U.S. Water News Online
LOS ANGELES -- The Pacific Gas & Electric Co. plans to
begin pumping 20,000 gallons a day of polluted groundwater out of the
Mojave Desert in an effort to keep it from reaching a major source of
Southern California's drinking water.
The groundwater, laced with chromium 6, has migrated to within
about 125 feet of the Colorado River, said Lisa Anderson, an
environmental engineer with the Metropolitan Water District of
The MWD operates the Colorado River Aqueduct, a major source of
Los Angeles' drinking water, and MWD officials say a plume of at
least 108 million gallons of tainted water is on course to 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
Although no traces of chromium 6 have been found in the river,
officials with the state Department of Toxic Substances said it is
crucial to begin heading off the plume now.
``We view the situation very seriously. That's why we're telling
PG&E to start pumping,'' said Ed Lowry, director of the Toxic
Substances Control Department. ``This needs to be addressed now.''
The plume is coming from PG&E's Topock natural gas compressor
station, which is located on the Arizona line, south of Needles.
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 is a known carcinogen when inhaled, but scientists
disagree over what danger it may pose in drinking water.
Anderson said chromium 6 levels in a monitoring well near the
river have ranged from non-detectable to more than 100 parts per
billion over the last few weeks, reaching 12,000 parts per billion in
the mass of the plume.
She said the maximum legal level for all types of chromium in
drinking water is 50 parts per billion.
PG&E engineers are to begin pumping the groundwater and
trucking it to a toxic waste dump.
MWD officials, meanwhile, are pushing for the state Department of
Toxic Substances to also require that the utility construct a
2,000-foot-long, 150-foot-deep underground barrier between the
leading edge of the plume and the river.
PG&E said it is evaluating the proposal.
``It looks to be a promising technique, if it can be installed to
work there,'' said Bob Doss, the company's chief environmental
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