Hill Canyon Treatment Plant Stormwater Diversion Project

Hill Canyon Treatment Plant Stormwater Diversion Project

The City is proposing improvements to the Hill Canyon Treatment Plant, including storm drain improvements, development of a new debris basin, and development of a new storm water channel to route the offsite storm water flow through and around the treatment plant in a dedicated channel/pipe to an existing discharge location. As part of the self-contained storm drainage system, the Hill Canyon Treatment Plant onsite storm water system includes an existing 30-inch diameter storm drain pipe that connects into a sump pump system and diverts flows to the adjacent sludge-drying beds. The project would demolish the existing sump pump area and structure and re-establish the connection to the existing 30-inch storm drain’s original outfall to transport off-site flows from the adjacent canyon in a dedicated pipeline. The project would include the addition of three storm drain pipes: Pipe A, Pipe B, and Pipe C. Pipe A, located upstream of the flow equalization basins, would divert on-site flows to the existing flow equalization basin’s overflow structure that is routed to the sludge-drying beds. Pipe A would be disconnected from the remaining downgradient 36 inch storm drain pipe. Pipe A would be 36 inches in diameter and have a full flow capacity of 55 cubic feet per second (cfs). Pipe B would receive off-site flows from the proposed channel at the upstream end and tie into the existing 30-inch storm drain at the downstream end just past the Pipe A disconnection point. Pipe B would be 24 inches in diameter and have a full flow capacity of 93 cfs. Pipe C would receive off-site flows from the proposed debris basin at the upstream end and outlet to the proposed channel at the downstream end. Pipe C would be 24 inches in diameter and would have a full flow capacity of 50 cfs. The proposed debris basin would be incorporated at the upstream end of the of the proposed storm drain pipe on the eastern side of the treatment plant to intercept all debris and allow clear water flows from the offsite canyon to continue downstream into the storm drain system pipe, where it is routed to the outfall location. The proposed channel would connect to the proposed debris basin at the upstream end by Pipe C. The proposed channel would convey 50 cfs flows.

Thousand Oaks

Ventura

Citywide

California Air Resources Board (ARB), California Department of Fish and Wildlife, South Coast Region 5 (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 Water Resources (DWR), California Native American Heritage Commission (NAHC), California Natural Resources Agency, California Regional Water Quality Control Board, Los Angeles Region 4 (RWQCB), State Water Resources Control Board, Division of Drinking Water, State Water Resources Control Board, Divison of Financial Assistance, California Department of Transportation, District 7 (DOT)

California Department of Transportation, District 7 (DOT)

Other (Stormwater basin)

Site Plan

Aesthetics, Agriculture and Forestry Resources, Air Quality, Biological Resources, Cultural Resources, Cumulative Effects, Drainage/Absorption, Energy, Flood Plain/Flooding, Geology/Soils, Greenhouse Gas Emissions, Hazards & Hazardous Materials, Hydrology/Water Quality, Land Use/Planning, Mandatory Findings of Significance, Mineral Resources, Noise, Population/Housing, Public Services, Recreation, Schools/Universities, Septic System, Sewer Capacity, Solid Waste, Transportation, Tribal Cultural Resources, Utilities/Service Systems, Vegetation, Wetland/Riparian, Wildfire