the
mapped stream, there was no evidence of a bed or bank within Wetland 5.
Wetland 5 was determined to be a Category II wetland with high water quality and
hydrologic functions and a moderate level of habitat functions (Attachment A).
Wetland 6
Wetland 6 is a depressional wetland located on the SPAA property within the shooting
range bordered by a sand embankment. This wetland was delineated by Watershed
(2023) as Wetland Rifle 3 and is not mapped by the City of Tukwila (2024), Seattle
(2024), WDFW (2024b), or NWI (USFWS 2024). The wetland could not be viewed from
public ROW. Based on the Watershed (2023) delineation, the wetland is a PEM wetland
vegetated by reed canarygrass, creeping buttercup (Ranunculus repens), and other
facultative grasses. The wetland is supported by seasonally high water table and
saturation.
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Wetland 6 was determined to be a Category III wetland with moderate water quality and
hydrologic functions and a low level of habitat functions (Attachment A).
Wetland 7
Wetland 7 is a depressional wetland located on the Seattle City Light transmission ROW
and was not viewable from the public ROW. This wetland was delineated by Watershed
(2023) as Wetland F/G and is mapped by the City of Tukwila (2024). This wetland
includes palustrine scrub-shrub and emergent habitats within the Project study area and
off-site palustrine forested habitat. Aerial imagery shows construction activities and the
placement of fill material within Wetland 7 in 2013, with potential compensatory
mitigation occurring in 2017. The potential compensatory mitigation is evidenced by the
installation of microtopography, large wood material, and sapling plantings. Surface
water appears to extend off site under mature trees adjacent to the BNSF rail yard.
There is no assumed outlet as determined using available topography.
Wetland 7 was determined to be a Category II wetland with moderate water quality and
habitat functions and high hydrologic functions (Attachment A).
Wetland 9
Wetland 9 is a depressional wetland that is assumed to be hydrologically connected to
Wetland 5. This wetland is mapped by NWI, WDFW, and the Cities of Seattle and
Tukwila (City of Seattle 2024; City of Tukwila 2024; USFWS 2024; WDFW 2024b).
Wetland 9 is separated from the Project and Wetland 5 by the approximately 200-foot-
wide BNSF rail yard. Wetland 9 was observed from the South Boeing Access Road
overpass. The east, west, and southern boundaries of Wetland 9 are marked by the
steep fill prisms associated with the rail yard, South Boeing Access Road, and uplands
associated with I-5. Wetland 9 could extend offsite to the north. The wetland was
observed to have palustrine forested, scrub-shrub, and emergent habitats with
vegetation similar to that of Wetland 5. The forested habitat was dominated by willow and
red alder. The scrub-shrub habitat included red osier dogwood, rose spirea, and willow
species. The herbaceous stratum included broadleaf cattail and reed canarygrass. No
outlet was observed; however, an outlet was assumed based on the stream mapped by
USGS and DNR that drains this wetland area to Wetland 5 and eventually Duwamish
River (DNR 2024a). There was no evidence of a bed or bank within Wetland 9. Wetland
9 was determined to be a Category II wetland with high water quality and hydrologic
functions and a moderate level of habitat functions (Attachment A).
3.2.2 Streams
There is a stream mapped by USGS and DNR (2024a) within the Alternative 2 study
area. This stream has an unknown duration of flow, no documented fish use and is not
mapped by the Cities of Seattle and Tukwila or King County (City of Seattle 2024; City of
Tukwila 2024; DNR 2024a; King County 2024; WDFW 2024a, 2024b). The mapped
stream flows from the north to south between I-5 and the BNSF railroad before turning
and flowing east to west to the north of South Boeing Access Road. The mapped stream
is then assumed to be piped to the Duwamish River. Wetlands 5 and 9 were delineated
Wetlands and Streams Technical Memorandum City of Tukwila Allentown Truck Reroute Environmental Impact Statement
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where the un-piped portions of this mapped stream occur. There was no evidence of a
defined bed or bank, and no OHWM indicators were observed within Wetlands 5 and 9
or anywhere else in the study area. These areas have been subject to significant human
alteration. Historical aerial imagery from 1936 shows that this area was tilled farmland
with an assortment of row crops and hay or pasture fields that were bordered by
drainage ditches. This mapped stream was likely created or formed from the stormwater
drainage system as the area was developed. Therefore, this mapped stream does not
meet the definition of a water course according to WAC 220-660-030(154) and is not
included in the results of this technical memorandum.
3.3 Alternative 3B
Wetlands within the Alternative 3B study area are described in Section 3.3.1. The stream
identified within the Alternative 3B study area is described in Section 3.3.2.
3.3.1 Wetlands
Wetlands 1, 2, 3, and 8 were identified within the Alternative 3B study area. These
wetlands are described below and shown in Figure 5.
Wetland 1
Wetland 1 is a narrow tidal fringe wetland located on the right bank of the Duwamish
River. NWI maps the Duwamish River as a permanently flooded tidal riverine wetland
with an unconsolidated bottom (USFWS 2024). Wetlands 1 and 8 are contiguous on both
banks of the Duwamish River and are separated by an unvegetated channel wider than
50 feet, so these wetlands were treated as separate wetland rating units and received
unique identifiers. Wetland 1 was observed from Railroad Avenue and was seen to
contain palustrine scrub-shrub and estuarine intertidal emergent habitats. The palustrine
scrub-shrub was densely vegetated by Himalayan blackberry (Rubus armeniacus) and
willow. The herbaceous stratum was vegetated by reed canarygrass, and the high tide
during the field reconnaissance covered other potential herbaceous species.
