Anderson Dam Seismic Retrofit Gets Closer to Construction

Anderson Reservoir is a critical water supply facility for Santa Clara County and is Valley Water’s largest owned and operated reservoir. Located near Morgan Hill, California, reservoir water releases support water supply, groundwater recharge, flood control, power generation, downstream aquatic habitat, maintenance, and emergency purposes. The Anderson Dam is seismically deficient and the dam spillway lacks the capacity to safely pass flood flows associated with the probable maximum flood. Horizon is assisting Valley Water with environmental planning services including CEQA compliance, FERC order compliance, permitting, and other technical studies.

Following an emergency order issued by the Federal Energy Regulatory Commission (FERC), Valley Water began drawing down the reservoir to Deadpool in October 2020. Construction of the low-level outlet tunnel is anticipated to commence in early 2021. Horizon is leading the consultant team helping Valley Water navigate environmental studies and permitting to comply with recent FERC orders, while also making progress on the larger dam replacement project EIR. Horizon tasks to date have included design alternatives review, impacts assessment, mitigation planning, sediment monitoring plan development, and preparation of construction specifications.

Central Coast Water Board Agricultural Order

The California Regional Water Quality Control Board, Central Coast Region (CCWB), is responsible for the protection of water quality in California’s central coast region, which includes approximately 538,940 acres of irrigated farmland in nine counties. CCWB currently regulates discharges from irrigated agriculture under its Irrigated Lands Regulatory Program using a permit called a conditional waiver of Waste Discharge Requirements (WDRs). CCWB intends to replace the current permit regulating discharges from irrigated lands in the central coast region (commonly referred to as “Agricultural Order 3.0”), thereby establishing “Agricultural Order 4.0”. The new permit established under Agricultural Order 4.0 would be WDRs rather than a waiver of WDRs, and thus would not be subject to a time limit.

Horizon Water and Environment assisted the Department of General Services and CCWB in the preparation of a draft environmental impact report (Draft EIR) to provide an up-to-date, transparent, and comprehensive evaluation of the environmental effects that could occur from implementing Agricultural Order 4.0. The Draft EIR was publicly reviewed in spring and summer 2020. A Final EIR is anticipated in 2021.

Phoenix Lake Dredging

Phoenix Lake is the primary drinking water supply for Sonora, Jamestown, Scenic View, and Mono Village. The lake is also a primary fill source for CAL FIRE helicopter operations. Phoenix Lake is an important natural resource too that supports migrating birds, aquatic wildlife, and wetland habitat.

Horizon has helped the Tuolumne County Utilities District (TUD) since 2010 to develop the Phoenix Lake Preservation and Restoration Plan (PLPRP) to restore lake capacity, reduce watershed sedimentation, improve water quality, and protect, enhance, and restore wetland habitat.

In summer 2020 sediment removal began at the lake. More than 160,000 cubic yards were removed to restore lake capacity, improve water quality, and protect wetland resources. Horizon provided biological monitoring and regulatory agency coordination during the construction process, working closely with TUD, construction manager Anchor QEA, and contractor Steve Manning Construction, Inc.

Horizon – Open for Business

Horizon Water and Environment remains open for business during the Coronavirus pandemic.  We are focused on helping our clients with their ongoing needs and projects.  Don’t hesitate to call or write a Horizon project manager to discuss your project needs.  Or contact Ken Schwarz at

Horizon – Open for Business

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