Hinkley groundwater contamination

Pacific Gas and Electric Company
Industry	Energy (Natural gas transmission and distribution)
Founded	1905
Headquarters	San Francisco, United States
Products	Natural gas transmission and distribution

From 1952 until 1966, the Pacific Gas and Electric Company (PG&E) released significant volumes of wastewater contaminated with chromium into unlined evaporation ponds located near Hinkley, California, situated in the Mojave Desert approximately 100 miles north-northeast of Los Angeles.

PG&E employed hexavalent chromium (chromium 6), an economical rust-prevention chemical, within its compressor station operations for natural gas pipelines. Hexavalent chromium compounds are known to be genotoxic carcinogens.

In 1993, legal assistant Erin Brockovich launched an inquiry into the health consequences stemming from this contamination. The resulting class-action lawsuit concluded with a $333 million settlement on July 2, 1996 (equivalent to roughly $ in today’s dollars). PG&E finalized all associated claims by 2008. Since then, Hinkley’s population has sharply decreased; by 2016, The New York Times characterized it as nearing ghost town status.

History

During the early 1950s, Pacific Gas & Electric (PG&E) established its initial compressor stations in Topock, Arizona and Hinkley. These facilities were integral to a statewide natural gas transmission network comprising eight compressor stations connected by 40,000 miles of distribution pipelines and 6,000 miles of main transport lines. Serving approximately 4.2 million customers from Bakersfield to Oregon’s border, the stations utilized hexavalent chromium additives as rust inhibitors within cooling towers and discharged contaminated water locally between 1952 and 1966. PG&E did not notify the local water authority about this pollution until 1987.

Following the discovery of illness clusters associated with hexavalent chromium exposure by legal clerk Erin Brockovich, residents of Hinkley initiated a class action lawsuit—Anderson, et al. v. Pacific Gas and Electric. The case proceeded through arbitration with damage awards capped at $400 million for more than 600 claimants. Initial compensation totaling around $120 million was awarded to 40 plaintiffs before PG&E agreed to a $333 million settlement in 1996, marking one of the largest class action resolutions in U.S. history at that time.

A pivotal element during settlement discussions was a 1987 study by Chinese researcher Jian Dong Zhang that linked chromium 6 contamination to cancer risk. However, in 1997 Zhang retracted his findings amid contentious circumstances involving ChemRisk, a consulting firm affiliated with PG&E. This retraction influenced regulatory approaches and delayed implementation of stricter drinking water standards.

In 2001, the California Environmental Protection Agency (CalEPA) formed the Chromate Toxicity Review Committee to evaluate chromium 6’s carcinogenicity. The committee’s conclusions minimized concerns about contamination impact and advocated for academic oversight rather than regulatory action. This influenced CalEPA’s decision to withdraw its 1999 public health goal concerning total chromium levels in drinking water.

After a lawsuit initiated by Engstron, Lipscomb and Lack representing around 900 plaintiffs alleging chromium pollution in both Hinkley and Kettleman City, California’s Senate held hearings in 2003 investigating potential manipulation of scientific reviews on chromium toxicity. Testimonies revealed how PG&E utilized the committee’s report to dispute contamination claims.

Since then, certain California-based researchers and organizations such as the Desert Sierra Cancer Surveillance Program and ChemRisk have contested assertions that chromium 6 is genotoxic or directly responsible for cancer clusters near Hinkley.

PG&E was mandated to discontinue use of chromium 6 and undertake groundwater remediation efforts. By 2008, the contaminated chromium plume was expanding; media focus intensified by 2011. PG&E commenced purchasing endangered properties and supplying bottled water to Hinkley residents by late 2010. By 2013, the plume spanned over six miles in length and two miles in width.

In 2006, PG&E reached a statewide settlement addressing additional hexavalent chromium claims for $295 million; in 2008 it resolved remaining Hinkley-related claims for $20 million. That same year, the U.S. Environmental Protection Agency (EPA) reacted to National Toxicology Program findings linking chromium 6 exposure to tumor development in rodent studies.

California became the first state to implement a maximum contaminant level (MCL) specifically for hexavalent chromium at 10 parts per billion (ppb) in July 2014. The EPA does not maintain a distinct MCL for hexavalent chromium but enforces a general chromium MCL of 100 ppb encompassing all forms combined.

Groundwater contamination

PG&E manages a compressor station in Hinkley that serves its natural gas transmission network, where the gas undergoes recompression roughly every . Cooling towers are employed at this facility to lower the temperature of the gas post-compression.

Between 1952 and 1966, the water used in these cooling towers contained hexavalent chromium, a known carcinogen, applied to inhibit corrosion. This water was held in unlined reservoirs, which permitted the hazardous substance to infiltrate the groundwater. Consequently, this led to groundwater pollution, impacting the surrounding soil and contaminating wells near the compressor station. Initially, the contaminated plume extended about long and nearly wide, but by 2013 it had grown to approximately long and almost wide.