Wetland 1 was determined to be a Category II wetland that met estuarine special
characteristics. Habitat functions were assessed and were determined to have a
moderate level of habitat functions (Attachment A).
Wetland 2
Wetland 2 is a tidal fringe wetland located within Codiga Park. This wetland is not
mapped by NWI, the City of Tukwila, or King County but is a partially restored wetland
that has been improved through channel modification, wetland plantings, riparian habitat
plantings, and habitat installations (USFWS 2024; City of Tukwila 2024; and King County
2024). The City of Tukwila (2024) maps this area as below the OHWM of the Duwamish
River. Palustrine forested and scrub-shrub habitats with estuarine intertidal emergent
habitats were observed from Codiga Park’s public trail. The palustrine forested habitat
was vegetated by black cottonwood and red alder, with the scrub-shrub habitat
consisting of willow species. The estuarine intertidal emergent habitat included
Lyngbye's sedge (Carex lyngbyei) and slough sedge (C. obnupta).
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Wetland 2 was determined to be a Category I wetland that met estuarine special
characteristics. Habitat functions were assessed and determined to have a moderate
level of habitat functions (Attachment A).
Wetland 3
Wetland 3 is a depressional wetland that is located in a low spot between two BNSF rail
yard storage areas and north of South 129th Street. This wetland is not mapped by NWI,
City of Tukwila, King County, or WDFW and was observed from the South 129th Street
elevated street surface (City of Tukwila 2024; King County 2024; USFWS 2024; WDFW
2024b). Wetland 3 was seen to have palustrine forested and scrub-shrub habitats
comprised of black cottonwood, red alder, and Himalayan blackberry. This wetland is
largely supported by high groundwater and surface runoff from the surrounding
developments and is located where the City of Tukwila (2024) maps a Type Ns stream.
The wetland drains from the north to the south, and a culvert outlet was observed that
discharges directly to the Duwamish River approximately 110 feet to the south.
Wetland 3 was determined to be a Category II wetland with high water quality and
hydrologic functions and a moderate level of habitat functions (Attachment A).
Wetland 8
Wetland 8 is similar to and shares the same description and functions as Wetland 1.
Wetlands 1 and 8 are contiguous on both banks of the Duwamish River and are
separated by an unvegetated channel greater than 50 feet, so these wetlands were
treated as separate wetland rating units and received unique identifiers.
3.3.2 Streams
The Duwamish River was identified within Alternative 3B study area (see Figure 5) and is
described below. The City of Tukwila maps a Type Ns stream and King County maps a
separate unclassified stream within the Alternative 3B study area near the intersection of
South 129th Street and Railroad Avenue (City of Tukwila 2024; King County 2024).
Standing water was observed where the City of Tukwila maps the Type Ns stream and
was mapped as Wetland 3 (see Section 3.3.1). This stream is positioned adjacent to the
BNSF rail yard and is assumed to be entirely artificial watercourse that was installed for
stormwater conveyance. This is supported by historical aerial imagery from 1936, which
shows this area was tilled farmland with an assortment of row crops and hay or pasture
fields (King County 2024). Therefore, this mapped stream does not meet the definition of
a water course according to WAC 220-660-030(154) and is not included in the results of
this technical memorandum. No evidence of the unclassified stream mapped by King
County was observed near the BNSF railyard or the Martin Luther King Jr Way South
crossing.
Duwamish River
The Duwamish River is a Type S stream. The stretch of Duwamish River adjacent to the
Alternative 3B study area is located within the Duwamish Estuary, which includes the
extent of tidal influence from the mouth to river mile 12 (King County 2001). The
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Duwamish River was historically and is regularly dredged to maintain a navigable
waterway. This action, paired with the tidally influenced water levels, have resulted in
steep and unvegetated banks. Both banks are armored with riprap within the study area
and contain patches of unvegetated and subtidal substrates. The OHWM of the
Duwamish River was observed and estimated to occur around 12 feet NAVD88, which
was higher than the HAT of 10.96 feet NAVD88 (NOAA 2024). The estimated OHWM of
the Duwamish River closely matches the OHWM mapped by the City of Tukwila (2024).
Two estuarine fringe wetlands (Wetlands 1 and 8) were conservatively estimated along
and just above the OHWM of the Duwamish River.
The Duwamish River is on the Clean Water Act Section 303(d) list for 10 different
parameters (Ecology 2024a) and has an approved Total Maximum Daily Load for
Ammonia (Ecology 2024b).
The Duwamish River is documented to provide rearing and migration habitat for Chinook
Salmon (Oncorhynchus tshawytscha), steelhead trout (O. mykiss), and Bull Trout
(Salvelinus confluentus), which are federally threatened species (WDFW 2024b, 2024c).
Other aquatic species documented to occur in the Duwamish Waterway include Coho
(O. kisutch) and Chum (O. keta) Salmon. Pink (O. gorbuscha) and Sockeye (O. nerka)
Salmon and Sea-run Cutthroat Trout (O. clarkii clarkii) are also documented to be
present but are considered rare (City of Seattle 2015; WDFW 2024b, 2024c).
