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South Plant Biogas and Heat Systems Improvement i ESA / 150513
Wetland Assessment May 2018
TABLE OF CONTENTS
South Plant Biogas and Heat Systems Improvements Project
Page
1.0 PROJECT AUTHORIZATION AND SCOPE OF WORK ................................................... 1
2.0 EXECUTIVE SUMMARY ..................................................................................................... 1
3.0 PROJECT OVERVIEW ....................................................................................................... 1
3.1 Project Description ..................................................................................................... 1
3.2 Site Conditions ........................................................................................................... 2
4.0 METHODS ........................................................................................................................... 3
4.1 Review of Existing Information ................................................................................... 3
4.2 On-site Investigation ................................................................................................... 3
4.2.1 Determining the Presence of Wetlands and Delineating Wetland
Boundaries ................................................................................................... 3
4.2.3 Assessing Wetland Functions ........................................................................ 4
5.0 REVIEW OF EXISTING INFORMATION ............................................................................ 4
5.1 Soils Mapping ............................................................................................................. 4
5.2 Wetland Inventories .................................................................................................... 4
6.0 RESULTS ............................................................................................................................ 5
6.1 Wetland Delineation ................................................................................................... 5
6.1.1 Wetland B ....................................................................................................... 5
6.1.1 Landscaped Amenity “wet area” (previously identified as “Wetland
A”) ................................................................................................................. 6
7.0 REGULATORY REQUIREMENTS ..................................................................................... 7
7.1 Federal Regulatory Requirements ............................................................................. 8
7.2 State Regulatory Requirements ................................................................................. 8
7.3 Local Regulatory Requirements ................................................................................. 8
8.0 PROJECT IMPACTS ......................................................................................................... 10
8.1 Project Impacts Reviewed Under RMC 4-3-050 – Critical Areas Regulations ........ 10
8.2 Project Impacts Reviewed Under RMC 4-3-090 - Shoreline Master Program
Regulations ........................................................................................................... 11
9.0 CONCLUSIONs ................................................................................................................. 11
10.0 LIMITATIONS .................................................................................................................. 11
11.0 REFERENCES ................................................................................................................ 12
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Appendices
A. Wetland Definition ........................................................................................................ A-1
B. Wetland Determination Data Sheets ............................................................................ B-1
C. Washington State Wetland Rating System and Rating Forms .................................... C-1
Figures and Photos
Figure 1. ................................................................................................................. Project Limits
Figure 2. ................................................................................................................... Vicinity Map
Figure 3. ......................................................................................................... Wetland Locations
Photos
Table of Contents
Page
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Acronyms and Abbreviations
COR City of Renton
Ecology Washington State Department of Ecology
ESA Environmental Science Associates
GPS Global Positioning System
HERB Heat and Energy Recovery Building
HSSG high pressure scrubber sludge gas
iMap Interactive Mapping
NRCS Natural Resources Conservation Service
NWI National Wetlands Inventory
PHS Priority Habitats and Species
PSE Puget Sound Energy
South Plant South Treatment Plant
USFWS U.S. Fish and Wildlife Service
WDFW Washington Department of Fish and Wildlife
WRIA Water Resource Inventory Area
WTD King County Wastewater Treatment Division
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1.0 PROJECT AUTHORIZATION AND SCOPE OF
WORK
Environmental Science Associates (ESA) was retained by Brown and Caldwell, on behalf of King County
Wastewater Treatment Division (WTD), to conduct a critical areas review for the South Treatment Plant
Biogas and Heat Systems Improvements Project. At the request of WTD, ESA conducted wetland
determinations on the project site and delineated wetland boundaries north of the project site, and
prepared this technical report. This report is organized to meet the requirements of City of Renton
Critical Areas Ordinance (Renton Municipal Code [RMC] 4-3-050). ESA’s scope of work was limited to the
identification and delineation of wetlands within the project area and within 200 feet of the project area
as required by (RMC 4-3-050(B)(1)(f)). Other types of critical areas regulated by the City, such as
streams, critical aquifer recharge areas, geologically hazardous areas, and frequently flooded areas, are
not addressed in this report.
2.0 EXECUTIVE SUMMARY
Review of the existing information did not indicate the presence of any wetlands within the project area.
One wetland (Wetland B) was identified and delineated off-site to the north in the Waterworks Gardens
during the September 2017 site visit (Figure 3). This wetland meets the regulatory definition of wetland
under RMC 4-30-050.B.1. During the field investigation on November 2016, ESA also identified a small
landscaped area with shallow surface water and wetland tolerant plants at the southwest end of a
shallow swale south of the proposed building location. This feature was initially identified as “Wetland
A” in the January 2018 Wetland Assessment Report. After further investigation, including review of
historic aerial photos and discussions with King County Wastewater Treatment Division staff regarding
past South Treatment Plant activities, this area was determined not to meet the regulatory definition of
wetland under RMC .4-30-050.B.1. This report has been updated to describe this finding.
3.0 PROJECT OVERVIEW
3.1 Project Description
King County proposes to replace South Plant’s Biogas Upgrading System (BUS) and heating system to
improve the beneficial use of digester gas at South Plant while also reliably supplying heat to meet
process and space heating demands. The King County South Plant Biogas and Heating Systems Project
includes construction of a Heat and Energy Recovery Building (HERB), a new thermal oxidizer, heating
system improvements within the existing Digester Equipment Building, and utility connections.
The approximately 11,862 square foot (SF) HERB would be located in an area allocated for future plant
expansion to meet capacity needs and regulatory requirements, where spoils from previous South Plant
construction and expansion projects at the site were placed, forming a mound. The site slopes gradually
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to the east towards the existing Solids MCC building and is maintained lawn grass over the mounded
spoils. Previously placed spoils would be removed and the existing slope would be re-graded as part of
building construction. Spoils excavated for the HERB (approximately 11,000 CY) would be moved to a
separate spoils placement location on the South Plant site, located south of the HERB and the existing
digesters within an open lawn area. Spoils would be compacted and seeded and planted to match
existing grades and vegetation type.
The project would include installation of new thermal oxidizer equipment located outside on a new
concrete pad (approximately 2,437 SF) immediately south of the existing waste gas burners. The thermal
oxidizer will combust waste gas from the BUS. See Figure 1, Project Limits.
3.2 Site Conditions
The project is located at King County WTD’s South Plant, in an industrial area of the City of Renton at
1200 Monster Road SW. The project would occupy King County Parcel Numbers 2423049097 and
2423049006, which are located in the NE Quarter, Section 24, Township 23 North, Range 9 East. The
subject parcels have been previously developed for South Plant construction and related expansion
projects. The project site consists of maintained lawn grass on sloped terrain, created by fill from
previous expansion projects.
The entire site is located within Water Resource Inventory Area (WRIA) 9, the Green - Duwamish
Watershed and the Lower Green River Subwatershed (King County, 2017a). The Green and Black rivers
join the Duwamish River to the northwest of the South Plant. The Green River comes from the
southwest of the South Plant while the Black River starts at a large wetland complex to the north and
continues to the west and joins the Green River (Figure 2). Springbrook Creek flows along the east
perimeter of the plant site before joining the Black River to the north.
The proposed site for the HERB is currently a gently sloping area of maintained lawn grass that was filled
and graded as part of previous South Plant construction and expansion projects. A shallow swale is
located to the east and to the south of the proposed building location.
The site where the new thermal oxidizer would be constructed is currently a gravel area with adjacent
grass/lawn areas immediately south of the existing waste gas burners.
Immediately north of the South Plant is Waterworks Gardens, a King County WTD-owned 8-acre public
park. The gardens feature public use trails and constructed detention ponds and wetlands established to
treat stormwater runoff from South Plant. These stormwater facilities feed into a natural wetland
system that eventually outfalls through a culvert to Springbrook Creek.
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4.0 METHODS
4.1 Review of Existing Information
ESA reviewed existing literature, maps, and other materials to identify wetlands in the study area. These
sources can only indicate the likelihood of the presence of wetlands; actual determinations must be
based on data obtained from field investigations. Key sources of information included the following:
Natural Resources Conservation Service (NRCS) soils mapping (2017).
National Wetlands Inventory (NWI) mapping (USFWS, 2017).
Washington Department of Fish and Wildlife (WDFW) Priority Habitats and Species (PHS) data
(2017).
King County Interactive Mapping (iMap) Tool (King County, 2017b).
City of Renton Critical Areas Map Series (City of Renton, 2017).
Washington Natural Heritage Program (WNHP) rare plant species and vegetation communities
mapping (WNHP, 2017).
4.2 On-site Investigation
4.2.1 Determining the Presence of Wetlands and Delineating Wetland
Boundaries
The characteristics of an area that result in its classification as “wetland” have been formally defined by
federal and state agencies, as described in Appendix A. Methods defined in Regional Supplements to the
U.S. Army Corps of Engineers 1987 Wetlands Delineation Manual were used to determine the presence
and extent of wetlands in the study area (Environmental Laboratory, 1987; Corps, 2010). The
Washington State Department of Ecology (Ecology) repealed Washington Administrative Code (WAC)
173-22-080 (the state wetland delineation manual) and replaced it with a revision of WAC 173-22-035
that states that delineations should be done according to the currently approved federal manual and
supplements (effective March 14, 2011).
