Cull Canyon Reservoir
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Because of its location near the Hayward fault, the California Division of Safety of Dams performed new studies and found that Cull Canyon Dam is not seismically stable and needs repair or removal. At one time, Cull Canyon Reservoir was 30 feet deep, designed to hold about 1,000cfs of water during a storm. It is now about 6 feet at its deepest and non-existent at its head near the swim lagoon area. De-silting could return the reservoir to its original design. Or, the dam could be removed, the natural creek and riparian habitat restored, and parkways added. The District will be working with the community to determine which actions to take. (Note: The existing swim area at Cull Canyon Regional Recreation Area will remain and be improved.) |
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Option 1: Area restored to its original design configuration with a larger lake. This would meet the State's seismic stability requirements by completely removing and reconstructing the existing dam, completely de-silting the existing site and ongoing annual de-silting (by far the most expensive option). |
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Option 2: Convert the existing dam to a flood detention basin (dry in the summer) and create a creek and riparian corridor along the original creek bed. The dam would be de-silted and seismically retrofitted. This would provide extensive wildlife habitat and likely improve creek water quality and conditions for fish habitat downstream. |
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Option 3: Remove the dam and recreate the original creek, riparian corridor and meadow as they were before the dam. The meadow area would become a natural detention basin for rain and may provide more open recreational opportunities than Option 2. This will restore stream habitat and improve water quality and conditions for fish habitat downstream. |
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Option 4: Convert the dam from a reservoir to a pond with minor flood detention benefits, restore the stream and restore other natural recreational amenities, without expensive de-silting. The District would introduce new green technology to biologically filter the water in the stream and send it to the existing swim lagoon at Cull Canyon Regional Recreation Area. This approach would provide a much higher swim water quality and lower the cost of maintaining the swim lagoon. It will restore stream habitat and improve water quality and conditions for fish habitat downstream. |
More engineering study and analysis is required to ensure all options meet state and federal dam safety requirements. The District is working with the community on preferences and costs.