3.4 Alternative 4
The Alternative 4 study area includes Wetlands 1, 2, 3, 8, 10, 11, and 12, the Duwamish
River and Stream 1 (see Figure 6 and Figure 7). Wetland 10 to 12 and Stream 1 are
described below. Wetlands 1, 2, 3, and 8 and the Duwamish River are described in
Section 3.3 for design Alternative 3B and are not repeated in this section.
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Figure 2. Wetland and Stream Overview Map
Wetlands and Streams Technical Memorandum City of Tukwila Allentown Truck Reroute Environmental Impact Statement
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Figure 3. No Action Alternative
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Figure 4. Alternative 2 Wetlands and Streams
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Figure 5. Alternative 3B Wetlands and Streams
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Figure 6. Alternative 4 Wetlands and Streams (Southern Portion)
Wetlands and Streams Technical Memorandum City of Tukwila Allentown Truck Reroute Environmental Impact Statement
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Figure 7. Alternative 4 Wetlands and Streams (Northern Portion)
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3.4.1 Wetlands
Wetlands 1, 2, 3, 8, 10, 11, and 12a and 12b, were identified within the Alternative 4
study area. Wetlands 10 to 12 are described below and wetlands 1, 2, 3, and 8 are
described in Section 3.3 for design Alternative 3B and are not repeated in this section.
One additional wetland was identified in the Wet.land (2022) delineation report but will be
filled as part of the proposed Vintage Housing development; therefore, is not included in
this technical memorandum.
Wetland 10
Wetland 10 is large slope and depressional wetland with some offsite riverine
components. This wetland is located within a drainage that slopes from the northeast to
the southwest toward I-5. This wetland was partially delineated by Wet.land (2022; see
Wetland C) and is not mapped by NWI, King County, or WDFW (USFWS 2024; King
County 2024; WDFW 2024b). Observed wetland vegetation includes willow, black
cottonwood, and Himalayan blackberry and Wetlland (2022) describes Oregon ash,
English hawthorn (Crataegus monogyna), salmonberry, and English Ivy. Surface water
near the bottom of the drainage was observed adjacent to I-5 road prism. Based on this,
it was assumed that there was no outlet and hydric soils.
The Wetland 10 rating was based on the Wet.land (2022) report but was updated to the
Ecology 2014 Update Version 2.0 (Hruby and Yahnke 2023). Based on this, Wetland 10
was determined to be a Category III wetland with moderate water quality, hydrologic, and
habitat functions (Attachment A).
Wetland 11
Wetland 11 is a small slope wetland that is located to the south of Stream 1 and
Wetlands 12a and 12b. This area is densely forested and cannot be viewed from the
road ROW but was estimated in the Wet.land (2022; see Wetland F) report but is not
mapped by NWI, King County, or WDFW 2024b (USFWS 2024; King County 2024;
WDFW 2024b). Wet.land (2022) describes Wetland 11 as having palustrine forested,
scrub-shrub, and emergent habitats vegetated by black cottonwood, Pacific willow (Salix
lucida), cascara (Frangula purshiana), English hawthorn, salmonberry, rose spiraea, lady
fern, stinging nettle (Urtica dioica), and youth-on-age. Wetland 11 is hydrologically
supported by a high groundwater table
The Wetland 11 rating was based on the Wet.land (2022) report but was updated to the
Ecology 2014 Update Version 2.0 (Hruby and Yahnke 2023). Based on this, Wetland 11
was determined to be a Category III wetland with moderate water quality, hydrologic, and
habitat functions (Attachment A).
Wetlands 12a and 12b
Wetlands 12a and 12b are riverine wetlands associated with Stream 1, a Type Np water.
This wetland was delineated by Wet.land (2022; see Wetlands A and AA) but is not
mapped by NWI, King County, or WDFW (USFWS 2024; King County 2024; WDFW
2024b). Wetlands 12a and 12b are mapped within a ravine that slopes from the east to
west beneath a mature broadleaf maple (Acer macrophyllum) canopy. Wetlands 12a,
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12b, and Stream 1 could not be observed from the road ROW. Wet.land (2022)
describes the vegetation as being dominated by black cottonwood, red osier dogwood,
vine maple (Acer circinatum), salmonberry, lady fern (Athyrium cyclosorum), and
piggyback plant (Tolmiea menziesii). The off -site hydrologic connection is described as
part of Stream 1 in Section 3.4.2 below.
The rating for Wetlands 12a and 12b were based on the Wet.land (2022) report but was
updated to the Ecology 2014 Update Version 2.0 (Hruby and Yahnke 2023). Based on
this, Wetlands 12a and 12b were determined to be a Category II wetlands with high
water quality and moderate hydrologic and habitat functions (Attachment A).
3.4.2 Streams
The Duwamish River and Stream 1 were identified within the Alternative 4 study area
(see Figure 6 and Figure 7). Stream 1 is described below, and the Duwamish River is
described in Section 3.3 for design Alternative 3B and is not repeated in this section.
Stream 1
Stream 1, known as Ryan Hill Creek, is mapped by the City of Tukwila (2024) as a Type
Np stream with an associated wetland; though, WDFW determined this stream to be a
Type F for a development permit despite no documented fish use (WDFW 2023, 2024a,
2024b, 2024c). The stream could not be observed from the public ROW due to access
issues and roadside vegetation. Stream 1 was estimated to be 2 to 3 feet wide based on
the Wet.land (2022) delineation report and based on available topography and contours.
