HomeMy WebLinkAboutP_2024-09-12 - Final - May Creek Trail South - Mitigation Plan
MAY CREEK TRAIL SOUTH
MITIGATION PLAN
CITY OF RENTON - PARKS PLANNING AND
DEVELOPMENT
PROJECT NO.: 30902211
DATE: SEPTEMBER 2024
WSP USA
1201 PACIFIC AVE. SUITE 550
TACOMA, WA 98402
PHONE: +1 206-431-2300
WSP.COM
TABLE OF CONTENTS
1 INTRODUCTION ......................... 1
2 PROJECT DESCRIPTION ....... 2
2.1 Construction Schedule and Project Elements ......................2
2.2 Mobilization and Site Preparation ..............................................2
2.3 Soft Surface Trail Section................................................................2
2.4 Boardwalk Trail Section ..................................................................2
2.5 Bridge Abutments ..............................................................................3
2.6 Bridge .......................................................................................................3
2.7 Frontage Improvements .................................................................3
3 PROJECT SITE ............................ 4
4 EXISTING SITE CONDITIONS5
4.1 Terrestrial and Riparian Habitats ............................................... 5
4.2 Aquatic Habitat and Basin Condition ...................................... 5
5 PROPOSED PROJECT
IMPACTS ....................................... 8
5.1 Wetland and Buffer Impacts ........................................................ 8
5.2 Stream Impacts .................................................................................. 8
5.3 Impacts to Fish and Wildlife Habitat Areas .......................... 8
6 MITIGATION SITE AND
ANALYSIS ................................... 10
6.1 Mitigation Sequencing .................................................................. 10
6.2 Mitigation Framework .................................................................... 11
6.3 Mitigation Site Selection ............................................................... 12
6.4 Mitigation Site Description .......................................................... 13
7 MITIGATION AND HABITAT
MANAGEMENT PLAN ............ 14
7.1 Mitigation Details ............................................................................. 14
7.2 Mitigation Credits ............................................................................. 16
7.3 Mitigation Objectives and Performance Criteria ............... 17
7.4 Maintenance/Monitoring Plan.................................................... 18
8 LONG-TERM MANAGEMENT
PLAN ............................................. 19
9 FINANCIAL ASSURANCES 20
10 REFERENCES ............................. 21
11 LIST OF ACRONYMS AND
ABBREVIATIONS .................... 22
TABLES
TABLE 1. WETLAND RESOURCE SUMMARY .................................................... 7
TABLE 2. STREAM RESOURCE SUMMARY ........................................................ 7
TABLE 3. WETLAND AND COMBINED BUFFER IMPACT
SUMMARY ........................................................................................... 8
TABLE 4. MITIGATION AND RESTORATION SITE PLANT
SPECIES ............................................................................................... 15
TABLE 5. COMPENSATORY MITIGATION ANALYSIS AND
PRESCRIBED MITIGATION RATIOS ................................. 17
LIST OF FIGURES
FIGURE 1. VICINITY MAP
FIGURE 2. PROJECT OVERVIEW
FIGURE 3. WETLAND AND STREAM OVERVIEW
FIGURE 4. SITE TOPOGRAPHY
FIGURE 5. WATERSHED MAP
FIGURE 6. PROJECT IMPACTS
FIGURE 7. COMPENSATORY MITIGATION AND OUT-OF-
KIND RESTORATION
APPENDICES
APPENDIX A FIGURES
APPENDIX B PHOTO LOG
APPENDIX C SELECT PLANTING PLANS
1 INTRODUCTION
WSP USA has been authorized by the City of Renton (City) Parks and Recreation Department to prepare permitting
documents for the proposed May Creek Trail South Project (Project) within the May Creek Greenspace (see Appendix A:
Figures 1 and 2). The City has the trail expansion planned within their Parks, Recreation, and Natural Areas Plan (City of
Renton 2020). The proposed project intends to build an ADA accessible trail south of May Creek and connect into the
existing trail network within the May Creek Greenway. The goal of the proposed project is to provide a recreational nature
trail within the property and enhance the ecological functions of the site in accordance with the City of Renton’s Shoreline
Master Program, USACE’s Section 404 Nationwide Program, and meet goals within the May Creek Basin Action Plan (King
County 2001).
The proposed project triggers compliance with the City’s Shoreline Master Program due as it is located within the
regulated shoreline buffer and Washington Department of Fish and Wildlife (WDFW) (Hydraulic Code) requirements will
also be necessary to receive approvals and permits for the project. It is anticipated that the project will not trigger
compliance with U.S. Army Corps of Engineers (USACE) (Section 404) and Ecology (Section 401) due to no cut or fill being
proposed in site waters. This habitat management and mitigation plan has been developed as part of the permitting
package to the City and other applicable agencies if needed. The project will impact multiple wetlands, May Creek, and
their associated buffers. These impacts will need to be mitigated for based on the requirements of the agencies reviewing
and approving the permits for the project.
2 PROJECT DESCRIPTION
The Proposed Project is to construct a soft surface trail, build a bridge spanning May Creek, and improve the frontage
along Lake Washington Boulevard North at the May Creek Park Greenway in Renton, Washington (Appendix A: Figure 2).
The proposed soft surface trail will be one-quarter mile in length, consisting of an approximate 6 foot width trail and 1-
foot shoulders at existing grade with two spurs (Spur 1 and Spur 2) leading to viewing areas with benches and a split -rail
fence. The trail will have portions located on a boardwalk where the trail intersects wetlands and will tie into an existing
trail on the north side of the creek. The bridge will be approximately 100 ft in length, approximately 6 ft in width and will
cross May Creek at the eastern portion of the site. The boardwalk trail and bridge will have grated decking and the
entirety of the trail will conform to ADA accessibility guidelines.
Additional details of project components are described in Section 2.1 to 2.7 below.
2.1 CONSTRUCTION SCHEDULE AND PROJECT ELEMENTS
The project is currently at the preliminary design phase with a 60% design set currently developed. The project is
currently managing site invasives species through a partnership with King County Noxious Weeds Program that started in
spring 2023. The anticipated construction start date for the Project is scheduled to start in late spring 2025 and subsequent
completion in fall 2025. The project will be completed in phases described in the following sections. Construction of all
elements will occur outside of the Ordinary High Water Mark (OHWM) of May Creek and are likely not subject to an in-
water work window.
2.2 MOBILIZATION AND SITE PREPARATION
This phase consists of clearing, grubbing, and removing trees that are within the trail, boardwalk, bridge alignment and
abutments, and construction laydown areas associated with the placement of the bridge. King County Noxious Weeds
Program will also be involved in this phase with the removal and clearing of invasive vegetation on the site within both
the mitigation areas and the non-compensatory mitigation restoration areas discussed later in this report. The
construction access for this project will be split between the north and south side of May Creek. South of May Creek, there
will be a graveled construction entrance off of Lake Washington Boulevard North where materials and mechanized
equipment (mini-excavator and materials hauler) will be brought in following the trail alignment. To the north of May
Creek, the access will be achieved through an existing WSDOT I -405 access road that ties into the existing trail. This access
will allow the truck mounted crane, bridge sections, and materials to be brough t in without the need for additional
clearing and grading within the May Creek greenspace. A 40-foot clear zone is the assumed clearing limits necessary to
stage the crane and allow for the placement of the span sections onto the footings this is shown in Appendix A: Figures 2
and 6. The foundations will be prepped either by hand or with a mini -excavator. To access the southern foundation, the
contractor will either place girders over the stream, use the crane to pass the mini-excavator over May Creek, or use the
finished boardwalk to bring it in from the south side of May Creek.
