PG&E; Steps Up Water Efforts

Pacific Gas & Electric Co. plans this week to install a larger pump to draw polluted groundwater out of the desert to keep it from reaching the Colorado River, a major source of Southern California’s drinking water.

Company officials told regional water-quality officials Tuesday that they could also build an underground barrier between the Colorado River and the plume of groundwater tainted by chromium 6. The tainted water has migrated to within about 125 to 150 feet of the river, officials said.

PG&E; also is considering the use of chemical agents that would break down the chromium before it reaches the river, company consultant Terry Herson said.

The plume is coming from PG&E;’s Topock natural gas compressor station, which is located on the California-Arizona state line, south of Needles, Calif.

The utility has used chromium 6 to control corrosion and mold in water cooling towers at the station, which helps move natural gas along a pipeline from Texas to Los Angeles. From 1951 to 1969, PG&E; dumped untreated wastewater in nearby percolation beds.

Chromium 6, also known as hexavalent chromium, is a known carcinogen when inhaled, but scientists disagree over what danger it may pose in drinking water. California, however, has set a standard of 50 parts per billion for chromium in drinking water.

The chromium concentration in the core of the plume is believed to be as much as 12,000 parts per billion.

In early March, PG&E; began pumping polluted groundwater into tanks to be trucked away for treatment in Los Angeles.

The Metropolitan Water District of Southern California is concerned that the plume of at least 108 million gallons of tainted water may reach its aqueduct on the Colorado River. They believe the water could reach the river at a point 42 miles upstream from intakes for both the MWD’s aqueduct and the Central Arizona Project, an agricultural and urban water delivery system.

Water from that area also goes to California’s Imperial Irrigation District, Palo Verde Irrigation District and Coachella Valley Water District.

“Our concern is that the chromium 6 not reach the river,” said Adan Ortega, an MWD spokesman. “It’s pretty straightforward.”

No traces of chromium 6 have been found in the river.