The mapped stream flows through a narrow ravine with a mature broadleaf maple
canopy before flowing to Martin Luther King Jr Way South. Inlet protection for a potential
culvert or pipe was observed from the roadway in this area. Stream 1 has an unknown
outlet and is assumed to discharge to the large wetland complex downslope and in
between I-5 and the BNSF rail yard and eventually the Duwamish River.
4.0 References
Anderson, Paul S., Susan Meyer, Dr. Patricia Olson, Erik Stockdale
2016 Determining the Ordinary High Water Mark for Shoreline Management Act Compliance in
Washington State. Shorelands and Environmental Assistance Program Washington
State Department of Ecology. Olympia, Washington.
Brinson, M.M.
1993 A Hydrogeomorphic Classification of Wetlands. Technical Report WRP-DE-4, prepared
for the U.S. Army Engineer Waterways Experiment Station. Vicksburg, Mississippi.
City of Seattle
2015 Seattle Biological Evaluation. May 2015.
http://www.seattle.gov/util/Documents/Reports/SeattleBiologicalEvaluation/SBEDocumen
t/index.htm
2024 Seattle Department of Construction & Inspections GIS. Seattle Department of
Construction & Inspections GIS (arcgis.com). Accessed September 2024.
Wetlands and Streams Technical Memorandum City of Tukwila Allentown Truck Reroute Environmental Impact Statement
26 | February 24, 2025
City of Tukwila
2024 Tukwila iMap. Tukwila iMap (arcgis.com). Accessed September 2024.
Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe
1979 Classification of Wetlands and Deepwater Habitats of the United States. Government
Printing Office, Washington, DC.
DNR (Washington Department of Natural Resources)
2024a Forest Practices Application Mapping Tool. https://fpamt.dnr.wa.gov/default.aspx.
Accessed September 2024.
2024b Washington Natural Heritage Program Wetlands of High Conservation Value Map
Viewer. https://www.dnr.wa.gov/NHPwetlandviewer. Accessed May 2024.
Ecology (Washington State Department of Ecology)
2024a Water Quality Atlas: Version 2.0.0.0.
https://apps.ecology.wa.gov/waterqualityatlas/wqa/startpage. Accessed May 2024.
2024b Water quality improvement projects: King County.
https://apps.ecology.wa.gov/waterqualityatlas/wqa/map?CustomMap=y&BBox=-
14338616,5395963,-12562831,6503994&RT=3&Layers=25&Filters=n,n,n,y,n,n
Environmental Laboratory
1987 Corps of Engineers Wetlands Delineation Manual. Technical Report Y-87-1. Department
of the Army, Waterways Experiment Station. Vicksburg, Mississippi.
FGDC (Federal Geographic Data Committee)
2013 Classification of Wetlands and Deepwater Habitats of the United States. Adapted from
Cowardin, Carter, Golet, and LaRoe (1997). FGDC-STD-004-2013. Second Edition.
Wetlands Subcommittee, Federal Geographic Data Committee and U.S. Fish and
Wildlife Service, Washington DC.
https://www.fgdc.gov/standards/projects/wetlands/nwcs-2013. Accessed May 2024.
King County
2021 Reconnaissance Assessment of the State of the Nearshore Report Including Vashon and
Maury Islands (WRIAs 8 and 9). Chapter 11.
https://your.kingcounty.gov/dnrp/library/2001/kcr762/PDFELEMENTS/SONR11.pdf
2024 King County iMap Interactive mapping tool. iMap (kingcounty.gov). Accessed September
2024.
Hruby, T., and A. Yahnke
2023 Washington State Wetland Rating System for Western Washington: 2014 Update
(Version 2). Publication #23-06-009. Washington Department of Ecology.
NOAA (National Oceanic and Atmospheric Administration)
2024 Datums for 9447130, Seattle WA.
https://tidesandcurrents.noaa.gov/datums.html?datum=NAVD88&units=0&epoch=0&id=9
447130&name=Seattle&state=WA.
Wetlands and Streams Technical Memorandum City of Tukwila Allentown Truck Reroute Environmental Impact Statement
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NRCS (Natural Resources Conservation Service)
2024a Web Soil Survey, King County Area, Washington. Version 14, June 4.
https://websoilsurvey.nrcs.usda.gov/app/. Accessed May 2024.
2024b USDA Field Office Climate Data for King County, Seattle Tacoma Airport Weather
Station. WETS Table. Created May 20.
Sumner, J.P., M.J. Vepraskas, and R.K. Kolka
2009 Methods to Evaluate Normal Rainfall for Short-Term Wetland Hydrology Assessment.
USDA (U.S. Department of Agriculture) Northern Research Station. Wetlands Volume
29, No. 3 (September 2009), pp. 1049–1062.
USACE (United States Army Corps of Engineers)
2010 Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Western
Mountains, Valleys, and Coast Region. ERDC/EL TR-10-3.
http://www.usace.army.mil/CECW/Documents/cecwo/reg/west _mt_finalssupp.pdf.
USFWS (United States Fish and Wildlife Service)
2024 National Wetlands Inventory. Wetlands Online Mapper.
http://www.fws.gov/wetlands/Data/Mapper.html. Accessed May 2024.
Watershed
2023 Site-wide Wetland Delineation Report for Seattle Police Athletic Association. June 2023.
WDFW (Washington Department of Fish and Wildlife)
2023 Personal email communication with Julian Douglas. March 8, 2023.
2024a SWIFD Web Map. https://geo.nwifc.org/swifd/. Accessed May 2024.