2.3 SOFT SURFACE TRAIL SECTION
The trail will be cut into the existing grade and will be cross-sloped to the outside edge for drainage along hillslopes and
crowned along flat sections. The trail will consist of a 6-ft tread and 1-ft shoulders on each side. The surfacing of the trail
will be mulched wood and the shoulders crushed stone. The underlayment of the wood chips will be crushed stone base
course. The grade will maintain a slope under 7% grade to maintain ADA accessibility and the cut and fill sections will
maintain a 2:1 slope throughout these sections.
2.4 BOARDWALK TRAIL SECTION
The proposed May Creek Trail South section will cross Wetland C in two (2) locations for a total of approximately 180 feet.
These crossings will transition from the soft surface trail section to a boardwalk section. The boardwalk will consist of a
timber boardwalk with a fiber-reinforced plastic (FRP) board slatted deck surface to allow drainage. The boardwalk will be
supported by micro piles and will have handrails and/or bull rails for pedestrian safety.
2.5 BRIDGE ABUTMENTS
Concrete bridge abutments will be positioned above the OHWM, floodway, and 100-year floodplain. Approximately 12
cubic yards of material will be excavated with micro piles placed before being backfilled with an underlayment of drainage
rock and subsequently cast-in-place with concrete to construct the new concrete abutments. Concrete wingwalls will be
poured concurrently with the foundation along the south abutment to minimize erosion risk at the bridge connections.
The concrete will be poured via a boom an d will span over May Creek for the southern abutment.
2.6 BRIDGE
The 100 foot length and 8 foot width clear span bridge will be comprised of concrete walkways at the north and south
portion of the bridge at the abutment locations, and an aluminum gangway type bridge with non -slip FRP slatted decking
for the length of the bridge in between the concrete walkways. The bridge measures 800 square feet total, and
approximately 320 square feet of this total is located over water as measured from the OHWM. The bridge will be
positioned approximately 2 to 10 feet above the OHWM. The bridge will be placed in two or three sections via a crane,
supported either via cantilevering and temporarily shored, and bolted together to form the clear span.
2.7 FRONTAGE IMPROVEMENTS
The project will be required to provide street improvements (i.e. parcel frontage improvements) on Lake Washington
Boulevard as part of the proposal pursuant to Renton Municipal Code (RMC) 4-6-060. These regulations trigger minimum
design standards for sidewalks, bicycle lanes, curbs, planting strips, etc. The project will not implement a planting strip to
reduce encroachment into shorelines and critical areas present at the edge of the property. The proposed frontage
improvements involve shifting the roadway to the west, realigning the two 11 foot travel lanes, two 5 foot bike lanes,
construction of a 5 foot sidewalk along the northeastern side of the roadway, and associated stormwater reconfiguration.
The existing stormwater consists of multiple piped conveyances, a short ditch section, and outfalls to a wetland on the
site. The proposed stormwater will consist of replacing the existing broken culvert to Wetland A and creating a new outfall
to Wetland A via a new conveyance under the sidewalk.
3 PROJECT SITE
The Proposed Project is located in King County in Section 32 of Township 24N Range 05E. The Project Area is 3.5 acres,
within the 8.21-acre tax parcel 322405-9109, and is defined as the limits of the Proposed Project Actions (Appendix A:
Figure 2).
The project site is bordered by Interstate 405 (I-405) to the east and bordered by Lake Washington Boulevard N to the west.
May Creek runs through the site and the OHWM was delineated in December 2022 by WSP Biologists. There is an existing
nature trail, May Creek Trail, on the north side of May Creek. There are four (4) wetlands located with the parcel,
delineated in October 2022 and January 2023 by WSP and documented in the May Creek Trail South Project Wetland and
Stream Study. These wetlands have been labeled as Wetlands A, B, C, and D.
4 EXISTING SITE CONDITIONS
4.1 TERRESTRIAL AND RIPARIAN HABITATS
Terrestrial and riparian habitats are lacking diversity within the project site. The site contains limited conifers and
deciduous tree cover and native shrubs throughout the upland and riparian/wetland areas. The area to the north of May
Creek was recently restored and has more functions than the south side of May Creek. The south side of May Creek is
degraded due to the majority of the site being covered in invasive species consisting of hybrid knotweed (Fallopia
bohemica), Himalayan blackberry (Rubus armeniacus/bifrons), English ivy (Hedera helix), English holly (Ilex aquifolium),
Portuguese laurel (Prunus lusitanica), reed canarygrass (Phalaris arundinacea), among other smaller infestations. A variety of
bird species and ungulates were observed using these habitats during surveys. The ungulates observed on-site were during
the later stages of the survey where the invasive Himalayan blackberry was cut to necessitate the wetland and stream
delineation. It is likely that the dense infestations limit larger s pecies to move through the site and is a degraded habitat
condition.
The adjacent land uses and level of development are generally high to moderate intensity. The City-owned land within the
project area and to the southeast and the west of the project site is part of the May Creek Greenspace and provides
recreational trails for the public and habitat connectivity for a variety of species. The following sections describe key
elements of the site conditions and Appendix B shows photos taken during site visits.
4.1.1 WETLANDS
Within the study area around the project site, four wetlands were identified and are shown in Appendix A: Figure 3. Three
wetlands are adjacent to the stream to the south of May Creek and one is to the north within the 100-year floodplain. The
wetlands contain habitats for riparian dependent species, with some forest cover, small diameter standing snags, limited
large woody debris (LWD), and thick invasive understory vegetation.
4.1.2 GEOGRAPHY AND SOILS
Topography in the project area is dominated by the May Creek stream valley that intersects the project area. The area to
the south of May Creek is dominated by a hillslope that extends from the flat 100-year floodplain boundary up to the
parcel boundary. The north side of the site is generally flat with a wide 100-year floodplain. The hillslope south of May
Creek gets progressively steeper from west to east (Appendix A: Figure 4). The surficial geology of the site is mapped as an
alluvium layer from the Holocene (USGS 1993). Mapped soil types in the project site include Norma sandy loam, Indianola
loamy sand, and alderwood gravelly sandy loam.(USDA – NRCS 2023).
4.1.3 VEGETATION
Upland habitat conditions within the project area are generally shrub dominated with a fragmented forest cover
consisting of Douglas fir (Pseudotsuga menzeseii), black cottonwood (Populus balsamifera), red alder (Alnus rubra), bigleaf
maple (Acer macrophyllum), and Sitka and Pacific willows (Salix sitchenis/lasiandra). Shrub vegetation has dense coverage
throughout the site and generally consist of a monoculture of Himalayan blackberry and hybrid knotweed, among other
smaller infestations of invasive vegetation including English holly (Ilex aquifolium) and Portuguese laurel (Prunus lusitanica).
4.2 AQUATIC HABITAT AND BASIN CONDITION
May Creek is a tributary to Lake Washington, draining an area of 14 square miles (King County 2001). May Creek flows
through the middle of the project site in a generally east to west direction. May Creek is a Type S water up to the boundary
of the City of Renton and Newcastle and a Type F water all the way to its mainstem headwaters at Lake Kathleen and the
north fork headwaters near Cougar Mountain (DNR 2023). There are multiple tributaries to May Creek throughout its
length with a similar length of Type F and Type N waters contributing to its watershed (DNR 2023). The streams are shown
in Appendix A: Figure 5.
The basin can be divided roughly into two halves. The upper, eastern portion of the basin is characterized by R -1 to R-4
residential and agricultural land uses and includes a significant portion of Cougar Mountain Regional Wildland Park.