The methodology outlined in the manual is based on three essential characteristics of wetlands: (1)
hydrophytic vegetation; (2) hydric soils; and (3) wetland hydrology. Field indicators of these three
characteristics must all be present in order to determine that an area is a wetland (unless problem areas
or atypical situations are encountered).
The “routine on-site determination method” was used to define the wetland boundaries at the project
site. The routine method is used for areas equal to or less than 5 acres in size, or for larger areas with
relatively homogeneous vegetative, soil, and hydrologic properties.
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Formal data plots were established, where information regarding each of the three wetland parameters
(vegetation, soils, and hydrology) was recorded. This information was used to distinguish wetlands from
non-wetlands. Wetland B, located off-site to the north, was investigated at a reconnaissance level, and
formal data plots were not established. The southern boundary of Wetland B was delineated with
sequentially numbered colored flagging imprinted with the words WETLAND DELINEATION. The
southern boundary of Wetland B is shown on Figure 33. Data plot locations were also marked with
colored flagging. Flagged points were recorded using a Global Positioning System (GPS) Trimble unit.
Wetland determination data forms are included in Appendix B.
4.2.3 Assessing Wetland Functions
Wetlands and buffers play important roles that provide valuable benefits to the environment and
society. Because detailed scientific knowledge of wetland functions is limited, evaluations of the
functions of individual wetlands are somewhat qualitative and dependent upon professional judgment.
For this project, wetland functions were assessed using Ecology’s Wetland Rating System for Western
Washington (Hruby, 2014). Although this system is designed to rate wetlands, it is based on whether a
particular wetland performs a particular function and the relative level to which the function is
performed. An assessment of wetland functions is inherent in the rating system. This system was
developed by Ecology to differentiate wetlands based on their sensitivity to disturbance, their
significance, their rarity, our ability to replace them, and the beneficial functions they provide to society.
Appendix C provides additional information about the rating system, wetland categories, and completed
rating forms for Wetland B.
5.0 REVIEW OF EXISTING INFORMATION
5.1 Soils Mapping
The NRCS maps soils within the site as Puyallup fine sandy loam. Puyallup fine sandy loam is not
considered a hydric soil type, although it has minor hydric inclusions. It is described as a well-drained
soil, typically found on terraces and floodplains. This soil forms in alluvium in areas with average annual
precipitation of 35 to 60 inches and mean annual temperature about 50 degrees Fahrenheit. Slopes are
typically 0 to 2 percent. Minor components in the soil include Briscott (hydric), Newberg (hydric),
Woodinville (hydric), Nooksack (nonhydric), and Oridia (hydric) (NRCS, 2017).
5.2 Wetland Inventories
Wetland maps prepared by the NWI do not indicate the presence of any on-site or off-site wetlands
within 200 feet of the project area. NWI mapping does show a riparian area associated with Springbrook
Creek, which is several hundred feet east of the project area (USFWS, 2017). The WDFW PHS database
does not identify any wetlands in the study area (WDFW, 2017).
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City of Renton (COR) Critical Areas Mapping (City of Renton, 2017) does not identify any wetlands on the
project site. COR mapping identifies a regulated shoreline associated with Springbrook Creek, east of the
study area. In addition, an off-site wetland is mapped north of the project area within Waterworks
Gardens.
No rare plant species or high-quality vegetation communities are mapped in the study area or vicinity
(WNHP, 2017).
6.0 RESULTS
To identify and delineate wetlands on the project site, ESA biologists conducted two field investigations.
The site was first visited by Claire Hoffman and Michael Muscari on November 22, 2016, and again by
Tobin Story and Michael Muscari on September 7, 2017. The following sections describe the results of
the two field visits.
6.1 Wetland Delineation
Review of the existing information did not indicate the presence of any wetlands within the project area.
On-site investigations also concluded that no wetlands occur within the project area. One wetland
(Wetland B) was identified and delineation off-site to the north in the Waterworks Gardens during the
September 2017 site visit (Figure 3). During the field investigation on November 2016, ESA also
identified a small area with shallow surface water and wetland tolerant plants at the southwest end of a
shallow swale south of the proposed building location.
Review of the existing information did not indicate the presence of any wetlands within the project area.
One wetland (Wetland B) was identified and delineated off-site to the north in the Waterworks Gardens
during the September 2017 site visit (Figure 3). This wetland was found to meet the regulatory definition
of wetland under RMC 4-30-050.B.1. During the field investigation on November 2016, ESA also
identified a small landscaped area with shallow surface water and wetland tolerant plants at the
southwest end of a shallow swale south of the proposed building location. This feature was previously
identified as “Wetland A” in the January 2018 Wetland Assessment Report. After further investigation,
including review of historic aerial photos and discussions with King County Wastewater Treatment
Division staff regarding past South Treatment Plant activities, this landscaped area was determined not
to meet the regulatory definition of wetland under RMC 4-30-050.B.1. Conditions in Wetland B and in
the landscaped wet area are described in detail below.
6.1.1 Wetland B
Overview. Wetland B consists of a series of depressions separated by a gravel pedestrian path, located
north of the South Plant fence. The wetland has a gentle slope to the east, toward Springbrook Creek.
Due to its offsite location, Wetland B was investigated at a reconnaissance level. Only the southern
boundary was delineated by ESA, and total wetland size was not estimated. Formal data plots were not
established for Wetland B. Confirmation of wetland presence and delineation of the wetland boundary
was based on the presence of obligate wetland vegetation, clearly visible hydrology indicators, and
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landscape topography. The wetland contains both palustrine emergent and palustrine forested
vegetation communities. The wetland appears to be an enhanced or modified wetland feature
associated with the constructed Waterworks Gardens, and only the south edge (nearest the property
boundary and proposed project) was delineated; the wetland continues further north. Flag locations
were surveyed using a handheld Trimble GPS unit. Photo 3 shows one of the seasonally ponded areas of
Wetland B that was dry during the September 2017 site visit.
Hydrology. The gravel path appears to be permeable and allows water exchange between depressions.
A portion of the wetland is a wide swale. Hydrology for the wetland appears to enter from stormwater
ponds to the west and north, and appears to exit through a 24-inch standpipe in the far eastern corner
of the wetland (Photo 4). Water exiting the wetland through the standpipe drains to Springbrook Creek.
Flow is unidirectional, as the standpipe elevation is approximately 15 feet higher than that of
Springbrook Creek. Water was not observed at the standpipe during the site visit, but clear signs of
prolonged inundation were observed in the vicinity. The wetland meets hydrology indicators B1, water
marks, and B8, sparsely vegetation concave surface.
Soils. Formal data plots were not established for Wetland B.
Vegetation. Two Cowardin vegetation classes were observed in Wetland B. Forested areas observed on
site consist of a forested overstory dominated by black cottonwood and red alder (Alnus rubra) with a
shrub understory of dogwood (Cornus alba), salmonberry (Rubus spectabilis), and Himalayan blackberry
(Rubus armeniacus). Vegetation in the palustrine emergent pockets consists primarily of cattail (Typha
latifolia), although other native emergent species may be present in small amounts.
Wetland Functions. Wetland B was rated as a depressional wetland. The wetland received an overall
score of 20 points, which corresponds to a Category II rating. The wetland received a moderate score for
water quality improvement functions (7 points); the wetland receives pollution inputs from several
sources and has significant vegetative cover necessary to filter pollutants. The water quality functions
provided by Wetland B have a high value to society, as Springbrook Creek, the Black River, and the
Green River are all on the Washington State 303d list for water quality. Wetland B received a high score
for hydrologic functions (8 points) due to a highly constricted outlet and significant depth of flooding
during wet periods. The hydrologic functions provided by Wetland B have a high value due to providing
flood attenuation for frequently flooded downstream reaches.
Wetland B received a moderate score (5 points) for habitat functions. The wetland has a diverse number
of habitats and hydroperiods, but lacks the landscape potential to support habitat since most of the
surrounding landscape is highly developed. The wetland buffer is generally disturbed.
6.1.1 Landscaped Amenity “wet area” (previously identified as
“Wetland A”)
The landscaped area that extends along the east and south sides of the HERB project site was
investigated with four data plots; locations for DP1, DP2, DP3, and DP4 are shown on Figure 3. At one of
the data plots (DP3) conditions met all three wetland parameters. Data sheets are included in Appendix
B. The wet area was estimated to be less than 2,000 square feet in size. Shallow surface water on highly
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compacted soil was observed in November 2016 (Photo 6). Photo 7 shows the southwest end of the
constructed swale that appears to bring surface flows to this wet area.
Based on the young age of the trees and shrubs, and the constructed nature of the landscaped area, it
appears as though this area is only recently developing wetland characteristics due to past development
activities. The landscape in the project area has been reworked many times over at least the last 30
years and conditions are considerably different than the natural state. King County Wastewater
Treatment Division staff have indicated that this area was constructed as a landscape amenity following
a major project to upgrade South Treatment Plant’s secondary treatment. Review of aerial imagery
(Google Earth) shows that in 1990 this entire area was an open field (Photo 8). In the mid-1990s, this
area was used for heavy equipment staging during the plant’s secondary treatment upgrade (Photo 9).
