West Antioch Creek Channel Improvement Project

West Antioch Creek Channel Improvement Project

The City of Antioch replaced an existing concrete-lined ditch and undersized culvert with an earthen channel and box culvert to address flooding issues in the area. Nomad prepared a Biological Resources Assessment, Wetland Delineation, and protocol-level rare plant survey report. Nomad’s technical reports were used in support of CEQA. Nomad assisted with obtaining regulatory permits including California Department of Fish and Wildlife’s Streambed Alteration Agreement, U.S. Army Corps of Engineers 404 permit, and Regional Water Quality Control Board 401 permit.

Nomad’s GIS department prepared figures for the project that clearly demonstrated the location of biological resources and calculated project impacts. The project was in Delta Smelt Habitat Critical Habitat and a Biological Opinion was required from U.S. Fish and Wildlife Service. Desilting of West Antioch Creek downstream of the project area was added to the original project late in the planning phase and did not have a clear project description or design analysis. The desilting project as designed would permanently and temporarily impact several acres of Delta Smelt critical habitat which required mitigation by USFWS during the consultation process.

Due to the time sensitivity of the culvert repair and urgency to prevent flooding, the project team decided to exclude the desilting project downstream to minimize project impacts to Delta Smelt, reduce mitigation costs, and keep the project on time and within budget. It was decided that desilting would be permitted at a later date once the desilting project could be properly designed to remove sediment at key locations, improve stream flow, while minimizing impacts to Delta Smelt.

Nomad conducted preconstruction surveys prior to the start of construction; provided environmental training to the construction team, and monitored construction in compliance with project permits. Nomad relocated western pond turtles and fish during channel dewatering. Nomad prepared a restoration plan for the project and oversaw restoration implementation. Nomad is currently under contract with the City of Antioch to permit sediment removal for a segment of West Antioch Creek downstream from the Channel Improvement project area.


LOCATION: Antioch, Contra Costa County
CLIENT: City of Antioch

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