Above May Canyon (the project location) the creek lies in a formerly dredged, straightened channel at the center of a wide,
very low gradient valley. The lower, western portion of the basin is inside the Urban Growth Boundary (primarily within
the jurisdiction of the City of Renton and City of Newcastle, Washington) and is fairly dense 6 to 8 unit per acre urban
residential developments. Within the City of Renton jurisdiction, the mainstem of May Creek is in a designated park and
runs through a steep, narrow, wooded canyon before flowing into east Lake Washington (King County 2016).
4.2.1 GENERAL AQUATIC CONDITIONS
May Creek is documented to contain high quality spawning habitat at the confluences of tributaries to the main stem
(King County 2001). Observations made during the project surveys indicated that the streambed contained moderate
amounts of large cobbles and mainly consists of streambed gravels, LWD was present throughout the site and shading was
moderate. In the Salmon Habitat Limiting Factors Report for Water Resource Inventory Area (WRIA) 8, all of the salmon
habitat parameters scored a poor rating where data was available (Kerwin 2001). According to this report the following
parameters limit fish habitat in May Creek: access/fish passage, floodplain connectivity, LWD, Pools, riparian cond ition,
water quantity, and hydrology. There are no physical barriers preventing migratory fish from accessing the site from
downstream waterbodies.
4.2.2 FLOODPLAIN, SIDE CHANNELS, AND ASSOCIATED AQUATIC FEATURES
There is a floodplain on both sides of May Creek throughout the project area. The majority of 100 -year flood flows extend
to the north due to the hillslope present on the south side of the stream. Based on observations made during the site visit
evidence pointed to some recent flood flows (deposited sediments, scour, etc.). The stream has moderate to low riparian
cover on both banks provided by native trees and invasive shrub cover. The stream receives stormwater runoff from Lake
Washington Boulevard North at the western side of the project and from I-405 east of the project. No surveys were
conducted upstream and downstream of the project area, so side channels and floodplain quality are unknown.
4.2.3 IN-STREAM AND RIPARIAN HABITAT CONDITIONS
The bed and bank of the May Creek within the site are in fair condition with some LWD observed, stream gravels are
abundant, and the riparian areas are well vegetated but are predominantly invasive species and lacks native species
diversity. The riparian areas were observed to harbor a variety of non-listed bird species, with ungulates observed on two
occasions moving through the site during field surveys. There is coho salmon spawning habitat present throughout the
project area (NWIFC 2023), with May Creek containing limited pool-riffle characteristics and small to medium gravels
being abundant in this reach of the stream.
4.2.4 WATER QUANTITY AND QUALITY
The May Creek basin encompasses roughly 26 miles of mapped streams, two small lakes, and over 400 acres of wetlands.
Headwater streams come off steep, forested ravines from the north, east, and south. Lower reaches of the May Creek
watershed are mostly urban runoff from roadways, commercial developments, and residential uses. Water quantity and
quality is ranked as poor within May Creek (Kerwin 2001).
4.2.5 FISH AND WILDLIFE HABITAT CONSERVATION AREAS
There is suitable habitat for listed aquatic threatened and/or endangered species within May Creek. No listed terrestrial
endangered species are expected to occur around the project site, such as Canada lynx (Lynx canadensis), wolves (Canis
lupus), or grizzly bears (Ursus arctos horribilis), as their known ranges are located well away from the project site in the
Cascade mountain range and no old-growth or late-seral forests are present within the site that would support Marbled
Murrelet (Brachyramphus marmoratus) or Northern Spotted Owl (Strix occidentalis caurina). The project site was observed to
harbor non-listed birds, deer, and urban-adapted small mammals.
There is documented spawning and rearing habitat for Endangered Species Act (ESA)-listed Chinook Salmon (Oncorhynchus
tshawytscha) and documented presence of Steelhead (O. mykiss) within the reach of May Creek within the project site.
There is also documented spawning and rearing for non-ESA-listed Coho Salmon (O. kisutch) (a dead coho was observed
during the field visit), and documented presence of Sockeye Salmon (O. nerka) within the reach of the project site (NWIFC
2023, Kerwin 2001).
4.2.6 WETLAND AND STREAM SUMMARY
The project area contains four wetlands and one stream. Tables 1 and 2 below describe the wetlands and streams.
Table 1. Wetland Resource Summary
Wetland Wetland Classification Area of Wetland
(acres) Cowardina HGMb Wetland Ratingc
Wetland A PFO/PSS Slope III 0.14
Wetland B PSS Riverine III 0.03
Wetland C PFO/PSS Slope III 0.80
Wetland D PSS Depressional III 0.03
Notes:
a Cowardin et al. (1979) class based on vegetation: PEM = palustrine emergent, PFO = freshwater forested, PSS = scrub-shrub wetland.
b HGM classification according to Brinson (1993).
c Wetland rating according to Hruby (2014).
Table 2. Stream Resource Summary
Stream ID WRIA Local
Jurisdiction
DNR Stream
Type1
Local
Jurisdiction
Stream Type2
Vegetation
Conservation
Area Width3
Flow Regime
May Creek 8 Cedar-
Sammamish
City of Renton S S 100 Perennial
Notes:
1 DNR (2023).
2 RMC 4-3-090C2b.
3 RMC Table 4-3-090F1
5 PROPOSED PROJECT IMPACTS
The project has been designed to avoid and minimize impacts to regulated resources following Mitigation Sequencing that
is described in Sections 6.0 and Section 7.0 below. The project will have unavoidable impacts from the construction of the
trail, the boardwalk, bridge, frontage improvements, and from the site restoration work.
The unavoidable impacts from the proposed project are described in the following sections and are broken down by
resource and impact type. The impacts are depicted in Appendix A: Figure 6. Please note that these impacts are based off of
a 60 percent design and may change as the design progresses to construction.
5.1 WETLAND AND BUFFER IMPACTS
Construction of the proposed project will directly impact one of the identified wetlands. . Wetland C will be permanently
impacted by shading where the proposed boardwalk sections are located. The permanent buffer impacts are all derived
from the direct placement of fill associated with the trail alignment and frontage improvements. Temporary impacts
include the construction of the trail, which includes the grubbing/clearing of invasive shrubs and emergent vegetatio n for
laydowns during construction. These were classified as short-term temporary as the shrubs are primarily invasive
Himalayan blackberry and will be replaced with native plantings in the same construction year These wetland and
combined upland buffer (shoreline and wetland) impacts are summarized in Table 3.
Table 3. Wetland and Combined Buffer Impact Summary
Wetland Permanent Grading Impacts
(sq ft)
Permanent Shading Impacts
(sq ft) Short-Term Temporary Impacts (sq ft)
A 0 0 0
B 0 0 0
C 0 ~1040 0
D 0 0 0
Wetland Total: 0 ~1040 0
Buffer Permanent Impacts (sq ft) Temporary Impacts (sq ft)
Buffer Total ~13,200 ~10,250
General Note – The site work will be completed over a 3 month timeframe with laydowns and access roads being in place for less than 6 months
5.2 STREAM IMPACTS
The proposed project will not have any work within the OHWM of May Creek. The only impacts would be from the shading
of the stream from the ~320 square feet of decking with a 8 foot bridge width spanning ~40 feet of May Creek. The decking
will be slatted and minimize the shading impacts on the stream.
5.3 IMPACTS TO FISH AND WILDLIFE HABITAT AREAS
The proposed project will likely not adversely impact ESA-listed chinook salmon (O. tshawytscha) steelhead trout (O.
mykiss)and non-listed coastal cutthroat trout (O. Clarkii), coho salmon (O. Kisutch), and sockeye salmon (O. nerka). The
following impacts have been avoided and minimized as follows: permanent impacts associated with the shading of May
Creek (minimized through slatted decking), ongoing stormwater runoff into May Creek from the roadway (outfalls to
wetlands not directly into May Creek), and turbidity impacts that may occur as part of site clearing and grading activities
(avoided through the use of silt fencing during construction and minimized through dense plantings, armoring of trail
drainages, and stabilization of cleared slopes). These impacts will be discussed further in the biological assessment
submitted with the shoreline substantial development permit package completed for the project.