2024b Priority Habitats and Species on the Web. https://geodataservices.wdfw.wa.gov/hp/phs/.
Accessed May 2024.
2024c SalmonScape. http://wdfw.wa.gov/mapping/salmonscape. Accessed May 2024.
Wet.land
2022. Village at 47th Project Critical Areas and Habitat Assessment Report & Mitigation Plan.
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Attachment A. Preliminary Wetland Rating Form
and Figures
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WL 1
Wetland 1 5/22/24
4/19/24T. Parry, T. Tumaliuan
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0.05
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0.10 0.25
2
7
0
1
-2
-1
2
✔
✔
✔
WL 1
✔
✔
WL 1
✔
WL 1
✔
✔
✔✔
✔
✔
✔
✔
✔
✔
✔
Access to Wetland 1 was limited. The wetland rating form questions were informed by aerial
photos, existing environmental documentation, and observation made from accessible
portions of the wetland. Binoculars were used where necessary.
WL 1
✔
✔
✔
II
WL 2
Wetland 2 5/22/24
4/19/24T. Parry, T. Tumaliuan
✔
I ✔
0 000
✔
WL 2
✔
✔
✔
✔
✔
WL 2
✔
✔
✔
✔
✔
WL 2
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
2
3
1
3
✔
WL 2
✔
✔
✔
✔
✔
✔
✔
✔
0.05
0.15
0.00 0.05
0.10 0.25
4
13
0
1
-2
-1
2
✔
✔
✔
WL 2
✔
✔
WL 2
✔
WL 2
✔
✔
✔✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
Access to Wetland 2 was limited. The wetland rating form questions were informed by aerial
photos, existing environmental documentation, and observation made from accessible
portions of the wetland.
WL 2
✔
✔
✔
I
WL 3
Wetland 3 5/22/24
4/19/24Parry T. Tumaliuan T.
Depressional
✔
✔
ESRI
II ✔
✔
7 8520
✔
✔✔
✔✔
✔
✔
✔✔✔
WL 3
1
2
3
4
5
6
7
8
WL 3
✔
✔
✔
✔
✔
Access to Wetland 3 was limited. The wetland rating form questions were informed by aerial
photos, existing environmental documentation, and observation made from accessible
portions of the wetland. Binoculars were used in the field where necessary.
WL 3
✔
✔
✔
WL 3
✔
2
0
✔3
✔4
9
✔
✔
✔
✔
✔
1
1
0
0
2
✔
✔
✔
✔
✔
1
1
2
4
✔
D3.1&D3.2 - Wetland discharges within 0.03 mi of Green River which is on the 303(d) list for
temperature, bacteria, and pH. D3.3 - Wetland is within the 12-digit HUC of the Duwamish
Waterway Ammonia-N TMDL
WL 3
✔2
3
3
8
✔
✔
✔
1
1
1
3
✔
2
0
2
✔
✔
✔
✔
✔
✔
WL 3
✔
✔
✔
✔
✔
✔
✔
✔
1
1
0
1
WL 3
✔
✔
✔
✔
✔
✔
✔
✔
0.05
0.15
0.00 0.05
0.10 0.25
3
6
0
1
-2
-1
2
✔
✔
✔
WL 3
✔
✔
WL 3
✔
WL 3
✔
✔
✔
✔
✔
WL 3
✔
✔
✔
NA
Figure 1: Cowardin plant classes.
Figure 2:Hydroperiods.
Figure 3:Location of outlet.
Figure 4:Boundary of area within 150 feet of the wetland.
Figure 5:Contributing basin.
Figure 6:1km polygon.
Figure 7:303(d) listed waters in basinfor the HUC12 in which the wetland is found.
Figure 8.TMDLS for the HUC12 in which the wetland is found.
Identified as Wetland B in Watershed (2023) report.WL 4a
Wetland 4a 5/22/24
4/19/24T. Parry, T. Tumaliuan
Depressional
✔
✔
ESRI
II ✔
✔
8 9522
✔
✔
✔✔
✔
✔
✔✔
✔
✔
WL 4a
1
2
2
3
4
5
6
7
WL 4a
✔
✔
✔
✔
Access to Wetland 4a was limited. The wetland rating form questions were informed by aerial
photos, Watershed report (2023), existing environmental documentation, and observation
made from accessible portions of the wetland. Binoculars were used in the field where
necessary.
WL 4a
✔
✔
✔
Railroad/Trash/Dumping
WL 4a
✔
3
0
✔
5
✔
0
8
✔
✔
✔
✔
✔
1
1
0
1
3
✔
✔
✔
✔
✔
0
1
2
3
✔
D3.1 - No assumed outlet.
D3.2 - Wetland is up-gradient of the Green River which is on the 303(d) list for temperature,
bacteria, and pH. D3.3 - Wetland is within the 12-digit HUC of the Duwamish Waterway Ammonia-N
TMDL
WL 4a
✔
4
3
5
12
✔
✔
✔
1
1
1
3
✔
2
0
2
✔
✔
✔
✔
✔
✔
WL 4a
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
4
2
1
2
✔
WL 4a
✔
✔
✔
✔
✔
0.02
7.50
0.05 0.07
4.00 11.50
1
10
0
1
-2
-1
1
✔
✔
✔
WL 4a
WL 4a
✔
WL 4a
✔
✔
✔
✔
✔
WL 4a
✔
✔
✔
NA
Figure 1: Cowardin plant classes.
Figure 2:Hydroperiods.
