Mendocino County Migration Barrier Inventory Report
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Mendocino County Migration Barrier Culvert Catalog
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Dark Gulch crossing at Orr Springs Road (above) is located in the South Fork. Big River Watershed and is ranked as the 7th highest priority project in Mendocino County.

The current crossing is extremely undersized and is estimated to overtop Orr Springs Road on about a 22-year storm discharge.
FishXing software determined that the culvert is a total barrier for adult coho salmon and steelhead, as well as all age classes of juveniles, due primarily to excessive velocities over steep slope, lack of depth at lower migration flows, and leap required to enter culvert. The engineering design and permitting activities for Dark Gulch will be completed in 2011 with funding through the California Coastal Conservancy. The preferred treatment for this site would be a properly-sized bridge or pipe-arch set on concrete footings.