An aerial image from 2002 shows relatively new landscaping including grading, construction of a
pathway, and planting of trees (Photo 10). Relatively current conditions are show in a 2017 aerial image
(Photo 11). This series of aerial photos shows that the landscape was altered in the past, including
stockpiling of spoils from other projects in the center of the field, use as staging area for construction,
and landscaping including construction of a walking path and planting of trees and shrubs. The shallow
swale flows south and then west along the edge of the field and terminates near the area we observed
shallow surface ponding in November.
RMC 4-30-050.B.1 exempts some artificially created wetlands from regulation.
Regulated wetlands do not include those artificial wetlands intentionally created from
nonwetland sites, including, but not limited to, irrigation and drainage ditches, grass-lined
swales, canals, detention facilities, wastewater treatment facilities, farm ponds, and landscape
amenities, or those wetlands created after July 1, 1990, that were unintentionally created as a
result of the construction of a road, street, or highway.
It is our conclusion that the area near DP3 containing wetland conditions is not a regulated wetland by
City of Renton Municipal Code 4-30-050.B.1.
The area around DP3 was created as a landscape amenity for the wastewater treatment facility in a
location that is poorly drained due to previous soil compaction. Plants tolerant to poorly drained
conditions were installed during landscaping. The landscape amenity appears to have been created in an
area that was not previously wetland, based on our site observations and the aerial imagery discussed
above. Water from this area does not flow out into the roadway to the west. Water ponds on the
compacted soil and remains in the area until evaporated or transpired by plants, causing wetland
conditions to develop in this artificially created feature. This wet area is isolated from any downslope
wetlands and streams.
7.0 REGULATORY REQUIREMENTS
This section provides an overview of regulations that may apply to the South Plant Biogas Project.
Before approving a project that will impact wetlands, agencies require project applicants to document
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that impacts have been avoided and minimized in accordance with the following preferred sequence for
mitigation (e.g., WAC 197-11-768):
a) Avoiding the impact altogether by not taking a certain action or parts of actions;
b) Minimizing impacts by limiting the degree or magnitude of the action;
c) Rectifying the impact by repairing, rehabilitating, or restoring the affected environment;
d) Reducing or eliminating the impact over time by preservation and maintenance operations
during the life of the action; or
e) Compensating for the impact by replacing, enhancing, or providing substitute resources or
environments.
Applicants for permits to alter wetlands or their buffers must demonstrate that the above sequence has
been followed to the greatest extent possible. Wetland impacts that cannot be avoided through the first
two steps of the above sequence will require compensatory mitigation.
7.1 Federal Regulatory Requirements
The U.S. Army Corps of Engineers regulates discharges of dredged or fill materials into waters of the
United States, including wetlands and streams, under Section 404 of the Clean Water Act. The South
Plant Biogas Project does not propose fill or other impacts to wetlands or waters of the U.S. As such, a
Section 404 permit is not anticipated.
7.2 State Regulatory Requirements
State permitting for activities in wetlands is administered by Ecology. The state certification process
under Section 401 of the federal Clean Water Act is usually triggered through a Section 404 permit
application. The South Plant Biogas Project does not propose fill or other impacts to wetlands or waters
of the U.S., and a Section 404 permit is not anticipated. As such, a Section 401 permit is not anticipated.
7.3 Local Regulatory Requirements
The City of Renton regulates critical areas and associated buffers through RMC 4-3-050, which requires
that wetlands be rated using the Washington State Wetland Rating System for Western Washington
2014 update (RMC 4-3-050(G)(9)(c)). Using the 2014 Wetland Rating System, Wetland is classified as a
Category II wetland with moderate habitat function (5 points). Wetland B requires a standard buffer
width of 150 feet (RMC 4-30-050(G)(2)).
In addition, RMC 4-3-050(G)(9)(d)(iv) requires applicants to document that increased wetland buffers
are not warranted. Increased buffer widths may be required if:
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a) The wetland is used by species listed by the federal or the state government as threatened,
endangered, and sensitive species and state-listed priority species, essential habitat for those
species or has unusual nesting or resting sites such as heron rookeries or raptor nesting trees or
evidence thereof; or
b) The buffer or adjacent uplands have a slope greater than 15 percent or is susceptible to erosion
and standard erosion control measures will not effectively prevent adverse wetland impacts.
c) The area is very fragile, or when a larger buffer is necessary to protect wetland functions and
values.
To the extent of our knowledge, Wetland B is not utilized by federal or state-listed species, nor does it
provide essential habitat for those species. Although the far eastern portion of the wetland is relatively
close to Springbrook Creek, it is physically disconnected from the creek, separated by approximately 15
feet vertically and 150 feet horizontally. The elevation difference precludes water from Springbrook
Creek entering the wetland, and thus there is no apparent connection for listed salmonids to access
habitat in Wetland B. A portion of the Wetland B buffer is located on slopes greater than 15 percent;
however, these slopes are heavily vegetated, and no clearing, grading, or other impact is proposed on
these slopes. Neither the wetland nor its buffer are especially fragile, and functions and values provided
by this wetland are adequately protected by the standard width buffer.
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8.0 PROJECT IMPACTS
8.1 Project Impacts Reviewed Under RMC 4-3-050 – Critical
Areas Regulations
As found in RMC 4-3-050(B)(1)(g), the City of Renton may not regulate certain upland sites separated
from critical areas, based on the following conditions: sites are separated from critical areas by pre-
existing, intervening, and lawfully created structures, roads, or other substantial existing improvements,
which must:
a) Separate the upland property from the critical area due to their height or width; and
b) Substantially prevent or impair delivery of most functions from the subject upland property to
the critical area.
In the case of this project, the north plant road separates Wetland B from all project areas. The north
plant road is approximately 20 feet wide, constructed of impervious material, with raised curbs
approximately 6 inches in height (Photo 5). In addition, an approximately 8-foot wide paved path is
located adjacent to road. The substantive width of the existing, impervious road, combined with the
width of an existing paved trail and presence of vertical curb will serve as an effective barrier. These
completely restrict and redirect the flow of ground and surface water, and otherwise impair delivery of
functions from upland sites located within the project area to Wetland B. Stormwater from the plant
road is collected and directed to the Waterworks Gardens located north of the plant. Current buffer
functions performed by the buffer area north of the existing plant road will not be altered by proposed
project actions.
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8.2 Project Impacts Reviewed Under RMC 4-3-090 -
Shoreline Master Program Regulations
Wetland B is physically disconnected from Springbrook Creek and is not within the 100-year floodplain
of Springbrook Creek, and, therefore, would not be considered an associated shoreline of Springbrook
Creek. However, if the City of Renton determines that the wetland is regulated as a shoreline, RMC 4-3-
090(D)(2)(d)(iv)(a) states that “Buffers shall not include areas that are functionally and effectively
disconnected from the wetland by a permanent road or other substantially developed surface of
sufficient width and with use characteristics such that buffer functions are not provided and that cannot
be feasibly removed, relocated, or restored to provide buffer functions.” As described above, the buffer
of Wetland B is separated by the intervening plant road and trail. The delivery of buffer functions from
the subject upland site to Wetland B is prevented by these intervening improvements. As a result,
shoreline jurisdiction would end at the north edge of the plant road and would not extend onto the
project site.
9.0 CONCLUSIONS
No wetlands were identified within the project area and one wetland was identified and delineated
within 200 feet of the project area. Wetland B is north of the project site and its regulated buffer does
not overlap the project site. Wetland B is a Category II wetland that requires a buffer of 150 feet for
high-impact land uses. The proposed project has been designed to avoid impacts to wetland areas and
associated buffers. No impacts are proposed to wetlands or wetland buffers as a result of this project.
No fill will be placed in wetlands or other waters of the U.S.
10.0 LIMITATIONS
Within the limitations of schedule, budget, scope-of-work, and seasonal constraints, we warrant that
this study was conducted in accordance with generally accepted environmental science practices,
including the technical guidelines and criteria in effect at the time this study was performed, as outlined
in the Methods section. The results and conclusions of this report represent the authors’ best
professional judgment, based on information provided by the project proponent in addition to that
obtained during the course of this study. No other warranty, expressed or implied, is made.
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11.0 REFERENCES
City of Renton. 2017. Online Mapping Portal. Available:
http://rp.rentonwa.gov/Html5Public/Index.html?viewer=CORMaps.
Corps (U.S. Army Corps of Engineers). 2005. Regulatory Guidance Letter No. 05-05: Ordinary High Water
Mark Identification. December 7, 2005.
Corps (U.S. Army Corps of Engineers). 2010. Regional Supplement to the Corps of Engineers Wetland
Delineation Manual: Western Mountains, Valleys, and Coast Region. Version 2. Wetlands
Regulatory Assistance Program. May 2010. ERDC/EL TR-10-3. Available:
https://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb1046494.pdf.
Corps (U.S. Army Corps of Engineers). 2014. 2014 NWPL Home v3.2 - Home Page, National Wetland
Plant List. Available: http://rsgisias.crrel.usace.army.mil/NWPL/.Environmental Laboratory. 1987.
Corps of Engineers Wetlands Delineation Manual. Technical Report Y-87-1. U.S. Army Engineer
Waterways Experiment Station, Vicksburg, Mississippi.
