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PG&E Again Under Scrutiny for Gas-Related Toxin Near Colorado River

California environmental officials have asked Pacific Gas and Electric Co. to step up its efforts to keep toxin-laced groundwater from its natural gas transmission pipeline operations near the California-Arizona border from seeping into the nearby Colorado River, which is a major source of drinking water for 18 million people in Southern California. Tainted groundwater from a nearby compressor station reportedly has gotten within 60 feet of the river, according to a Los Angeles Times news report last week.

The toxin is hexavalent chromium, or "chromium 6," which was used by the PG&E utility in the 1950 and '60s at a natural gas pipeline compressor station near Topock. So far, state officials report that no traces of the toxin have been found in the nearby river water, and PG&E utility officials were quoted as saying there was no indication that toxin-laced groundwater had reached the river.

Last April, the utility began using a larger pump to draw chromium 6-tainted groundwater out of the desert floor around the Colorado River at the California-Arizona border, preventing it from reaching the river waters. At that time, the tainted water reportedly had migrated within 125 to 150 feet of the river, and PG&E's utility told the water officials that the utility was prepared to construct an underground barrier to further protect the river water.

PG&E utility operators near the border are now required to test ground water at selected wells weekly, under mandates from the state environmental officials. The utility also is now required to increase pumping maximum capacity of the treatment system and install an additional well through which more wastewater can be extracted. These added measures were required on Feb. 14 after a sample found a reading of 354 parts-per-billion (ppb) at one well, greatly exceeding the state limit of 50 ppb for chromium 6, according to the LA Times report.

Much more minimal readings in shallower wells, however, have caused state officials and the utility to question whether the situation is worsening.

When the problem surfaced last year, the regional water district serving much of Southern California publicly worried that the underground plume of some 108 million gallons of tainted water with concentrations of chromium 6 at the 12,000 parts/billion level might reach a Colorado River aqueduct and an intake point used by water suppliers in both California and Arizona.

Chromium 6 is the toxic chemical that made "Erin Brockovich," the woman and the motion picture, famous four years ago, relating to some of PG&E's utility natural gas transmission operations in the Mojave Desert, about 130 miles northeast of Los Angeles.

PG&E's gas utility officials and others have expressed confidence that their ongoing efforts will be successful in preventing any contaminated water supplies from getting into the Colorado River near Topock, AZ, where a major PG&E natural gas transmission pipeline picks up interstate supplies from the Southwest.

The center of the concerns is the disposal of quantities of water containing chromium 6 that the utility used from 1951 through 1969 as a means of preventing corrosion and mold in water cooling towers at its isolated gas pipeline receiving station along the Colorado River. The underground plume of tainted water that had been dumped untreated in percolation beds for 18 years is now threatening the river.

Beginning about a year ago, PG&E's removal program took 20,000 gallons of groundwater daily from three extraction wells at Topock, trucking the contaminated water away to a toxic waste disposal site. State officials at that time were satisfied the pumping would move the chromium 6-tainted groundwater away from the river supplies.

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