The first of two 28,000-horsepower pump turbines at the San Diego County Water Authority’s Lake Hodges Pump Storage Project has begun operations. The facility is now available to help meet the region’s water and energy demands, by providing 20,000 acre-feet of emergency water storage and up to 20 megawatts (MW) of electricity for the region, enough power for 13,000 homes.
“This is visionary and innovative infrastructure that will pay water supply and power reliability dividends for decades,” Water Authority Board Chair Michael T. Hogan said. “The hydroelectric operations will also benefit our ratepayers by generating revenue that will help offset the facility’s operating costs.”
The $196 million Lake Hodges project is a key part of the Water Authority’s $1.5 billion Emergency Storage Project, a system of reservoirs, pipelines and pumping stations designed to ensure that up to a six-month supply of locally stored water will be available for the San Diego region if a disaster or other event interrupts imported water deliveries.
The Lake Hodges project connects the city of San Diego’s Lake Hodges to the Water Authority’s Olivenhain Reservoir and the regional water distribution system for the first time. Previously, Lake Hodges water was available only to local customers of the Santa Fe Irrigation District and San Dieguito Water District.
The connection, via an underground pipeline, will make 20,000 acre-feet of water in Lake Hodges available for emergency use around the county. An acre-foot is about 326,000 gallons, or enough to supply two average single-family households of four people for a year. The project enables the Water Authority to add imported water to Lake Hodges to provide a more consistent water supply and lake level during dry years. It can also move captured runoff out of Lake Hodges during wet years for storage elsewhere, reducing the potential for lost water from overflows of the reservoir’s dam. Lake Hodges has the largest watershed of all lakes in the region.
In addition, the project generates hydroelectric power for the region by sending water from Olivenhain Reservoir through the pump turbines as it flows approximately 770 feet downhill into Lake Hodges. Power is being generated during daylight hours when electricity demand is highest, and water is pumped back into Olivenhain Reservoir during off-peak hours when energy costs less.
When both pump turbines are operational, the Lake Hodges facility will have the capacity to generate 40 MW of electricity on demand to help meet the region’s energy needs. The Water Authority expects the second pump turbine to begin operations in 2012.
“This is a great new asset for the regional power system,” said Michael R. Niggli, president and chief operating officer of San Diego Gas & Electric (SDG&E). “The Lake Hodges project will enhance reliability by adding capacity and flexibility to SDG&E’s system, allowing us to better manage power supplies during periods of peak electrical demand. This project also represents a ‘win-win’ for both water and electricity customers in the greater San Diego area by providing needed energy and water supply infrastructure at a lower cost than if two projects were to be built to meet those needs separately.”
The entire Lake Hodges project consists of the 1.25-mile pipeline tunnel connecting Lake Hodges and Olivenhain Reservoir, a pump station, an electrical switchyard, an inlet-outlet structure under the surface of Lake Hodges, and modifications to the pump station to enable hydroelectricity generation. The pump station facility is built mostly underground near the shore of Lake Hodges and contains vertical space equivalent to a 10-story office building.
The emergency water storage benefits from the Lake Hodges Project will be realized once the Water Authority finishes another key element of the Emergency Storage Project – the San Vicente Dam Raise project in Lakeside. The dam raise project, the largest such project in the United States, will raise the current dam by 117 feet to more than double the capacity of the city of San Diego’s San Vicente Reservoir. It will provide an additional 52,100 acre-feet of regional emergency water storage capacity and up to 100,000 acre-feet of carryover storage – water stored in wet years for subsequent use in dry years. Construction is under way with completion expected in 2013.