HomeMy WebLinkAboutRS_Standard_Stream_Study_180309_v1
January 5, 2018
Chris Dew, King County WTD
Jessica Conquest, Environmental Science Associates
Karmen Martin, Environmental Science Associates
South Plant Biogas and Heating Systems (Temporary Construction Entrance) - Standard Stream Study
(for Shoreline Exemption Submittal)
As part of King County’s South Plant Biogas and Heating System Project, King County proposes to construct a
temporary construction entrance which will provide construction machinery access to the proposed onsite spoils
placement area. Work will be restricted to temporary grading for installation of the temporary construction
entrance. Construction and use of the temporary construction entrance would occur within a portion of the
shoreline jurisdiction of Springbrook Creek. This memorandum was prepared by Environmental Science
Associates to address information specified in RMC Section 4-8-120D.19 for a “Standard Stream Study”, and as
identified in the City of Renton Shoreline Exemption Submittal Requirements Bulletin.
Springbrook Creek was extensively modified and straightened for agricultural drainage in the 1920s by King
County Drainage District No. 1. The channel area abutting the project was improved in the 1980s and 1990s for
flood control by the City of Renton in cooperation with the Natural Resource Conservation Service. The stream is
constrained and channelized throughout the shoreline (City of Renton, 2010). Levees that define the streambank
limit the width of the riparian corridor (Parametrix, 2010).
Springbrook Creek is classified as Shoreline High Intensity under the City’s Shoreline Management Program.
Existing vegetation along the shoreline is typical native riparian forest species and includes a mixture of red alder,
willow species, Himalayan blackberry and sedges (Carex spp.) along with some ornamental trees. Conifers are
almost exclusively absent, and in those areas where shade is absent, reed canary grass is abundant. The
Springbrook Creek vegetated riparian area is separated from the project site by the plant driveway (Road “N”).
Chinook, Chum, Coho, Steelhead Trout, and Cutthroat Trout are found in Springbrook Creek, utilizing the habitat
primarily for migration (City of Renton, 2010). According to Washington Department of Fish and Wildlife
(WDFW) SalmonScape fish distribution data, fall Chinook, fall chum, and winter steelhead are present and coho
rear in the creek (WDFW, 2017). Under Washington State Water Quality Standards, Springbrook Creek is
categorized as “Spawning Rearing and Migration Habitat” for aquatic life use and “Primary Contact” for
recreational use. The Creek is on Washington Department of Ecology’s 303(d) list for violation of dissolved
oxygen and fecal coliform bacteria standards (Category 5) (King County, 2017).
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Construction and use of the temporary construction entrance would result in no net loss of ecological functions or
processes. Existing vegetation on the proposed temporary construction entrance site consists of herbaceous
species (grasses). The structural and species diversity is low. No trees would be removed within the shoreline, and
there would be no impacts to the existing vegetated riparian buffer. Minor grading would be required for
construction of the temporary construction entrance. A temporary erosion and sediment control plan will be
developed and implemented during construction and operation of the temporary construction entrance to ensure
no changes in turbidity or water quality as a result of the project. Post construction, the temporary construction
entrance would be regraded and revegetated. No permanent changes to drainage conditions would occur.
The City’s Shoreline Master Program (SMP) includes regulations that, when met, ensure no net loss of shoreline
ecological functions (RMC 4-3-090). Specifically, by avoiding and minimizing impacts to shoreline resources,
this project complies with the City’s SMP and achieves the “no net loss” objective. Project effects in relation to
shoreline processes and ecological functions outlined in RMC 4-8-090 are provided in Table 1. As shown in the
table, the project will have neutral effects on each process or function.
TABLE 1.
POTENTIAL EFFECTS ON SHORELINE PROCESSES AND ECOLOGICAL FUNCTIONS
Shoreline Process or Ecological Function Project Effects
Fish and Wildlife Habitat The project will ensure the maintenance of species
composition and structural diversity in the vegetated riparian
area. Habitat connectivity will be maintained.
Food Chain Support The activity will have no effect on food chain support. The
temporary construction entrance site is physically
disconnected from the vegetated riparian corridor by the
existing plant driveway, which substantially prevents delivery
of functions from the site.
Water temperature maintenance The activity will have no effect on water temperature in
Springbrook Creek.
Water flow The activity will result in no changes to flow regimes.
Erosion and accretion During construction, a temporary erosion and sedimentation
control plan will be implemented to minimize and control
erosion from stormwater.
Groundwater recharge and discharge The activity will have no effect on groundwater recharge and
discharge from the project site.
Sediment delivery/transport and storage During construction, a temporary erosion and sedimentation
control plan will be implemented to minimize and control
erosion from stormwater.
LWD recruitment The activity will not remove any trees from the shoreline.
Preservation of trees will ensure no net loss of woody debris
recruitment.
Organic matter input The activity will have no effect on organic matter input. The
temporary construction entrance site is physically
disconnected from the vegetated riparian corridor by the
existing plant driveway, which substantially prevents delivery
of functions from the site.
Nutrient and pathogen removal The project will ensure the maintenance of species
composition and structural diversity in the vegetated riparian
area that provides the specified ecological functions.
Stream channel formation/maintenance The activity will have no effect on stream channel formation
and maintenance
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References
City of Renton. 2010. Shoreline Master Program Update Draft Restoration Plan. March 2010. 552-1779-031.
King County. 2017. Stream Report: Springbrook Creek – 0317. Accessed on 12/8/17. Available at:
http://green2.kingcounty.gov/streamsdata/watershedinfo.aspx?locator=0317
Parametrix. 2010. Shoreline Master Program Revised Draft Shoreline Inventory and Analysis. Prepared by
Parametrix, Bellevue, Washington. March 2010.
Washington Department of Fish and Wildlife (WDFW). 2017. SalmonScape. Accessed on 12/11/2017. Available
at: http://apps.wdfw.wa.gov/salmonscape/