Ash disposal at the Four Corners coal power plant presents potential long-term liability for Southern California Edison ratepayers, even if the utility successfully sells its interest in the plant, two environmental groups contend. The utilities that own the plant--operated on Navajo land in New Mexico by Arizona Public Service--have been disposing of toxic metal-laden ash in ponds since 1963, according to a report filed with the U.S. Environmental Protection Agency. Now, the operator plans to expand and improve the facility. That means Edison, as a co-owner, would have to help foot the bill. \u201cThe concern is that there\u2019s existing contamination,\u201d explained Suma Peesapati, Earthjustice attorney, adding that expanding the disposal facility without remediation could make it worse. Earthjustice, the Sierra Club\u2019s legal arm, raised the issue last month in Edison\u2019s general rate case proceeding for 2012-14 before the California Public Utilities Commission. It asked regulators to compel Edison to divulge information about the coal ash facility, including how much expansion work would cost and what already may be known about the long-term financial liability. However, CPUC administrative law judge Melanie Darling threw out the Earthjustice motion, said Peesapati. The CPUC judge acted after Edison attorney Gloria Eng late last month responded that the company has a duty to pay its share of costs related to safety, environmental compliance, and reliability at the plant. The Edison attorney also maintained that the information was not relevant to the rate case, though she admitted it might be helpful for the environmental groups to have for a later lawsuit seeking corrective action at the coal waste ponds. Edison spokesperson Gil Alexander said that the utility hopes to complete sale of its interest in the Four Corners plant to Arizona Public Service before the end of the year. He added that under the terms of the sale agreement pending before the CPUC Edison generally \u201cwill continue to be responsible for its pro rata share of plant environmental liabilities, to the extent they arise from the pre-sale operations of the plant.\u201d Meanwhile, he said the utility\u2019s share of improvement projects underway at the ash disposal facility totals about $2.5 million. The total liability is unknown. In light of increased interest in the potential impacts of the ash disposal facility on water, Arizona Public Service is taking a number of steps, according to a filing with the federal EPA. The company is enhancing monitors at the site that measure seepage of water, raising one of the dams that retains water in one of the ponds, plus studying whether additional enhancements may be needed to maintain the integrity of the facility. While the commission closed the book on the matter in Edison\u2019s rate case, it\u2019s likely to come up in a separate proceeding in which Edison wants the CPUC to approve the sale of its interest in the plant to Arizona Public Service, according to Peesapati. In support of its decision, she said the CPUC would examine related environmental issues. The potential dangers of coal ash waste ponds at virtually every coal power plant in the nation burst into public consciousness after a major spill at the Tennessee Valley Authority\u2019s Kingston plant in 2008 polluted tributaries to the Tennessee River. Following the accident, the Environmental Protection Agency proposed new standards for coal impoundments under the Resource Conservation & Recovery Act. To date, the federal agency has yet to finalize its proposal, so what ultimately could be required remains unknown. Unlike the TVA plant--which lies in a humid climate zone with abundant surface water--Four Corners is situated in a desert with little surface water, except when it rains. Lined disposal ponds built in 2003 are adequate, according to an engineering evaluation Arizona Public Service filed with the EPA in 2009. Earthjustice contends otherwise. In its 2010 report, the organization shows that groundwater is contaminated with a variety of toxic metals. It also reveals that the disposal facility contaminates surface water when it runs during the rainy season, although it\u2019s not a source of drinking water. The problem may not be the lined disposal ponds, but instead the unlined ponds lying below the new impoundments.