The Mojave Desert groundwater thatCadiz Inc.wants to sell to Southland suburbs contains hexavalent chromium, a carcinogen, in amounts that are hundreds of times greater than the state’s public health goal for drinking water.

The presence of the toxic heavy metal, which occurs naturally in the aquifer Cadiz proposes to tap, could force the company to undertake expensive treatment, driving up the cost of the project and ultimately the price of its water.

The chromium contamination is one of several concerns raised by the Metropolitan Water District of Southern California, which owns and operates the 242-mile-long Colorado River Aqueduct that Cadiz would use to transport its supplies to customers.

Metropolitan has also informed Cadiz that the aqueduct space the company is counting on may not always be available, especially during dry years when demand for the Cadiz water would likely be the greatest.

The issues, described in environmental documents released last week, add to the hurdles Cadiz faces as it pursues a project that would push the boundaries of California’s nascent private water market.

They also underscore that though the company is promoting its water as an alternative to imported supplies threatened by drought and environmental restrictions, its groundwater would also be imported 200 miles from the eastern Mojave to coastal customers and could be subject to delivery limits.

“Our aqueduct is probably the most valuable possession we have. So we’re going to be extremely careful,” said Jeffrey Kightlinger, general manager of Metropolitan, which built the aqueduct and has for decades used it to convey Colorado River supplies to millions of Southern Californians.

Metropolitan and Cadiz have a complicated history. More than a decade ago they planned a major water storage and pumping project in the Mojave that the Metropolitan board voted down in 2002, killing the proposal. Cadiz subsequently sued the agency, waging a costly legal battle that ended when it dropped the lawsuit shortly before a scheduled trial.

Now Cadiz needs Metropolitan’s approval for use of the aqueduct, which is key to its latest proposal to withdraw and sell enough groundwater from beneath its Mojave holdings near Amboy to supply 100,000 homes each year. The sales could reap $1 billion to $2 billion in revenue for Cadiz over the life of the project.

The proposal has drawn opposition from U.S. Sen. Dianne Feinstein (D-Calif.), a powerful Mojave advocate, conservation groups and desert residents who fear the pumping will harm the environment of surrounding public lands, including the Mojave National Preserve.

An international company that operates industrial salt works at neighboring dry lakes has filed two lawsuits to block the project and environmental groups are expected to file more legal challenges.

There are currently no federal or state standards for hexavalent chromium, also known as chromium 6, in drinking water. But the state, citing international research that drinking water exposure has been linked to an increase in stomach tumors and liver cancer deaths, last year set a public health goal that will be used in the development of a regulatory standard.

At 14 parts per billion to 16 parts per billion, the chromium 6 levels in the Cadiz water far exceed the public health goal of .02 parts per billion. The ultimate state standard, expected in two to three years, will undoubtedly be higher than the health goal. But even if Cadiz supplies meet the new standard, Metropolitan could still require treatment before the groundwater is pumped into the aqueduct.

“Just having some [chromium 6] in our water could be a detriment to some of our folks,” Kightlinger said, noting that some Southland cities blend Metropolitan supplies with their own chromium-tainted groundwater to reduce pollution levels. “We would have to do more analysis and see what the final standard is and do some modeling” before deciding whether treatment by Cadiz would be required, he added.

Scott Slater, president and general counsel of Cadiz, said chromium treatment could cost as much as $400 an acre-foot. “The worst case would be that we had to treat at every individual well,” he said, adding that the company hopes some form of limited treatment combined with blending the groundwater with river water in the aqueduct would suffice, bringing costs to below $150 an acre-foot. (Cadiz proposes to pump an annual average of 50,000 acre-feet.)

Whatever the costs, they would be covered by contract provisions, Slater said. “The price of the water could go up or the profits of the company could go down.”

He dismissed Metropolitan’s suggestion that there might not be enough room in the aqueduct to accommodate Cadiz shipments, noting that long-term drought in the Colorado River basin has reduced the agency’s deliveries.

“The Colorado River Aqueduct has not been full since 2003,” he said. “I don’t think that you can…project forward and come to the reasonable conclusion that the aqueduct’s not going to be able to take 50,000 acre-feet of water.”

But Kightlinger said Metropolitan has spent the past decade developing supplementary programs, such as acquiring irrigation water and holding supplies in Lake Mead, that could fill the aqueduct in dry years.

“We would pull [the Mead water] and say there is no wheeling capacity available. We’ve filled up our aqueduct,” Kightlinger said. “That’s just something they need to understand.”