Dry Creek Habitat Enhancement Project, Miles 2-6 - Draft Environmental Impact Report
The Sonoma County Water Agency (Water Agency), as Lead Agency, has prepared this Draft Environmental Impact Report (EIR) for Dry Creek Habitat Enhancement Project, Miles 2–6 (proposed project) to provide the public and responsible and trustee agencies reviewing the Dry Creek Habitat Enhancement Project an analysis of the potential effects, both beneficial and adverse, on the environment.1 This project is intended to fulfill federal mandates to implement habitat enhancement within Dry Creek to create both winter and summer rearing habitats for juvenile steelhead and coho salmon, with an emphasis on improving habitats for the survival of juvenile coho salmon while allowing the Water Agency to maintain the existing flow range in Dry Creek for water supply purposes.
Russian River - Cotati Intertie Pipeline Seismic Hazard Mitigation
The Water Agency owns, operates, and maintains a 48-inch diameter steel water supply pipeline (referred to as the Russian River-Cotati Intertie) that crosses the southern and eastern aqueduct transmission lines and crosses the Russian River in Sonoma County. The pipeline is buried at a relatively shallow depth (approximately 7 feet below ground surface) across the Russian River channel and stream banks, and crosses seismically unstable terrain.
The Local Hazard Mitigation Plan (LHMP) identifies the Russian River-Cotati Intertie Intertie crossing of the Russian River as vulnerable to potential ground deformation, liquefaction, and lateral spread resulting from strong ground shaking in the soil at or below the elevation of the pipeline. The LHMP states that pipeline failure from an earthquake would isolate the Mirabel collector wells from the Russian River-Cotati Intertie Intertie Pipeline.
The proposed project is needed to address seismic concerns related to reliable delivery of water to the Water Agency’s service area and prevent the loss of an essential water service due to a moderate or severe earthquake along the Rodger's Creek/Hayward Fault.