Reservoir’s 1st 4 Wells Are Ready

It will be Ventura County’s largest body of water, a little bigger than Lake Casitas and more than four times the volume of Lake Piru, but don’t make any plans to haul out the boat and fishing tackle. This one is underground.

After more than a decade of research and development, the Calleguas Municipal Water District today will officially open the first phase of its massive water storage project in Las Posas Basin.

The reservoir, which was built with equal parts common sense and sophisticated engineering, is entirely underground, using existing ground-water basins to store as much as 300,000 acre-feet of drinking water.

The storage basin--which can hold enough water to supply 600,000 families for a year--will be tapped in the event of emergencies like severe droughts and earthquakes, when the district’s usual supply has been cut short or is completely out of operation.

“Pumping in the water when we’ve got it and pumping it out when we don’t is the answer we’ve been looking for,” said Patrick Miller, Calleguas board president. “It’s a model program that other agencies in the region should be looking at.”

Although only the first phase of the $50-million project has been completed, Calleguas officials envision a network of as many as 30 wells operating in and around Las Posas Valley, pumping water imported from northern rivers into the ground for storage.

The first phase contains four wells, which will be able to pump 1,500 gallons of water per minute into the underground basin.

The second phase, which is still under construction on land off Grimes Canyon Road, will contain 16 wells and should be running within the next year.

Depending on the wells’ performance, a third phase of construction may begin.

Calleguas, which supplies about 500,000 customers in communities like Simi Valley and Thousand Oaks, receives its water from the Metropolitan Water District in Los Angeles and relies on an 8-foot tunnel running through Santa Susana Pass for delivery.

If that were to rupture during an earthquake, officials say, the district and its customers could be in trouble.

“We’ve always been in some kind of jeopardy here,” said Donald Kendall, Calleguas general manager. “There’s always been a worry that if something were to happen like an earthquake, water would be in pretty short supply, so being able to store enough of it should make everyone a little more comfortable.”

Calleguas faced that kind of scenario immediately after the 1994 Northridge earthquake, when damage to the district’s underground network of pipes and pumps cut off the normal water supply.

To keep customers flush with water, Calleguas began pumping from Bard Reservoir north of Thousand Oaks until repairs could be made.

Although a new $200-million pipeline transporting water from Lake Castaic is expected to be built in the next decade, the underground reservoir will also allow Calleguas to meet increased demand in the future as more people move to the area.

More water could be pumped out of the basin during peak demand to supplement the district’s normal supply and replaced when demand is lower.

The project is also being viewed as a model by other agencies, some from as far away as China and the Netherlands, as a cost-effective and environmentally sensitive way to stockpile water for leaner times.

MWD, for instance, is considering constructing similar well fields along the Colorado River for emergency use in the event the 444-mile-long California Aqueduct were damaged.

“It’s not a new technology, but this method is a first for Southern California and is something other agencies are taking a look at,” Miller said.

Calleguas’ Las Posas project differs substantially from other underground aquifers, such as that fed by the Freeman Diversion Dam near Saticoy. The diversion dam allows water to percolate naturally from large gravel pits at the dam into an aquifer under the Oxnard Plain.

Although the water is used by some farmers to irrigate their fields, it is not designed to be used for drinking and is not stored in the event of an emergency.