MOORPARK, Calif. — More than two decades ago, two water distributors came up with a tantalizing idea to increase reserves in parched Southern California: create an underground lake so vast it could hold enough to blanket Los Angeles — all 469 square miles — under a foot of water.
The reservoir deep within the earth would be injected with water imported from the snowy Sierra Mountains and other distant sources, which could be pumped back to the surface when needed to soak avocado and lemon groves and keep drinking fountains, espresso machines and toilets gurgling.
Officials boasted that the subterranean vault would become a model for preserving scarce supplies and combating droughts, not just in California but globally. Instead, clusters of wells and skeletal metal piping stand as a cautionary and costly reminder that the promise of water, the fuel of California’s economy and growth, can be as permanent as a mirage.
“They had a great vision,” said Reddy Pakala, who as Ventura County’s water director was expecting to benefit from the 18-mile-long trough running below orchards, tree farms and ranches. “It doesn’t work the way they told us it would work.”
The Las Posas Basin Aquifer Storage and Recovery Project, about 50 miles northwest of Los Angeles, illustrates the risks of what’s known as groundwater banking — warehousing water below ground in aquifers to pump out during dry spells or emergencies.
Imagine a bathtub beneath the earth. If geologic conditions are right, water can be added to such a basin, supplementing naturally occurring groundwater and creating a reserve for future use, much like a water tank.
But at Las Posas, water instead disappeared.
The project, now owned solely by wholesaler Calleguas Municipal Water District in Ventura County, promised to raise local groundwater levels up to 300 feet. Yet groundwater levels dropped steeply when the system went into operation, potentially threatening supplies for nearby residents, ranches and businesses that also draw water from the basin.
“The teacup appears to have a leak in it,” said Robert Eranio, general manager of the nearby Crestview Mutual Water Co., a Calleguas buyer that pipes water to homes.
An Associated Press review of government documents, along with dozens of interviews, found that the venture was marred by insufficient research, poor judgment and hollow assurances — all with a hefty price tag for ratepayers. The cost, estimated in 1995 at $47 million, has gradually tripled to about $150 million. More than $56 million in long-term debt remains.
Calleguas touted the project in the fall of 2010 as a “resounding success” that raised groundwater levels. And yet a year earlier, the company knew the aquifer wasn’t working properly. Not long after the declaration of “success,” the primary financial backer pulled out after Calleguas didn’t deliver the promised water.
Where once officials projected the basin could hold nearly 100 billion gallons — ready for distribution with the flip of a pump switch — the reserve is now only about one-tenth of that, according to officials.
“What was known about the basin wasn’t the whole picture,” Calleguas general manager Susan Mulligan said. “It doesn’t work for a drought. The basin doesn’t store it.”
The project was announced formally in 1991 with the promise that the reservoir could hold enough for a roughly three-year supply for the more than 600,000 people who use Calleguas’ water, which is sold to cities, local agencies and companies that in turn provide water for residents, ranches and businesses.
According to company documents, Calleguas boasted that the project would “virtually drought-proof” its service area. The basin also was meant to resolve a vulnerability for the company: Almost all of Calleguas’ water is imported through a single pipeline, meaning customers could be left dry if an earthquake or other disaster caused serious damage.
“Groundwater storage would significantly improve the region’s water supply reliability . . . ,” a 1994 memo said.
Early signs were encouraging. Technical studies beginning in the late 1980s and a later pilot project concluded that Las Posas could hold huge amounts of water. However, documents show, researchers also found unusual fluctuations in water levels. During one injection test, levels first increased then dropped in monitoring wells.
Researchers later discounted those findings. And it was only after most of the project had been built that serious problems began to appear.