2725 32ND AVE NE 2018-01-02 MF Import

WEYERKWUSER COMPANY SMITH ISLAND LANDFILL BIOLOGICAL ASSESSMENT acting to prevent the river from flowing into the ditch. This seal also prevents fish and wildlife passage into the ditch. During low tide periods, the tide gate opens to allow ditch water to discharge into the river. Because of the tide gate, fish habitat is limited since the c :tch water levels fluctuate significantly on a daily basis. For example, the water level is periodically drawn down to less than two inches in some areas. Impacts to Critical Areas Wetlands No impacts to wetlands regulated by the City or Snohomish County will occur during the proposed work on the Outfall 005 closure or the landfill closure. The buffer of the wetland north of the landfill access road includes a portion of a dike that is used as an access road to the landfill and treatment system. Erosion control measures will be employed along the dike and wetland border to ensure that the wetland is protected from project activities. Fish and Wildlife Habitat Areas As noted above, Outfall 005 is not currently providing significant habitat value to salmonid species because the tide gate forms a barrier to fish passage. Closure of the outfall c.ilvert will therefore not result in adverse impacts to habitat. Flows from the ditch into the river are not significant in volume compared to overall Snohomish River flows, and discharge from Outfall 001 also enters the Snohomish River estuary; therefore, there will be no net effect on quantity of flows required for fish habitat in the estuary. In addition, routing of previously untreated stormwater through the Smith Island treatment system should generally improve water quality as compared to existing conditions by permitting the settling of solids from the runoff. This will result in a net benefit to habitat and endangered species in the estuary. Temporary impacts could occur as a result of construction to block the culvert if water containing construction materials (e.g., concrete) or sediment were to reach the Snohomish River. To minimize the potential for this to occur, construction would take place in the dry season when little or no water is flowing in the ditch. In addition, the downstream end of the culvert would be protected with silt fences or similar measures to prevent any impacted water from Leaching the river. Mitigation Measures As described in the "Impacts to Critical Areas' section above, erosion and sedimentation control measures would be used to reduce the potential for sediments and/or contaminants to reach the river or nearby wetland areas. Following construction, the ditch conveying nmoff to the treatment system would be revegetated with native grasses to provide habitat and additional water quality benefits. In addition, the project itself would serve as a form of mitigation by providing treatment of currently unheated flows from the vicinity of the landfill. EVERETT BIOLOGICAL ASSESSMENT.DOC