HomeMy WebLinkAboutL2ST_SegA_CAR_2015_Working_WPLake to Sound Trail—Segment A Final Critical Area Study
Prepared for
/
Parks Division
201 South Jackson, Seventh Floor
Seattle, Washington 98104
Prepared by
Parametrix
719 2nd Avenue, Suite 200
Seattle, WA 98104
T. 206.394.3700 F. 1.855.542.6353
www.parametrix.com
CITATION
Parametrix. 2015. Lake to Sound Trail—Segment A Final Critical Area Study. Prepared by Parametrix, Seattle, Washington. April 2015.
TABLE OF CONTENTS
1. INTRODUCTION 1-1
1.1 PROJECT OVERVIEW 1-1
1.2 PROJECT FEATURES 1-1
1.3 PROJECT AREA AND SETTING 1-2
1.4 PROJECT PURPOSE AND NEED 1-2
1.5 PURPOSE OF REPORT 1-4
1.6 STUDY AREA 1-4
1.7 APPLICABLE LAWS AND REGULATIONS 1-4
2. METHODS 2-1
2.1 REVIEW OF EXISTING INFORMATION 2-1
2.2 FIELD INVESTIGATION 2-1
2.3 WETLANDS 2-1
2.3.1 Identification and Delineation 2-1
2.3.2 Wetland Classification and Rating 2-3
2.3.3 Wetland Functional Assessment 2-4
2.4 STREAMS 2-4
2.5 FISH AND WILDLIFE HABITAT CONSERVATION AREAS 2-6
2.6 AREAS OF SPECIAL FLOOD HAZARD 2-7
2.7 IMPACT ASSESSMENT 2-7
3. RESULTS 3-1
3.1 GENERAL HABITAT CHARACTERISTICS 3-1
3.1.1 Land Use 3-1
3.1.2 Topography 3-1
3.1.3 Soils 3-1
3.1.4 Vegetation 3-1
3.1.5 Fish and Wildlife 3-2
3.2 WETLANDS IN STUDY AREA 3-2
3.3 STREAMS 3-14
3.3.1 Green and Black River Basins 3-14
3.3.2 Green River 3-15
3.3.3 Black River 3-16
3.4 FISH AND WILDLIFE HABITAT CONSERVATION AREAS 3-18
3.5 AREAS OF SPECIAL FLOOD HAZARD 3-18
4. IMPACTS 4-1
4.1 WETLANDS 4-1
4.1.1 Permanent Wetland Impacts 4-1
4.1.2 Permanent Wetland Buffer Impacts 4-1
4.1.3 Temporary Wetland Impacts 4-2
4.1.4 Temporary Wetland Buffer Impacts 4-2
4.2 STREAMS 4-2
4.2.1 Permanent Stream Impacts 4-2
4.2.2 Permanent Stream Buffer Impacts 4-20
4.2.3 Temporary Stream Impacts 4-21
4.2.4 Temporary Stream Buffer Impacts 4-21
4.3 FISH AND WILDLIFE HABITAT CONSERVATION AREAS 4-21
4.4 AREAS OF SPECIAL FLOOD HAZARD 4-21
5. MITIGATION 5-1
5.1 AVOIDANCE AND MINIMIZATION 5-1
5.2 RESTORATION OF TEMPORARY IMPACTS 5-1
5.3 COMPENSATORY MITIGATION 5-2
5.3.1 Regulatory Requirements for Compensatory Mitigation 5-2
5.3.2 Site Selection 5-3
5.3.3 Mitigation Site Existing Conditions 5-3
5.3.4 Proposed Mitigation 5-4
5.3.5 Mitigation Goals, Objectives, and Performance Standards 5-4
6. MONITORING AND MAINTENANCE 6-1
6.1 MONITORING 6-1
6.1.1 Quantitative Monitoring 6-1
6.1.2 Qualitative Monitoring 6-1
6.2 MAINTENANCE 6-2
6.3 CONTINGENCY MEASURES 6-2
7. REFERENCES 7-1
LIST OF FIGURES
1-1 Vicinity Map 1-3
3-1 Critical Areas 3-3
3-2 Critical Areas 3-4
3-3 Critical Areas 3-5
3-4 Drainage Basins, Subbasins, and Site Characteristics 3-19
4-1 Critical Areas Impacts 4-3
4-2 Critical Areas Impacts 4-5
4-3 Critical Areas Impacts 4-7
4-4 Critical Areas Impacts 4-9
4-5 Critical Areas Impacts 4-11
4-6 Critical Areas Impacts 4-13
4-7 Critical Areas Impacts 4-15
4-8 Critical Areas Impacts 4-17
4-9 Critical Areas Impacts 4-19
LIST OF TABLES
2-1 Key to Plant Indicator Status Categories 2-2
2-2 Criteria for Wetland Rating Categories as Specified by Ecology and the City of Renton 2-3
2-3 Criteria for Stream Classifications as Specified by Washington State and the Cities of Renton and Tukwila 2-5
2-4 Criteria for FWHCA Designations as Specified by the Cities of Renton and Tukwila 2-6
3-1 Summary of Wetlands in the Project Area 3-6
3-2 Summary of Wetland Functions for Wetlands in the Project Area 3-6
4-1 Wetland and Buffer Impacts 4-1
4-2 Stream and Buffer Impacts 4-2
6-1 Contingency Measures for the Mitigation Site 6-3
APPENDICES
A Wetland Determination Data Forms
B Wetland Rating Forms
C Wetland Functions and Values Forms
D Site Photographs
E Mitigation Plans
ACRONYMS
AASHTO American Association of State Highway and Transportation Officials
BMP best management practice
CFR Code of Federal Regulations
cfs cubic feet per second
Cities City of Renton and City of Tukwila
CMAQ Congestion Mitigation and Air Quality Improvement (program)
Corps U.S. Army Corps of Engineers
CWA Clean Water Act
DNR Washington State Department of Natural Resources
Ecology Washington State Department of Ecology
EPA U.S. Environmental Protection Agency
ESA Endangered Species Act
FAC Facultative
FACU Facultative Upland
FACW Facultative Wetland
FEMA Federal Emergency Management Agency
FHWA Federal Highway Administration
FWHCA fish and wildlife habitat conservation area
HGM hydrogeomorphic classification
HPA Hydraulic Project Approval
LWD large woody debris
NEPA National Environmental Policy Act
NRCS Natural Resources Conservation Service
OBL Obligate
OHWM ordinary high water mark
PAA Potential Annexation Area
PEM palustrine emergent
PFO palustrine forested
RCW Revised Code of Washington
RM river mile
SEPA State Environmental Policy Act
SMP Shoreline Master Program
TESC temporary erosion and sediment control
TMC Tukwila Municipal Code
TNW Traditional Navigable Water
UPL Upland
USDA U.S. Department of Agriculture
USFWS U.S. Fish and Wildlife Service
WAC Washington Administrative Code
WDFW Washington Department of Fish and Wildlife
WRIA Water Resource Inventory Area
WSDOT Washington State Department of Transportation
INTRODUCTION
Project Overview
King County, together with the Cities of Renton and Tukwila, Washington State Department of Transportation (WSDOT), and the Federal Highway Administration (FHWA), is proposing to develop
a 1.2-mile segment of what will ultimately be the 16-mile Lake to Sound Trail. The 1.2-mile segment is referred to as Segment A of the Lake to Sound Trail. Segment A extends from Naches
Avenue SW, runs parallel to the railroad tracks north of the Black River Riparian Forest, across a proposed non-motorized pedestrian bridge northeast of Monster Road, and under two
railroad bridges to the Green River Trail at the north end of the Starfire Sports Complex in Fort Dent Park (Figure 1-1).
Segment A, as well as the longer Lake to Sound Trail, is part of a Regional Trail System that provides non-motorized, alternative transportation and a recreational corridor for multiple
trail users, including bicyclists, pedestrians, skaters, and others. A goal of the Lake to Sound Trail is to provide non-motorized transportation facilities to economically disadvantaged
communities in southwest King County that have been historically underserved by such facilities.
Once complete, Segment A would become part of a larger planned system that would serve employment and residential centers in South King County and connect to regional trails in Seattle
and the greater Regional Trail System network. Segment A provides a much needed trail connection between the regional growth centers of Renton and Tukwila and safe passage under the
heavy rail lines. In addition to the Green River Trail, Segment A will connect to the Interurban Trail to the south, and in the future to the Cedar River Trail.
Project Features
Segment A is typically approximately 12 feet of asphalt pavement bounded by two 2-foot-wide shoulders and 1-foot-wide clear zones, in accordance with American Association of State Highway
and Transportation Officials’ (AASHTO) guidelines. The project includes:
Constructing a 12-foot-wide asphalt pavement trail with soft-surface (gravel) shoulders.
Performing minor grading to construct the trail (approximately 1,410 cubic yards of cut and 2,980 cubic yards of fill, disturbing an area of approximately 0.72 acre outside the proposed
trail footprint).
Performing ground improvements which would disturb an area of approximately 0.17 acre in addition to other disturbances from the trail.
Installing a new trail bridge over the Black River to the east of the existing Monster Road Bridge, which cannot be improved to safely accommodate the envisioned trail use.
Installing a pedestrian-actuated signal crossing of Monster Road south of the bridge.
Constructing an undercrossing feature beneath two railroad bridges to protect trail users from potential falling debris.
Installing one box culvert for terrestrial habitat enhancement.
Building retaining walls near the south approach to Monster Road, north of the proposed pedestrian bridge over the Black River, and on either side of the box culvert.
Installing split-rail fencing and plantings to discourage incursions into sensitive areas and to improve visual screening for sensitive wildlife.
Constructing two approximately 10-foot by 20-foot pull-out rest areas (one at the northern perimeter of the Black River Riparian Forest and one east of Monster Road and northwest of
the Black River pump station)
Project Area and Setting
The Segment A project area is a linear corridor mostly within an existing trail corridor (see Figure 1-1). Segment A is located in Section 13, Township 23 North, Range 4 East, Willamette Meridian.
Two parallel railroad tracks (BNSF and Union Pacific) cross the western quarter of the proposed trail corridor on elevated bridges heading north-south. Another set of BNSF railroad
tracks are located north of the eastern three-quarters of the proposed trail corridor with an east-west bearing. These tracks tie into the north-south tracks north of the project area.
East of the railroad bridges, the proposed trail alignment is within the city of Renton; west of the railroad bridges the proposed trail alignment is within the city of Tukwila. The
project area is described from east to west below.
The east terminus is located at a cul-de-sac on Naches Avenue SW near an office park. The eastern three-quarters of the proposed trail alignment from Naches Avenue SW to the new pedestrian
bridge northeast of Monster Road (approximately 4,100 linear feet) follows an existing gravel maintenance road south of the BNSF east-west railroad tracks and north of the Black River,
along the northern perimeter of the Black River Riparian Forest. The gravel maintenance road is currently used for walking and pet exercise. The existing road surface in most of this
portion consists of compacted gravel ranging from 10 to 12 feet wide. Areas immediately outside the edge of the existing gravel surface generally consist of grasses, low-growing annual
plants, blackberry thickets, and native riparian trees. Uses outside this portion of the project area include a concrete recycling plant and an area zoned for light industrial uses
just north of the railroad tracks.
The proposed trail alignment crosses over the Black River using a proposed new non-motorized pedestrian bridge northeast of Monster Road Bridge, then crosses Monster Road south of the
river. For the western quarter of the proposed trail alignment, west of Monster Road, the alignment lies south of the Black River. For the first 150 feet west of Monster Road, the alignment
is on existing paved surfaces, and then it follows a dirt footpath that joins an existing dirt road beneath the railroad bridges for 650 feet. The westernmost 600 feet of the proposed
trail alignment is on maintained lawns associated with Fort Dent Park. West of the railroad bridges, the area south of the proposed trail alignment is dominated by Fort Dent Park and
the Starfire Sports Complex. The confluence of the Black and Green rivers is located just north of the west end of the Segment A project area. Commercial businesses are north of the
Black River and south of the trail corridor.
Project Purpose and Need
The purpose of the Segment A project is to design and construct an alternative non-motorized transportation corridor and multi-use recreational trail between Naches Avenue SW in Renton
and the Green River Trail in Tukwila. Segment A would provide non-motorized access to recreation and employment centers and would complete a link in the Regional Trail System network.
The trail is intended to safely accommodate a variety of user groups such as bicyclists, pedestrians, runners, wheelchair users, and skaters. Trail design standards will safely accommodate
different ages and skill levels within those groups.
Figure 1-1. Vicinity Map
Completion of Segment A would provide the following benefits:
Serve local and regional non-motorized transportation needs and provide access to the trail for local communities.
Help satisfy the regional need for recreational trails and provide safe recreational opportunities to a wide variety of trail users.
Provide a critical link in the Regional Trail System.
Provide economic and health benefits to communities along the trail.
Purpose of Report
Investigation of critical areas is required by the City of Renton Shoreline Master Program (SMP), as outlined in Renton Municipal Code 4-3-090 (Shoreline Master Program Regulations),
and Tukwila Municipal Code (TMC) 18.44 and 18.45 (Shoreline Overlay and Environmentally Sensitive Areas). This Critical Area Study is intended to provide information in support of project
planning and to facilitate permitting. This report describes wetlands, streams (watercourses), fish and wildlife habitat conservation areas (FWHCAs), and Areas of Special Flood Hazard.
It also presents measures included in the project design to avoid and minimize impacts on these critical areas.
Specific objectives of this report are as follows:
Review, compile, and analyze existing wetland, stream, and FWHCA data for the project site and vicinity.