6 MITIGATION SITE AND ANALYSIS
6.1 MITIGATION SEQUENCING
All projects need to consider avoidance and minimization of impacts to aquatic resources under federal, state, and local
regulations. Impacts that remain unavoidable must then be compensated through mitigation. Federal regulations follow
guidance provided by the USACE for issuance of a Clean Water Act permit. The WDFW administers the hydraulic code
requirements through issuance of a hydraulic project approval. The City of Renton allows for the alteration of their
shoreline through RMC 4-3-090 Shoreline Master Program Regulations.
All of these agencies require the following sequencing to be met when impacts to regulated aquatic resources will occur.
1. Avoiding the impact through feasible and prudent alternatives.
2. Minimizing the unavoidable impacts through use of best management practices and low impact construction
methods.
3. Rectifying the impact to the resource by repairing, rehabilitating, or restoring the impact to preconstruction or
historical conditions.
4. Mitigating for the unavoidable permanent and temporary impacts to the resource.
5. Monitoring the impacts and compensation projects and taking appropriate corrective measures.
The following sections describe the measures that have been incorporated into the project design to comply with this
sequencing.
6.1.1 AVOIDANCE MEASURES
The project was designed to avoid impacts to aquatic resources through multiple measures as listed below:
— Siting the bridge footings and trail outside of the OHWM of May Creek and outside of all wetlands.
— The trail was routed to avoid wetlands as much as possible but total avoidance is not feasible based on existing
conditions and site topography. There is a need to maintain grades and widths that are ADA accessible while following
the existing topography to minimize grading needs. Wetland C was difficult to fully avoid as it spans the entire width
of the parcel from May Creek’s OHWM to the north up to the property boundary to the south. A boardwalk is proposed
to cross the wetland which is discussed below in the minimization measures in Section 6.1.2 below.
— A wall is proposed along Lake Washington Boulevard North to avoid fill into Wetland A near the trail entry point.
— The trail was designed to stay outside of the 100-year floodplain other than from the spur viewpoints, but as part of
the City of Renton’s Shoreline Master Program, it is an allowed use for public trails to have a viewpoint within the
sight and reach of May Creek.
6.1.2 MINIMIZATION MEASURES
To minimize the unavoidable impacts to Wetland C, the following measures were taken:
— The trail section through Wetland C has been designed as a slatted/grated boardwalk supported on micropiles to
minimize compaction of the soils and maintain the hydrology/interflow of water within the wetland.
— As part of the overall site restoration plan, invasive species infestations will be removed and dense riparian and
wetland vegetation will be planted throughout the site to improve the screening between the adjacent developments
that are present to the south and west.
— The trail will be built to be permeable and is not a paved surface, allowing for infiltration of precipitation (albeit less
than native soil material due to trail compaction).
6.1.3 RECTIFYING IMPACTS
The only areas that will be impacted temporarily is the areas necessary for clearing and grubbing outside of the
permanent trail corridor, the small construction laydowns near the viewpoint spurs, and the crane laydown along north
bridge footing. Post-construction these areas will have the soil ripped (to restore the site from potential compaction) and
will be replanted with native vegetation.
6.1.4 REDUCING OR ELIMINATING IMPACTS OVER TIME
To reduce the impacts to wetlands and streams over time the following measures have been implemented:
— Use of split rail fencing has been added along the viewing spurs to reduce off-trail use
— Railings will be placed along the boardwalks to reduce off -trail use
— Invasive species will be removed and native vegetation will be planted in additional areas aside from those for
compensatory mitigation areas to reduce the spread of invasives into those areas.
— The invasive species management was started in March 2023 to reduce the coverage and improve the success of the
future native plantings.
6.1.5 COMPENSATING FOR THE IMPACTS
To compensate for the unavoidable impacts both temporary and permanent, a comprehensive invasive species
management plan and native riparian vegetation planting plan is proposed to enhance the existing functions of on -site
wetlands and buffers. The mitigation proposed is in alignment with the May Creek Basin Action Plan and the WRIA 8
Salmon and Steelhead Habitat Limiting Factors report.
6.2 MITIGATION FRAMEWORK
Compensatory mitigation is required to offset the unavoidable losses resulting from project activities to wetlands, streams,
and their upland buffers as described in the previous section. These activities are regulated, authorized, and permitted by
various government entities described in the previous section. Each of these agencies follows a no net loss of values and
functions of existing aquatic resources. Their preferred alternative for mitigation does differ and is discussed below.
Federal and state agencies, in this case the USACE, Ecology, and WDFW, respectively, outline their mitigation approach as
follows (in order of preference).
1. Mitigation banks and in-lieu fee programs. These mitigation approaches are preferred because they
consolidate resources and involve more financial planning and scientific expertise, reducing the risk of failed mitigation
projects.
2. Permittee-responsible mitigation. Under this approach, the permittee performs the mitigation and is
responsible for its implementation and success through monitoring activities. Mitigation sites can be located on site or off
site within the same watershed.
Local agencies, in this case the City of Renton, outline their preferences for mitigation activities related to wetlands,
streams, and upland buffers in RMC 4-3-090 D 2.a. and 4-5-050L1.d. Their preferred mitigation approach is as follows.
No Net Loss Required. “Shoreline use and development shall be carried out in a manner that prevents or mitigates adverse impacts
to ensure no net loss of ecological functions and processes in all development and use. Permitted uses are designed and condu cted to
minimize, in so far as practical, any resultant damage to the ecology and environment (RCW 90.58.020). Shoreline ecological functions
that shall be protected include, but are not limited to, fish and wildlife habitat, food chain support, and water te mperature maintenance.
Shoreline processes that shall be protected include, but are not limited to, water flow; erosion and accretion; infiltration; groundwater
recharge and discharge; sediment delivery, transport, and storage; large woody debris recruitme nt; organic matter input; nutrient and
pathogen removal; and stream channel formation/maintenance.”
The general goals of a mitigation plan are as follows as described under RMC 4 -3-050L :
1. On-Site Mitigation: Mitigation shall be provided on site, unless on-site mitigation is not scientifically feasible due
to physical features of the property. The burden of proof shall be on the applicant to demonstrate that mitigation cannot
be provided on site.
2. Off-Site Mitigation: When mitigation cannot be provided on site, mitigation shall be provided in the immediate
vicinity of the permitted activity on property owned or controlled by the applicant, and identified as such through a
recorded document such as an easement or coven ant, provided such mitigation is beneficial to the habitat area and
associated resources.
3. In-Kind Mitigation: In-kind mitigation shall be provided except when the applicant demonstrates and the City
concurs that greater functional and habitat value can be achieved through out -of-kind mitigation.
The proposed project took into consideration the mitigation approaches described above by determining the feasibility of
each method for mitigating project impacts. There are no approved mitigation banks with a service area that covers the
project area in WRIA 8 (Cedar-Sammamish). There is an approved in-lieu fee program (ILF) within WRIA 8, the King County
Mitigation Reserves program. Both of the ILF sites within WRIA 8 are outside of the May Creek watershed. Additionally, the
ILF sites actions were to improve floodplain storage and off-channel habitat which are not functions impacted by this
project. The ILF program is likely not suitable as a mitigation instrument based on those reasons.
