Scotts Flat Spillway Improvements Project

Scotts Flat Spillway Improvements Project

The Proposed Project involves the replacement of the existing Scotts Flat Spillway trapezoidal chute with a rectangular chute (i.e., new chute floor with vertical side walls) and a new subdrain system, along with a flip bucket terminal structure. The upper plunge pool would be removed and replaced, the lower plunge pool would be excavated, and new rock armoring would be installed, all to meet the updated PMF flow of up to 23,990 cfs and help with erosion and scour protection. During construction of the Proposed Project, there would be no changes to existing reservoir level or stream releases. This is because construction would occur during the dry season when only the unimpaired low level outlet is in use, not the spillway. During construction, prior to each rainy season, the construction site would be stabilized, and repairs paused such that the spillway can pass flooding flows should it be necessary. Additionally, post-construction operations would be the same as current reservoir, release, and hydropower operations; no changes are proposed. For public safety during active construction, public access and recreation activities would not be permitted in the Proposed Project area but could resume at the end of each construction season when the site is stabilized. NID public noticing to the community for such construction-related closures began in 2025 and has continued through 2026. The new spillway chute, upper plunge pool, and lower plunge pool improvements would be located within the same approximate footprint as the existing facility. The total footprint for the Proposed Project (which includes the work areas and all staging/access) occupies approximately 31 acres.

Nevada City

Nevada

Citywide, Countywide, Northern California

California Air Resources Board (ARB), California Department of Fish and Wildlife, North Central Region 2 (CDFW), California Department of Forestry and Fire Protection (CAL FIRE), California Department of Parks and Recreation, California Department of Toxic Substances Control (DTSC), California Department of Transportation, District 3 (DOT), California Department of Water Resources (DWR), California Fish and Game Commission (CDFGC), California Governor's Office of Emergency Services (OES), California Highway Patrol (CHP), California Native American Heritage Commission (NAHC), California Natural Resources Agency, California Regional Water Quality Control Board, Central Valley Sacramento Region 5 (RWQCB), California State Lands Commission (SLC), Central Valley Flood Protection Board, Delta Protection Commission, Delta Stewardship Council, Office of Historic Preservation, Sierra Nevada Conservancy, State Water Resources Control Board, Division of Drinking Water, State Water Resources Control Board, Division of Drinking Water, District 9, State Water Resources Control Board, Division of Water Quality, State Water Resources Control Board, Division of Water Rights, State Water Resources Control Board, Divison of Financial Assistance

Other (Channel/Spillway)

Spillway Repair

Aesthetics, Agriculture and Forestry Resources, Air Quality, Biological Resources, Cumulative Effects, Energy, Flood Plain/Flooding, Geology/Soils, Greenhouse Gas Emissions, Growth Inducement, Hazards & Hazardous Materials, Hydrology/Water Quality, Land Use/Planning, Mineral Resources, Noise, Population/Housing, Public Services, Recreation, Solid Waste, Transportation, Tribal Cultural Resources, Vegetation, Wetland/Riparian, Wildfire