Identify and document wetlands, streams, and FWHCAs in the study area.
Evaluate potential impacts on wetlands, streams, FWHCAs, and their associated buffers from the proposed trail.
Identify mitigation measures to protect wetlands, streams, FWHCAs, and their associated buffers, and present compensatory mitigation for unavoidable impacts.
Other critical areas regulated by the Cities of Renton and Tukwila, such as geologically hazardous areas and critical aquifer recharge areas, are not addressed in this report.
Study Area
For the field investigation, the study area comprises the area within 100 feet of the trail corridor, from Naches Avenue SW parallel to the railroad tracks north of the Black River Riparian
Forest, across Monster Road, and under two railroad bridges to the Green River Trail at the north end of the Starfire Sports Complex in Fort Dent Park.
Applicable Laws and Regulations
King County is receiving federal funding through the Congestion Mitigation and Air Quality Improvement (CMAQ) program for the design of this segment of the Lake to Sound Trail. Federal
funding triggers requirements for compliance with the National Environmental Policy Act (NEPA), Section 7(c) of the Endangered Species Act (ESA), and the National Historic Preservation
Act. An Environmental Classification Summary, ESA Biological Assessment, and Cultural Resources Survey Report have been prepared for this project.
Wetlands and streams within the study area are subject to federal, state, and City of Renton or City of Tukwila regulations. At the federal level, wetlands and streams are regulated
by Section 404 of the Clean Water Act (CWA), which regulates placement of fill in waters of the United States. The U.S. Army Corps of Engineers (Corps) is responsible for issuing permits
under Section 404 of the CWA.
In June 2007 and December 2008 (revised version), the Corps and the U.S. Environmental Protection Agency (EPA) issued a joint memorandum that clarifies CWA jurisdiction following the
Supreme Court’s decision in the Rapanos case. Guidance in the memorandum identifies situations where a developer may need to obtain a CWA Section 404 permit before completing work in
wetlands, tributaries, or other waters of the United States.
CWA jurisdiction may also be extended to waters that are not Traditional Navigable Waters (TNWs) of the United States if either of the following two standards is met. The first standard
extends regulatory jurisdiction to non-navigable tributaries of TNWs that are relatively permanent and wetlands that directly abut (there is a surface connection) these waters. The
second standard requires a case-by-case determination (“significant nexus” analysis) for non-navigable tributaries that are not relatively permanent tributaries and adjacent wetlands
that have characteristics that may significantly affect TNWs.
Activities that affect wetlands and streams may also require a water quality certification (Section 401 of the CWA), which is administered at the federal level by the EPA and implemented
at the state level by the Washington State Department of Ecology (Ecology). Ecology reviews projects for compliance with state water quality standards and makes permitting and mitigation
decisions based on the nature and extent of impacts, as well as the type and quality of wetlands or streams being affected. Activities that use, divert, obstruct, or change the flow
of a water of the state, including some wetlands, typically require a Hydraulic Project Approval (HPA) permit. Washington Administrative Code (WAC) chapter 220-110 regulates water-crossing
structures and describes requirements for a HPA from the Washington Department of Fish and Wildlife (WDFW).
Under the Renton SMP (4-3-050 and 4-3-090) and TMC (16.52, 18.44 and 18.45), the Cities of Renton and Tukwila designate and regulate activities within critical areas and their buffers,
including wetlands, streams, special flood hazards, and FWHCAs. These regulations describe the Cities’ requirements for the identification, rating, and categorization of wetlands, streams,
FWHCAs, and buffers; mitigation and performance standards; as well as the requirements for Critical Area Studies (or Sensitive Area Special Studies). Development of the proposed trail
would require land use and shoreline permits from the Cities. All local permit applications and other land use decisions are also subject to State Environmental Policy Act (SEPA) review,
unless specifically exempted.
METHODS
This report is based on a review of existing information and field investigations. The goal of these efforts is to document existing information to reflect current site conditions and
collect new information for conducting the project design and assessing impacts.
Review of Existing Information
Prior to conducting fieldwork, biologists reviewed maps and materials including, but not limited to:
King County iMap (King County 2015).
Natural Resources Conservation Service (NRCS) Web Soil Survey (USDA, NRCS 2010a).
National Wetlands Inventory online interactive mapper (U.S. Fish and Wildlife Service [USFWS] 2010).
Washington State Department of Natural Resources (DNR) Natural Heritage Program database (DNR 2014).
Priority Habitats and Species database (WDFW 2015).
SalmonScape fish database and mapping application (WDFW 20144).
A Catalog of Washington Streams and Salmon Utilization, Volume 1, Puget Sound Region (Williams et al. 1975).
Water Resource Inventory Area (WRIA) 9 (Green/Duwamish River) Limiting Factors Analysis (WSCC 2000).
Field Investigation
Project biologists performed field investigations over multiple site visits between November 2010 and February 2011 to identify and document wetlands. The biologists also conducted site
visits on February 1 and March 29, 2011 to characterize streams, FWHCAs, and potential off-site compensatory mitigation areas. Site investigations in the vicinity of the mitigation
area were conducted during multiple site visits in March 2012.
Wetlands
Identification and Delineation
The methods specified in the Corps of Engineers Wetlands Delineation Manual (Environmental Laboratory 1987) were used by project biologists to delineate on-site wetlands. Additionally,
the methods specified in the Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Western Mountains, Valleys, and Coast Region (Version 2.0) (Corps 2010) were used.
These methods comply with those in the Washington State Wetland Identification and Delineation Manual (Ecology 1997).
Wetlands are defined as those areas that are inundated or saturated by surface or groundwater 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. An area must have at
least one positive indicator of wetland vegetation, soils, and hydrology to be considered a wetland. The delineated wetlands were instrument-surveyed by professional land surveyors.
Wetland determination data forms from the Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Western Mountains, Valleys, and Coast Region (Version 2.0) (Corps
2010) were recorded for each wetland (Appendix A).
Vegetation
The dominant plants and their wetland indicator status were evaluated to determine if the vegetation was hydrophytic. Hydrophytic vegetation is generally defined as vegetation adapted
to prolonged saturated soil conditions. To meet the hydrophytic vegetation criterion, more than 50 percent of the dominant plants must be Facultative (FAC), Facultative Wetland (FACW),
or Obligate (OBL), based on the plant indicator status category assigned to each plant species by the USFWS (Reed 1988, 1993). Table 2-1 lists the definitions of the indicator status
categories.
Scientific and common plant names follow currently accepted nomenclature. Most names are consistent with Flora of the Pacific Northwest (Hitchcock and Cronquist 1973) and the PLANTS
Database (USDA, NRCS 2010b). During the field investigations, dominant plant species were observed and recorded on data forms for each sample plot (Appendix A).
Table 2-1. Key to Plant Indicator Status Categories
Plant Indicator Status Category
Symbol
Definition
Obligate Wetland Plants
OBL
Plants that almost always (> 99% of the time) occur in wetlands, but which may rarely (< 1% of the time) occur in non-wetlands.
Facultative Wetland Plants
FACW
Plants that often (67% to 99% of the time) occur in wetlands, but sometimes (1% to 33% of the time) occur in non-wetlands.
Facultative Plants
FAC
Plants with a similar likelihood (33% to 66% of the time) of occurring in both wetlands and non-wetlands.
Facultative Upland Plants
FACU
Plants that sometimes (1% to 33% of the time) occur in wetlands, but occur more often (67% to 99% of the time) in non-wetlands.
Upland Plants
UPL
Plants that rarely (< 1% of the time) occur in wetlands, and almost always (> 99% of the time) occur in non wetlands.
Source: Environmental Laboratory (1987)
Soils
Generally, an area must have hydric soils to be a wetland. Hydric soil forms when soils are saturated, flooded, or ponded long enough during the growing season to develop anaerobic conditions
in the upper part. Biological activities in saturated soil result in reduced oxygen concentrations that produce a preponderance of organisms using anaerobic processes for metabolism.
Over time, anaerobic biological processes result in certain soil color patterns, which are used as indicators of hydric soil. Typically, low-chroma colors are formed in the soil matrix.
Brightly-colored redoximorphic features form within the matrix under a fluctuating water table. Other important hydric soil indicators include organic matter accumulations in the surface
horizon, reduced sulfur odors, and organic matter staining in the subsurface. Soils were examined by excavating sample plots to a depth of 18 inches or more to observe
soil profiles, colors, and textures. The depths of the sample plots ranged between 18 and 20 inches deep with varying widths, with the exception of two upland sample plots that were
shallower because of the presence of quarry spalls or cobbles. Munsell color charts (GretagMacbeth 2000) were used to describe soil colors.
Hydrology
The project area was examined for evidence of hydrology. An area is considered to have wetland hydrology when soils are ponded or saturated consecutively 12.5 percent (sometimes 5 to
12.5 percent) of the growing season. In King County (Sea-Tac Airport station), the growing season generally lasts from early March (March 9) to mid-November (November 17) (USDA, NRCS
2002), so ponding or saturation must be present for approximately 32 consecutive days. Primary indicators of hydrology include surface inundation and saturated soils. Secondary indicators
of hydrology include drainage patterns, watermarks on vegetation, water-stained leaves, and oxidized root channels.
Wetland Classification and Rating
Delineated wetlands were classified according to the USFWS Classification of Wetlands and Deepwater Habitats of the United States (Cowardin et al. 1979). Hydrogeomorphic (HGM) classifications
were assigned to wetlands using the Corps methods established in a Hydrogeomorphic Classification System for Wetlands (Brinson 1993). Wetlands were rated according to the Renton SMP
(4-3-090 D.2.d.ii) and the Washington State Wetland Rating System for Western Washington – Revised (Hruby 2004) (Appendix B). Table 2-2 summarizes the state and local jurisdiction wetland
rating criteria for each wetland category. Buffer widths assigned to wetlands in the project area reflect requirements of the Renton SMP( 4-3-090 D.2.d.iv.(c)). No wetlands were identified
within the City of Tukwila.
Table 2-2. Criteria for Wetland Rating Categories as Specified by Ecology and the City of Renton
Ecologya
Category I
Wetlands of exceptional value in terms of protecting water quality, storing flood water and stormwater, and/or providing habitat for wildlife as indicated by a rating system score of
70 points or more. These are wetland communities of infrequent occurrence that often provide documented habitat for sensitive, threatened, or endangered species and/or have other attributes
that are very difficult or impossible to replace if altered.
Category II
Wetlands that have very important resources as indicated by a rating system score of between 51 and 69 points. These wetlands occur more commonly than Category I wetlands but still
require a high level of protection.
Category III
Wetlands that have important resource value as indicated by a rating system score of between 30 and 50 points.
Category IV
Wetlands that are of limited resource value as indicated by a rating system score of less than 30 points. They typically have vegetation of similar age and class, lack special habitat
features, and/or are isolated or disconnected from other aquatic systems or high quality upland habitats.
Rentonb
Wetlands shall be rated based on categories that reflect the functions and values of each wetland. Wetland categories shall be based on the criteria provided in the Washington State
Wetland Rating System for Western Washington, revised August 2004 (Ecology Publication #04-06-025). These categories are generally defined above.
a Hruby (2004)
b Renton SMP (4-3-090 D.2.d.ii)
Wetland Functional Assessment
Functions of individual wetlands were assessed using the WSDOT Wetland Functions Characterization Tool for Linear Projects (Null et al. 2000) (Appendix C). This method allows evaluation
of wetland function, using best professional judgment and readily observed environmental characteristics. For example, an area of open water may provide habitat for waterfowl or aquatic
animals. The upland habitats and buffers surrounding wetlands were also considered in the evaluation, because adjacent land uses affect the performance of wetland functions. Project
biologists reviewed the indicator characteristics present for each wetland and assigned a summary rating of low, moderate, or high for each wetland function.
Functions that were considered most relevant to this project are grouped into three categories: habitat, water quality, and hydrological support. Habitat functions include providing
fish, avian species, and other wildlife access to food, cover, and breeding and rearing opportunities. Hydrological functions assessed include groundwater recharge/discharge, base flow
support, and flood flow alteration (storage and desynchronization). Water quality functions include protection and enhancement through sedimentation, erosion protection, and nutrient
retention/nutrient transformation.
Streams
The Cities of Renton and Tukwila do not specifically define streams, but refer to streams as water courses. The City of Renton defines a watercourse as a channel in which a flow of water
occurs either continuously or intermittently (Renton SMP 4-6-100).
The City of Tukwila defines watercourses as 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 surface water flows naturally, including the Green/Duwamish River. The channel or bed need not contain water year-round. Watercourses do not include irrigation
ditches, stormwater 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.
The edges (ordinary high water mark [OHWM]) of project area streams were identified by project biologists and instrument-surveyed by professional land surveyors.
Streams associated with the project (Green River and Black River) in the city of Tukwila (west of the railroad bridges) are regulated under TMC 18.44, while in the city of Renton (east
of the railroad bridges), the Black River and all of the Black River Riparian Forest is regulated under Renton SMP 4-3-090. Table 2-3 lists the stream classification criteria as specified
by these entities. Buffer widths assigned to streams in the project area reflect requirements of the Renton SMP (4-3-090 D.2.d.iv.(c)) and TMC (18.45.080.D).
Table 2-3. Criteria for Stream Classifications as Specified by Washington State
and the Cities of Renton and Tukwila
Washington Statea
Type S
Streams and waterbodies that are designated “shorelines of the state” as defined in Chapter 90.58.030 (Revised Code of Washington [RCW]).
Type F
Streams and waterbodies that are known to be used by fish, or meet the physical criteria to be potentially used by fish. Fish streams may or may not have flowing water all year; they
may be perennial or seasonal.