The remaining method for mitigating project impacts is the permittee-responsible approach. This strategy also follows the
City of Renton’s preferences as dictated by RMC 4-5-050L, that mitigation should start with on-site opportunities. The on-
site opportunities include enhancement of wetlands and buffers for the site. are currently degraded due to invasive
species and lack of native vegetation diversity. This approach would also meet key actions discussed in the WRIA 8 Salmon
and Steelhead Habitat Limiting Factors report by increasing LWD recruitment into the future by planting conifers and by
restoring the on-site riparian buffers that were degraded by historic land uses.
On-site in-kind mitigation was found to provide the best and highest value enhancement within the subbasin based on the
mitigation ratio’s required. The proposed project aligns the with the goals and recommended actions within WRIA 8 by
contributing to improving the limiting factors described in the WRIA 8 report and the May Creek Basin Action Plan. These
reports concluded that the riparian conditions and LWD recruitment in which the project site is located (May Creek
Canyon) is one of the priority action areas to plant native conifers and restore the site to minimize ongoing erosion issues.
The project will meet the recommended actions by removing and managing invasive species within the project site, plant
conifers along the banks of May Creek, control erosion of the streambanks through live staking of native willows, increase
riparian habitat diversity, and increase future LWD recruitment. These actions are a key component of why this project is
consistent with RMC 4-9-090D2.a., which requires that mitigation provide “no net loss of shoreline function”. The on-site
wetland mitigation has been maximized to the extent possible where it is still possible to have a high likelihood of success.
Section 7 describes the mitigation ratios that can be achieved with t he proposed on-site mitigation and how they match up
with the prescribed ratios in RMC 4-3-090D2.d.iv. for wetlands and RMC 4-3-050J.4.d. for wetland buffers.
The project is following an “enhancement only” approach which is typically not recommended by agencies due to the loss
of overall wetland areas not being compensated for with new “creation or re-establishment” areas. This was taken into
consideration during the development of this mitigation plan, but due to the density of existing wetlands within the site
and inability to provide more wetland area without augmenting May Creek, the enhancement approach was used. This
falls in line with the main issue with the site, which is the pervasive invasive species coverage and the mitigation proposed
for the project seeks to fix this issue and improve the existing wetland and stream functions that are limited in the May
Creek Basin.
6.3 MITIGATION SITE SELECTION
Potential mitigation areas were reviewed and selected through a watershed approach and from project team meetings
using the following criteria.
— The mitigation site should be located in the same watershed (WRIA 8) and within the same subbasin drainage as the
project site (May Creek).
— The mitigation site should benefit similar habitats and species that are impacted at the project site.
The applicant reviewed mitigation sites within the May Creek subbasin. There are opportunities for on -site in-kind
mitigation through the removal invasive species and wetland and riparian buffer restoration and enhancements. As
previously discussed, additional opportunities for off-site in-kind mitigation were not evaluated for this project.
The on-site in-kind option was chosen because improvements to the resources in the project site would be the closest and
highest value improvement to aquatic/riparian resources available. The on-site mitigation actions will compensate for
unavoidable site impacts and enhance the wetland and riparian function, future LWD recruitment within the May Creek
watershed, and result in key actions to restoring salmonid habitat shown to be limiting within the WRIA 8 basin and
specifically May Creek (Kerwin 2001, King County 2001).
6.4 MITIGATION SITE DESCRIPTION
The mitigation site is the project site; as described in Section 3.0.
6.4.1 SITE PROTECTION INSTRUMENT
The City of Renton will provide a conservation easement on the site pending internal discussions and through the City
Permitting Process.
7 MITIGATION AND HABITAT
MANAGEMENT PLAN
Project impacts could span the jurisdiction of four agencies: the USACE, Ecology, WDFW, and the City of Renton. It is
anticipated that the USACE will not require review of this project due to no cut/fill being required in the wetlands as part
of the proposal. Additionally, the USACE will not require review of this mitigation plan as the project will result in impacts
to less than 1/10th of an acre of wetlands per the Nationwide Permit general condition 23. The impacts to wetlands,
streams, and upland buffers will be offset through the restoration and enhancement of these resources within the project
site. RMC 4-3-090D2.d.iv. states that mitigation ratios for impacts to Category III wetlands are 8:1 for wetland
enhancement. Upland buffer impacts require a mitigation ratio of 1:1 for enhancements to impacted riparian buffers
under RMC4-3-050J.4.d.
The impacts to the existing wetlands, stream banks, and riparian areas will be mitigated for via enhancements to on -site
wetlands and riparian buffers. The primary objective of the mitigation plan is to have no net loss of ecological function
present at the Project Site.
The proposed mitigation includes three elements, (1) removal of the pervasive invasive species present throughout the
site in wetlands and riparian buffers, (2) management of the invasive species in the future to control their proliferation, (3)
riparian enhancements through native riparian vegetation planting, and (4) reestablishment of temporarily impacted
riparian buffers from construction. The proposed enhancement work is described in detail in Section 7.1 below.
7.1 MITIGATION DETAILS
The proposed mitigation is a comprehensive wetland and riparian enhancement project that will include removing
multiple infestations of invasive species and installing native riparian vegetation. All of the site work except for the
restoration of temporary impacts will occur before or concurrently to construction of project. Individual mitigation
components are described below and shown in Appendix A: Figure 7:
7.1.1 INVASIVE SPECIES REMOVAL
Currently, the entire site is covered in infestations of Himalayan blackberry, hybrid Japanese knotweed, English ivy,
English holly, Portuguese laurel, among others. The City of Renton has partnered with King County Healthy Lands Project
to develop a multi-year management plan to remove, treat, and manage these species through 2029. After this period the
City will take over long-term management activities. The City of Renton will have ongoing maintenance plans post -
construction to manage invasives, remove garbage, provide plantings maintenance, and monitor the site into the future.
The invasives species removal covers ~3.28 acres in total, of which ~0.48 acres will be claimed as mitigation credit for this
project. The reason for claiming this smaller credit area is that it already exceeds the required mitigation ratios,
incorporates protective buffers around the compensation site, and does not set strict monitoring requirements for the City
to adhere to. The invasives and subsequent native plantings will still receive maintenance and monitoring in the non-
compensatory mitigation areas as part of the City’s long -term management plan for the entire site.
7.1.2 NATIVE RIPARIAN VEGETATION PLANTINGS
The City will replant native vegetation over disturbed uplands and wetlands post invasive species management and during
and after the construction of the project. Native vegetation will be replaced within the footprint of the construction and
crane laydowns to the north of May Creek. The areas to be planted includes ~3.28 acres in total with ~0.48 acres being
claimed as mitigation credit. A temporary irrigation system will be placed to help the plantings survive during the first few
growing seasons post restoration.
Planting will include native bare-root trees and shrubs installed through small excavations dug by hand. All plants will be
sourced locally and be from stocks native to the Puget Sound lowlands. Plant materials will generally be in 1 -gallon
containers or live stakes, but bare-root stock may be selected depending on timing and availability. Additional information
on plants that may be selected for the mitigation are detailed but not limited to those in Table 4. The planting areas were
broken down based on changes in soil type and hydrologic regime and are shown in the landscape sheets in Appendix C.
