Draft January 2018
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DRAFT BIOLOGICAL RESOURCES ASSESSMENT COPELAND CREEK DETENTION BASIN AND TRAIL PROJECT SONOMA COUNTY, CALIFORNIA Prepared for: City of Rohnert Park 130 Avram Avenue Rohnert Park, California 94928 Contact: Mary Grace Pawson Prepared by: 853 Lincoln Way Auburn, California 95603 Contact: Lisa Achter JANUARY 2018 January 9, 2018 9810 Mary Grace Pawson Director of Development Services City of Rohnert Park 130 Avram Avenue Rohnert Park, California 94928 Subject: Biological Resources Assessment for the Copeland Creek Detention Basin and Trail Project, Sonoma County, California Dear Ms. Pawson: In November of 2017, Dudek biologist Lisa Achter conducted a reconnaissance level general biological field survey at the Copeland Creek Detention Basin and Trail project site in Sonoma County, California (Figure 1). The focus of the survey was to characterize existing site conditions, document biological resources, and to summarize potential biological constraints associated with the proposed development and associated improvements to the site. A description of the methods and results of the biological survey and related recommendations is provided below. 1 SITE LOCATION AND PROJECT DESCRIPTION The 128-acre project site is located just east of the City of Rohnert Park, at 6626 Petaluma Hill Road (Figure 2). The project site is characterized by relatively flat terrain in the western portion of the site where the proposed detention basin will be located, and rolling hills in the eastern portion of the site where the trail will be located (Figure 2). Copeland Creek flows from east to west along the southern boundary and through the southwestern corner of the site. Elevation within the project site varies from approximately 175 feet above mean sea level (AMSL) in the southwestern flatlands to 400 feet AMSL in the hills of the eastern portion of the site. The site is situated immediately east of Petaluma Hill Road (APN 047-132-038) in Township 6 North, Range 7 West, and Sections 20, 21, 28, 29 and 30 in the 7.5-minute U.S. Geological Survey (USGS) Cotati quadrangle. The center of the site location corresponds to 38°20'37" north latitude and 122°39'33" west longitude. Annual grassland is the dominant vegetation community within the site; however, a small patch of coast live oak (Quercus agrifolia) woodland occurs in the center of the site on a hill that divides the western and eastern portions of the site, and oaks occur sporadically throughout the eastern portion of the site (Figure 3). Surrounding land use includes rural residential lots to the north that are Ms. Mary Grace Pawson Subject: Biological Resources Assessment for the Copeland Creek Detention Basin and Trail Project, Sonoma County, California dominated by annual grassland habitat, Crane Creek Regional Park to the east, Sonoma State University and residential development to the west, and a nursery to the south of the Copeland Creek corridor. No structures exist on the project site. The proposed project involves construction of an off-channel detention basin in the western portion of the site and a future recreational trail on undeveloped pastureland in the eastern portion of the site. The detention basin would be designed for a 10-year storm event and construction would include associated maintenance and access structures north of Copeland Creek. A recreational trail is proposed on the eastern portion of the property and would extend from the basin to Crane Creek Regional Park to the east. This multi-benefit project, developed with collaboration from the Sonoma County Water Agency (SCWA), Sonoma County Agricultural Preservation and Open Space District, Sonoma County Regional Parks, County of Sonoma, and City of Rohnert Park would improve flood protection for area residents, reduce sediment deposits downstream in Copeland Creek, assist groundwater recharge, improve salmonid habitat, provide salmonid refugia, conserve energy resulting from reduced pumping and importation of potable surface water, and create a site for public access and education about the hydrology, water cycle, fish habitat, and geomorphic processes in the upper Copeland Creek Watershed. 