Type Np
Streams that have flow year round, but do not meet the physical criteria of a Type F stream. This also includes streams that have been proven not to contain fish using methods described
in the Forest Practices Board Manual Section 13.
Type Ns
Streams that do not have surface flow during at least some portion of the year, and do not meet the physical criteria of a Type F stream.
Rentonb
Class 1
Class 1 waters are perennial salmonid-bearing waters which are classified by the City and State as Shorelines of the State.
Class 2
Class 2 waters are perennial or intermittent salmonid-bearing waters which meet one or more of the following criteria:
(a) Mapped on Figure Q4, Renton Water Class Map, as Class 2; and/or
(b) Historically and/or currently known to support salmonids, including resident trout, at any stage in the species lifecycle; and/or
(c) Is a water body (e.g., pond, lake) between one half (0.5) acre and twenty (20) acres in size.
Class 3
Class 3 waters are non-salmonid-bearing perennial waters during years of normal rainfall, and/or mapped on Figure Q4, Renton Water Class Map, as Class 3.
Class 4
Class 4 waters are non-salmonid-bearing intermittent waters during years of normal rainfall, and/or mapped on Figure Q4, Renton Water Class Map, as Class 4.
Class 5
Class 5 waters are non-regulated non-salmonid-bearing waters which meet one or more of the following criteria:
(a) Flow within an artificially constructed channel where no naturally defined channel had previously existed; and/or
(b) Are a surficially isolated water body less than one-half (0.5) acre (e.g., pond) not meeting the criteria for a wetland as defined in subsection M of this Section.
Tukwila c
Type 1 (S)
Watercourses inventoried as Shorelines of the State, under RCW 90.58. These watercourses shall be regulated under TMC Chapter 18.44, Shoreline Overlay.
Type 2 (F)
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.
Type 3 (Np)
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.
Type 4 (Ns)
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.
a WAC 222-16-031
b Renton SMP (4-3-050 L.1.a)
c TMC (18.45.100.A)
RCW = Revised Code of Washington
Fish and Wildlife Habitat Conservation Areas
Proposed alterations to FWHCAs are regulated by both Cities (referred to as Fish Conservation Areas by the City of Renton). As defined in the Renton SMP, critical habitats are Category 1
wetlands and habitat associated with the documented presence of species proposed or listed by the federal government or the State of Washington as endangered, threatened, candidate,
sensitive, monitor, or priority species. Areas designated as FWHCAs by the City of Tukwila are mapped by the City; they include areas with which endangered, threatened, or sensitive
species have a primary association, as well as habitats and species of local importance. Table 2-4 provides a list of habitat types afforded protection under the City of Tukwila critical
area regulations.
Project biologists reviewed existing information (listed under Section 2.1), the USFWS King County Species List, and NOAA Fisheries Service Species List to identify any potential FWHCAs
in the project vicinity. See the Vegetation and Wildlife Discipline Report (Parametrix 2015a) for additional information about FWHCAs associated with wildlife species.
Table 2-4. Criteria for FWHCA Designations as Specified by the Cities of Renton and Tukwila
Rentona
1.
Areas with which endangered, threatened, and sensitive species have a primary association;
2.
Waters of the State (i.e., the Green/Duwamish River itself);
3.
State natural area preserves and natural resource conservation areas;
4.
Areas critical for habitat connectivity; and
5.
The approximate location and extent of known fish and wildlife habitat conservation areas are identified in the Shoreline Inventory and Characterization Report and are shown on the
Sensitive Areas in the Shoreline Jurisdiction map. Only the salmon habitat enhancement project sites completed or underway are shown as Fish and Wildlife Conservation Areas on the Sensitive
Areas in the Shoreline Jurisdiction Map. Streams are shown as watercourses. The river is not shown as
a Fish and Wildlife Habitat Conservation Area for the sake of simplicity. Fish and wildlife habitat conservation areas correlate closely with the areas identified as regulated watercourses
and
wetlands and their buffers, as well as off-channel habitat areas created to improve salmon habitat (shown on the Sensitive Areas Map) in the Shoreline jurisdiction. The Green/Duwamish
River is recognized as the most significant fish and wildlife habitat corridor. In addition Gilliam Creek, Riverton Creek, Southgate Creek, Hamm Creek (in the North Potential Annexation
Area (PAA), and Johnson Creek (South PAA) all provide salmonid habitat.
Tukwilab
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.
a Renton SMP (4-3-090)
b TMC (18.45.150)
Areas of Special Flood Hazard
The City of Tukwila and the City of Renton regulate Areas of Special Flood Hazard (TMC 16.52 and RMC 4-3-050) to minimize loss and damages caused by flooding. Areas of Special Food Hazard
are defined as the land in the floodplain subject to one percent or greater chance of flooding in any given year (TMC 16.52.030 and RMC 4-3-050.I) Floodplain elevations were taken from
Federal Emergency Management Agency (FEMA) Federal Insurance Rate Map (FIRM), Map Number 53033C0976F and Map Number 53033C0957F. (FEMA 1995). The project team depicted the floodplain
boundary in the project plans and floodplain figures using City of Renton GIS data (Renton 2015), which is a digital interpretation of the 1995 FEMA FIRM. A floodplain analysis was
performed for the Lake to Sound – Segment A project and is provided in the Final Technical Information Report (Parametrix 2015b).
Impact Assessment
Impacts on wetlands, streams, FWHCAs, and associated buffers were assessed by overlaying the proposed design onto project base maps showing wetlands, streams, FWHCAs, and buffer locations.
Impact areas were determined as the area of intersection between the proposed design and the base maps. In some areas, multiple impact types (e.g., stream buffer and wetland buffer)
were present in a single location. In this report, all stream and riparian buffer impacts are reported; however, for purposes of compensatory mitigation, overlapping impacts were assigned
based on the following hierarchy: wetland, stream (below OHWM), wetland buffer, and stream buffer impacts. Areas of Special Flood Hazard impacts include any site activity that will
place material at or below the 100-year floodplain elevation within a floodplain boundary.
RESULTS
This section describes overall site conditions as well as the specific condition of the wetlands, streams, FWHCAs, and buffers within the study area (as defined in Section 1.6).
General Habitat Characteristics
Characteristics of the project area, including land use, topography, soils, vegetation, and fish and wildlife are described below.
Land Use
The primary land use in the areas surrounding the project is commercial business and recreational park. In contrast to regional trends, much of the area consists of relatively undisturbed
riparian hardwood forest. The area in Renton, south of the BNSF railroad corridor, is dominated by large trees and dense thickets of shrubby wetland (Black River Riparian Forest). The
portion north of the railroad corridor, however, consists of an active concrete recycling plant and an area zoned for light industrial uses, supporting essentially no vegetation. The
western end of the study area extends into Fort Dent Park in Tukwila. Additionally, some of the properties near the project area, specifically at the eastern end of the study area,
have office park structures with associated driveways, parking lots, lawns, and ornamental plantings.
Topography
The project area is generally flat, sloping gently from the east to the west. To the north is a gravel mining operation and an apartment complex, which are located at a considerably
higher elevation than the project area. Additionally, there are steep slopes down from the banks of the Black River, south of the project area, between the Black River Pump Station
and Monster Road. Elevations in the project area range from approximately 15 feet to 25 feet.
Soils
The majority of the study area is mapped as Woodinville silt loam (USDA, NRCS 2010a). A small portion of the study area (near the northeastern most part) is mapped as Tukwila muck. The
Woodinville series consists of deep, poorly drained soils formed in recent alluvium on flood plains and low terraces. Slopes are 0 to 2 percent. The Tukwila series consists of deep,
very poorly drained soils formed in organic material that is stratified with diatomaceous earth and volcanic ash. Tukwila soils are in depressions on stream terraces and glacial uplands.
Slopes are 0 to 1 percent. Information on soils observed during field investigations is provided in Section 3.2.
Vegetation
Vegetation within the project area consists of both wetland and upland species. Wetlands in the project area contain emergent, shrub, and forested habitats. Dominant vegetation includes
reed canarygrass (Phalaris arundinacea), black cottonwood (Populus balsamifera), salmonberry (Rubus spectabilis), red-osier dogwood (Cornus sericea), western redcedar (Thuja plicata),
Pacific willow (Salix lucida), Oregon ash (Fraxinus latifolia), and narrow-leaf cattail (Typha angustifolia).Wetland habitats on the site are further detailed in Section 3.3.
Upland plant communities within the project area consist primarily of upland forest and herbaceous vegetation. Vegetation includes red alder (Alnus rubra), tall fescue (Schedonorus phoenix),
salmonberry,
reed canarygrass, Himalayan blackberry (Rubus armeniacus), black cottonwood, western redcedar, western swordfern (Polystichum munitum), bigleaf maple (Acer macrophyllum), red elderberry
(Sambucus racemosa), and snowberry (Symphoricarpos albus).
The DNR Natural Heritage Program does not identify any rare plants within or in the vicinity of the project area.
Fish and Wildlife
Wildlife species present in the study area are adapted to a wide variety of conditions. Characteristic species include European starlings (Sturnus vulgaris), American robins (Turdus
migratorius), American crows (Corvus brachyrhynchos), dark-eyed juncos (Junco hymalis), spotted towhees (Pipilo maculatus), house finches (Carpodacus mexicanus), house sparrows (Passer
domesticus), black-capped chickadees (Poecile atricapillus), Virginia opossums (Didelphis virginiana), raccoons (Procyon lotor), deer mice (Peromyscus maniculatus), and Norway rats
(Rattus norvegicus).
The Duwamish and lower Green River serves as a migration and rearing area for anadromous salmonids, with no spawning habitat available (Williams et al. 1975). Three Pacific salmon species
inhabit the Green/Duwamish River basin in significant numbers, Chinook (Oncorhynchus tshawytscha), coho (O. kisutch), and chum (O. keta) salmon. Pink (O. gorbuscha) and sockeye (O.
nerka) salmon are occasionally seen in the Green River basin, but the Green River is primarily a chum, coho, and Chinook salmon stream (Williams et al. 1975). Although sockeye salmon
are occasionally seen in streams that are not tributaries to lakes, sockeye almost always require a rearing lake below or near their spawning area (Foerster 1972). Anadromous game fish
using these waters include steelhead (O. mykiss), sea-run cutthroat trout (O. clarki clarki), Dolly Varden (Salvelinus malma), and bull trout (Salvelinus confluentus).
WDFW (2011) data indicate that Chinook salmon, coho salmon, steelhead trout, and cutthroat trout have documented presence within the Black River in the study area. The type of use is
listed as migration for all species except coho, which use the lower Black River for juvenile rearing. Conditions favorable for Chinook salmon spawning and rearing do not exist in the
project area; recent information and historical records (Harza 1995; Williams et al. 1975) indicate that Chinook do not use this area for these life history activities. However, very
small numbers of adult fall Chinook migrating up the Green River occasionally stray into the Black River and become trapped above the Black River Pump Station (the pump station cannot
pass adult salmon downstream). Adult Chinook were observed entering the Black River and attempting to spawn near the SW 27th Street culvert, in Springbrook Creek, 2.3 miles upstream
of the project area, in fall 1997 (WSCC 2000).
Wetlands in Study Area
The National Wetlands Inventory identifies four wetlands in the study area: three palustrine forested wetlands with a seasonally flooded hydrologic regime and one constructed riverine
lower perennial unconsolidated bottom wetland with a permanently flooded hydrologic regime.
Biologists identified and delineated five wetlands in their entirety (Wetlands 3, 4, 5, 6, and 7) and delineated portions of larger wetland complexes in the study area (Wetlands 1/2
Complex and BR) (Figures 3-1 through 3-3). All wetlands are within the city of Renton. Classifications of the delineated wetlands are provided in Table 3-1; wetland functions are summarized
in Table 3-2. General wetland characteristics are discussed below. Also included in this report is specific information for each of the sample plots (Appendix A), wetland rating forms
(Appendix B), wetland functional assessment forms (Appendix C), and site photographs (Appendix D).
Figure 3-1. Critical Areas
Figure 3-2. Critical Areas
Figure 3-3. Critical Areas
Table 3-1. Summary of Wetlands in the Project Area
Wetland
Area (acre)
City of Rentona
Buffer Widthb (feet)
Ecology Ratingc
USFWS Classificationd
HGM Classificatione
1/2 Complex
>50 f
II
100
II
PFO
Riverine/
Depressional
3
0.18
IV
50
IV
PEM/PFO
Depressional
4
0.04
IV
50
IV
PFO
Depressional
5
0.30
III
75
III
PEM
Depressional
6
0.83
III
75
III
PEM
Depressional
7
0.88
III
75
III
PEM/PFO
Slope
BR
~1.9 f
II
100
II
PFO
Riverine/
Depressional
a Renton SMP (4-3-090 D.2.d.ii)
b Renton SMP (4-3-090 D.2.d.iv.(c))
c Hruby (2004)
d Cowardin et al. (1979)
e Brinson (1993)
f Wetland size estimated based on aerial interpretation
PFO = palustrine forested, PEM = palustrine emergent
Table 3-2. Summary of Wetland Functions for Wetlands in the Project Area
Wetland
Flood Flow Alteration
Sediment Removal
Nutrient and Toxicant Removal
Erosion Control and Shoreline Stabilization
Production of Organic Matter and its Export
General Habitat Suitability
Habitat for Aquatic Invertebrates
1/2 Complex
High
Moderate
Moderate
Moderate
High
Moderate
High
3
Low
Low
Low
NA
Moderate
Low
Low
4
Low
Low
Low
NA
NA
Low
Low
5
Moderate
High
High
NA
Low
Low
Low
6
Low
Low
Low
NA
Low
Low
Low
7
Low
NA
NA
NA
Low
Low
Low
BR
High
Moderate
Moderate
Moderate
High
Moderate
High
Table 3-2. Summary of Wetland Functions for Wetlands in the Project Area (continued)
Wetland
Habitat for Amphibians
Habitat for Wetland-Associated Mammals
Habitat for Wetland-Associated Birds
General Fish Habitat
Native Plant Richness
Education or Scientific Value
Uniqueness and Heritage
1/2 Complex
Moderate
Moderate
Moderate
Moderate
Low
NA
NA
3
Low
NA
NA
NA
NA
NA
NA
4
Low
NA
NA
NA
NA
NA
NA
5
Low
NA
Low
NA
NA
NA
NA
6
Low
NA
NA
NA
NA
NA
NA
7
NA
NA
NA
NA
NA
NA
NA
BR
Moderate
Moderate
Moderate
Moderate
Low
NA
NA
Note: Functions assessed using WSDOT method (Null et al. 2000); see Appendix C for indicator characteristics present in each wetland.
