The reservoir will be formed by two earth/rockfill dams about 4.4 miles apart within the Domenigoni and Diamond Valleys, as well as, a roller-compacted concrete or alternative earth/rockfill saddle dam. Hydraulic structures associated with the reservoir consist of an inlet / outlet structure, tunnel, spillway, and emergency outlet. The east and west dams are about 180 feet and 280 feet in height, respectively, and incorporate a central clay core with rock shell and a bentonite slurry wall cut-off. The total volume of the east and west dams is approximately 85 Million cubic yards.
The reservoir will receive water from both the State Water Project (SWP) and the Colorado River Aqueduct (CRA). The San Diego Canal (SDC) and a new 12-foot-diameter pipeline within the SDC right-of-way will deliver water supply from the SWP and from the CRA to the reservoir. Water from the SDC will be diverted into the pumping forebay located near the west dam of Domenigoni Reservoir. From this forebay, the water will be pumped into the reservoir by pump-turbines by a 40 MW pump-generating (P/G) plant through a 16-foot-diameter tunnel within the north abutment of the west dam and discharged to the tunnel via the inlet/outlet structure.
Delivery from the reservoir to the CRA will be released through the 12-foot-diameter pipeline, bypassing the pump-generating plant. This pipeline is nine miles long and discharges into the Casa Loma Canal through a 22 MW energy recovery plant. In most circumstances, water will be discharged into the energy recovery plant tailwater pond through energy-dissipating bypass valves rather than through the energy recovery turbines at the energy recovery plant. This procedure is used because water delivered from the SWP to the SDC will be passing through the turbines.
The Domenigoni Valley Reservoir Project involves the design and construction of the following elements:
An earthfill/rockfill embankment on the west end of the reservoir. This west Dam will be 1.8 miles long and 280 feet high; will require 54 million cubic yards of fill; will incorporate a central clay core with rock shell, a bentonite slurry-wall cutoff and drains; and will require excavation of approximately 60 feet to a hard alluvial foundation.
An earthfill/rockfill embankment on the east end of the reservoir. This east dam will be 2.2 miles long and 180 feet high; will require 330 million cubic yards of fill; will also incorporate a central clay core with rock shell, a bentonite slurry-wall cutoff and drains and will require excavation of 90 feet down to bedrock.
A large roller-compacted concrete saddle dam along a low point in the hill that forms the northern boundary of the site. The saddle dam will require 1 million cubic yards of fill.
A pump generator (P/G-1) and forebay at the north abutment of the west dam and substation. A generating Plant (G2) at the head of the San Diego Canal and a substation. An inlet/outlet structure and tunnel. Maximum inflow will be 2100 cubic feet per second (CFS); maximum outflow, 2200 cfs. Withdrawal will be at 25-foot intervals, spilling 90 feet below into the carryover pool that will be at an elevation of 1600 to 1625 feet, a spillway located in the south abutment of the west dam and an emergency outlet.
Borrow areas for the project will be located within the project area, primarily in the hills on the southern edge of the valleys and on the valley floor. The project will also include relocation of 7 miles of Newport Road, which currently runs through the valley; 1.5 miles of the SDC; and utilities.
This project also consists of the design of a 54-inch diameter treated effluent pipeline, approximately 11,000 lineal feet long.