District Plans to Store Water in Underground Aquifer

Ventura County’s largest imported water supplier on Monday unveiled a plan to use a vast subterranean basin near Moorpark as an underground reservoir.

Over the next year, the Calleguas Municipal Water District will pump about 1,000 acre-feet, or about 326 million gallons, of treated water 936 feet below ground into the North Las Posas Basin.

“The overall plan is to have water injected into the aquifer and be able to draw it out,” said Patrick Miller, chairman of the Calleguas board of directors.

One advantage to storing water underground is that it will prevent evaporation, in contrast to the loss of water that takes place in open-air reservoirs aboveground, Miller said.

The $700,000 pilot project is a combined effort by Calleguas and its supplier, the Metropolitan Water District of Southern California.

Kurt O. Reithmayr, a Calleguas director, said that storing state water during the winter months when water is cheap could ultimately help keep prices down.

“We can buy water cheaper and inject it in here,” he said.

Studies of the basin indicate that it can store about as much as Castaic Lake in Los Angeles County, about 300,000 acre-feet. One acre-foot is 326,000 gallons of water, enough to supply two families of four for a year.

Increasing demand by customers in both Los Angeles and Ventura counties is the driving force behind the search for more water storage, officials said. Calleguas’ only existing storage reservoir is Lake Bard, which holds 10,000 acre-feet.

Twenty-seven water agencies in Camarillo, Moorpark, Oxnard, Simi Valley and Thousand Oaks get supplies through Calleguas from the MWD.

About 30 politicians and water officials who gathered at a pump station outside Moorpark to hear about Calleguas’ plans hailed the project as an alternative to building an aboveground reservoir.

By increasing storage capabilities, Ventura County will be less vulnerable to fluctuations in supplies and prices during a drought or if pipelines are cut off in an emergency, Supervisor John K. Flynn said.

“It creates a water bank, and it increases our reliability,” he said.

Improved water quality is another advantage to mixing imported water with ground water, he said. Brackish ground water in the basin will be naturally diluted to safe levels.

Gina Manchester, general manager of the Camrosa Water District in Camarillo, said water officials for years have grappled with the lack of long-term storage in the eastern part of the county.

“We want to put water in at a reduced price during a wet season to be able to draw it out in a dry season,” she said.

Manchester said her agency last year conducted a similar experiment to store water underground in the Santa Rosa Basin.

That project, a combined effort of the Camrosa and Calleguas water districts, successfully held about 500 acre-feet of water underground. But it was put on hold last month because of conservation measures imposed by Calleguas, she said.

“It was very successful,” Manchester said.

Using wells owned by the Ventura County Water Works, Calleguas plans to pump in about 100 acre-feet of water by the end of this month. The agency will tap into the basin in summer when customers use more water and add another 900 acre-feet next winter.

During the trial period, monitors attached to the test well will study water quality and track the movement of water in the ground.

The water will be used to supply Calleguas’ customers in eastern Ventura County as well as MWD’s other customers in western Los Angeles County, said Donald Kendall, a project manager for MWD.

Kendall said the basin could be used as a permanent underground reservoir that could supply all of Ventura County for several years without replenishment.

But it will take several years to fill it. Calleguas plans in 1993 to begin building two new conduits to carry state water into Ventura County.

One will run along the Santa Clara River from Newhall and another will cross the Santa Susana Mountains near Simi Valley. Those pipes will be completed by the end of the decade and will eventually be connected to the North Las Posas Basin, Kendall said.

NORTH LAS POSAS BASIN

The Calleguas Municipal Water District plans to hold supplies of treated water in the North Las Posas Basin, a vast underground reservoir near Moorpark. Studies indicate it can hold up to 300,000 acre-feet of water.