Table 4. Mitigation and Restoration Site Plant Species
Scientific Name Common Name Size Spacing % Cover
Live Stakes
Salix sitchensis Sitka willow Live stakes 3 feet on center 50
Salix scouleriana Scouler’s willow Live stakes 3 feet on center 50
Sandy Loam Floodplain Bench
Pseudotsuga menziesii Douglas’ fir 5-gallon container 4 feet on center 40
Picea sitchensis Sitka spruce 5-gallon container 4 feet on center 20
Abies grandis Grand fir 5-gallon container 4 feet on center 20
Acer macrophyllum Big leaf maple 5-gallon container 4 feet on center 20
Symphoricarpos albus Snowberry 2-gallon container 2-4 feet on center 15
Oemeleria cerasiformis Osoberry 2-gallon container 2-4 feet on center 15
Acer circinatum Vine maple 2-gallon container 2-4 feet on center 20
Corylus cornuta Beaked hazelnut 2-gallon container 2-4 feet on center 20
Mahonia aquifolium Tall Oregon grape 2-gallon container 2-4 feet on center 15
Polystichum munitum Sword fern 1-gallon container 3 feet on center 100
Wetland Restoration
Populus balsamifera Black cottonwood 5-gallon container 3 feet on center 50
Alnus rubra Red alder 5-gallon container 3 feet on center 50
Salix sitchensis Sitka willow Live stakes 2-4 feet on center 20
Salix lasiandra Pacific willow Live stakes 2-4 feet on center 20
Cornus sericea Red-Osier Dogwood 2-gallon container 2-4 feet on center 20
Rubus spectabilis Salmonberry 2-gallon container 2-4 feet on center 20
Physocarpus capitatus Pacific ninebark 2-gallon container 2-4 feet on center 20
Wetland C Seasonally Inundated Bench
Salix lasiandra Pacific willow Live stakes 3 feet on center 25
Salix sitchensis Sitka willow Live stakes 3 feet on center 25
Fraxinus latifolia Oregon ash Live stakes/2-gallon containers 3 feet on center 20
Cornus alba/sericea Red twig dogwood Live stakes 3 feet on center 20
Oplopanax horridus Devils’ Club 2-gallon container 2-4 feet on center 10
Upland Forest
Pseudotsuga menziesii Douglas Fir 5-gallon container 8 feet on center 30
Tsuga heterophylla Western Hemlock 5-gallon container 8 feet on center 30
Picea sitchensis Sitka Spruce 5-gallon container 8 feet on center 20
Acer macrophyllum Bigleaf Maple 5-gallon container 8 feet on center 20
Scientific Name Common Name Size Spacing % Cover
Acer circinatum Vine Maple 2-gallon container 2-4 feet on center 5
Corylus cornuta Beaked Hazelnut 2-gallon container 2-4 feet on center 10
Rosa nutkana Nootka rose 2-gallon container 2-4 feet on center 15
Gaultheria shallon Salal 2-gallon container 2-4 feet on center 15
Amelanchier anifolia Serviceberry 2-gallon container 2-4 feet on center 5
Vaccinium ovatum Evergreen
huckleberry
2-gallon container 2-4 feet on center 15
Oemeleria cerasiformis Osoberry 2-gallon container 2-4 feet on center 10
Ribes sanguinieum Red flowering currant 2-gallon container 2-4 feet on center 5
Lonicera involucrata Black twinberry 2-gallon container 2-4 feet on center 5
Physocarpus capitatus Pacific ninebark 2-gallon container 2-4 feet on center 5
Mahonia aquifolium Tall Oregon grape 2-gallon container 2-4 feet on center 10
Polystichum munitum Sword fern 1-gallon container 3 feet on center 100
7.2 MITIGATION CREDITS
Table 6 in Section 7.2.2 below provides a detailed breakdown of the proposed impacts and proposed compensatory
mitigation. Appendix A: Figure 7 provides a graphic of the areas claimed as mitigation credit. Additional planting areas will
be done out of kind and will not be subject to the objectives and performance standards discussed in Section 7.3.
7.2.1 MITIGATION AREA PERIMETER BUFFER
The proposed compensatory mitigation areas implemented a 40-foot perimeter buffer for purposes of defining the credit
generating area, as recommended in Table 6C-3 inset below and is from the “Version 2 – Wetland Mitigation in Washington
State-Part 1” interagency mitigation guidance document (Ecology 2021).
All of the wetlands on-site are rated as Category III with low levels of habitat function, with the unpaved trail being a low
impact land use type. The wetlands would be required to have a 40 foot perimeter buffer from the trail, which is visualized
in Appendix A: Figure 7. Additionally, the buffer needs to consider the level of intended function from the proposed
wetland Category and habitat score. The habitat functions would likely not improve above “low” due to the lack of
connectivity from the high impact land use types that surround the May Creek greenspace and would likely remain as
“low” post project based on the Ecology Wetland Rating System.
7.2.2 PROPOSED COMPENSATORY MITIGATION
Table 6 below describes the habitat types, impacts, and mitigation credits generated. On -site actions target improvements
to stream and wetland ecological functions that are impacted by the proposed project and have been historically degraded
by development of the adjacent roadway and historic landowners, as illustrated by the following elements in Table 5
below.
Table 5. Compensatory Mitigation Analysis and Prescribed Mitigation Ratios
Habitat Type Impact Functional
Impact
Debit
Area
(sf)
Prescribed
Ratio1
Total
Debits
(sf)
Mitigation
Action
Credit
Area
(sf)
Total
Credits
minus
Debits (sf)
Mitigation Actions
Wetlands
Wetland
Permanent impact
from clearing of
vegetation and
boardwalk
placement
Shading impacts
to Wetland C 1,020 1 :1 1,020
Wetland
Enhancement –
Removal of
invasive
species and
native
plantings
+4,541 +3,521
Overall City of Renton Mitigation Ratio 4.45:1
Combined Shoreline and Wetland Buffers
Riparian Buffer
Removal of
vegetation and fill
associated with
the trail footprint
Permanent loss of
habitat function 13,200 1:1 13,200
Restoration
and
enhancement
of buffer.
16,397 +3,197
Riparian Buffer
Temporary
vegetation
clearing for
equipment access
Temporal loss of
habitat function 10,250 1 :1 10,250
Restoration
and
enhancement
of impacted
buffer.
10,250 0
Overall City of Renton Mitigation Ratio 1.14:1
1 – Ratios based on in RMC 4-3-090D2.d.iv. for wetlands and RMC 4-3-050J.4.d. for wetland buffers
As shown above, the project is able to meet the prescribed mitigation ratios in in RMC 4 -3-090D2.d.iv. for wetlands and
RMC 4-3-050J.4.d. for buffers. As discussed in Section 6.3, the on-site mitigation has been maximized to the extent practical
without creating additional impacts on site. Temporary buffer impacts will be rectified post -construction and not through
additional buffer enhancement outside of the 40-foot perimeter buffer.
7.3 MITIGATION OBJECTIVES AND PERFORMANCE CRITERIA
In order to meet the goals of the project mitigation, the following objectives and performance standards have been
identified for the project. Performance standards assume that a minimum monitoring period of 5 years is required for
plantings. At the completion of construction, an as-built map will be provided to document as-built conditions and serve
as a guide for future monitoring efforts. The proposed mitigation plan has the following objectives (OBJ) and performance
standards (PS).
1 Objective: Achieve a no net loss of function to aquatic resources by retaining a dense and diverse tree and
shrub coverage throughout the site.
a PS1.1: Tree and shrub survival.
i Year 1: 100% survival of all trees/shrubs
ii Year 2: 90% survival of all trees/shrubs
b PS1.2: Tree, shrub, and emergent coverage.
i Year 3: >30% tree/shrub/emergent cover
ii Year 4: >50% tree/shrub/emergent cover
iii Year 5: > 70% tree/shrub/groundwater cover
c PS1.3: Vegetation diversity.
i All monitoring years will have at least 5 trees, 8 shrubs and 3 native groundcover species present.
2 Objective: Remove and manage invasive species.
a PS2.1: Removal of invasive vegetation.
i Year 0: All invasive species within the mitigation areas will be cut and sprayed or removed by hand.
ii Years 1 through 5: Invasive species cover for King County Class A weeds will be 0%.
iii Years 1 through 5: Invasive species cover for King County Class B and C regulated and non -regulated weeds
will be <20% cover.