Figure 3:Boundary of area within 150 feet of the wetland.
Figure 4:Contributing basin.
Figure 5:1km polygon.
Figure 6:303(d) listed waters in basinfor the HUC12 in which the wetland is found.
Figure 7.TMDLS for the HUC12 in which the wetland is found.
Identified as Wetland A in Watershed (2023) report.WL 4b
Wetland 4b 5/22/24
4/19/24T. Parry, T. Tumaliuan
Depressional
✔
✔
ESRI
III ✔
✔
7 7519
✔
✔
✔
✔
✔
✔✔
✔
✔
✔
WL 4b
1
2
2
3
4
5
6
7
WL 4b
✔
✔
✔
✔
Access to Wetland 4b was limited. The wetland rating form questions were informed by aerial
photos, Watershed report (2023), existing environmental documentation, and observation
made from accessible portions of the wetland. Binoculars were used in the field where
necessary.
WL 4b
✔
✔
✔
Railroad/Trash/Dumping
WL 4b
✔
3
0
✔3
✔4
10
✔
✔
✔
✔
✔
0
1
0
1
2
✔
✔
✔
✔
✔
0
1
2
3
✔
D3.1 - No assumed outlet.
D3.2 - Wetland is up-gradient of the Green River which is on the 303(d) list for temperature,
bacteria, and pH. D3.3 - Wetland is within the 12-digit HUC of the Duwamish Waterway Ammonia-N
TMDL
WL 4b
✔
4
3
3
10
✔
✔
✔
0
1
1
2
✔
2
0
2
✔
✔
✔
✔
✔
✔
WL 4b
✔
✔
✔
✔
✔
✔
✔
✔
✔
4
1
1
2
✔
WL 4b
✔
✔
✔
✔
✔
✔
✔
✔
0.02
7.50
0.05 0.07
4.00 11.50
4
12
0
1
-2
-1
1
✔
✔
✔
WL 4b
WL 4b
✔
WL 4b
✔
✔
✔
✔
✔
WL 4b
✔
✔
✔
NA
Figure 1: Cowardin plant classes.
Figure 2:Hydroperiods.
Figure 3:Boundary of area within 150 feet of the wetland.
Figure 4:Contributing basin.
Figure 5:1km polygon.
Figure 6:303(d) listed waters in basinfor the HUC12 in which the wetland is found.
Figure 7.TMDLS for the HUC12 in which the wetland is found.
WL 5
Wetland 5 5/22/24
4/19/24T. Parry, T. Tumaliuan
Depressional
✔
✔
ESRI
II ✔
✔
8 8622
✔
✔
✔✔
✔
✔
✔✔
✔
✔
WL 5
1
2
3
4
5
6
7
8
WL 5
✔
✔
✔
✔
Access to Wetland 5 was limited. The wetland rating form questions were informed by aerial
photos, existing environmental documentation, and observation made from accessible portions
of the wetland. Binoculars were used in the field when necessary.
WL 5
✔
✔
✔
Railroad/Trash/Dumping
WL 5
✔
2
0
✔
5
✔
2
9
✔
✔
✔
✔
✔
1
1
0
1
3
✔
✔
✔
✔
✔
1
1
2
4
✔
D3.1&3.2 - Wetland is upgradient and discharges (within 0.30 mi) into the Green River which is on
the 303(d) list for temperature, bacteria, and pH). D3.3 - Wetland is within the 12-digit HUC of the
Duwamish Waterway Ammonia-N TMDL.
WL 5
✔2
5
0
7
✔
✔
✔
1
1
1
3
✔
2
0
2
✔
✔
✔
✔
✔
✔
WL 5
✔
✔
✔
✔
✔
✔
✔
✔
✔
2
2
1
3
✔
WL 5
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
0.00
0.15
0.00 0.00
0.10 0.25
5
13
0
1
-2
-1
2
✔
✔
✔
WL 5
✔
WL 5
✔
✔
WL 5
✔
✔
✔
✔
✔
WL 5
✔
✔
✔
NA
Figure 1: Cowardin plant classes.
Figure 2:Hydroperiods.
Figure 3:Location of outlet.
Figure 4:Boundary of area within 150 feet of the wetland.
Figure 5:Contributing basin.
Figure 6:1km polygon.
Figure 7:303(d) listed waters in basinfor the HUC12 in which the wetland is found.
Figure 8.TMDLS for the HUC12 in which the wetland is found.
Identified as Wetland Rifle 3 in Watershed (2023) report.WL 6
Wetland 6 5/22/24
4/19/24T. Parry, T. Tumaliuan
Depressional
✔
✔
ESRI
III ✔
✔
7 6316
✔
✔✔✔
✔
✔
✔
✔✔
✔
WL 6
1
2
2
3
4
5
6
7
WL 6
✔
✔
✔
✔
Access to Wetland 6 was limited. The wetland rating form questions were informed by the
Watershed report (2023), aerial photos, and existing environmental documentation.
WL 6
✔
✔
✔
Shooting range
WL 6
✔
2
0
✔
0
✔4
6
✔
✔
✔
✔
✔
0
1
0
1
2
✔
✔
✔
✔
✔
0
1
2
3
✔
D3.2 - Wetland is up-gradient of Green River which is on the 303(d) list for temperature, bacteria,
and pH). D3.3 - Wetland is within the 12-digit HUC of the Duwamish Waterway Ammonia-N TMDL.
