Syphon Reservoir Improvement Project

The Syphon Reservoir Improvement Project, managed by the Irvine Ranch Water District in Orange County, California, involves replacing an existing 59-foot engineered dam with a new 138-foot dam. This upgrade will increase the recycled water storage capacity from 500 to 5,000 acre-feet, with the dam crest elevation rising to 468 feet above mean sea level. Key infrastructure components include a new spillway to prevent overtopping, a seepage control drainage system, a circulation and aeration system, and the demolition and expansion of strainer and disinfection facilities for filtration, chlorination, and de-chlorination. The project also includes the construction of new onsite access and maintenance roads. All construction must meet or exceed the safety and design requirements of the California Department of Water Resources, Division of Safety of Dams. Environmental compliance is a critical component of the project, as it requires adherence to the NPDES General Permit for stormwater runoff and the implementation of a Stormwater Pollution Prevention Plan. Additionally, the project is subject to an Incidental Take Permit from the California Department of Fish and Wildlife due to the permanent removal of 64.21 acres and temporary impact on 26.76 acres of Crotch's bumble bee habitat. Mitigation measures, including worker education and habitat preservation, have been established to ensure impacts to this candidate species remain below significance.