2 SITE EVALUATION METHODS 2.1 Preliminary Review Special-status plant and wildlife species present or potentially present on the site were identified through a desktop literature search using the following sources: U.S. Fish and Wildlife Service (USFWS) Information, Planning, and Conservation (IPaC) Trust Resource Report; California Department of Fish and Wildlife (CDFW) California Natural Diversity Database (CNDDB); and the California Native Plant Society (CNPS) online Inventory of Rare and Endangered Vascular Plants. Additionally, the Natural Resources Conservation Service (NRCS), Web Soil Survey (WSS) was queried to determine soil types present within the project boundary (USDA 2017). The database searches for the CNDDB and CNPS reports included the 7.5’ USGS Cotati quadrangle and surrounding eight quadrangles. The IPaC search included the project site and a five-mile buffer surrounding the site. Special-status species include those that are listed as threatened, endangered, or a candidate species, or species of special concern by the CDFW, USFWS or CNPS. Only California Rare Plant Rank (CRPR) 1 and 2 plant species were included in the CNPS search. Following a review of these resources, Dudek also reviewed relevant life 9810 2 January 2018 Ms. Mary Grace Pawson Subject: Biological Resources Assessment for the Copeland Creek Detention Basin and Trail Project, Sonoma County, California history information on those species documented as occurring in the region, including habitat type, soils, and elevation preferences. 2.2 Field Assessment The biological reconnaissance survey was performed by Dudek biologist Lisa Achter on November 9, 2017, and consisted of walking throughout the site and along the periphery of the site to characterize and map existing vegetation communities, evaluate the relative quality and potential of on-site habitats to support the special-status species identified during the preliminary database and resources review (discussed above), and to identify any other sensitive biological resources present or potentially present within the site. An aerial photograph (Google Earth 2017) and georeferenced mobile map with an overlay of the property boundary, and surrounding buffer was utilized to map vegetation communities and record any special-status or sensitive biological resources while in the field. Incidental observations of wildlife or wildlife sign and dominant plant species were also recorded. Since the field assessment was conducted outside the breeding/blooming season of special-status plant and wildlife species known to occur in the region and potentially occurring on the site, focused or protocol-level surveys for these species were not conducted. However, any incidental observations of such species were documented. Concurrent with the biological reconnaissance survey described above, Dudek botanist Laura Burris conducted a wetland delineation on the project site to identify and map wetlands and other aquatic features likely to be under the jurisdiction of the U.S. Army Corps of Engineers pursuant to Section 404 of the federal Clean Water Act. Potentially jurisdictional features were initially identified based on aerial signatures and field observations according to the Federal Manual for Identifying and Delineating Jurisdictional Wetlands, Interim Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Arid West Region, and the U.S. Army Corps of Engineers Jurisdictional Determination Form Instructional Guidebook, as well as criteria developed under CDFW Section 1602, Lake and Streambed Alteration Agreements. 3 RESULTS 3.1 Soils Six soil types, as mapped by the NRCS (USDA 2017) occur within the project site (Figure 4). These include: Clear Lake clay loam (0–2% slopes, 2–5% slopes), Clear Lake clay, 0–2% slopes, Goulding cobbly clay loam, 5–15% slopes, Goulding-Toomes complex, 9–50% slopes, Riverwash, and Toomes rocky loam, 2–30% slopes. 9810 3 January 2018 Ms. Mary Grace Pawson Subject: Biological Resources Assessment for the Copeland Creek Detention Basin and Trail Project, Sonoma County, California Clear Lake clay and loam soils are very deep, poorly drained soils that formed in fine textured alluvium derived from sandstone and shale. Clear Lake soils are present in basins and swales of drainageways. Goulding soils consist of shallow, somewhat excessively drained soils formed in material weathered from metavolcanic or metasedimentary rocks. Goulding soils are located on mountains with slopes from 5% to 75%. Toomes series consist of very shallow and shallow, well to somewhat excessively drained soils formed in material weathered from tuff breccia, basalt and andesite. These soils occur on ridges and plateaus with slopes from 2% to 75%. Riverwash lands are excessively drained and consist of highly stratified, water- and wind-deposited, stony, cobbly, and gravelly sand, loamy sand, and sandy loam and contain only a small amount of silt and clay. Additionally, they are subject to flooding, scouring, and deposition during and immediately following storms (USDA 2017). 3.2 Vegetation Communities and Land Cover Types Four vegetation communities or land cover types were identified and mapped during the field assessment using the classifications described in A Manual of California Vegetation (MCV) by Sawyer and Keeler-Wolf (2009). Generic descriptions from the MCV are presented for each of the