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Fish Passage Improvement Program (FPIP)

York Creek

Photo of Diversion Structure York Creek Diversion Structure Before Initiating the Project


York Creek originates from the Coast Range on the western side of the Napa Valley watershed at an elevation of approximately 1,800 feet (550 m) and flows through a narrow canyon before joining the Napa River northeast of St. Helena, Napa County. Two structures were identified in the late 1990´s as impeding fish passage in York Creek: York Creek Dam and a diversion structure.

The 5 ft high concrete masonry diversion structure diverted water from York Creek to the St. Helena Lower Reservoir. The channel of York Creek that was impacted by the diversion configuration was known to provide spawning and rearing habitat for steelhead.

The second structural impediment to anadromous fish migration was York Creek Dam. It was an earthfill dam located approximately 0.5 miles (0.8 km) upstream of the diversion structure. The dam blocked steelhead from approximately 2 miles of habitat found upstream.


Major modifications of the diversion structure were completed in 2004. The modifications involved removal of the concrete masonry diversion structure, creation of cascading steps with resting pools of sufficient depth for steelhead, bank stabilization and native plant generation. A proposed infiltration gallery designed to prevent juvenile salmonid entrainment may be placed in the streambed after a one or two year trial period without any water diversion. The project has opened 0.5 miles of habitat and improved stream function and fish passage upstream to the York Creek Dam.

The Fish Passage Improvement Program´s (FPIP) role in the project included developing preliminary engineering designs, drawings, and specifications for the modification, and completing an Initial Study (1.6 MB) and Environmental Impact Report , biological assessment, 401 Water Quality Certification application, 1601 Notification of Streambed Alteration, a Preconstruction Notification for the U.S. Army Corps of Engineers (USACE), and obtaining grant funding.

FPIP assisted the City of St. Helena in engineering aspects and pursuing the environmental documentation to remove York Creek Dam until 2003. In 2003, the City and USACE began the process to obtain funding under the USACE Continuing Authorities Program. In 2007, the City prepared a Draft Environmental Impact Report for the Upper York Creek Ecosystem Restoration Project, which includes removal or modification of the dam and appurtenances, removal of accumulated sediment, and restoration of the local ecology of York Creek. USACE has recently completed the first phase of the project, which included feasibility studies, and now has funding in place to continue the second phase, implementation of the project. Upon completion of final engineering designs and environmental review, construction is expected to begin in 2010.

Photo of restored York Creek
York Creek After Completion of the Project

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