Hruby, T. 2014. Washington State Wetland Rating System for Western Washington – Revised. October
2014. Ecology publication number 14-06-029. Olympia, WA.
King County. 2017a. Map of WRIA 9. Green/Duwamish and Central Puget Sound Watershed. Available:
http://www.govlink.org/watersheds/9/. Accessed November 2017.
King County. 2017b. King County iMap, Interactive Mapping Tool. Available at:
http://www.kingcounty.gov/services/gis/Maps/imap.aspx. Accessed November 2017.Munsell Color.
2000. Munsell Soil Color Charts. GretagMacbeth, New Windsor, New York.
NRCS (Natural Resources Conservation Service). 1995. Hydric Soils List for Washington. Revised
December 15, 1995.NRCS (Natural Resources Conservation Service). 2010. Field Indicators of
Hydric Soils in the United States - A Guide for Identifying and Delineating Hydric Soils. Version 7.0,
2010. ftp://ftp-fc.sc.egov.usda.gov/NSSC/Hydric_Soils/FieldIndicators_v7.pdf.
NCRS (Natural Resources Conservation Service). 2017. Online soils mapping. Available:
http://websoilsurvey.sc.egov.usda.gov/App/HomePage.htm.
USFWS (U.S. Fish and Wildlife Service). 2017. National Wetlands Inventory – online wetlands mapping.
Available: http://www.fws.gov/wetlands/Data/Mapper.html.
Vepraskas, M.J. 1999. Redoximorphic Features for Identifying Aquic Conditions. Technical Bulletin 301.
North Carolina Agricultural Research Service, North Carolina State University, Raleigh, North
Carolina.
WDFW (Washington Department of Fish and Wildlife). 2017. Priority habitats and species online
mapping. Available: http://wdfw.wa.gov/mapping/phs/.
WNHP (Washington Natural Heritage Program). 2017. Rare plant species and vegetation communities
GIS mapping.
South Plant Biogas and Heat Systems Improvement 13 ESA / 150513
Wetland Assessment May 2018
FIGURES AND PHOTOGRAPHS
EXISTING SPOILS TO BE
REMOVED
FIGURE 1 - PROJECT LIMITS
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^_
King County SouthTreatment Plant
Project Site
B la c k R iv e r
DuwamishRiver
GreenRiverWaterworks Gardens
Spr
i
ngbr
ookCr
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k
61stAveSSW 27th St
MartinLutherKing Jun i o r W a y S
S 143rd St
Baker Blvd
Tukwila Parkway
RentonAveS
Andover Park WS 133rd St
Andover Park ESWSunset Blvd
MonsterRdSWS 132nd St
Southcenter Blvd
SW 7th St
Strander Blvd
S Langston Rd
SW 16th St
LindAveSWI
n
t
e
r
u
r
b
a
n
Av
e
SSW Grady
Way
OakesdaleAveSW6
8
t
h
Av
e
S
W Valley RdPath: U:\GIS\GIS\Projects\15xxxx\D150513_SouthPlantBioGas\03_MXDs_Projects\Fig01_Vicinity.mxd, anakae 1/11/2017SOURCE: City of Renton 2015; OSM 2015; ESA 2017
0 2,000
Feet
South Plant Biogas and Heat Systems Improvements Figure 2
Vicinity Map
N
Project Site
Wetland B
Heating and Energy Recovery Building
Thermal Oxidizer $$$$150-ft. Wetland Buffer
buffer ends at r
o
a
d
e
d
g
e
$$Plant Road
12812
5
1
2
6 130129126128
127
DP-2
DP-1
DP-4
DP-3
Path: U:\GIS\GIS\Projects\15xxxx\D150513_SouthPlantBioGas\03_MXDs_Projects\Fig3_Wetlands_PDF.mxd, cstruthers 4/25/2018SOURCE: NAIP 2015 South Treatment Plant Biogas and Heat Systems Improvements Project
Figure 3Wetland Delineation
N 0 200
Feet
Wetland Survey Points
Wetland
Grading Contours
Project Area
150-ft. Wetland Buffer
Study Area
Photo 1. Proposed Thermal Oxidizer Site (November 2016).
Photo 2. Proposed HERB construction site to the right.
Northeast end of constructed swale in foreground (November 2016).
Photo 3. One of the seasonally ponded areas of Wetland B, off-site to the north
(September 2017).
Photo 4. Outlet to Wetland B (September 2017).
Photo 5. Looking west along Plant Road just north of the proposed HERB site. Wetland B
is off-site to the right of photo (November 2016).
Photo 6. Shallow ponding on compacted soil near DP3 (November 2016).
Photo 7. Looking east at southwest end of constructed swale near DP4 (November 2016).
Photo 8. Aerial image from 1990 showing proposed project area was open field.
Photo 9. Aerial image from mid-1990 during South Treatment Plant’s upgrade to
secondary treatment.
Photo 10. Aerial image from 2002 showing new landscaping.
Photo 11. Aerial image from 2017 showing approximate existing site conditions.
South Plant Biogas and Heat Systems Improvement A-1 ESA / 150513
Wetland Assessment May 2018
APPENDIX A: WETLAND DEFINITION AND METHODOLOGY
South Plant Biogas & Heat Systems Improvement A-3 ESA / 150513
Wetland Assessment May 2018
Wetland Definition
Wetlands are formally defined by the U.S. Army Corps of Engineers (Corps) (Federal Register 1982), the
Environmental Protection Agency (EPA) (Federal Register 1988), the Washington Shoreline Management
Act (SMA) of 1971 and the Washington State Growth Management Act (GMA) as follows:
… 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. Wetlands generally include swamps, marshes,
bogs, and similar areas (Federal Register, 1982, 1986).
In addition, the SMA and the GMA definitions add:
Wetlands do not include those artificial wetlands intentionally created from
non-wetland site, including, but not limited to, irrigation and drainage ditches,
grass-lined swales, canals, detention facilities, wastewater treatment facilities,
farm ponds, and landscape amenities, or those wetlands created after July 1,
1990 that were unintentionally created as a result of the construction of a
road, street, or highway. Wetlands may include those artificially created
wetlands intentionally created from non-wetland areas to mitigate the
conversion of wetlands.
Methods defined in the Western Mountains, Valleys, and Coast Regional Supplement (Corps, 2010) to
the U.S. Army Corps of Engineers 1987 Wetlands Delineation Manual (Manual) were used to determine
the presence and extent of wetlands on the subject property and within 200 feet. These methods are
consistent with state requirements in WAC 173-22-035.
The methodology outlined in the manuals is based upon three essential characteristics of wetlands: (1)
hydrophytic vegetation; (2) hydric soils; and (3) wetland hydrology. Field indicators of these three
characteristics must all be present in order to determine that an area is a wetland (unless problem areas
or atypical situations are encountered). These characteristics are discussed below.
Vegetation
Plants must be specially adapted for life under saturated or anaerobic conditions to grow in wetlands.
The Corps of Engineers has determined the estimated probability of each plant species’ occurrence in
wetlands and has accordingly assigned a “wetland indicator status” (WIS) to each species (Corps, 2016).
Plants are categorized as obligate (OBL), facultative wetland (FACW), facultative (FAC), facultative
upland (FACU), upland (UPL), not listed (NL), or no indicator status (NI). Definitions for each indicator
status are listed below. Species with an indicator status of OBL, FACW, or FAC are considered adapted
for life in saturated or anaerobic soil conditions. Such species are referred to as “hydrophytic”
vegetation.
Key to Wetland Indicator Status codes:
OBL Obligate: species that almost always occur wetlands under natural conditions (est. probability
>99%).
South Plant Biogas & Heat Systems Improvement A-4 ESA / 150513
Wetland Assessment May 2018
FACW Facultative wetland: species that usually occur in wetlands (est. probability 67 to 99%), but are
occasionally found in non-wetlands.
FAC Facultative: Species that are equally likely to occur in wetlands or non-wetlands (est. probability
34 to 66%).
FACU Facultative upland: species that usually occur in non-wetlands (est. probability 67 to 99%), but
are occasionally found in wetlands.
UPL Upland: species that almost always occur in non-wetlands under normal conditions (est.
probability >99%).
NL Not listed: species that are not listed by USFWS (1988, 1993) and are presumed to be upland
species.
NI No indicator: species for which insufficient information is available to determine status, or which
were not evaluated by USFWS.
Areas of relatively homogeneous vegetative composition can be characterized by “dominant” species.
The indicator status of the dominant species within each vegetative stratum is used to determine if the
plant community may be characterized as hydrophytic. The vegetation of an area is considered to be
hydrophytic if more than 50% of the dominant species have an indicator status of OBL, FACW, or FAC.
The Regional Supplements provide additional tests for evaluating the presence of hydrophytic
vegetation communities including the prevalence index, morphological adaptations, and wetland non-
vascular plants. The Supplements also address difficult situations where hydrophytic vegetation
indicators are not present but hydric soils and wetland hydrology are observed.
Soils
Hydric soils are indicative of wetlands. Hydric soils are defined as soils that are saturated, flooded, or
ponded long enough during the growing season to develop anaerobic conditions in the upper part of the
soil profile (Federal Register, 1994). The Natural Resources Conservation Service (NRCS), in cooperation
with the National Technical Committee for Hydric Soils, has compiled lists of hydric soils (NRCS, 1995).