Wetland 1/2 Complex
Size: >50 acre (>2,178,000 square feet)
City of Renton Rating: Category II
Ecology Rating: Category II
Buffer: 100 feet
USFWS Classification: Palustrine Forested
HGM Classification: Riverine/Depressional
Sample Plots: W1-SP1, W1-SP2, W2-SP1, and W2-SP2
The Wetland 1/2 Complex is located west and east of the north end of Naches Avenue SW and north of the Black River, extending outside the study area to the south and east (Figure 3-3).
Wetland 1/2 Complex was initially delineated as two separate wetlands in the field, but after further review of hydrologic conditions and connections, it was determined to be one wetland
complex.
Wetland hydrology is supported by overbank flow from the Black River, stormwater runoff from nearby surfaces, and a shallow groundwater table. A large openwater area (Black River) located
upgradient of the Black River Pump Station is associated with the Wetland 1/2 Complex. Much of the interior of the Wetland 1/2 Complex is seasonally inundated, while some outer portions
are saturated. Inundation was observed throughout most of the wetland with depths of up to 12 inches of water. The wetland drains to the Black River, which meets the Green River near
the western portion of the study area.
The Wetland 1/2 Complex is composed of a forested community. Vegetation is dominated by black cottonwood, salmonberry, Himalayan blackberry, red alder, Pacific willow, and common ladyfern
(Athyrium filix-femina).
Soil west and south of the proposed trail (W1-SP1) was examined to a depth of 20 inches, consisting of two layers. The top layer is an 18-inch dark gray (2.5Y 4/1) clay loam and the
lower layer is a gray (2.5Y 6/1) clay loam. East of the proposed trail (W2-SP1), the top layer is a 9-inch very dark grayish brown (10YR 3/2) silt loam with yellowish brown (10YR 5/6)
redoximorphic features. The lower layer is a gray (10YR 6/1) silty clay loam. Soils in the wetland are mapped by the NRCS as Woodinville silt loam.
The buffer surrounding the Wetland 1/2 Complex consists of generally disturbed areas of upland grasses and forbs near the existing gravel maintenance road to the east and north, and
forested areas closer to the wetland. Vegetation in the generally forested buffer includes red alder, bigleaf maple, western swordfern, salmonberry, black cottonwood, red elderberry,
and Himalayan blackberry. A portion of the buffer located north of Wetland 1 and adjacent to an existing gravel maintenance road has been planted with native vegetation and includes
western redcedar, salmonberry, grand fir (Abies grandis), and bigleaf maple. Other portions of the buffer north of the Wetland 1/2 Complex have historically been filled with asphalt,
concrete rubble, and other debris.
The Wetland 1/2 Complex is a palustrine forested wetland under the Cowardin (1979) system, and is a riverine/depressional wetland under the HGM system (Brinson 1993). According to the
City of Renton (SMP 4-3-090 D.2.d.ii) and Ecology, the Wetland 1/2 Complex is rated a Category II. The wetland scored 56 points on Ecology’s rating form (22 points for water quality,
16 points for hydrologic functions, and 18 points for habitat functions) (Appendix B). The City of Renton requires a 100-foot buffer for Category II wetlands with a habitat score of
less than 20 points (SMP 4-3-090 D.2.d.iv).
Wetland 3
Size: 0.18 acre (7,625 square feet)
City of Renton Rating: Category IV
Ecology Rating: Category IV
Buffer: 50 feet
USFWS Classification: Palustrine Scrub-shrub /Palustrine Emergent
HGM Classification: Depressional
Sample Plots: W3-SP1 and W3-SP2
Wetland 3 is located north of Wetland 1 and south of the existing gravel maintenance road and BNSF rail tracks (Figure 3-3). A portion of Wetland 3 is adjacent to the maintenance road.
Wetland hydrology is supported by surface water coming from a culvert located north of the wetland under the BNSF rail tracks. The source appears to be surface runoff from the concrete
recycling plant to the north. Soils were saturated, and some pockets of inundation were observed in channels and micro-depressions. The wetland is seasonally saturated. Water flows
from Wetland 3 into a small drainage channel that drains to Wetland 1.
Wetland 3 consists of a shrub community and an emergent community. The emergent community is dominated by reed canarygrass and the shrub community is dominated by young Oregon ash with
some Himalayan blackberry.
The sample plot was examined to a depth of 18 inches and consisted of four layers that appear to have been historically disturbed. Soils examined in Wetland 3 are composed of a 2-inch
layer of duff above a 6-inch layer of dark gray (5Y 4/1) clay loam. Beneath those layers is a 6-inch layer of dark gray (5Y 4/1) gravelly clay loam with strong brown (7.5YR 5/6) redoximorphic
features over a 4-inch layer of dark gray (5Y 4/1) sandy clay loam with strong brown (7.5YR 5/6) redoximorphic features. Some areas of the wetland contain debris in the soil. Soils
in the wetland are mapped by the NRCS as Woodinville silt loam.
The buffer of Wetland 3 consists primarily of upland grasses and forbs on fill. The buffer is dominated by Himalayan blackberry and black cottonwood. The soils have been historically
disturbed and contain asphalt, concrete, and other construction debris.
Wetland 3 is a palustrine scrub-shrub/palustrine emergent wetland under the Cowardin (1979) system, and is a depressional wetland under the HGM system (Brinson 1993). According to the
City of Renton (SMP 4-3-090 D.2.d.ii) and Ecology, Wetland 3 is rated a Category IV. The wetland scored 29 points on Ecology’s rating form (14 points for water quality, 5 points for
hydrologic functions, and 10 points for habitat functions) (Appendix B). The City of Renton requires a 50-foot buffer for Category IV wetlands with a habitat score of less than 20 points
(SMP 4-3-090 D.2.d.iv).
Wetland 4
Size: 0.04 acre (1,700 square feet)
City of Renton Rating: Category IV
Ecology Rating: Category IV
Buffer: 50 feet
USFWS Classification: Palustrine Forested
HGM Classification: Depressional
Sample Plots: W4-SP1 and W4-SP2
Wetland 4 is located just southwest of Wetland 3 and north of the Wetland 1/2 Complex (Figure 3-3). Wetland 4 likely was originally excavated.
Wetland hydrology is supported primarily by runoff from the fill surrounding Wetland 4 and possibly from a subsurface connection to Wetland 3. Wetland 4 is seasonally saturated. Soils
were saturated in the wetland and some pockets of inundation were observed in small depressions. Wetland 4 does not have an outlet.
Wetland 4 consists of a forest community dominated by Oregon ash and black cottonwood. The understory is thinly populated with reed canarygrass.
The sample plot was examined to a depth of 18 inches and consisted of two layers. Soils examined in Wetland 4 are composed of a 10-inch layer of dark gray (5Y 4/1) clay loam with strong
brown (7.5YR 4/6) redoximorphic features. Beneath this layer is an 8-inch layer of dark gray (5Y 4/1) silty clay loam with strong brown (7.5YR 4/6) redoximorphic features. Soils in
the wetland are mapped by the NRCS as Woodinville silt loam.
The buffer of Wetland 4 consists of an upland forest community dominated by black cottonwood and Himalayan blackberry. The soils have been disturbed and contain asphalt, concrete, and
other construction debris.
Wetland 4 is a palustrine forested wetland under the Cowardin (1979) system, and is a depressional wetland under the HGM system (Brinson 1993). According to the City of Renton (SMP 4-3-090
D.2.d.ii) and Ecology, Wetland 4 is rated a Category IV. The wetland scored 25 points on Ecology’s rating form (10 points for water quality, 9 points for hydrologic functions, and 6
points for habitat functions) (Appendix B). The City of Renton requires a 50-foot buffer for Category IV wetlands with a habitat score of less than 20 points (SMP 4-3-090 D.2.d.iv).
Wetland 5
Size: 0.30 acre (13,192 square feet)
City of Renton Rating: Category III
Ecology Rating: Category III
Buffer: 75 feet
USFWS Classification: Palustrine Emergent
HGM Classification: Depressional
Sample Plots: W5-SP1 and W5-SP2
Wetland 5 is located north of the existing gravel maintenance road, east of Monster Road, and south of the BNSF rail tracks (Figure 3-1). The wetland is possibly a created feature because
the slopes are lined with quarry spalls and there are culverts at the inlet and the outlet, as well as a catch basin located just south of the wetland.
Wetland hydrology is supported by surface water coming from a culvert located north of the wetland under the BNSF rail tracks outside of the study area. The source is likely overflow
from detention ponds located on the concrete recycling plant to the north. Wetland 5 is occasionally inundated. The wetland was inundated to a depth of approximately 18 inches during
one site investigation, while soils were saturated with no inundation during another site visit. Water flows from Wetland 5 into a culvert that drains to the buffer of the Black River
to the south.
Wetland 5 consists of an emergent community, although shrubs are located along the eastern boundary. The emergent community is dominated by narrow-leaf cattail. The dominant shrub along
the boundary is red-osier dogwood.
The sample plot was examined to a depth of 18 inches and consisted of a single layer. Soils examined in Wetland 5 are composed of a dark gray (2.5Y 4/1) sandy loam with strong brown
(7.5YR 5/8) redoximorphic features. Soils in the wetland are mapped by the NRCS as Woodinville silt loam.
The buffer of Wetland 5 consists primarily of upland shrubs and young trees on fill. The buffer is dominated by Himalayan blackberry and red alder. The soils have been disturbed and
contain quarry spalls and other rocks and debris.
Wetland 5 is a palustrine emergent wetland under the Cowardin (1979) system, and is a depressional wetland under the HGM system (Brinson 1993). According to the City of Renton (SMP 4-3-090
D.2.d.ii) and Ecology, Wetland 5 is rated a Category III. The wetland scored 49 points on Ecology’s rating form (22 points for water quality, 16 points for hydrologic functions, and
11 points for habitat functions) (Appendix B). The City of Renton requires a 75-foot buffer for Category III wetlands with a habitat score of less than 20 points (SMP 4-3-090 D.2.d.iv).
Wetland 6
Size: 0.83 acre (36,210 square feet)
City of Renton Rating: Category III
Ecology Rating: Category III
Buffer: 75 feet
USFWS Classification: Palustrine Emergent
HGM Classification: Depressional
Sample Plots: W6-SP1 and W6-SP2
Wetland 6 is located in the fork of the existing gravel maintenance roads west of the Black River Pump Station (Figure 3-1). A portion of Wetland 6 is adjacent to the maintenance road.
Wetland hydrology is supported by surface water runoff from the surrounding compacted soils. Soils were saturated in portions of the wetland and inundated in two small depressions. Wetland
6 does not have an inlet or outlet and is seasonally saturated.
Wetland 6 consists of an emergent community dominated by reed canarygrass. A small stand of black cottonwood is located on the western edge.
The sample plot was examined to a depth of 18 inches and consisted of two layers that appear to have been historically disturbed. Soils examined in Wetland 6 are composed of a 4-inch
layer of very dark gray (2.5Y 3/1) clay loam with dark olive brown (2.5Y 3/3) redoximorphic features. Beneath this layer is a 14-inch layer of dark gray (2.5Y 4/1) fine sandy loam with
dark yellowish brown (10YR 4/6) redoximorphic features. Soils in the wetland are mapped by the NRCS as Woodinville silt loam.
The buffer of Wetland 6 consists primarily of upland grasses and forbs on fill. The buffer is dominated by bentgrasses (Agrostis spp.), tall fescue, Himalayan blackberry, and black cottonwood.
The buffers are dissected on three sides of the wetland by the gravel maintenance roads.
Wetland 6 is a palustrine emergent wetland under the Cowardin (1979) system, and is a depressional wetland under the HGM system (Brinson 1993). According to the City of Renton (SMP 4-3-090
D.2.d.ii) and Ecology, Wetland 6 is rated a Category III. The wetland scored 41 points on Ecology’s rating form (16 points for water quality, 17 points for hydrologic functions, and
8 points for habitat functions) (Appendix B). The City of Renton requires a 75-foot buffer for Category III wetlands with a habitat score of less than 20 points (SMP 4-3-090 D.2.d.iv).
Wetland 7
Size: 0.88 acre (38,508 square feet)
City of Renton Rating: Category III
Ecology Rating: Category III
Buffer: 75 feet
USFWS Classification: Palustrine Emergent/Palustrine Forested
HGM Classification: Depressional
Sample Plots: W7-SP1 through W7-SP6
Wetland 7 is located south of the existing gravel trail, northeast of the Black River Pump Station, and north of the Black River (Figure 3-2). Wetland 7 is located topographically above
the existing trail.