WL 6
✔2
0
3
5
✔
✔
✔
0
1
1
2
✔
2
0
2
✔
✔
✔
✔
✔
✔
WL 6
✔
✔
✔
✔
✔
✔
✔
0
1
1
0
WL 6
✔
✔
✔
✔
0.00
9.00
2.00 2.00
4.00 13.00
0
2
0
1
-2
-1
0
✔
✔
✔
WL 6
WL 6
WL 6
✔
✔
✔
✔
✔
WL 6
✔
✔
✔
NA
Figure 1: Cowardin plant classes.
Figure 2:Hydroperiods.
Figure 3:Boundary of area within 150 feet of the wetland.
Figure 4:Contributing basin.
Figure 5:1km polygon.
Figure 6:303(d) listed waters in basinfor the HUC12 in which the wetland is found.
Figure 7.TMDLS for the HUC12 in which the wetland is found.
Identified as Wetland F/G in Watershed (2023) report.WL 7
Wetland 7 5/29/24
4/19/24T. Parry, T. Tumaliuan
Depressional
✔
✔
ESRI
II ✔
✔
7 8520
✔
✔
✔✔
✔
✔
✔✔
✔
✔
WL 7
1
2
2
3
4
5
6
7
WL 7
✔
✔
✔
✔
Access to Wetland 7 was limited. The wetland rating form questions were informed by the
Watershed (2023) report, aerial photos, and existing environmental documentation.
WL 7
✔
✔
✔
WL 7
✔
2
0
✔
5
✔4
11
✔
✔
✔
✔
✔
1
1
0
0
2
✔
✔
✔
✔
✔
0
1
2
3
✔
D3.2 - Wetland is up-gradient of Green River which is on the 303(d) list for temperature, bacteria,
and pH). D3.3 - Wetland is within the 12-digit HUC of the Duwamish Waterway Ammonia-N TMDL.
WL 7
✔2
3
3
8
✔
✔
✔
1
1
1
3
✔
2
0
2
✔
✔
✔
✔
✔
✔
WL 7
✔
✔
✔
✔
✔
✔
✔
✔
✔
1
2
2
1
WL 7
✔
✔
✔
✔
✔
✔
✔
0.00
6.00
2.00 2.00
3.00 9.00
3
9
0
1
-2
-1
1
✔
✔
✔
WL 7
WL 7
✔
WL 7
✔
✔
✔
✔
✔
WL 7
✔
✔
✔
NA
Figure 1: Cowardin plant classes.
Figure 2:Hydroperiods.
Figure 3:Boundary of area within 150 feet of the wetland.
Figure 4:Contributing basin.
Figure 5:1km polygon.
Figure 6:303(d) listed waters in basinfor the HUC12 in which the wetland is found.
Figure 7.TMDLS for the HUC12 in which the wetland is found.
WL 8
Wetland 8 5/22/24
4/19/24T. Parry, T. Tumaliuan
✔
✔
0 000
✔
WL 8
✔
✔
✔
✔
✔
WL 8
✔
✔
✔
✔
✔
WL 8
✔
✔
✔
✔
✔
✔
✔
✔
✔
2
2
1
1
WL 8
✔
✔
✔
✔
✔
✔
✔
0.05
0.15
0.00 0.05
0.10 0.25
2
8
0
1
-2
-1
2
✔
✔
✔
WL 8
✔
✔
WL 8
✔
WL 8
✔
✔
✔✔
✔
✔
✔
✔
✔
✔
✔
Access to Wetland 8 was limited. The wetland rating form questions were informed by aerial
photos, existing environmental documentation, and observation made from accessible
portions of the wetland.
WL 8
✔
✔
✔
II
WL 9
Wetland 9 5/22/24
4/19/24T. Parry, T. Tumaliuan
Depressional
✔
WATOR
II ✔
8 7520
✔
✔✔
✔✔✔
✔✔
✔
✔
✔✔
✔
WL 9
1
2
3
4
5
6
7
8
WL 9
✔
✔
✔
✔
WL 9
✔
✔
✔
✔
✔
WL 9
✔
2
0
✔
5
✔
2
9
✔
✔
✔
✔
✔Railroad
1
1
0
1
3
✔
✔
✔
✔
✔
1
1
2
4
✔
D3.1&3.2 - Wetland is upgradient and discharges (within 0.30 mi) into the Green River which is on
the 303(d) list for temperature, bacteria, and pH). D3.3 - Wetland is within the 12-digit HUC of the
Duwamish Waterway Ammonia-N TMDL.
WL 9
✔2
3
0
5
✔
✔
✔
1
1
1
3
✔
2
0
2
✔
✔
✔
✔
✔
✔
WL 9
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
1
3
1
1
WL 9
✔
✔
✔
✔
✔
✔
0.01
0.15
0.03 0.04
0.10 0.25
2
8
0
1
-2
-1
1
✔
✔
✔
WL 9
✔
WL 9
✔
WL 9
✔
✔
✔
✔
✔
✔
WL 9
✔
✔
✔
NA
Figure 1: Cowardin plant classes.
Figure 2:Hydroperiods.
Figure 3:Location of outlet.
Figure 4:Boundary of area within 150 feet of the wetland.
Figure 5:Contributing basin.
Figure 6:1km polygon.
Figure 7:303(d) listed waters in basinfor the HUC12 in which the wetland is found.
Figure 8.TMDLS for the HUC12 in which the wetland is found.