These lists identify soil series mapped by the NRCS that meet hydric soil criteria. It is common, however,
for a map unit of non-wetland (non-hydric) soil to have inclusions of hydric soil, and vice versa.
Therefore, field examination of soil conditions is important to determine if hydric soil conditions exist.
The NRCS has developed a guide for identifying field indicators of hydric soils (NRCS, 2010). This list of
hydric soil indicators is considered to be dynamic; revisions are anticipated to occur on a regular basis as
a result of ongoing studies of hydric soils. In general, anaerobic conditions create certain characteristics
in hydric soils, collectively known as “redoximorphic features,” that can be observed in the field
(Vepraskas, 1999). Redoximorphic features include high organic content, accumulation of sulfidic
material (rotten egg odor), greenish- or bluish-gray color (gley formation), spots or blotches of different
color interspersed with the dominant or matrix color (mottling), and dark soil colors (low soil chroma)
(NRCS, 2010; Vepraskas, 1999). Soil colors are described both by common color name (for example,
“dark brown”) and by a numerical description of their hue, value, and chroma (for example, 10YR 2/2) as
South Plant Biogas & Heat Systems Improvement A-5 ESA / 150513
Wetland Assessment May 2018
identified on a Munsell soil color chart (Munsell Color, 2000). Soil color is determined from a moist soil
sample.
The Regional Supplements provide methods for difficult situations where hydric soil indicators are not
observed, but indicators of hydrophytic vegetation and wetland hydrology are present.
Hydrology
Water must be present in order for wetlands to exist; however, it need not be present throughout the
entire year. Wetland hydrology is considered to be present when there is permanent or periodic
inundation or soil saturation at or near the soil surface for more than 14 consecutive days during the
growing season at a minimum frequency of 5 years in 10 (Corps, 2010).
Indicators of wetland hydrology include observation of ponding or soil saturation, water marks, drift
lines, drainage patterns, sediment deposits, oxidized rhizospheres, water-stained leaves, and local soil
survey data. Where positive indicators of wetland hydrology are observed, it is assumed that wetland
hydrology occurs for a sufficient period of the growing season to meet the wetland criteria, as described
by Corps (2010). The Regional Supplements provide methods for evaluating situations in wetlands that
periodically lack indicators of wetland hydrology but where hydric soils and hydrophytic vegetation are
present.
South Plant Biogas Heat Systems Improvement B-1 ESA / 150513
Wetland Assessment May 2018
APPENDIX B: WETLAND DETERMINATION DATA SHEETS
South Plant Biogas Heat Systems Improvement C-1 ESA / 150513
Wetland Assessment May 2018
APPENDIX C: WASHINGTON STATE WETLAND RATING
SYSTEM AND RATING FORMS
South Plant Biogas Heat Systems Improvement C-1 ESA / 150513
Wetland Assessment May 2018
Washington State Wetland Rating System
The observed wetlands were rated using the Washington State Department of Ecology’s Wetland Rating
System for Western Washington (Hruby, 2014). This system was developed by Ecology to differentiate
wetlands based on their sensitivity to disturbance, their significance, their rarity, our ability to replace
them, and the beneficial functions they provide to society. Wetlands are categorized using the Ecology
rating system according to the following criteria:
Category I wetlands represent a unique or rare wetland type; or are more sensitive to disturbance; or
are relatively undisturbed and contain ecological attributes that are impossible to replace within a
human lifetime.
Category II wetlands are difficult, though not impossible, to replace, and provide high levels of some
functions.
Category III wetlands have a moderate level of function. They have been disturbed in some ways, and
are often less diverse or more isolated from other natural resources in the landscape than Category II
wetlands.
Category IV wetlands have the lowest levels of functions and are often heavily disturbed.
Wetland name or number Wetland B
Name of wetland (or ID #):Date of site visit:9/7/2017
Rated by Trained by Ecology? Yes No Date of training Mar-15
HGM Class used for rating Wetland has multiple HGM classes? Yes No
NOTE: Form is not complete with out the figures requested (figures can be combined ).
Source of base aerial photo/map
OVERALL WETLAND CATEGORY II (based on functions or special characteristics )
1. Category of wetland based on FUNCTIONS
Category I - Total score = 23 - 27 Score for each
X Category II - Total score = 20 - 22 function based
Category III - Total score = 16 - 19 on three
Category IV - Total score = 9 - 15 ratings
(order of ratings
is not
important )
M M 9 = H, H, H
H L 8 = H, H, M
H M Total 7 = H, H, L
7 = H, M, M
6 = H, M, L
6 = M, M, M
5 = H, L, L
5 = M, M, L
4 = M, L, L
3 = L, L, L
2. Category based on SPECIAL CHARACTERISTICS of wetland
None of the above
Coastal Lagoon
Interdunal
Value
Score Based on
Ratings 7 8 5 20
H
CHARACTERISTIC Category
Estuarine
Wetland of High Conservation Value
Bog
Mature Forest
Old Growth Forest
Depressional & Flats
RATING SUMMARY – Western Washington
List appropriate rating (H, M, L)
HydrologicImproving
Water Quality
MSite Potential
Landscape Potential
Habitat
M
FUNCTION
Biogas Wetland B
T. Story
Wetland Rating System for Western WA: 2014 Update
Rating Form - Effective January 1, 2015 1 WSDOT Adapted Form - March 2, 2015
Wetland name or number Wetland B
Maps and Figures required to answer questions correctly for
Western Washington
Depressional Wetlands
Map of: Figure #
Cowardin plant classes
Hydroperiods
Location of outlet (can be added to map of hydroperiods )
Boundary of area within 150 ft of the wetland (can be added to another figure )
Map of the contributing basin
1 km Polygon: Area that extends 1 km from entire wetland edge - including
polygons for accessible habitat and undisturbed habitat
Screen capture of map of 303(d) listed waters in basin (from Ecology website)
Screen capture of list of TMDLs for WRIA in which unit is found (from web)
Riverine Wetlands
Map of: Figure #
Cowardin plant classes
Hydroperiods
Ponded depressions
Boundary of area within 150 ft of the wetland (can be added to another figure )
Plant cover of trees, shrubs, and herbaceous plants
Width of unit vs. width of stream (can be added to another figure )
Map of the contributing basin
1 km Polygon: Area that extends 1 km from entire wetland edge - including
polygons for accessible habitat and undisturbed habitat
Screen capture of map of 303(d) listed waters in basin (from Ecology website)
Screen capture of list of TMDLs for WRIA in which unit is found (from web)
Lake Fringe Wetlands
Map of: Figure #
Cowardin plant classes
Plant cover of trees, shrubs, and herbaceous plants
Boundary of area within 150 ft of the wetland (can be added to another figure )
1 km Polygon: Area that extends 1 km from entire wetland edge - including
polygons for accessible habitat and undisturbed habitat
Screen capture of map of 303(d) listed waters in basin (from Ecology website)
Screen capture of list of TMDLs for WRIA in which unit is found (from web)
Slope Wetlands
Map of: Figure #
Cowardin plant classes
Hydroperiods
Plant cover of dense trees, shrubs, and herbaceous plants
Plant cover of dense, rigid trees, shrubs, and herbaceous plants
(can be added to another figure )
Boundary of area within 150 ft of the wetland (can be added to another figure )
1 km Polygon: Area that extends 1 km from entire wetland edge - including
polygons for accessible habitat and undisturbed habitat
Screen capture of map of 303(d) listed waters in basin (from Ecology website)
Screen capture of list of TMDLs for WRIA in which unit is found (from web)
To answer questions:
D 1.3, H 1.1, H 1.4
D 1.4, H 1.2
D 1.1, D 4.1
D 2.2, D 5.2
D 4.3, D 5.3
H 2.1, H 2.2, H 2.3
D 3.1, D 3.2
D 3.3
To answer questions:
H 1.1, H 1.4
H 1.2
R 1.1
R 2.4
R 1.2, R 4.2
R 4.1
R 2.2, R 2.3, R 5.2
H 2.1, H 2.2, H 2.3
L 1.2
L 2.2
L 3.1, L 3.2
L 3.3
H 2.1, H 2.2, H 2.3
R 3.1
R 3.2, R 3.3
To answer questions:
L 1.1, L 4.1, H 1.1, H 1.4
S 3.1, S 3.2
S 3.3
S 4.1
S 2.1, S 5.1
To answer questions:
H 1.1, H 1.4
H 1.2
S 1.3
H 2.1, H 2.2, H 2.3
Wetland Rating System for Western WA: 2014 Update
Rating Form - Effective January 1, 2015 2 WSDOT Adapted Form - March 2, 2015
Wetland name or number Wetland B
For questions 1 -7, the criteria described must apply to the entire unit being rated.
1. Are the water levels in the entire unit usually controlled by tides except during floods?
NO - go to 2 YES - the wetland class is Tidal Fringe - go to 1.1
1.1 Is the salinity of the water during periods of annual low flow below 0.5 ppt (parts per thousand)?
NO - Saltwater Tidal Fringe (Estuarine)YES - Freshwater Tidal Fringe
NO - go to 3 YES - The wetland class is Flats
If your wetland can be classified as a Flats wetland, use the form for Depressional wetlands.