Wetland hydrology is supported by precipitation and surface water runoff from the surrounding compacted soils. Soils were saturated in portions of the wetland and inundated in small
depressions and shallow, narrow drainages throughout the wetland. Wetland 7 likely drains to the south and east below the soil surface and is seasonally saturated.
Wetland 7 contains emergent and forested communities. The emergent portion is dominated by reed canarygrass and the forested portion is dominated by a stand of red alders on the eastern
side of the wetland.
The sample plot located within the emergent community was examined to a depth of 18 inches and consisted of two layers. Soils examined in Wetland 7 are composed of an 8-inch layer of
dark gray (2.5Y 4/1) silt loam with dark yellowish brown (10YR 3/6) redoximorphic features. Beneath this layer is a 10-inch layer of dark greenish gray (10Y 4/1) silt loam with dark
yellowish brown (10YR 4/6) redoximorphic features. Soils in the wetland are mapped by the NRCS as Woodinville silt loam.
The buffer of Wetland 7 consists primarily of upland grasses and forbs to the north and west, shrubs to the south, and a narrow forested stretch to the east. The buffer is dominated
by reed canarygrass, black cottonwood, and Himalayan blackberry.
Wetland 7 is a palustrine emergent/palustrine forested wetland under the Cowardin (1979) system, and is a depressional wetland under the HGM system (Brinson 1993). According to the City
of Renton (SMP 4-3-090 D.2.d.ii) and Ecology, Wetland 7 is rated a Category III. The wetland scored 37 points on Ecology’s rating form (16 points for water quality, 4 points for hydrologic
functions, and 17 points for habitat functions) (Appendix B). The City of Renton requires a 75-foot buffer for Category III wetlands with a habitat score of less than 20 points (SMP
4-3-090 D.2.d.iv).
Wetland BR
Size: >1.5 acres (>65,340 square feet)
City of Renton Rating: Category II
Ecology Rating: Category II
Buffer: 100 feet
USFWS Classification: Palustrine Forested/Palustrine Emergent
HGM Classification: Riverine/Depressional
Sample Plots: WBR-SP1 and WBR-SP2
Wetland BR is southeast of the existing gravel trail, east-northeast of the Black River Pump Station, and north of the Black River (Figure 3-2). Wetland BR is hydrologically associated
with the Black River and is part of the greater Black River Riparian Forest.
Wetland hydrology is supported by overbank flow from the Black River, stormwater runoff from nearby surfaces, and a shallow groundwater table. A large openwater area (Black River) located
upgradient of the Black River Pump Station is associated with Wetland BR. Much of the interior of Wetland BR is seasonally inundated, while some outer portions are saturated. Shallow
inundation was observed throughout most of the wetland with depths of up to 2 inches of water. The wetland drains to the Black River, which meets the Green River near the western portion
of the study area.
Wetland BR is composed of forested and emergent communities. Vegetation is dominated by red alder, Pacific willow, reed canarygrass, yellow flag iris (Iris pseudacorus), and common ladyfern
in the forested community. The emergent community is dominated by common cattail.
Soil in Wetland BR was examined to a depth of 18 inches and consisted of three layers. The top layer is a 5-inch very dark gray (2.5Y 3/1) silt loam with organics. The middle layer is
a dark greenish gray (10Y 4/1) clay loam with strong brown (7.5YR 4/6) redoximorphic features. The lower layer is also a dark greenish gray (10Y 4/1) soil with strong brown (7.5YR 4/6)
redoximorphic features, but has a texture of loamy sand. Soils in the wetland are mapped by the NRCS as Woodinville silt loam.
The buffer surrounding Wetland BR consists of a slope primarily dominated by Himalayan blackberry and reed canarygrass. Some planted trees are located on the slope as well. They include
western redcedar, Douglas fir (Pseudotsuga menziesii), and Sitka spruce (Picea sitchensis). Much of the buffer has been historically disturbed.
Wetland BR is a palustrine forested wetland under the Cowardin (1979) system, and is a riverine/depressional wetland under the HGM system (Brinson 1993). According to the City of Renton
(SMP 4-3-090 D.2.d.ii) and Ecology, Wetland BR is rated a Category II. The wetland scored 54 points on Ecology’s rating form (24 points for water quality, 12 points for hydrologic functions,
and 18 points for habitat functions) (Appendix B). The City of Renton requires a 100-foot buffer for Category II wetlands with a habitat score of less than 20 points (SMP 4-3-090 D.2.d.iv).
Streams
Additional information is provided in the Stream Discipline Report (Parametrix 2015c).
Green and Black River Basins
The Black River Basin makes up part of the Green River Watershed, which also includes Springbrook Creek, Mill Creek, Soos Creek, Jenkins Creek, Covington Creek, Newaukum Creek, Crisp
Creek, and other tributaries. The Green River Watershed contains a population of about 400,000 people and is approximately 492 square miles (King County 2012). Land use varies considerably
throughout the watershed. In the Upper Green River sub-watershed it is used primarily for forest productions. The Middle Green sub-watershed is a mix of residential, commercial forestry,
and agricultural land uses. The Lower Green River sub-watershed, in which the project area is located, is a mix of residential, industrial, and commercial land uses. The Green-Duwamish
Estuary sub-watershed is a mix of residential and industrial uses (King County 2012).
The project site is located within WRIA 9, the Green-Duwamish River basin. The Duwamish River is defined as the portion of the Green/Duwamish River system downstream from the confluence
of the Black River (River Mile [RM] 11.0) to Elliott Bay (RM 0.0), while the Green River extends upstream from the Black River. For this report, the term ‘Duwamish River’ pertains to
the first 11 miles of the river system, while the term ‘Green River’ pertains to both the portion of river above RM 11.0 and the river system as a whole. Historically, the Green, White,
Black, and Cedar rivers flowed into the Duwamish River, and the system drained an area of over 1,600 square miles. In the early 1900s, the Black, White, and Cedar rivers were diverted,
reducing the Green River drainage over 60 percent to just 483 square miles (Blomberg 1988). Also, in 1913 the City of Tacoma constructed a diversion dam on the Green River, near the
town of Palmer, at about RM 50.0. In 1963, the Howard Hanson Dam was built at RM 53.0. Both of these structures completely blocked fish migration to the upper Green River and its tributaries.
Flow in the Green River is regulated by the operation of the Howard Hanson Dam. River velocities are dissipated as the river widens and currents converge with tidal pressures. Characterized
by wet and dry seasons, discharge of the river varies seasonally. The wet season extends from November to July, and the dry season from August to October. The mean monthly flow rate
in the lower Duwamish varies from 400 cubic feet per second (cfs) in August to 2,600 cfs in January. Stream banks are sloped and diked to contain flows of up to 11,000 cfs (Williams
et al. 1975). According to the Federal Emergency Management Agency (FEMA), the maximum regulated flow for the 100-year recurrence interval is 12,000 cfs at the project site.
The Lower Green River basin begins at the Auburn Narrows (RM 31) and continues to just downstream of the confluence with the Black River in Tukwila (RM 11). The lower Green River basin
is composed of two areas that are split by the Black River basin to the north and the Mill Creek basin to the south. The lower Gren River basin is mostly on the urban side of the urban
growth boundary and contains portions of the cities of Kent, Auburn, Tukwila, Federal Way, and SeaTac. Land uses include residential, commercial, industrial, and agricultural, as well
as major highways, including Interstate 5. There are extensive areas of office/commercial and multi-family residential development. This area has developed rapidly over the past 20
years.
Green River
Stream Type
The project alignment intersects the Green River at about RM 11.0 on the right bank of the river (see Figure 1-1). According to the DNR stream typing system, the Green River is a Type
S stream, designated as a shoreline of the state. Within the project area, the stream is located within the local jurisdiction of the City of Tukwila, which also classifies the Green
River as a Type S stream. The shoreline jurisdiction extends 200 feet from the river OHWM. According to the Tukwila SMP (Section 7.7), “the buffer will extend 125 feet landward from
the ordinary high watermark, determined at the time of development or redevelopment of the site or when levee replacement or repair is programmed.” The remaining 75 feet landward of
the buffer is also regulated under the Tukwila SMP.
Fish Habitat
Identified limiting habitat factors in the lower Green River Watershed include (1) urbanization, water diversions, and revetments that have resulted in disconnection of the river from
floodplain off-channel habitats such as sloughs and adjacent wetlands, (2) reduction of large woody debris and associated instream complexity, such as pools and riffles, (3) creation
of adult salmon migration problems due to low flows, (4) chronic water quality problems, and (5) severe reductions in riparian habitats and associated functions (WSCC 2000). Currently,
the reach within the study area is used by all native anadromous salmonid species for rearing and migration (see Fish Presence below).
Water Quality Conditions
The Green River has no listed exceedances on the 2012 Ecology 303(d) list within or immediately adjacent to the project limits (Ecology 2015). A 303(d) reach is located over 0.5 mile
upstream from the project area, with recorded exceedances for stream temperature, dissolved oxygen, and fecal coliform.
Biological Conditions
Fish Presence
The Duwamish and lower Green River serves as a migration and rearing area for anadromous salmonids, with no spawning habitat available (Williams et al. 1975). Three Pacific salmon species
inhabit the Green/Duwamish River basin in significant numbers: Chinook, coho, and chum salmon. Pink and sockeye salmon are occasionally seen in the Green River basin, but the Green
River is primarily a chum, coho, and Chinook salmon stream (Williams et al. 1975). Although sockeye salmon are occasionally seen in streams that are not tributaries to lakes, sockeye
almost always require a rearing lake below or near their spawning area (Foerster 1972). Other anadromous fish using these waters include steelhead, sea-run cutthroat trout, Dolly Varden,
and bull trout.
Studies of juvenile salmonids in the Duwamish and lower Green River (Williams et al. 1975; Warner and Fritz 1995) have demonstrated the species presence, their timing within the project
vicinity, and various characteristics of the fish. These investigations show that subyearling Chinook and chum salmon use shallow-water shoreline habitats of various characteristics
during their migration to the ocean. Juvenile pink salmon are likely to be found in the same areas during their spring migration period. The young salmon appear to prefer relatively
protected shorelines with gradual slopes and depths of less than about 6 feet. However, they are also found along hard, steep to vertical substrates that are either natural or artificial.
The young salmon tend to remain close to the shoreline but apparently cross deep water at night (Stober et al. 1973; Bax et al. 1979).
Yearling Chinook, steelhead, and coho also use shoreline areas but appear to be less shoreline-oriented than the subyearling migrants. The substantially larger yearlings are commonly
found in the near-surface water well away from the shoreline. Subadult and adult bull trout and Dolly Varden are likely to forage within the project vicinity during their late spring
to summer migrations into Puget Sound.
Juvenile salmon migrating past the project site include Chinook produced from the Soos Creek Hatchery, located about 39 miles upstream from the site. The juvenile migration period potentially
extends from late February through mid-June. During this period, wild fish commonly occur farther upstream and are more numerous in tributaries compared to hatchery fish.
Stream Buffer Conditions
Overstory riparian vegetation on the right bank of the river is generally limited to a relatively narrow (20 to 50 feet wide) zone with a sparse overstory of deciduous and coniferous
trees. Trees include scattered Douglas fir, black cottonwood, western redcedar, and non-native alder (Alnus spp.) and spruce (Picea spp.) species. Understory vegetation consists primarily
of shrubs, with sumac (Rhus spp.), poison hemlock (Conium maculatum), red-osier dogwood, bitter cherry (Prunus emarginata), and substantial amounts of Himalayan blackberry. Invasive
vegetation dominates the outer portion of the riparian zone, including a large amount of Himalayan blackberry and various grass species. A single line of ornamental trees is present
on the south edge of the riparian zone, directly adjacent to Fort Dent Park. In addition, portions of the riparian zone consist of patches of bare ground. The vegetation is not adequate
to provide the full range of riparian functions, although low to moderate levels of stream shading, large woody debris (LWD) recruitment, leaf litter production, and bank stability
are provided by the existing riparian zone. Much of the shrub vegetation overhangs the river, offering some overhead cover for fish.
Black River
Stream Type
According to the DNR stream typing system, the Black River is a Type S stream, designated as a shoreline of the state. Within the project area, the stream is located within the local
jurisdictions of the Cities of Tukwila and Renton (see Figure 1-1), although the majority of the Black River is within Renton. Within Renton, the Black River is classified as a Class
1 water (shoreline of the state) (Renton SMP 4-3-090 F.1). The regulated buffer within shoreline jurisdiction (the Standard Vegetation Conservation Buffer width) includes lands within
100 feet, as measured on a horizontal plane, from the OHWM.
Within Tukwila, the stream is classified as a Type S (shoreline of the state) stream. The regulated buffer extends 200 feet from the river OHWM. According to the Tukwila SMP (Section
7.7), “the buffer will extend 125 feet landward from the ordinary high watermark, determined at the time of development or redevelopment of the site or when levee replacement or repair
is programmed.” The remaining 75 feet landward of the buffer is also regulated under the Tukwila SMP.
Fish Habitat
The Black River enters the Green River near Tukwila, on the right bank, at RM 11.0. On the Black River, a dam and pump station, which is approximately 600 feet upstream of Monster Road,
prevent tidal upstream inundation of the river channel and maintain downstream flow, regardless of tidal influences. A Denil fishway allows upstream fish passage at the pump station,
and an air lift pump arrangement aids downstream migrants in passing the structure during the spring months (Harza 1995).
The project site is located in a developed setting, zoned industrial, with large amounts of impervious surface within the project vicinity. A large gravel pit (Stoneway Concrete) is
located north of the Monster Road Bridge; warehouses and an industrial operation are located to the north and south of the trail alignment; and railroad tracks run both parallel and
perpendicular to the trail alignment.