7.4 MAINTENANCE/MONITORING PLAN
The presence of tree species at the mitigation area requires a minimum monitoring period of 5 years following completion
of construction. Monitoring is per City and WDFW requirements. The USACE will likely not require any mitigation for the
project due to the project not placing fill or cutting in wetlands and subsequent impacts being less than 1/10th of an acre.
The City and WDFW may require monitoring up to 10 years as part of the permit process. The primary objective of the
monitoring period is to ensure that performance criteria identified in Section 7.3 are being met and the site is successful.
Regular maintenance of the site will be required to ensure the success of the planting and to remove non-native species to
prevent their establishment. The following elements represent typical maintenance activities that may occur during the
monitoring period.
— Any damaged/dead plants will be replaced within the first year.
— Temporary irrigation may be needed to facilitate plant establishment.
— Once the site is established the temporary irrigation will be removed in Year 2 or 3 depending on plant
establishment noted during annual monitoring periods.
— Tree tubes and other herbivory protection will need to be removed from any deceased plants or those that have
established well and no longer need the protection.
— The use of herbicides may be needed to control non-native species. Annual monitoring will determine whether these
control measures are needed and make recommendations for the use of herbicides prior to application.
— Annual monitoring reports will be prepared and submitted to the agencies to document conditions. The annual
reports will summarize the status of the site with respect to the performance criteria and maintenance activities
conducted during the prior year.
— Adaptive management strategies for the subsequent year will be included as necessary to achieve the performance
criteria.
— The site has historic beaver activity and is frequently used by ungulates as noted during the site investigations
and may require additional management strategies to ensure tree and shrub survival.
— Debris and trash cleanup will be conducted during monitoring visits.
— A partnership with King County Healthy Lands Project will be in place for the first 4 years of the mitigation site
establishment and will monitor/treat invasive species.
— Monitoring reports will be prepared in accordance with the following schedule.
— As-built Report – completed within one month of construction completion.
— Annual Monitoring Reports – shall be submitted by November 30 of each year of monitoring.
8 LONG-TERM MANAGEMENT PLAN
A long-term management plan will need to be developed for the mitigation sites. The mitigation area will be maintained
for the five-year monitoring as part of normal maintenance associated with the trail on the property.
The objective of a long-term management plan is to ensure that the mitigation site is maintained and monitored to ensure
the ecological functioning of the established mitigation site after the required period of active site management and
monitoring has concluded. The plan will identify specific tasks or performance standards that will be monitored during
the long-term monitoring period to assess different elements of the site that relate to overall site condition and ongoing
ecological function at the site. The long-term management plan and associated long-term monitoring plan for each site
will describe site-specific objectives, related tasks, and performance standards used to provide information about the
following elements.
— Qualitative assessment of overall site condition
— Photo documentation of representative site conditions
— Qualitative assessment of listed noxious weeds
— Qualitative assessment of other specified non-native invasive weeds
— Sources of trash or vandalism
If a long-term management plan is deemed necessary by the regulating bodies, a document will be created and will be
submitted to WDFW and the City of Renton for approval prior to the conclusion of the monitoring period for the
mitigation area. Additionally, it is anticipated that the City of Renton will have landscapers actively managing the site
long-term and take the necessary actions to maintain the mitigation areas.
9 FINANCIAL ASSURANCES
The applicant will be financially responsible for the mitigation site and will provide a cost estimate associated with
construction. The applicant will be financially responsible for the construction, maintenance, and monitoring of the
mitigation site. The applicant will physically construct the required mitigation, conduct routine maintenance, and
perform annual monitoring. A Performance Surety may be required if improvements cannot be completed prior to final
acceptance of the construction of the mitigation areas due to weather conditions which may negatively affect the success
of the project. The performance surety shall equal one hundred fifty (150) percent of the cost of the mitigation project,
and the required improvements shall be installed in a satis factory manner within six (6) months or less. A maintenance
surety shall be required on all mitigation projects to ensure that the improvement successfully survives the monitoring
periods set above. The amount of the maintenance surety shall be equal to fifteen (15) percent of the cost of the mitigation
and the term of the surety shall reflect the term of the monitoring program. A cash deposit shall be submitted with all
sureties prior to final acceptance of the project to cover the estimated City costs to review the yearly monitoring reports
and conduct a site inspection to ensure the performance standards are being met.
10 REFERENCES
— Brinson. 1993. A Hydrogeomorphic Classification for Wetlands. Accessed online at:
https://www.lrl.usace.army.mil/Portals/64/docs/regulatory/Mitigation/a%20hydrogeomorph%20classificaiton%20fo
r%20wetlands%20WRP-DE-4.pdf
— City of Renton. 2020. Parks, Recreation, and Natural Areas Plan. Available online at:
https://www.rentonwa.gov/cms/one.aspx?portalId=7922741&pageId=8838909
— Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of wetlands and deepwater habitats of the
United States. U.S. Fish and Wildlife Service, Washington, DC.
— [DNR] Washington State Department of Natural Resources. 2023. Forest Practices Water Typing. Available at:
https://fpamt.dnr.wa.gov/default.aspx.
— [Ecology]. 2021. Version 2 – Wetland Mitigation in Washington State Part 1: Agency Policies and Guidance (Publication
# 21-06-003). Olympia, WA: Washington State Department of Ecology.
— Hruby, Thomas. 2014. Washington State Wetland Rating System for Western Washington: 2014 Update (Publication
#14-06-029). Olympia, WA: Washington State Department of Ecology.
— Kerwin 2001. Salmon Habitat Limiting Factors in WRIA 8.
— King County. 2001. May Creek Basin Action Plan. Accessed October 2022 at:
https://your.kingcounty.gov/dnrp/library/2001/kcr726.pdf
— King County. 2016. May Creek-0440 Stream Report. Access October 2022 at:
https://green2.kingcounty.gov/streamsdata/watershedinfo.aspx?Locator=0440
— [NWIFC] Northwest Indian Fisheries Commission. Statewide Washington Integrated Fish Distribution (SWIFD) Web
Map. 2023. Accessed August16, 2023. Available at: https://geo.nwifc.org/swifd/
— [USDA] Natural Resources Conservation Service (NRCS). 2023. Web Soil Survey. Accessed February 2023 at:
https://websoilsurvey.sc.egov.usda.gov/App/WebSoilSurvey.aspx.
