Pointing to a long pattern of dumping hazardous materials, the Metropolitan Water District of Southern California (MWD) successfully prodded Pacific Gas & Electric to begin cleaning up groundwater laced with hexavalent chromium this week. The move is an attempt to keep the chemical from seeping into the Colorado River. According to MWD, the chemical, also known as chromium 6, could contaminate the water supply of 18 million Southern Californians. On March 8, PG&E started pumping 10,000 to 20,000 gallons per day of contaminated groundwater from extraction wells, a cleanup process that the state Department of Toxic Substances Control (DTSC) estimates could take years. The utility did not respond to calls on who will pick up the tab for the treatment. In a February 16 letter to the DTSC, MWD reported that chromium 6?tainted groundwater from PG&E?s Topock natural gas compressor station was within 125 feet of the river. MWD was alarmed by the contaminated mass that measured close to 12,000 parts per billion of chromium 6, a known carcinogen. The acceptable level in the state?s drinking water is 50 ppb. Chromium 6 was used at Topock to reduce corrosion. Dumping hazardous waste at Topock was ?standard operating procedure? for PG&E and is similar to the way it ran the Hinkley and Kettleman plants, charged Bob Muir, spokesperson for MWD, the state?s largest water supplier. The Hinkley facility was featured in the movie Erin Brockovich. MWD has warned that the 11,900 ppb of chromium 6 that has been detected in contaminated groundwater is not far off the peak concentration detected at the highly publicized PG&E compressor site at Hinkley. PG&E settled parts of the chromium 6 litigation for $333 million. The suits alleged that ingesting and inhaling the chemical poisoned residents. According to Ed Masry, the attorney who with Brockovich spearheaded the legal challenge, clients are set to return to court this month to take up elements of that suit. MWD also disclosed that PG&E discharged mercury, asbestos, solvents, and other hazardous wastes in the past at the Southern California facility, located near the state?s border with Arizona. Between 1951 and 1969, PG&E released untreated wastewater containing chromium 6 from cooling towers into water evaporation ponds near the plant, according to MWD. From 1970 to 1974, treated wastewater was pumped into an unregulated injection well. Ron Baker, spokesperson for the DTSC, said it has taken years for chemicals to migrate from evaporation ponds down to the groundwater. Jon Tremayne, spokesperson for PG&E, acknowledged that between 1951 and 1964 the utility dumped untreated wastewater but said that since 1964 it has treated wastewater to remove chromium 6. Baker said that before the federal Environmental Protection Agency introduced regulatory oversight in the 1970s, dumping untreated waste on the ground was the norm for many industrial facilities. There is much dispute within the scientific community as to what constitutes a safe level of chromium 6 in drinking water. Because of the high levels found in the sample taken by the toxics department, there is no question ?that something needs to be done to stop spreading [the contamination] from endangering the Colorado River, and that?s what we?re doing,? Baker said. MWD views pumping as a short-term fix and has called on PG&E to build an underground barrier, known as a ?slurry wall,? along the leading edge of the contamination plume as more effective protection against contamination. While the toxics department has ordered PG&E to conduct an 18- to 24-month assessment of the barrier proposal, questions remain about whether this approach will seal off the contamination. The proposed wall would be the equivalent of an 8- to 10-story building and could raise a host of environmental issues, according to Baker. These include potential impacts on wildlife reserves in the region.