3. Does the entire wetland unit meet all of the following criteria?
NO - go to 4 YES - The wetland class is Lake Fringe (Lacustrine Fringe)
4. Does the entire wetland unit meet all of the following criteria?
The wetland is on a slope (slope can be very gradual ),
The water leaves the wetland without being impounded.
NO - go to 5 YES - The wetland class is Slope
5. Does the entire wetland unit meet all of the following criteria?
The overbank flooding occurs at least once every 2 years.
NO - go to 6 YES - The wetland class is Riverine
NOTE: The Riverine unit can contain depressions that are filled with water when the river is not flooding.
If hydrologic criteria listed in each question do not apply to the entire unit being rated, you probably have a unit
with multiple HGM classes. In this case, identify which hydrologic criteria in questions 1 - 7 apply, and go to
Question 8.
At least 30% of the open water area is deeper than 6.6 ft (2 m).
HGM Classification of Wetland in Western Washington
If your wetland can be classified as a Freshwater Tidal Fringe use the forms for Riverine wetlands.
If it is Saltwater Tidal Fringe it is an Estuarine wetland and is not scored. This method cannot be
used to score functions for estuarine wetlands.
The vegetated part of the wetland is on the shores of a body of permanent open water (without any
plants on the surface at any time of the year) at least 20 ac (8 ha) in size;
The water flows through the wetland in one direction (unidirectional) and usually comes from seeps.
It may flow subsurface, as sheetflow, or in a swale without distinct banks.
NOTE: Surface water does not pond in these type of wetlands except occasionally in very small and shallow
depressions or behind hummocks (depressions are usually <3 ft diameter and less than 1 ft deep).
The unit is in a valley, or stream channel, where it gets inundated by overbank flooding
from that stream or river,
2. The entire wetland unit is flat and precipitation is the only source (>90%) of water to it.
Groundwater and surface water runoff are NOT sources of water to the unit.
Wetland Rating System for Western WA: 2014 Update
Rating Form - Effective January 1, 2015 3 WSDOT Adapted Form - March 2, 2015
Wetland name or number Wetland B
NO - go to 7 YES - The wetland class is Depressional
NO - go to 8 YES - The wetland class is Depressional
NOTES and FIELD OBSERVATIONS:
7. Is the entire wetland unit located in a very flat area with no obvious depression and no overbank flooding?
The unit does not pond surface water more than a few inches. The unit seems to be maintained by high
groundwater in the area. The wetland may be ditched, but has no obvious natural outlet.
8. Your wetland unit seems to be difficult to classify and probably contains several different HGM classes. For
example, seeps at the base of a slope may grade into a riverine floodplain, or a small stream within a
Depressional wetland has a zone of flooding along its sides. GO BACK AND IDENTIFY WHICH OF THE
HYDROLOGIC REGIMES DESCRIBED IN QUESTIONS 1-7 APPLY TO DIFFERENT AREAS IN THE UNIT
(make a rough sketch to help you decide). Use the following table to identify the appropriate class to use for
the rating system if you have several HGM classes present within the wetland unit being scored.
6. Is the entire wetland unit in a topographic depression in which water ponds, or is saturated to the surface, at
some time during the year? This means that any outlet, if present, is higher than the interior of the wetland.
Riverine
Treat as
ESTUARINE
Slope + Lake Fringe
Depressional + Riverine along stream
within boundary of depression
Depressional + Lake Fringe
Riverine + Lake Fringe
NOTE: Use this table only if the class that is recommended in the second column represents 10% or more of
the total area of the wetland unit being rated. If the area of the HGM class listed in column 2 is less than 10%
of the unit; classify the wetland using the class that represents more than 90% of the total area.
HGM classes within the wetland unit
being rated
Slope + Riverine
Slope + Depressional
Depressional
Depressional
If you are still unable to determine which of the above criteria apply to your wetland, or if you have more than
2 HGM classes within a wetland boundary, classify the wetland as Depressional for the rating.
Salt Water Tidal Fringe and any other
class of freshwater wetland
HGM class to
use in rating
Riverine
Depressional
Lake Fringe
Wetland Rating System for Western WA: 2014 Update
Rating Form - Effective January 1, 2015 4 WSDOT Adapted Form - March 2, 2015
Wetland name or number Wetland B
D 1.1. Characteristics of surface water outflows from the wetland:
points = 3
points = 2
points = 1
points = 1
Yes = 4 No = 0
Wetland has persistent, ungrazed, plants > 95% of area points = 5
Wetland has persistent, ungrazed, plants > ½ of area points = 3
Wetland has persistent, ungrazed plants > 1/10 of area points = 1
Wetland has persistent, ungrazed plants < 1/10 of area points = 0
D 1.4. Characteristics of seasonal ponding or inundation:
This is the area that is ponded for at least 2 months. See description in manual.
Area seasonally ponded is > ½ total area of wetland points = 4
Area seasonally ponded is > ¼ total area of wetland points = 2
Area seasonally ponded is < ¼ total area of wetland points = 0
Total for D 1 Add the points in the boxes above 9
Rating of Site Potential If score is: 12 - 16 = H 6 - 11 = M 0 - 5 = L Record the rating on the first page
D 2.1. Does the wetland unit receive stormwater discharges?Yes = 1 No = 0 1
Yes = 1 No = 0
D 2.3. Are there septic systems within 250 ft of the wetland?Yes = 1 No = 0 0
Source Yes = 1 No = 0
Total for D 2 Add the points in the boxes above 2
Rating of Landscape Potential If score is: 3 or 4 = H 1 or 2 = M 0 = L Record the rating on the first page
Yes = 1 No = 0
Yes = 1 No = 0
Yes = 2 No = 0
Total for D 3 Add the points in the boxes above 4
Rating of Value If score is: 2 - 4 = H 1 = M 0 = L Record the rating on the first page
D 3.3. Has the site been identified in a watershed or local plan as important
for maintaining water quality (answer YES if there is a TMDL for the basin in
which the unit is found )?
D 1.2. The soil 2 in below the surface (or duff layer) is true clay or true organic
(use NRCS definitions ).
D 1.3. Characteristics and distribution of persistent plants (Emergent, Scrub-shrub, and/or
Forested Cowardin classes):
D 2.4. Are there other sources of pollutants coming into the wetland that are
not listed in questions D 2.1 - D 2.3?
D 3.1. Does the wetland discharge directly (i.e., within 1 mi) to a stream, river,
lake, or marine water that is on the 303(d) list?
D 2.2. Is > 10% of the area within 150 ft of the wetland in land uses that
generate pollutants?
D 3.2. Is the wetland in a basin or sub-basin where an aquatic resource is on the 303(d) list?
D 3.0. Is the water quality improvement provided by the site valuable to society?
1
1
2
0
3
DEPRESSIONAL AND FLATS WETLANDS
1
0
Water Quality Functions - Indicators that the site functions to improve water quality
D 1.0. Does the site have the potential to improve water quality?
2
Wetland has an unconstricted, or slightly constricted, surface outlet
that is permanently flowing
Wetland has an intermittently flowing stream or ditch, OR highly
constricted permanently flowing outlet.
Wetland is a depression or flat depression (QUESTION 7 on key)
with no surface water leaving it (no outlet).
Wetland is a flat depression (QUESTION 7 on key), whose outlet is
a permanently flowing ditch.
4
D 2.0. Does the landscape have the potential to support the water quality function of the site?
Wetland Rating System for Western WA: 2014 Update
Rating Form - Effective January 1, 2015 5 WSDOT Adapted Form - March 2, 2015
Wetland name or number Wetland B
D 4.1. Characteristics of surface water outflows from the wetland:
points = 4
points = 2
points = 1
points = 0
Marks of ponding are 3 ft or more above the surface or bottom of outlet points = 7
Marks of ponding between 2 ft to < 3 ft from surface or bottom of outlet points = 5
Marks are at least 0.5 ft to < 2 ft from surface or bottom of outlet points = 3
The wetland is a “headwater” wetland points = 3
Wetland is flat but has small depressions on the surface that trap water points = 1
Marks of ponding less than 0.5 ft (6 in)points = 0
The area of the basin is less than 10 times the area of the unit points = 5
The area of the basin is 10 to 100 times the area of the unit points = 3
The area of the basin is more than 100 times the area of the unit points = 0
Entire wetland is in the Flats class points = 5
Total for D 4 Add the points in the boxes above 10
Rating of Site Potential If score is: 12 - 16 = H 6 - 11 = M 0 - 5 = L Record the rating on the first page
D 5.1. Does the wetland unit receive stormwater discharges?Yes = 1 No = 0 1
D 5.2. Is > 10% of the area within 150 ft of the wetland in land uses that generate excess runoff?
Yes = 1 No = 0
Yes = 1 No = 0
Total for D 5 Add the points in the boxes above 3
Rating of Landscape Potential If score is: 3 = H 1 or 2 = M 0 = L Record the rating on the first page
points = 2
points = 1
Flooding from groundwater is an issue in the sub-basin.points = 1
points = 0
There are no problems with flooding downstream of the wetland.points = 0
Yes = 2 No = 0
Total for D 6 Add the points in the boxes above 2
Rating of Value If score is: 2 - 4 = H 1 = M 0 = L Record the rating on the first page
1
1
D 5.3. Is more than 25% of the contributing basin of the wetland covered with intensive human
land uses (residential at >1 residence/ac, urban, commercial, agriculture, etc.)?