— USGS. 2023. Geologic map of surficial deposits in the Seattle 30' by 60' quadrangle, Washington. Accessed online at:
https://ngmdb.usgs.gov/Prodesc/proddesc_12654.htm
11 LIST OF ACRONYMS AND
ABBREVIATIONS
City City of Renton
DNR Washington State Department of Natural Resources
Ecology Washington State Department of Ecology
ESA Endangered Species Act
LWD large woody debris
NRCS Natural Resources Conservation Service
OHWM ordinary high water mark
RMC Renton Municipal Code
USACE U.S. Army Corps of Engineers
USGS United States Geological Survey
WDFW Washington Department of Fish and Wildlife
WRIA 8 Water Resource Inventory Area
APPENDIX
A FIGURES
Legend
Project Site
May CreekWatershed
City Boundaries
Newcastle
Renton
Project Name: May Creek Trail South
In: City of RentonCounty of: KingState of: WashingtonCoordinate System: NAD83 WA State Plane North (US ft)
0 1 20.5 Miles
Figure 1. Vicinity Map
¯
Lake Washington
Mercer Island
Newcastle
City of Renton
Bryn Mawr-Skyway
See Inset
Cougar MountainRegional Wildland Park
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3224059049
3224059005
2212000000
051850TR-B
3224059038
3224059050 3224059054
3224059081
32240590413224059039
051850TR-H
0518500620
0518500630
3224059108
0518500640
0518500610
051850TR-P
3224059059
Figure 2. Project Overview
Legend
King CountyTax Lots
!!Existing CityTrails
ProposedBoardwalk
ProposedBridge
Proposed TrailFootprint
FrontageImprovements
StormwaterImprovements
Project Name: May Creek Trail South
In: City of RentonCounty of: KingState of: WashingtonCoordinate System: NAD83 WA State Plane North (US ft)
0 100 20050Feet¯
Trail Spurs w/ OverlooksTrail Spurs w/ Overlooks
SP-8
WD-SP9
WC-SP6WC-SP7
WB-SP4
WA-SP3
WA-SP2
C
A
B
D
Figure 3. Wetland and Stream Overview
May Creek
Lake Washington Boulevard N
Legend
Study
Wetland DataPoints
DelineatedWetlands
Wetland Buffers
DelineatedOHWM
RegulatedShoreline
VegetationConservationArea
FEMAFloodway
Project Name: May Creek Trail South
In: City of RentonCounty of: KingState of: WashingtonCoordinate System: NAD83 WA State Plane North (US ft)
0 100 20050Feet¯
5
4
56
5
2
50
48
36
46
3840
34
44
42
32
3
0
5
8
6
0
62
6
4
66 6870
72
74 7678
8 0
8
2
84
2
8
86
88
90
9 2 9 4
96
98
1
0
0
2
6
102
104
1
0
8112
56 30
40
6 4
38
58
40
34
3 4
36
3
6
36
30
68
36
1 0 2
66
26
30
62
32
30
38
26
3
2
38
40
60
34
4
0
60
32
32
64
38
38
36
3
4
36
3
2
62
40
30
40
58
3 6
Figure 4. Site Topography Legend
Study Area
2ft SurveyedContours
Project Name: May Creek Trail South
In: City of RentonCounty of: KingState of: WashingtonCoordinate System: NAD83 WA State Plane North (US ft)
0 100 20050Feet¯
M
ay Creek
Tibbetts Creek
C
o
a
l
C
r
e
e
k
McDonald Creek
0 2 7 6 A -5
0 2 7 6 C -1
Project Site
Figure 5. Project Site Contributing Watershed Legend
Project Site
May CreekWatershed
King CountyStreams
CityBoundaries
Newcastle
Renton
Project Name: May Creek Trail South
In: City of RentonCounty of: KingState of: WashingtonCoordinate System: NAD83 WA State Plane North (US ft)
0 10.5 Miles¯
C
A
B
D
May CreekLake Washington Boulevard N
Figure 6. Project Impacts Legend
DelineatedWetlands
Wetland Buffers
DelineatedOHWM
RegulatedShoreline
AE Floodplain
Bridge StreamShading Impacts
BoardwalkShading Impacts
Wetland BufferImpacts
Permanent
Temporary
Shoreline BufferImpacts
Permanent
Temporary
Project Name: May Creek Trail South
In: City of RentonCounty of: KingState of: WashingtonCoordinate System: NAD83 WA State Plane North (US ft)
0 100 20050Feet¯
LaydownsLaydowns
Crane and Material LaydownsCrane and Material Laydowns
Site Access via existingI-405 Construction Access.No impacts are expected throughthe use of this access road.
C
A
B
D
Figure 7. Project Mitigation
and Out-of-Kind Restoration
May Creek
Lake Washington Boulevard N
Legend
Delineated
OHWM
Delineated
Wetlands
Regulated
Shoreline
Wetland Buffers
Vegetation
Conservation
Area
40' Trail Buffer
Compensatory Mitigation
Wetland
Enhancement
Wetland Buffer
Enhancement
Shoreline Buffer
Enhancement
Out-of-Kind Restoration
Wetland
Enhancement
Wetland Buffer
Enhancement
Shoreline Buffer
Enhancement
Upland
Enhancement
Project Name: May Creek Trail South
In: City of Renton
County of: King
State of: Washington
Coordinate System: NAD83 WA State Plane North (US ft)
0 100 20050
Feet¯
APPENDIX
B PHOTO LOG
May Creek Photo Log
WSP USA Page 1 Project Photo Log
May Creek South Trail Project
Photo 1: Overview of the south side of May Creek where the trail is Proposed
Photo 2: Site photo along the edge of Lake Washington Boulevard N looking north.
May Creek Photo Log
WSP USA Page 2 Project Photo Log
May Creek South Trail Project
Photo 3: Proposed bridge crossing location over May Creek looking west.
Photo 4: Looking south from May Creek at the center of the Parcel.
May Creek Photo Log
WSP USA Page 3 Project Photo Log
May Creek South Trail Project
Photo 5: Looking north towards May Creek and the proposed trail spurs.
Photo 6: Wetland A looking south from flowing outlet to May Creek during January
hydrology verification.
May Creek Photo Log
WSP USA Page 4 Project Photo Log
May Creek South Trail Project
Photo 7: Culvert that conveys flow into Wetland A from Lake Washington Boulevard
N.
Photo 8: Wetland A looking south from outlet to May Creek.
May Creek Photo Log
WSP USA Page 5 Project Photo Log
May Creek South Trail Project
Photo 9: Southwestern boundary of Wetland A looking east from Lake Washington
Boulevard N towards May Creek and the proposed trail spurs.
Photo 10: Wetland A looking north towards May Creek from southern boundary at
proposed trail location.
May Creek Photo Log
WSP USA Page 6 Project Photo Log
May Creek South Trail Project
Photo 11: Interior of wetland A looking northeast towards May Creek.
Photo 12: Wetland B looking southeast from May Creek.
May Creek Photo Log
WSP USA Page 7 Project Photo Log
May Creek South Trail Project
Photo 13: Dead Coho Salmon (Oncorhycus kisutch) observed near Wetland B.
Photo 14: Wetland C along May Creek looking east.
May Creek Photo Log
WSP USA Page 8 Project Photo Log
May Creek South Trail Project
Photo 15: Wetland C data point location (WC-DP7) with surface water present .
Photo 16: Wetland C looking southwest (Trail alignment will be along the slope on
the left of the photo).
May Creek Photo Log
WSP USA Page 9 Project Photo Log
May Creek South Trail Project
Photo 17: Wetland C looking north towards May Creek from the toe of the southern
slope.
Photo 18: Wetland C southwestern leg looking southwest.
May Creek Photo Log
WSP USA Page 10 Project Photo Log
May Creek South Trail Project
Photo 19: Wetland C groundwater seep (flowing in October during drought
conditions) near the southern edge of the property looking south.
Photo 20: Wetland C and May Creek looking southwest with bank undercutting.
(senesced vegetation is mainly hybrid knotweed)
May Creek Photo Log
WSP USA Page 11 Project Photo Log
May Creek South Trail Project
Photo 21: Wetland D looking east.
Photo 22: Wetland D water table at surface at WD-10.
May Creek Photo Log
WSP USA Page 12 Project Photo Log
May Creek South Trail Project
Photo 23: May Creek looking south from Lake Washington Boulevard Bridge.
Photo 24: Log jam in May Creek looking east from center of parcel.
May Creek Photo Log
WSP USA Page 13 Project Photo Log
May Creek South Trail Project
Photo 25: Proposed bridge crossing location looking southwest. Wetland B is to the
left of the photo and Wetland C is to the right.
Photo 26: Recent downed tree with signs of beaver activity along the base of the
tree.
APPENDIX
C SELECT
PLANTING PLANS