Instream habitat within the project area is dominated by run-type channel morphology, with maximum stream depths of greater than 6 feet. At the time of the site visit (February 2011),
the wetted width was approximately 25 feet, and no pools or riffles were observed. Bank-full width was estimated at 30 feet. Streambed material consisted almost exclusively of sands
and silts. The streambanks are relatively steep (approximately a 50-degree angle) and bank condition appears to be relatively stable. Underneath the Monster Road Bridge, both streambanks
are 100 percent armored with riprap, from the edge of the water to the bridge deck.
No LWD was observed in the study area, and the presence of the pump station above the project site precludes LWD recruitment from upstream. Overall, the quality of fish habitat is poor,
with little habitat diversity. Within the study area, the Black River would probably be used for migration or possibly rearing, although instream cover is somewhat limited.
Water Quality Conditions
The Black River from RM 0.25 to 1.44 is on the 2012 Ecology 303(d) list for exceeding the fecal coliform criteria (Ecology 2015). This exceedance includes the reach of the Black River
between Monster Road Bridge and the Black River Pump Station.
Biological Conditions
Fish Presence
WDFW (2014, 2015) data indicate that Chinook salmon, chum salmon, coho salmon, steelhead trout, and cutthroat trout have been documented in the Black River within the study area. The
type of use is listed as migration for all species except coho, which use the lower Black River for juvenile rearing. Conditions favorable for Chinook salmon spawning and rearing do
not exist in the project area. Recent information, as well as historical records (Harza 1995; Williams et al. 1975), indicate that Chinook do not use this area for spawning and rearing.
However, very small numbers of adult fall Chinook migrating up the Green River occasionally stray into the Black River and become trapped above the Black River Pump Station (the pump
station cannot pass adult salmon downstream). In the fall of 1997, adult Chinook were observed entering the Black River and attempting to spawn near the SW 27th Street culvert in Springbrook
Creek, 2.3 miles upstream of the project area (WSCC 2000).
Bull trout are not known to occur in the Black River and there are no documented occurrences of spawning (WDFW 1998). Water temperatures in the Black River basin are too high to support
reproduction by this species (Harza 1995; Rieman and Chandler 1999).
Stream Buffer Conditions
The stream buffers in the Black River within the project area are relatively degraded, of limited widths, and composed of herbaceous, shrub, and non-native species. Downstream of Monster
Road Bridge, the stream buffer widths vary between 50 and 100 feet on the north side of the river to about 75 to 150 feet on the south side. Upstream of the bridge, vegetated buffer
widths average from 100 to 150 feet on both sides of the Black River. The vegetated buffer consists of lightly forested and herbaceous plant communities, although the forested zone
is restricted to within 50 feet of the river. Vegetation includes
red alder, tall fescue, salmonberry, reed canarygrass, Himalayan blackberry, black cottonwood, western redcedar, western swordfern, bigleaf maple, red elderberry, and snowberry.
Under existing conditions, the riparian corridor is not fully functioning, but it does provide some functions that support aquatic species, including some level of small woody debris
or LWD recruitment, overhead stream cover, bank stability, leaf litter recruitment, and water quality maintenance.
Fish and Wildlife Habitat Conservation Areas
The Black River Riparian Forest is designated as a Natural Area by the City of Renton and is therefore considered a Class 1 Fish Habitat Conservation Area. Regulations for Class 1 Streams
and Lakes that would serve as FWHCAs are provided in the Renton SMP development and use standards, including but not limited to SMP 4-3-090 D.2.c.iii.
The Black River Riparian Forest is primarily forested riparian and wetland habitat, which supports a diverse wildlife community, including bald eagles (Haliaeetus leucocephalus) and
a colony of great blue herons (Ardea herodias) that has actively nested here every year since 1986 and has been one of the largest such colonies in the Puget Sound region (Stenberg
2007). Data from the WDFW Priority Habitats and Species program indicate that the Black River Riparian Forest is also used by many waterfowl species, including bufflehead (Bucephala
albeola), mallard (Anas platyrhynchos), gadwall (Anas strepera), wigeon (Anas americana), scaup (Aythya affinis), and green-winged teal (Anas crecca) (WDFW 2011a). Other bird species
commonly found in riparian and wetland habitats in the Puget Lowlands include osprey (Pandion haliaetus), red-tailed hawk (Buteo jamaicensis), and a variety of songbirds. Mammals present
may include coyotes (Canis latrans), raccoons (Procyon lotor), beavers (Castor canadensis), mice (Mus musculus), voles (Microtus pennsylvanicus), and moles (Scalopus aquaticus). Reptiles
and amphibians that use these habitats include garter snakes (Thamnophis sirtalis), Pacific chorus frogs (Pseudacris regilla), and long-toed salamanders (Ambystoma macrodactylum).
Areas of Special Flood Hazard
Portions of the Segment A trail alignment are located within the Green and Black River floodplains (Figure 3-4). The threshold discharge areas (TDAs) identified for the site are depicted
in Figure 3-4 and described in the Technical Information Report (Parametrix 2015b). The length of trail within Areas of Special Flood Hazard, as well as the cut and fill quantities,
are provided in Section 4-4.
Figure 3-4. Drainage Basins, Subbasins, and Site Characteristics
IMPACTS
This chapter describes the extent and type of permanent and temporary impacts on critical areas and associated buffers that would occur as a result of the proposed project (Figures 4-1
through 4-9).
Wetlands
No wetlands would be permanently or temporarily affected as a result of this project. However, some impacts on wetland buffers are unavoidable (Table 4-1; Figures 4-1 through 4-9). Some
overlap between stream buffers and wetland buffers occurs in the project area. Where this overlap occurs, impacts on these areas were calculated as wetland buffers.
Table 4-1. Wetland and Buffer Impacts
Wetland
City of Renton
Ratinga
Wetland
Buffer
Perm. Impacts acres
(square feet)
Temp. Impacts
acres
(square feet)
Perm. Impacts acres
(square feet)
Temp. Impacts
acres
(square feet)
1/2 Complex
II
0.00 (0)
0.00 (0)
0.27 (11,941)
0.07 (2,848)
3
IV
0.00 (0)
0.00 (0)
0.06 (2,695)
0.01 (600)
4
IV
0.00 (0)
0.00 (0)
0.00 (0)
0.00 (0)
5
III
0.00 (0)
0.00 (0)
0.14 (6,154)
0.02 (980)
6
III
0.00 (0)
0.00 (0)
0.01 (531)
0.02 (874)
7
III
0.00 (0)
0.00 (0)
0.00 (0)
0.00 (0)
BR
II
0.00 (0)
0.00 (0)
0.00 (0)
0.00 (0)
Totalb
0.00 (0)
0.00 (0)
0.49 (21,321)
0.12 (5,302)
a Renton SMP (4-3-090.D.2.d.ii)
b Total acreage of impact was determined by converting the square footage of the total impact into acres and then rounding to the nearest 0.01 acre. Total quantities include buffer
impact areas that occur where wetland and stream buffers overlap.
Perm. = Permanent, Temp. = Temporary
Permanent Wetland Impacts
No wetlands would be permanently affected as a result of this project.
Permanent Wetland Buffer Impacts
Permanent impacts on the buffers of four wetlands would result from minor grading to construct a modular block retaining wall and widen the trail (see Figures 4-1 through 4-9).
A total of approximately 0.49 acre (21,321 square feet) of impacts on project area wetland buffers are anticipated as a result of this project. This total includes those buffers that
overlap with stream buffers. These buffers are generally low functioning and are composed primarily of grasses and forbs along the existing maintenance road edge. These impacts would
affect the buffers of the Wetland 1/2 Complex, Wetland 3, Wetland 5, and Wetland 6 (Table 4-1).
Temporary Wetland Impacts
No wetlands would be temporarily affected as a result of this project.
Temporary Wetland Buffer Impacts
Temporary impacts on wetland buffers would occur from construction-related activities including, but not limited to, clearing vegetation. A total of approximately 0.12 acre (5,302 square
feet) of temporary impacts on wetland buffers are anticipated as a result of the construction of the Segment A portion of the Lake to Sound Trail. This total includes those buffers
that overlap with stream buffers. These impacts would affect the buffers of the Wetland 1/2 Complex, Wetland 3, Wetland 5, and Wetland 6 (Table 4-1).
Streams
This section describes the extent and type of temporary and permanent effects on streams and aquatic resources that could occur as a result of the proposed project. The project would
result in 0.60 acre (25,926 square feet) of permanent impacts and 0.10 acre (4,455 square feet) of temporary impacts on stream buffers of streams in the study area (Table 4-2; Figures
4-1 through 4-5). Impacts that would occur where stream and wetland buffers overlap were calculated as wetland buffer impacts.
Table 4-2. Stream and Buffer Impacts
Stream
City of Tukwila (T) a/Renton (R)b
Typing
Stream
Buffer
Perm. Impacts acres
(square feet)
Temp. Impacts
acres
(square feet)
Perm. Impacts acres
(square feet)
Temp. Impacts
acres
(square feet)
Green River
S (T)
0.00 (0)
0.00 (0)
0.06 (2,418)
0.01 (559)
Black River
S (T)/1 (R)
0.00 (0)
0.00 (0)
0.54 (23,508)
0.09 (3,896)
Total c
0.00 (0)
0.00 (0)
0.60 (25,926)
0.10 (4,455)
a Stream typing according to Tukwila SMP (Section 7.7)
b Stream typing according to Renton SMP (4-3-090 F.1)
c Total acreage of impact was determined by converting the square footage of the total impact into acres and then rounding to the nearest 0.01 acre. Total quantities do not include
areas that occur where wetland and stream buffers overlap; these areas were calculated as wetland impacts (see Table 4-1).
Perm. = Permanent, Temp. = Temporary
Permanent Stream Impacts
The project does not include construction activities below the OHWM of any stream; therefore, the project would not result in any stream fill, nor would alterations to fish passage structures
be required.
The new pedestrian bridge over the Black River would be 109 feet long and 12 feet wide. The portion of the bridge spanning the OHWM of the river would be approximately 44 feet long,
meaning approximately 528 square feet of the river would be affected by shading from the bridge. Shade from overwater structures such as bridges can be a migration barrier for fish.
Juvenile salmonids avoid dark, shaded areas under structures, resulting in loss of access to habitat, blockage of movement, and potentially increased exposure to predators. In addition,
shade from overwater structures can provide hiding cover for some non-native species, such as smallmouth bass, that prey on native fish.
Figure 4-1. Critical Areas Impacts
Figure 4-2. Critical Areas Impacts
Figure 4-3. Critical Areas Impacts
Figure 4-4. Critical Areas Impacts
Figure 4-5. Critical Areas Impacts
Figure 4-6. Critical Areas Impacts
Figure 4-7. Critical Areas Impacts
Figure 4-8. Critical Areas Impacts
Figure 4-9. Critical Areas Impacts
The Black River is not considered to be an important migratory corridor for salmonids because the Black River pump station immediately upstream of the study area presents a substantial
barrier to upstream and downstream migration. In addition, reaches of the Black River and Springbrook Creek upstream of the project action area are unlikely to provide suitable spawning
or rearing habitat for Chinook salmon or high-quality spawning or rearing habitat for steelhead. Moreover, the narrow footprint and north-south orientation of the bridge (minimizing
the amount of time that any given point receives shade over the course of a day) would further diminish the potential for the structure to cast shade that presents a migration barrier
for any juvenile salmonids that may pass through the project action area.
All bridge components spanning the Black River would be designed and installed in accordance with the provisions of the HPA and other permits issued for the project. Per WAC 220-660-030,
the HPA would include provisions designed to ensure no net loss of habitat functions necessary to sustain fish life. Compliance with the provisions of the HPA and other permits would
be expected to avoid or minimize the potential for adverse effects resulting from bridge construction. Any unavoidable impacts would be addressed through compensatory mitigation.
Permanent Stream Buffer Impacts
Permanent impacts on stream buffers would occur where the proposed trail alignment encroaches into currently vegetated areas within the regulatory buffers on the Green River and the
Black River. As previously discussed, there is some overlap between stream buffers and wetland buffers. The total amount of riparian buffer that would be subjected to permanent impacts
would be 0.73 acre (31,641 square feet) (see Figures 4-2 through 4-5). Of this area, 0.13 acre (5,715 square feet) also falls within wetland buffers and are identified as wetland buffer
impacts for regulatory purposes. For this analysis, therefore, the project would result in 0.60 acre (25,926 square feet) of permanent impacts to riparian buffers (Table 4 2).
Permanent riparian buffer impacts would occur along the Black River and the Green River. In almost all cases, the quality of the riparian buffer that would be permanently displaced is
low to moderate. Much of the riparian impact area along the Black River consists of grass or non-native herbaceous and shrub species. However, there would be removal of some scattered
larger trees (approximately 10 trees of greater than 4 inches diameter at breast height from the riparian buffer).
The existing buffer functions are still somewhat degraded, compared to fully forested conditions, and these functions are provided at a low or moderate level. The predominant cover type
within the project footprint is urban, consisting primarily of the gravel surface of the existing maintenance road. Where the existing surface is not composed of gravel, a worn dirt
trail exists and is largely free of trees and shrubs. Clearing for trail construction would affect approximately 0.44 acre and is not expected to reduce species diversity or result
in a substantial reduction in plant cover in the study area. Some low-growing plants would be replaced with hard surfaces, however, and the overhead canopy may be slightly reduced in
some places. Based on the nature and location of buffer impacts, no substantial degradation of riparian functions (e.g., fish and wildlife habitat, food chain support, water temperature
maintenance) or process (e.g., water flow; erosion and accretion; infiltration; groundwater recharge and discharge; sediment delivery, transport, and storage; LWD recruitment; organic
matter input; nutrient and pathogen removal; stream channel formation/maintenance) would result from permanent project-related clearing. No substantial effects on stream habitat or
fish resources in any of the project area streams are anticipated.