The existing or potential outflow from the wetland is so constrained
by human or natural conditions that the water stored by the wetland
cannot reach areas that flood. Explain why
2
0
5
D 4.2. Depth of storage during wet periods: Estimate the height of ponding above the bottom of
the outlet. For wetlands with no outlet, measure from the surface of permanent water or if dry, the
deepest part.
D 4.3. Contribution of the wetland to storage in the watershed: Estimate the ratio of the area of
upstream basin contributing surface water to the wetland to the area of the wetland unit itself.
D 6.1. The unit is in a landscape that has flooding problems. Choose the description that best
matches conditions around the wetland unit being rated. Do not add points. Choose the highest
score if more than one condition is met.
D 6.2. Has the site been identified as important for flood storage or flood
conveyance in a regional flood control plan?
Hydrologic Functions - Indicators that the site functions to reduce flooding and stream degradation
D 4.0. Does the site have the potential to reduce flooding and erosion?
2
Wetland is a depression or flat depression with no surface water
leaving it (no outlet)
Wetland has an unconstricted, or slightly constricted, surface outlet
that is permanently flowing
Wetland has an intermittently flowing stream or ditch, OR highly
constricted permanently flowing outlet
Wetland is a flat depression (QUESTION 7 on key), whose outlet is
a permanently flowing ditch
3
D 5.0. Does the landscape have the potential to support hydrologic function of the site?
D 6.0. Are the hydrologic functions provided by the site valuable to society?
The wetland captures surface water that would otherwise flow down-gradient into areas
where flooding has damaged human or natural resources (e.g., houses or salmon redds):
Flooding occurs in a sub-basin that is immediately down-
gradient of unit.
Surface flooding problems are in a sub-basin farther down-
gradient.
DEPRESSIONAL AND FLATS WETLANDS
Wetland Rating System for Western WA: 2014 Update
Rating Form - Effective January 1, 2015 6 WSDOT Adapted Form - March 2, 2015
Wetland name or number Wetland B
HABITAT FUNCTIONS - Indicators that site functions to provide important habitat
H 1.0. Does the site have the potential to provide habitat?
Aquatic bed 4 structures or more: points = 4
Emergent 3 structures: points = 2
Scrub-shrub (areas where shrubs have > 30% cover)2 structures: points - 1
Forested (areas where trees have > 30% cover)1 structure: points = 0
If the unit has a Forested class, check if :
H 1.2. Hydroperiods
Permanently flooded or inundated 4 or more types present: points = 3
Seasonally flooded or inundated 3 types present: points = 2
Occasionally flooded or inundated 2 types present: points = 1
Saturated only 1 types present: points = 0
Permanently flowing stream or river in, or adjacent to, the wetland
Seasonally flowing stream in, or adjacent to, the wetland
Lake Fringe wetland 2 points
Freshwater tidal wetland 2 points
H 1.3. Richness of plant species
If you counted:> 19 species points = 2
5 - 19 species points = 1
< 5 species points = 0
H 1.4. Interspersion of habitats
None = 0 points Low = 1 point Moderate = 2 points
All three diagrams
in this row are
HIGH = 3 points
2
Check the types of water regimes (hydroperiods) present within the wetland. The water regime
has to cover more than 10% of the wetland or ¼ ac to count (see text for descriptions of
hydroperiods ).
2
Count the number of plant species in the wetland that cover at least 10 ft2.Different patches of the same species can be combined to meet the size threshold and you do
not have to name the species. Do not include Eurasian milfoil, reed canarygrass, purple
loosestrife, Canadian thistle 1
Decide from the diagrams below whether interspersion among Cowardin plants classes
(described in H 1.1), or the classes and unvegetated areas (can include open water or mudflats)
is high, moderate, low, or none. If you have four or more plant classes or three classes and open
water, the rating is always high.
These questions apply to wetlands of all HGM classes.
The Forested class has 3 out of 5 strata (canopy, sub-canopy, shrubs, herbaceous,
moss/ground-cover) that each cover 20% within the Forested polygon
2
H 1.1. Structure of plant community: Indicators are Cowardin classes and strata within the
Forested class. Check the Cowardin plant classes in the wetland. Up to 10 patches may be
combined for each class to meet the threshold of ¼ ac or more than 10% of the unit if it is smaller
than 2.5 ac. Add the number of structures checked.
Wetland Rating System for Western WA: 2014 Update
Rating Form - Effective January 1, 2015 7 WSDOT Adapted Form - March 2, 2015
Wetland name or number Wetland B
H 1.5. Special habitat features:
Large, downed, woody debris within the wetland (> 4 in diameter and 6 ft long)
Standing snags (dbh > 4 in) within the wetland
Total for H 1 Add the points in the boxes above 10
Rating of Site Potential If Score is: 15 - 18 = H 7 - 14 = M 0 - 6 = L Record the rating on the first page
H 2.0. Does the landscape have the potential to support the habitat function of the site?
H 2.1 Accessible habitat (include only habitat that directly abuts wetland unit ).
Calculate:
3 % undisturbed habitat + (5 % moderate & low intensity land uses / 2 ) = 5.5%
If total accessible habitat is:
> 1/3 (33.3%) of 1 km Polygon points = 3
20 - 33% of 1 km Polygon points = 2
10 - 19% of 1 km Polygon points = 1
< 10 % of 1 km Polygon points = 0
H 2.2. Undisturbed habitat in 1 km Polygon around the wetland.
Calculate:
21 % undisturbed habitat + (5 % moderate & low intensity land uses / 2 ) = 23.5%
Undisturbed habitat > 50% of Polygon points = 3
Undisturbed habitat 10 - 50% and in 1-3 patches points = 2
Undisturbed habitat 10 - 50% and > 3 patches points = 1
Undisturbed habitat < 10% of 1 km Polygon points = 0
H 2.3 Land use intensity in 1 km Polygon: If
> 50% of 1 km Polygon is high intensity land use points = (-2)
≤ 50% of 1km Polygon is high intensity points = 0
Total for H 2 Add the points in the boxes above -1
Rating of Landscape Potential If Score is: 4 - 6 = H 1 - 3 = M < 1 = L Record the rating on the first page
Site meets ANY of the following criteria:points = 2
It has 3 or more priority habitats within 100 m (see next page)
It is mapped as a location for an individual WDFW priority species
Site has 1 or 2 priority habitats (listed on next page) with in 100m points = 1
Site does not meet any of the criteria above points = 0
Rating of Value If Score is: 2 = H 1 = M 0 = L Record the rating on the first page
Check the habitat features that are present in the wetland. The number of checks is the number
of points.
It has been categorized as an important habitat site in a local or
regional comprehensive plan, in a Shoreline Master Plan, or in a
watershed plan
Undercut banks are present for at least 6.6 ft (2 m) and/or overhanging plants extends
at least 3.3 ft (1 m) over a stream (or ditch) in, or contiguous with the wetland, for at
least 33 ft (10 m)
Stable steep banks of fine material that might be used by beaver or muskrat for denning
(> 30 degree slope) OR signs of recent beaver activity are present (cut shrubs or trees
that have not yet weathered where wood is exposed )
At least ¼ ac of thin-stemmed persistent plants or woody branches are present in areas
that are permanently or seasonally inundated (structures for egg-laying by amphibians )
3
It is a Wetland of High Conservation Value as determined by the
Department of Natural Resources
1
Invasive plants cover less than 25% of the wetland area in every stratum of plants (see
H 1.1 for list of strata )
0
1
-2
H 3.0. Is the habitat provided by the site valuable to society?
H 3.1. Does the site provide habitat for species valued in laws, regulations, or policies? Choose
only the highest score that applies to the wetland being rated .
It provides habitat for Threatened or Endangered species (any plant
or animal on the state or federal lists)
Wetland Rating System for Western WA: 2014 Update
Rating Form - Effective January 1, 2015 8 WSDOT Adapted Form - March 2, 2015
Wetland name or number Wetland B
Aspen Stands: Pure or mixed stands of aspen greater than 1 ac (0.4 ha).
Herbaceous Balds: Variable size patches of grass and forbs on shallow soils over bedrock.
Cliffs: Greater than 25 ft (7.6 m) high and occurring below 5000 ft elevation.
Priority habitats listed by WDFW (see complete descriptions of WDFW priority habitats, and the counties in
which they can be found, in: Washington Department of Fish and Wildlife. 2008. Priority Habitat and Species
List. Olympia, Washington. 177 pp.
Oregon White Oak: Woodland stands of pure oak or oak/conifer associations where canopy
coverage of the oak component is important (full descriptions in WDFW PHS report p. 158 – see
web link above ).
Riparian: The area adjacent to aquatic systems with flowing water that contains elements of both
aquatic and terrestrial ecosystems which mutually influence each other.
Westside Prairies: Herbaceous, non-forested plant communities that can either take the form of a
dry prairie or a wet prairie (full descriptions in WDFW PHS report p. 161 – see web link above ).