Identified as Wetland C in Wet.land (2022) report10
Wetland 10 5/22/24
4/19/24T. Parry, T. Tumaliuan
Depressional
✔
WATOR
III ✔
6 6618
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔✔
✔
10
1
2
3
4
5
6
7
8
10
✔
✔
✔
✔
10
✔
✔
✔
✔
✔
10
✔
2
0
✔3
✔
0
5
✔
✔
✔
✔
✔
0
1
0
1
2
✔
✔
✔
✔
✔
1
1
2
4
✔
10
✔2
5
3
10
✔
✔
✔
0
1
0
1
✔
1
0
1
✔
✔
✔
✔
✔
✔
10
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
2
3
1
2
✔
10
✔
✔
✔
✔
✔
✔
✔
2.00
5.50
2.00 4.00
3.00 8.50
2
10
0
1
-2
-1
2
✔
✔
✔
10
✔
✔
10
✔
✔
10
✔
✔
✔
✔
✔
✔
10
✔
✔
✔
NA
Identified as Wetland F in Wetl.land (2022) report11
Wetland 11 5/12/24
10/16/24T. Parry
Slope
✔
✔
WATOR
III ✔
✔
5 5616
✔
✔
✔✔✔
✔
✔✔
✔
✔
11
11
✔
✔
✔
✔
✔
✔
✔
Access to Wetland 11 was limited. The wetland rating form questions were informed by aerial
photos and existing environmental documentation. No field observations could be made.
11
✔
✔
✔
11
✔
✔
✔
✔
✔
✔
✔
✔
0
0
3
3
0
0
0
1
1
2
4
✔
✔
✔
11
✔
✔
✔
1
0
1
0
1
✔
✔
✔
11
✔
✔
✔
✔
✔
✔
✔
✔
4
0
1
3
✔
11
✔
✔
✔
✔
✔
2.00
5.50
2.00 4.00
3.00 8.50
1
9
0
0
-2
-2
2
✔
✔
✔
11
✔
✔
11
✔
✔
11
✔
✔
✔
✔
✔
✔
11
✔
✔
✔
NA
Identified as Wetland A in Wetl.land (2022) report
12a
12a 12/31/24
10/14/16Trey Parry
Riverine
✔
✔
WATOR
II ✔
✔
8 7621
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
12a
12a
✔
✔
✔
✔
✔
✔
✔
12a
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
12a
2
8
10
2
1
0
1
0
4
0
0
2
2
✔
✔
✔
✔
12a
✔
✔
✔
✔
✔
✔
✔
6
7
13
0
1
1
2
1
0
1
✔
✔
✔
12a
✔
✔
✔
✔
✔
✔
✔
✔
✔
2
2
2
2
✔
12a
✔
✔
✔
✔
✔
✔
✔
✔
2.00
5.50
2.00 4.00
3.00 8.50
3
11
0
0
-2
-2
2
✔
✔
✔
12a
✔
✔
12a
✔
✔
12a
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
12a
✔
✔
✔
NA
Identified as Wetland AA in Wetl.land (2022)
report12b
12b 12/31/24
10/14/16Trey Parry
Riverine
✔
✔
WATOR
II ✔
✔
8 7621
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
12b
1
2
3
4
5
6
7
8
9
10
12b
✔
✔
✔
✔
✔
✔
✔
12b
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
12b
0
8
8
2
1
0
1
0
4
0
0
2
2
✔
✔
✔
✔
12b
✔
✔
✔
✔
✔
✔
✔
6
7
13
0
1
1
2
1
0
1
✔
✔
✔
12b
✔
✔
✔
✔
✔
✔
✔
✔
1
1
1
1
12b
✔
✔
✔
✔
✔
✔
✔
✔
2.00
5.50
2.00 4.00
3.00 8.50
3
7
0
0
-2
-2
2
✔
✔
✔
12b
✔
✔
12b
✔
✔
12b
✔
✔
✔
✔
✔
✔
✔
✔
✔
✔
12b
✔
✔
✔
NA
Wetlands and Streams Technical Memorandum City of Tukwila Allentown Truck Reroute Environmental Impact Statement
February 24, 2025
Attachment B. Site Photos
Wetlands and Streams Technical Memorandum City of Tukwila Allentown Truck Reroute Environmental Impact Statement
February 24, 2025
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Wetlands and Streams Technical Memorandum City of Tukwila Allentown Truck Reroute Environmental Impact Statement
February 24, 2025
Photograph 1: Wetland 1 as photographed facing east along the right bank of the Duwamish River and
along Railroad Avenue.
Photograph 2: Wetland 2 as photographed along the trail system within Codiga Park.
Wetlands and Streams Technical Memorandum City of Tukwila Allentown Truck Reroute Environmental Impact Statement
February 24, 2025
Photograph 3: Wetland 3 as photographed from the South 129th Street ramp. Surface water is visible
through the overhead canopy.
Photograph 4: Wetland 4a as photographed from the South Boeing Access Road. Surface water and
hydrophytic vegetation is visible through the overhead canopy.
Wetlands and Streams Technical Memorandum City of Tukwila Allentown Truck Reroute Environmental Impact Statement
February 24, 2025
Photograph 5: Wetland 5 photographed facing south from the northern extent of the wetland near Airport
Way South.
Photograph 6: Wetland 8 as photographed facing south across the Duwamish River from Railroad
Avenue.
Wetlands and Streams Technical Memorandum City of Tukwila Allentown Truck Reroute Environmental Impact Statement
February 24, 2025
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