Temporary Stream Impacts
The project does not include construction activities below the OHWM of any stream; therefore, the project would not temporarily affect any streams.
Temporary Stream Buffer Impacts
Temporary impacts on stream buffers would occur from minor clearing and grading during project construction, as well as from potential erosion, sedimentation, and noise disturbance during
construction. As previously discussed, there is some overlap between stream buffers and wetland buffers. The total amount of riparian buffer that would be subjected to temporary impacts
would be 0.11 acre (5,312 square feet) (see Figures 4-2 through 4-5). Approximately 0.01 acre of this area (857 square feet) also falls within wetland buffers and are identified as
wetland buffer impacts for regulatory purposes. For this analysis, therefore, the project would result in 0.10 acre (4,455 square feet) of temporary impacts to riparian buffers (Table 4 2).
Temporary riparian buffer impacts would occur along a very small portion of the Green River, with the vast majority of impacts occurring within the Black River riparian buffer. Because
the portions of the affected buffer are degraded (as discussed above) and these riparian areas would be replanted once construction is complete, temporary clearing is not expected to
have a substantial effect on stream habitat or fish resources in any of the project area streams.
Construction activities occurring directly adjacent to project area streams could increase turbidity and total suspended solid levels. However, no earthwork or riparian clearing would
occur within 25 feet of the OHWM of the Green River or below the OHWM of the Black River. Along most of the proposed trail corridor, no ground-disturbing work would take place within
40 feet of any streams. Furthermore, any construction-related effects would be avoided through the development and implementation of best management practices (BMPs), including temporary
erosion and sediment control (TESC) and spill prevention control and countermeasures plans.
Fish and Wildlife Habitat Conservation Areas
Additional information is in the Stream Discipline Report (Parametrix 2015c).
The Black River Riparian Forest is designated as a Natural Area by the City of Renton and is therefore considered a Class 1 Fish Habitat Conservation Area. The clearing and grading for
trail construction would permanently convert some existing vegetated cover within the area of the project footprint to a developed condition. Nearly all clearing would occur along the
existing maintenance road, most of which consists of hardened surfaces or low functioning vegetated cover dominated by non-native plants. Some low-growing plants would be replaced with
hard surfaces, and the overhead canopy may be slightly reduced in some places. No impacts on wetlands or streams would occur. See the Vegetation and Wildlife Discipline Report (Parametrix
2015a) for additional information about potential impacts to FWHCAs associated with wildlife species.
Areas of Special Flood Hazard
Approximately 1,050 feet of the Segment A trail alignment near the western end of the proposed trail corridor (from A-Line Station 1+00 to Station 11+50) would be below the elevation
of the 100-year floodplain. Other trail segments in TDA 3 and TDA 5 would be located within the mapped floodplain of the Black River (Figure 3-4) but the elevation of the constructed
trail would be above the floodplain elevation (Parametrix 2015b).
The proposed vertical alignment of the trail would approximate existing grade as close as possible while providing smooth transitions for ADA compliance and positive drainage towards
the river. Between A-Line Stations 1+00 and 12+25, approximately 217 cubic yards of fill would be placed and approximately 242 cubic yards of excavation would occur, for an overall
net removal of approximately 25 cubic yards of material below the floodplain elevation. Detailed calculations and further information are provided in the Lake to Sound Trail – Segment
A Final Technical Information Report (Parametrix 2015b).
MITIGATION
The Lake to Sound Trail – Segment A project would mitigate impacts on wetlands and streams in accordance with the mitigation sequencing requirements established by NEPA, CWA, and local
wetland protection programs (TMC 18.45 and Renton SMP 4.3.090). According to NEPA (40 Code of Federal Regulations [CFR] paragraphs 1508.20), the definition of mitigation is as follows:
Avoiding the impact all together by not taking a certain action or parts of an action.
Minimizing impacts by limiting the degree or magnitude of the action and its implementation.
Rectifying the impact by repairing, rehabilitating, or restoring the affected environment.
Reducing or eliminating the impact over time by preservation and maintenance operations during the life of the action.
Compensating for the impact by replacing or providing substitute resources or environments.
Avoidance and Minimization
Consistent with the above sequencing requirements, a high priority was placed on avoiding and minimizing critical area and buffer impacts. Wetlands and streams in the study area have
been avoided to the greatest extent feasible with no permanent or temporary impacts anticipated. King County would apply the following strategies to critical area and buffer impacts
during the design, permitting, and construction phases:
Use a retaining wall to narrow the trail footprint in the vicinity of wetland boundaries and some riparian buffers.
Limit earthwork near streams and wetlands to the dry season to reduce the potential for sediment runoff.
Construct the trail on an existing gravel maintenance road to minimize impacts on functioning riparian buffers.
Where feasible, widen the trail on the north side of the existing corridor to minimize impacts on buffers and wildlife habitat.
Use appropriate sediment and erosion control BMPs (e.g., mulching, matting, and netting; filter fabric fencing; sediment traps) to reduce the risk of erosion and reduce or minimize the
chance of sediments entering project waterbodies.
Prepare and implement a TESC plan for clearing or removing vegetation, grading, ditching, filling, excavating, and conducting embankment compaction to minimize and control pollution
and erosion from all vegetation or ground-disturbing activities.
Restoration of Temporary Impacts
All temporarily affected areas would be restored to pre-construction conditions and re-planted or seeded with native species.
Compensatory Mitigation
Because permanent impacts on wetland buffers and stream buffers could not be completely avoided, King County would replace the buffer area and functions lost through compensatory mitigation.
Mitigation measures for offsetting these impacts on wetland buffers and stream buffers are described below and included in the Mitigation Plan (Appendix E).
Regulatory Requirements for Compensatory Mitigation
The City of Renton SMP (4-3-090 D.2.d.x.e) states that “Compensation for wetland buffer impacts shall occur at a minimum 1:1 ratio. Compensatory mitigation for buffer impacts shall include
enhancement of degraded buffers by planting native species.” Therefore, impacts on wetland buffers would be replaced at a ratio of 1:1 at a minimum. Stream buffer would be replaced
at a ratio of 1:1 at a minimum, as well. No wetlands were observed in the portion of the study area within the city of Tukwila.
The following provisions of RMC 4-10-095 Shoreline Master Program Nonconforming Uses, Activities, Structures, and Sites apply to the proposed development
F. Partial and Full Compliance, Alteration of an Existing Structure or Site
Major Alteration
Expansion of impervious surface by more than 25%;
Install site improvements that protect the ecological functions and processes of the shoreline, consisting of either:
Full compliance with Vegetation Conservation provisions of RMC 4-3-090F1, Vegetation Conservation, consisting of revegetation of a native community of the full required* buffer, or 100%
of the area between an existing building and the water’s edge if the full buffer cannot be planted, or at least 10 ft., or
An alternate mitigation proposal prepared by a qualified professional and approved by the Administrator of the Department of Community and Economic Development or designee that would
provide at least equal protection of ecological functions and processes as the full required* setback and buffer.
This requirement is met by a revegetation plan for areas between the trail and OHWM where the trail is within the 100 foot Vegetation Conservation Area of the Black River.
This provision will be implemented for wetland buffers in conjunction with RMC 4-03-090.D.2.d.xii. Vegetation Management Plan Required: In order to maintain effective buffer conditions
and functions, a vegetation management plan shall be required for all buffer areas, to include:
(a) Maintaining adequate cover of native vegetation including trees and understory; if existing tree cover is less than a density of twenty (20) trees per acre, planting shall be required
consisting of seedlings at a density of three hundred (300) stems per acre or the equivalent;
(b) Providing a dense screen of native evergreen trees at the perimeter of the buffer if existing vegetation is not sufficient to prevent viewing adjacent development from within the
buffer. Planting shall be required equivalent to two (2) rows of three feet (3') high stock of native
evergreens at a triangular spacing of fifteen feet (15'), or three (3) rows of gallon containers at a triangular spacing of eight feet (8'). Fencing may be required if needed to block
headlights or other sources of light or to provide an immediate effective visual screen;
(c) Providing a plan for control of invasive weeds, and removal of existing invasive species;
(d) Providing for a monitoring and maintenance plan for a period of at least five (5) years, except this provision may be waived for single family residential lots at the discretion
of the Administrator of the Department of Community and Economic Development or designee.
King County developed plans for habitat improvements or restoration to mitigate the effects of the project. This mitigation plan focuses on providing compensatory mitigation measures
for riparian and wetland buffers at equal or greater functions than would be affected by the project. The mitigation sites would be planted at a ratio of at least 1:1 to offset project
impacts. The riparian buffer component of the overall mitigation would consist of planting native trees and shrubs within the regulated riparian buffer of a fish-bearing stream (Black
River). Although mitigation was considered upstream or downstream of the project, or at a similar subbasin in the same geographic area, on-site mitigation (within the project area and
regulated buffer of the Black River) was selected as the preferred option. Any trees with trunks larger than 4 inches in diameter that are removed within sensitive areas or shoreline
zones in the City of Tukwila would be replaced as prescribed by TMC requirements.
Site Selection
The regulations of the local jurisdictions (Cities of Tukwila and Renton) identify a preference for compensatory mitigation to be conducted within the same subbasin and on site (TMC 18.45.090
F.5; Renton SMP 4-3-090 D.2.d x.(i)). However, the Cities may consider off-site compensation if the applicant demonstrates that this provides a greater ecological benefit. King County
considered multiple mitigation opportunities located on the project site. The identification of available parcels for mitigation is dependent upon size, current site conditions, land
use, real estate conditions, local jurisdiction code, and future land use proposals.
Based on the Cities’ preference for on-site mitigation, project staff first considered opportunities within the trail right-of-way for compensatory mitigation. On-site mitigation opportunities
within the trail corridor are constrained by the narrow linear right-of-way, limited buffer area available for enhancement, and adjacent land uses and features (e.g., railroad tracks).
Off-site opportunities in the same subbasin and out of the subbasin (in the same WRIA) were also explored.
The proposed mitigation sites are located outside of the trail right-of-way, but near the trail (Appendix E). The first site (Mitigation Site 1) was selected because it is located in
the vicinity of both stream (Black River) buffer and wetland (Wetlands 7 and BR) buffer, dominated by invasive species, and large enough to accommodate all of the project’s wetland
buffer mitigation needs at a single location. The second site (Mitigation Site 2) was selected because it is within the buffer of the Black River and adjacent to the trail. The proposed
mitigation sites are located within the city of Renton and are owned by the City of Renton. Currently the proposed Mitigation Site 1 is being used as a natural area and is part of the
Black River Riparian Forest. Mitigation Site 2 is on the sloped banks of the Black River at the western end of the Black River Riparian Forest.
Mitigation Site Existing Conditions
Proposed Mitigation Site 1 is located between the Black River, Wetland 7, and Wetland BR. It is dominated by reed canarygrass and Himalayan blackberry.
Proposed Mitigation Site 2 is located northeast of Monster Road, north and south of the Black River. It is dominated by Himalayan blackberry with butterfly bush (Buddleja sp.). Few native
species are present in low numbers including Scouler’s willow (Salix scouleriana), snowberry, Indian plum (Oemleria cerasiformis), and Douglas spirea (Spiraea douglasii) at the water
edge. A few trees are scattered on the site, primarily black cottonwood. The top of bank on the south side of the river consists of grasses and forbs, including poison hemlock. Rock
and broken pieces of concrete are on top of and within the soil.
Proposed Mitigation
Proposed conceptual mitigation includes enhancement of approximately 0.49 acre of wetland buffer and 0.38 acre of stream buffer at Mitigation Site 1 and enhancement of approximately
0.22 acre of stream buffer at Mitigation Site 2 (see Appendix E). The proposed enhancement at both mitigation sites would include a combination of invasive vegetation removal, tilling
of soil, addition of compost (where needed) and mulch, and planting of native vegetation. Riparian mitigation may also consist of planting, or underplanting, in an area where existing
riparian conditions are degraded. This type of mitigation would offset the project’s impacts on stream resources by maintaining or enhancing those riparian functions that support water
quality and fish habitat. The riparian functions that would benefit from mitigation include LWD recruitment, stream temperature regulation, bank stability, leaf litter recruitment,
and water quality functions. The goal of the mitigation effort is to augment the Black River corridor by establishing native vegetation and enhancing buffer functions of the stream
and Wetland 7 in areas dominated by invasive species. These efforts would meld with previous and future enhancement activities performed by others.
Impacts to FWHCAs, outside of wetland and stream buffers, would be compensated for with additional plantings where views toward the heron nesting colony are not already obscured by existing
vegetation. Such plantings, combined with fence installation along the southern edge of the alignment of the trail adjacent to the Black River Riparian Forest, are expected to reduce
the potential for disturbance to wildlife in the natural area. These plantings would be qualitatively monitored for general health and rigor in conjunction with the wetland buffer compensatory
mitigation monitoring (qualitative) during Years 1, 2, and 3.
Mitigation Goals, Objectives, and Performance Standards
The overall goal of the mitigation is to replace the habitats and functions lost as a result of the project. The proposed mitigation would accomplish this by enhancing 0.49 acre of wetland
buffer and 0.60 acre of stream buffer. Specific goals and objectives formulated to achieve this result are presented below.