Instream: The combination of physical, biological, and chemical processes and conditions that
interact to provide functional life history requirements for instream fish and wildlife resources.
Nearshore: Relatively undisturbed nearshore habitats. These include Coastal Nearshore, Open
Coast Nearshore, and Puget Sound Nearshore. (full descriptions of habitats and the definition of
relatively undisturbed are in WDFW report – see web link on previous page ).
Snags and Logs: Trees are considered snags if they are dead or dying and exhibit sufficient decay
characteristics to enable cavity excavation/use by wildlife. Priority snags have a diameter at breast
height of > 20 in (51 cm) in western Washington and are > 6.5 ft (2 m) in height. Priority logs are > 12
in (30 cm) in diameter at the largest end, and > 20 ft (6 m) long.
Talus: Homogenous areas of rock rubble ranging in average size 0.5 - 6.5 ft (0.15 - 2.0 m),
composed of basalt, andesite, and/or sedimentary rock, including riprap slides and mine tailings. May
be associated with cliffs.
Caves: A naturally occurring cavity, recess, void, or system of interconnected passages under the
earth in soils, rock, ice, or other geological formations and is large enough to contain a human.
Note: All vegetated wetlands are by definition a priority habitat but are not included in this list because they are
addressed elsewhere.
WDFW Priority Habitats
Count how many of the following priority habitats are within 330 ft (100 m) of the wetland unit: NOTE : This
question is independent of the land use between the wetland unit and the priority habitat.
Biodiversity Areas and Corridors: Areas of habitat that are relatively important to various species
of native fish and wildlife (full descriptions in WDFW PHS report ).
Old-growth/Mature forests: Old-growth west of Cascade crest – Stands of at least 2 tree species,
forming a multi-layered canopy with occasional small openings; with at least 8 trees/ac (20 trees/ha)
> 32 in (81 cm) dbh or > 200 years of age. Mature forests – Stands with average diameters
exceeding 21 in (53 cm) dbh; crown cover may be less than 100%; decay, decadence, numbers of
snags, and quantity of large downed material is generally less than that found in old-growth; 80-200
years old west of the Cascade crest.
http://wdfw.wa.gov/publications/00165/wdfw00165.pdf or access the list from here:
http://wdfw.wa.gov/conservation/phs/list/
Wetland Rating System for Western WA: 2014 Update
Rating Form - Effective January 1, 2015 9 WSDOT Adapted Form - March 2, 2015
Wetland name or number Wetland B
Wetland Type Category
Check off any criteria that apply to the wetland. List the category when the appropriate criteria are met.
SC 1.0. Estuarine Wetlands
Does the wetland meet the following criteria for Estuarine wetlands?
The dominant water regime is tidal,
Vegetated, and
With a salinity greater than 0.5 ppt
Yes - Go to SC 1.1 No = Not an estuarine wetland
SC 1.1.
Yes = Category I No - Go to SC 1.2
SC 1.2.Is the wetland unit at least 1 ac in size and meets at least two of the following three conditions?
Yes = Category I No = Category II
SC 2.0. Wetlands of High Conservation Value (WHCV)
SC 2.1.
Yes - Go to SC 2.2 No - Go to SC 2.3
SC 2.2.Is the wetland listed on the WDNR database as a Wetland of High Conservation Value?
Yes = Category I No = Not WHCV
SC 2.3.Is the wetland in a Section/Township/Range that contains a Natural Heritage wetland?
http://www1.dnr.wa.gov/nhp/refdesk/datasearch/wnhpwetlands.pdf
Yes - Contact WNHP/WDNR and to SC 2.4 No = Not WHCV
SC 2.4.
Yes = Category I No = Not WHCV
SC 3.0. Bogs
SC 3.1.
Yes - Go to SC 3.3 No - Go to SC 3.2
SC 3.2.
Yes - Go to SC 3.3 No = Is not a bog
SC 3.3.
Yes = Is a Category I bog No - Go to SC 3.4
SC 3.4.
Yes = Is a Category I bog No = Is not a bog
NOTE: If you are uncertain about the extent of mosses in the understory, you may
substitute that criterion by measuring the pH of the water that seeps into a hole dug at
least 16 in deep. If the pH is less than 5.0 and the plant species in Table 4 are present,
the wetland is a bog.
Is an area with peats or mucks forested (> 30% cover) with Sitka spruce, subalpine fir,
western red cedar, western hemlock, lodgepole pine, quaking aspen, Engelmann
spruce, or western white pine, AND any of the species (or combination of species) listed
in Table 4 provide more than 30% of the cover under the canopy?
CATEGORIZATION BASED ON SPECIAL CHARACTERISTICS
Is the wetland within a National Wildlife Refuge, National Park, National Estuary
Reserve, Natural Area Preserve, State Park or Educational, Environmental, or Scientific
Reserve designated under WAC 332-30-151?
The wetland is relatively undisturbed (has no diking, ditching, filling, cultivation, grazing,
and has less than 10% cover of non-native plant species. (If non-native species are
Spartina , see page 25)
At least ¾ of the landward edge of the wetland has a 100 ft buffer of shrub, forest, or un-
grazed or un-mowed grassland.
The wetland has at least two of the following features: tidal channels, depressions with
open water, or contiguous freshwater wetlands.
Has WDNR identified the wetland within the S/T/R as a Wetland of High Conservation
Value and listed it on their website?
Has the WA Department of Natural Resources updated their website to include the list
of Wetlands of High Conservation Value?
Does the wetland (or any part of the unit) meet both the criteria for soils and vegetation
in bogs? Use the key below. If you answer YES you will still need to rate the
wetland based on its functions .
Does an area within the wetland unit have organic soil horizons, either peats or mucks,
that compose 16 in or more of the first 32 in of the soil profile?
Does an area within the wetland unit have organic soils, either peats or mucks, that are
less than 16 in deep over bedrock, or an impermeable hardpan such as clay or volcanic
ash, or that are floating on top of a lake or pond?
Does an area with peats or mucks have more than 70% cover of mosses at ground
level, AND at least a 30% cover of plant species listed in Table 4?
Wetland Rating System for Western WA: 2014 Update
Rating Form - Effective January 1, 2015 10 WSDOT Adapted Form - March 2, 2015
Wetland name or number Wetland B
SC 4.0. Forested Wetlands
Yes = Category I No = Not a forested wetland for this section
SC 5.0. Wetlands in Coastal Lagoons
Does the wetland meet all of the following criteria of a wetland in a coastal lagoon?
Yes - Go to SC 5.1 No = Not a wetland in a coastal lagoon
SC 5.1. Does the wetland meet all of the following three conditions?
The wetland is larger than 1/10 ac (4350 ft2)
Yes = Category I No = Category II
SC 6.0. Interdunal Wetlands
In practical terms that means the following geographic areas:
Long Beach Peninsula: Lands west of SR 103
Grayland-Westport: Lands west of SR 105
Ocean Shores-Copalis: Lands west of SR 115 and SR 109
Yes - Go to SC 6.1 No = Not an interdunal wetland for rating
SC 6.1.
Yes = Category I No - Go to SC 6.2
SC 6.2.Is the wetland 1 ac or larger, or is it in a mosaic of wetlands that is 1 ac or larger?
Yes = Category II No - Go to SC 6.3
SC 6.3.
Yes = Category III No = Category IV
Category of wetland based on Special Characteristics
If you answered No for all types, enter “Not Applicable” on Summary Form
The wetland is relatively undisturbed (has no diking, ditching, filling, cultivation, grazing),
and has less than 20% cover of aggressive, opportunistic plant species (see list of
species on p. 100).
At least ¾ of the landward edge of the wetland has a 100 ft buffer of shrub, forest, or un-
grazed or un-mowed grassland.
Is the wetland west of the 1889 line (also called the Western Boundary of Upland
Ownership or WBUO)? If you answer yes you will still need to rate the wetland
based on its habitat functions.
Is the wetland 1 ac or larger and scores an 8 or 9 for the habitat functions on the form
(rates H,H,H or H,H,M for the three aspects of function)?
Is the unit between 0.1 and 1 ac, or is it in a mosaic of wetlands that is between 0.1 and
1 ac?
The wetland lies in a depression adjacent to marine waters that is wholly or partially
separated from marine waters by sandbanks, gravel banks, shingle, or, less frequently,
rocks
The lagoon in which the wetland is located contains ponded water that is saline or
brackish (> 0.5 ppt) during most of the year in at least a portion of the lagoon (needs to
be measured near the bottom )
Does the wetland have at least 1 contiguous acre of forest that meets one of these
criteria for the WA Department of Fish and Wildlife’s forests as priority habitats? If you
answer YES you will still need to rate the wetland based on its functions.
Old-growth forests (west of Cascade crest): Stands of at least two tree species,
forming a multi-layered canopy with occasional small openings; with at least 8 trees/ac
(20 trees/ha) that are at least 200 years of age OR have a diameter at breast height
(dbh) of 32 in (81 cm) or more.
Mature forests (west of the Cascade Crest): Stands where the largest trees are 80-
200 years old OR the species that make up the canopy have an average diameter (dbh)
exceeding 21 in (53 cm).
Wetland Rating System for Western WA: 2014 Update
Rating Form - Effective January 1, 2015 11 WSDOT Adapted Form - March 2, 2015