The creeping plume of chemically laced drinking water that plagued the Mojave Desert town of Hinkley and led to a major motion picture about the scandal has continued to spread despite a long-standing order for Pacific Gas and Electric Co. to clean up the mess.

Higher than normal levels of cancer-causing hexavalent chromium, or chromium 6, have been detected over the past year in groundwater more than a half-mile beyond the previous boundary of contamination in the San Bernardino County farming community, water quality regulators revealed last week.

The toxic spillage at a PG&E facility southeast of Hinkley was first exposed by Erin Brockovich, a paralegal at a Southern California firm whose court battle on behalf of sickened residents against the giant utility was recounted in a 2000 movie starring Julia Roberts.

Representatives of PG&E said the levels of chromium 6 in the new location were never above California's safe drinking water standard and have recently been reduced to natural background levels. Still, many farmers and ranchers in the area are angry that the tainted water remains a threat two decades after PG&E stopped discharging the chemical.

"The plume is migrating, and this is a violation of the cleanup order," said Carmela Gonzalez, one of many residents of Hinkley who is demanding action. "It is outrageous that this has been allowed to continue. People are fed up."

Hexavalent chromium was used by PG&E between 1952 and 1966 to fight corrosion in the cooling towers at a compressor station about 12 miles west of Barstow. The wastewater from the cooling towers was discharged into unlined ponds. Some of the contaminated runoff percolated into the groundwater, polluting a 2-mile-long, nearly mile-wide portion of the aquifer.

Reports of illness

Dozens of townsfolk reported falling sick, and some allegedly died from exposure to the carcinogen. Breast cancer, Hodgkin's disease, lung, brain and gastrointestinal cancers, miscarriages, and kidney and ovarian tumors were blamed on the poisoned water.

The utility was ordered to clean up the water after a legal battle spearheaded by Brockovich. The film "Erin Brockovich" focused on a 1996 case that ended with a $333 million settlement on behalf of more than 600 Hinkley residents.

Other lawsuits involving 1,100 people exposed to chromium 6 from PG&E facilities in Kings, Riverside and San Bernardino counties were also settled, the last one for $20 million in 2008.

At that time, the utility appeared to have controlled the spread of the chromium 6 in Hinkley. Then a local farmer with water rights north of the PG&E facility began a pumping operation that experts believe sucked the plume northward.

The Lahontan Regional Water Quality Control Board, which oversees the Hinkley area, issued a cleanup and abatement order in August 2008, instructing PG&E to stop the expansion of the underground chromium plume by Dec. 31 of that year.

The plume nevertheless continued spreading. It is now 2.6 miles long and 1.3 miles wide and extends 0.6 miles farther northeast than it did two years ago, said Lisa Dernbach, the senior engineering geologist for the water board.

Dernbach said increased levels of chromium have recently been detected in about 12 domestic drinking water wells. That's in addition to the dozens of wells previously affected. Not only that, Dernbach said, but chromium has also been found in what she called "the lower aquifer," an area of groundwater separated from the upper aquifer by a layer of clay.

Domestic wells

"This is important," she said, "because the pollution originally affected only the upper aquifer, and a lot of the domestic wells were tapped into the lower aquifer because it was believed to be uncontaminated."

Reports of sick and dying residents continue, including the deaths of three people who Gonzalez said once lived in a house that PG&E purchased and demolished - two died from cancer - but there is no direct evidence of a link between the reported health problems and chromium 6.

Lahontan officials have not slapped PG&E with a notice of violation, a common enforcement tool.

"In this case the enforcement committee decided that a verbal enforcement action to Pacific Gas and Electric Co. was appropriate in part because PG&E was cooperative and working to develop a plan to address the violation, which they have since implemented," said Chuck Curtis, the supervising engineer for the water quality control board.

Bob Doss, PG&E's principal engineer for gas transmission and distribution remediation, said the chromium plume has been expanding and contracting for years, but is, for the most part, corralled.

The trick now, he said, is to move forward with a PG&E action plan that was recently submitted to the Lahontan board. The proposal is to reduce chromium levels to naturally occurring background levels of less than 3.2 parts per billion.

A series of hydraulic and biological methods are being used, Doss said, including the injection of ethanol into the groundwater, a process that converts hexavalent chromium into trivalent chromium, which is not harmful.

PG&E is also growing feed crops like alfalfa using contaminated water, a process that essentially filters out the chromium 6, at a utility-owned dairy.

"The goal, quite simply put, is to continue to use our agricultural treatment in the one area and expand that into other areas," Doss said. "It's a natural beneficial use that makes a lot of sense. It dilutes the plume."

The highest concentration of chromium found in a resident's well over the past year has been about 14 parts per billion, according to Dernbach. The state drinking water standard for chromium is 50 parts per billion. The most toxic area, at the source of the plume, has a concentration of 9,030 parts per billion of total chromium, Dernbach said.

Many forms of chromium

One issue is that the standards do not specifically single out chromium 6, which is one of many forms of chromium. The California Department of Public Health does not currently have a standard for chromium 6 in drinking water, but last year the Office of Environmental Health Hazard Assessment proposed a ceiling of 0.06 parts per billion.

That standard, if it eventually gets approved, would mean that virtually all of the well water in the Hinkley Valley is unsafe to drink.

"Here you have a community that is suffering because their wells have been contaminated, and PG&E hasn't even received a violation," Gonzalez said. "California needs to know that this plume is growing. Erin Brockovich didn't fix it, and Hinkley residents aren't getting justice."

Brockovich, whose law firm said she was out of the country, did not respond to an e-mail about the expanding chromium plume.