Mitigation Goal
Goal: Enhance 0.49 acre of wetland buffer and 0.60 acre of stream buffer to native forested upland.
Achievement of this goal is expected to increase the production of organic matter by planting trees and shrubs in the enhanced buffer; increase wildlife habitat; and improve biological
diversity by planting with a variety of native riparian plant species.
Mitigation Objectives and Performance Standards
Objective 1: Establish a minimum of 0.49 acre of forested wetland buffer and 0.60 acre of forested stream buffer by planting native trees and shrubs.
Performance Standards:
Year 1 Survival of planted woody species in enhanced wetland buffer and stream buffer areas will be at least 80 percent.
Year 3 Native woody species will achieve a minimum of 35 percent areal cover in the enhanced wetland buffer and stream buffer areas.
Year 5 Native woody species will achieve a minimum of 60 percent areal cover in the enhanced wetland buffer and stream buffer areas.
Objective 2: Limit invasive non-native species throughout the mitigation site planting areas.
Performance Standard:
Years 1–5 Himalayan blackberry, cutleaf blackberry (Rubus laciniatus), Scotch broom (Cytisus scoparius), butterfly bush, poison hemlock, Canada thistle (Cirsium arvense), bull thistle
(Cirsium vulgare), and reed canarygrass will not exceed 20 percent areal cover in all planting areas.
Objective 3: Provide upland wildlife habitat.
Performance Standard:
Increase in areal cover of native woody species in the planted buffer, as measured in Objective 1 to be used as a surrogate to indicate increasing habitat functions.
Objective 4: Protect the mitigation site from anthropogenic disturbance.
Performance Standard:
Years 1–5 Conduct yearly qualitative monitoring to assess the status of the sites during the 5-year monitoring period for human disturbance, including but not limited to filling, trash,
and vandalism.
MONITORING AND MAINTENANCE
Monitoring
The mitigation areas would be monitored during and after construction. During construction, monitoring would ensure that the BMPs are observed to minimize impacts, and the on-site construction
work (including earthwork and planting) would be coordinated to ensure that the site is constructed as designed.
After construction is completed, an “as-built” mitigation report would be submitted to the Cities of Renton and Tukwila within 1 month of mitigation installation. Post-construction monitoring
of the mitigation areas would be performed over a 5-year period by qualified biologists. Monitoring would be performed quarterly the first year and annually for subsequent years to
ensure that the goals and objectives of the mitigation are being met. A combination of qualitative and quantitative monitoring activities would be used to assess the management objectives
and associated performance standards described in this mitigation proposal. Activities would include conducting site visits to monitor unnatural site disturbance, taking photographs
to document site development, and collecting data for the quantitative evaluation of performance standards. The results of the monitoring will be submitted to the Cities of Renton and
Tukwila following each monitoring event.
Appropriate contingency measures will be developed, as needed, by a qualified professional to ensure that the sites develop healthy vegetation that meets the obligations described in
this mitigation plan and the associated permits.
Quantitative Monitoring
The following bulleted items describe the methods to be used for the quantitative monitoring, monitoring schedule, and report deadlines.
The mitigation sites will be assessed by an appropriate quantitative vegetative cover field assessment methodology. The line intercept method will be used for determining percent areal
cover for woody and invasive species.
Quantitative vegetation assessments will follow the same method in each consecutive monitoring year.
Quantitative vegetation assessments will be performed between June 15 and September 15 of each monitoring year.
Monitoring reports will be sent to agencies requiring monitoring reports by February 15 of the following year.
Quantitative monitoring will include photographic documentation of the sites from permanent photograph stations.
Qualitative Monitoring
Qualitative assessment will be performed yearly to visually assess the health of plants and identify areas that may need control of non-native invasive species or other maintenance activities.
Additionally, during Years 1, 2, and 3 the screening plantings (SP-1 on Sheet MP1 in Appendix E) will
also be qualitatively monitored to visually assess the health of the plants and identify areas that may need control of non-native invasive species or other maintenance activities.
Maintenance
The proposed mitigation is intended to achieve the performance standards with minimal ongoing maintenance. Planted vegetation species should be adapted to varying site conditions in
the Puget Sound lowland; however, supplemental irrigation might be needed during the first two growing seasons after installation to ensure the long-term survival of the plants. The
need for irrigation would be evaluated based on the conditions observed during the establishment period.
To ensure rapid establishment of the plant community, trees and shrubs would be planted closer together than would generally occur in natural mature stands. Some natural mortality is
expected to occur during the monitoring period. All dead and downed woody material would be left in place to provide microhabitats for wildlife. Plants would be replaced as needed to
meet performance standards.
Maintenance to control nuisance species in the mitigation areas may be necessary. During the monitoring period, if it becomes evident that invasive species are impeding establishment
of desirable native plants, measures would be implemented to control nuisance species. A progressively aggressive approach would be used to control nuisance species. Control measures
would first include hand cutting and/or grubbing and removal; if this fails, an environmentally sensitive herbicide (Rodeo® or equivalent) may be applied.
Contingency Measures
If monitoring indicates that the sites are not meeting performance standards, contingency measures would be implemented (Table 6-1). Site conditions would be evaluated to determine the
cause of the problem and the most appropriate countermeasures.
Information from the annual monitoring program will be used to identify any maintenance and/or corrective actions. If problems are identified in monitoring, King County biologists will
determine the cause of the problem and implement proper maintenance or corrective activities. These activities will be discussed in the annual monitoring report.
Table 6-1. Contingency Measures for the Mitigation Site
Problem
Contingency Measure
Less than 80% of planted woody species survive in Year 1
King County biologists (or other qualified biologist) would assess the site to determine what conditions are preventing the plants from thriving. Appropriate measures would be taken
to correct any conditions that are limiting growth. Lost plants would be replaced with appropriate native species unless appropriate native woody species are volunteering at a rate
sufficient to replace them. Additional measures (such as providing additional protection) would be considered if necessary. Additional protection could include the use of an herbivore
repellent (Plantskydd or equivalent).
Percent cover for woody species not met in Year 3 or 5
King County biologists (or other qualified biologist) would assess the sites to determine what conditions are preventing the plants from thriving. Appropriate measures would be taken
to correct any conditions that are limiting growth.
Invasive species exceed percent cover threshold
Implement/revise invasive species control plan.
Performance standards not met at Year 5
Continue the monitoring regime for 1 additional year. The sites would continue to be evaluated every year until they meet the stated performance standards associated with management
objectives. Other contingency measures may be implemented during this period.
REFERENCES
Bax, N. J., E.O. Salo, and B.P. Snyder. 1979. Salmonid outmigration studies in Hood Canal. Final report, phase VI. FRI-UW-7921, 89 p. Fish. Res. Inst., Univ. Wash., Seattle.
Blomberg, G., C. Simenstad, and P. Hickey. 1988. Changes in Duwamish River estuary habitat over the past 125 years. Pages 437-454 in Proceedings. First annual meeting on Puget Sound
research. Volume 2. Prepared by the Puget Sound water quality authority. Seattle, Washington.
Brinson, M.M. 1993. A Hydrogeomorphic Classification for Wetlands. Wetlands Research Program Technical Report WRP-DE-4. U.S. Army Corps of Engineers Waterways Experiment Station, Vicksburg,
Mississippi.
Corps (U.S. Army Corps of Engineers). 2010. Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Western Mountains, Valleys, and Coast Region. U.S. Army Corps of
Engineers Engineer Research and Development Center, Vicksburg, Mississippi.
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, D.C.
DNR (Washington Department of Natural Resources). 2014. Natural Heritage Program GIS Layer. Olympia, Washington.
DNR (Washington Department of Natural Resources). 2010b. DNR Forest Practices Water Typing. Available at: http://www.dnr.wa.gov/BusinessPermits/Topics/ForestPracticesApplications/Pages/fp_watertypin
g.aspx.
Ecology (Washington State Department of Ecology). 1997. Washington State Wetland Identification and Delineation Manual. Publication #96-94. Olympia, Washington.
Ecology (Washington State Department of Ecology). 2015. 2012 Washington State Water Quality Assessment (305[b] report and 303[d] list). Available at http://www.ecy.wa.gov/programs/wq/303d/currentasse
ssmt.html. Accessed February 3, 2015.
Environmental Laboratory. 1987. Corps of Engineers Wetland Delineation Manual. Technical Report Y-87-1, Environmental Laboratory, Department of the Army, Waterways Experiment Station,
Vicksburg, Mississippi.
FEMA (Federal Emergency Management Agency). 1995. Flood Insurance Rate Map for King County, Washington, and Incorporated Areas. Map Number 53033C0976F and Map Number 53033C0957F. Effective
September 29, 1989; latest revision May 16, 1995.
Foerster, R.E. 1972. The sockeye salmon. Bulletin 162. Ottawa, Canada: Fisheries Research Board of Canada. 422 p.
GretagMacbeth. 2000. Munsell Soil Color Charts. New Windsor, New York.
Harza. 1995. Comprehensive fisheries assessment of the Springbrook, Mill, and Garrison Creek watershed. Bellevue, Washington: prepared for City of Kent, Washington.
Hitchcock, C.L. and A. Cronquist. 1973. Flora of the Pacific Northwest. University of Washington Press, Seattle, Washington.
Hruby, T. 2004. Washington State Wetlands Rating System for Western Washington - Revised. Washington State Department of Ecology, Publication No. 04-06-025.
King County. 2012. Green River Watershed. Available at: http://www.kingcounty.gov/environment/watersheds/green-river.aspx. Accessed February 27, 2012.
King County. 2015. King County iMap Interactive Mapping Tool. Available at: <http://www.kingcounty.gov/operations/gis/Maps/iMAP.aspx>. Accessed April 2015.
Null, W.S., G. Skinner, and W. Leonard. 2000. Wetland Functions Characterization Tool for Linear Projects. Washington State Department of Transportation Environmental Affairs Office.
Olympia, Washington.
Parametrix. 2015a. Lake to Sound Trail – Segment A Vegetation and Wildlife Discipline Report. April 2015. Seattle, Washington.
Parametrix. 2015b. Lake to Sound Trail – Segment A Final Technical Information Report. April 2015. Seattle, Washington.
Parametrix. 2015c. Lake to Sound Trail – Segment A Stream Discipline Report. April 2015. Seattle, Washington.
Reed, P.B., Jr. 1993. National List of Plant Species that Occur in Wetlands, Northwest Region 9 Supplement. U.S. Department of the Interior, Fish and Wildlife Service. Washington, D.C.
Reed, P.B., Jr. 1988. National List of Plant Species that Occur in Wetlands. U.S. Department of the Interior, Fish and Wildlife Service. Washington, D.C.
Renton, City of. 2015. GIS data. FEMA Floodplain Boundary. Available at: http://rentonwa.gov/government/default.aspx?id=29887. Data Downloaded March 30, 2015.
Rieman, B.E. and G.L. Chandler. 1999. Empirical evaluation of temperature effects on bull trout distribution in the Northwest. Final Report, Contract No. 12957242-01-0. U.S. Forest Service,
Rocky Mountain Research Station, Boise, Idaho.
Stenberg, K. 2007. The Black River Heron Colony: An Annotated History. Quailcroft Environmental Services, Sammamish, WA.
Stober, Q.J, S.J. Walden, and D.T. Griggs. 1973. Juvenile salmonid migration through Skagit Bay, pp.35-70. In Ecological studies of proposed Kiket Island nuclear power site. Edited by
Q.J. Stober and E.O. Salo. FRI-UW-7304. 537pp.
USDA, NRCS (U.S. Department of Agriculture, Natural Resources Conservation Service). 2002. Climate Information. King County, Washington. Available at: <ftp://ftp.wcc.nrcs.usda.gov/support/climate/wet
lands/wa/53053.txt>. Water and Climate Center, Portland, Oregon.
USDA, NRCS. 2010a. Web Soil Survey Online Interactive Mapper. Available at: <http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx>.
Accessed December 2010.
USDA, NRCS. 2010b. The PLANTS Database. Available at: http://plants.usda.gov. National Plant Data Center, Baton Rouge, Louisiana.
USFWS (U.S. Fish and Wildlife Service). 2010. National Wetlands Inventory (NWI), Online Interactive Mapper. Available at: http://www.fws.gov/wetlands/.
Warner, E.J., and R.L. Fritz. 1995. The distribution and growth of Green River chinook salmon (Oncorhynchus tshawytscha) and chum salmon (Oncorhynchus keta) outmigrants in the Duwamish
Estuary as a function of water quality and substrate. Muckleshoot Indian Tribe, Auburn, Washington.
WDFW (Washington Department of Fish and Wildlife). 2015. PHS on the Web: An interactive map of WDFW priority habitats and species information for project review. Available online at:
http://wdfw.wa.gov/mapping/phs/. Accessed February 2, 2015.
WDFW (Washington Department of Fish and Wildlife). 2014. Salmonscape fish database and mapping application. Available online at: https://fortress.wa.gov/dfw/salmonscape/. Accessed January
16, 2014.
Williams, W.R., R.M. Laramie, and J.J. Ames. 1975. A Catalog of Washington Streams and Salmon Utilization. Volume 1, Puget Sound Region. Washington Department of Fisheries, Olympia,
Washington.
WSCC (Washington State Conservation Commission). 2000. Habitat Limiting Factors and Reconnaissance Assessment Report: Green/Duwamish and Central Puget Sound Watersheds (Water Resource
Inventory Area 9 and Vashon Island), Olympia, Washington. December 2000.
Wetland Determination Data Forms
Wetland Rating Forms
Wetland Functions and Values Forms
Site Photographs
Mitigation Plans