In Hinkley, hexavalent chromium concentrations averaged 1.19 parts per billion (ppb), with maximum levels reaching 20 ppb. At PG&E’s Topock Compressor Station, average levels were 7.8 ppb, peaking at 31.8 ppb. By comparison, California’s proposed health guideline for hexavalent chromium in 2011 was set at 0.02 ppb. Although the EPA raised the federal maximum contaminant level (MCL) for total chromium to 100 ppb in 1991, California retained a more stringent limit of 50 ppb. CalEPA noted in 2015 that when these limits were established, hexavalent chromium ingestion was not recognized as a cancer risk, unlike current scientific consensus.

Contaminant plume

Testing conducted in August 2010 revealed that the polluted plume was advancing into the lower aquifer. By September 2013, CalEPA documented its expansion to approximately long and wide. In 2015, the California Regional Water Quality Control Board for the Lahontan Region issued a directive to PG&E mandating cleanup of the chromium contamination. At that point, the plume measured about " in length and in width," covering Hinkley Valley and extending into Harper Dry Lake Valley.

Remediation efforts

By 2013, PG&E had allocated more than $750 million toward cleanup activities. Sheryl Bilbrey, who led PG&E's remediation program, highlighted the project's complexity and regulatory hurdles contributing to delays: "This is an extremely complex undertaking. We operate under strict regulatory oversight with numerous stakeholders involved. It is crucial that we execute this correctly."

As part of the 2013 Science for Sale series on PBS NewsHour, journalist Miles O'Brien interviewed Kevin Sullivan, PG&E’s director of chromium remediation. At that time, PG&E had addressed a portion of the contamination but anticipated another four decades to complete the cleanup fully. Measures included installing a concrete barrier nearly half a mile long to contain the plume, injecting ethanol to chemically reduce chromium VI to chromium III, and cultivating alfalfa crops on affected land. Environmental advocate Erin Brockovich expressed astonishment that PG&E had not yet fulfilled cleanup commitments made over ten years prior. Communications with the Water Board in 2014 confirmed that chromium contamination from PG&E’s Hinkley Compressor Station had reached the lower aquifer at concentrations exceeding drinking water standards. Documentation of cleanup progress is available through CalEPA resources.

Controversies

A report from the National Toxicology Program in 2007 identified that high doses of chromium VI induced gastrointestinal cancers in rodents at concentrations exceeding 5 mg/L (5 ppm or 5,000 ppb).

Hexavalent chromium levels averaged 1.19 ppb in Hinkley with peaks up to 20 ppb; at PG&E’s Topock Compressor Station averages were 7.8 ppb with peaks reaching 31.8 ppb (PG&E Background Study). In 2013, Bilbrey acknowledged ongoing scientific disputes regarding chromium VI toxicity and cited unresolved regulatory issues as causes for project delays. Subsequently, in July 2014, CalEPA established an MCL of 10 ppb for chromium-6 after studies linked its ingestion to cancer risk.

CalEPA

In July 2014, California became the pioneer state to implement a maximum contaminant level (MCL) for hexavalent chromium (chromium 6) in drinking water, establishing a threshold of 10 parts per billion (ppb). A 2015 report by the United States Geological Survey (USGS), which referenced the EPA’s 2010 health effects assessment, revisited federal regulatory standards. Following California's initiative, Illinois partnered with USGS on related studies published that same year. The EPA had proposed in 2010 that Cr(VI) be designated as likely carcinogenic when consumed over a lifetime. Measurements for chromium 6 concentrations are expressed in micrograms or milligrams per liter (μg/L and mg/L), where 50 μg/L corresponds to 50 ppb.

John Morgan

Since 1988, the California Cancer Registry (CCR) has documented all cancer cases statewide. The Desert Sierra Cancer Surveillance Program (DSCSP) oversees regions including Hinkley in San Bernardino County. Epidemiologist John Morgan joined DSCSP in 1995 and has authored over 100 abstracts and reports, many subjected to peer review. His research frequently disputes assertions linking chromium contamination to a cancer cluster in Hinkley, often minimizing reported cancer incidence there.

In his notably cited 2010 CCR analysis, Morgan determined that cancer rates in Hinkley "remained unremarkable from 1988 to 2008." Alongside co-author M. E. Reeves, he observed that the 196 cancer cases recorded between 1996 and 2008 were fewer than anticipated based on demographic and regional cancer statistics.

At the 2012 North American Association of Central Cancer Registries Conference, Morgan used visual aids to highlight that although inhaled Cr[VI] is recognized as carcinogenic, the carcinogenic potential of ingested aqueous Cr[VI] is still debated. He disseminated his results through letters and poster presentations.

Nevertheless, a 2013 inquiry by the Center for Public Integrity revealed shortcomings in Morgan’s methodology, including disregarding what others consider a legitimate cancer cluster and omitting individuals exposed to the most severe contamination zones, casting doubt on the reliability of his conclusions.

Dennis Paustenbach

Dennis Paustenbach serves as a consultant and expert witness for corporations engaged in litigation related to product safety and environmental concerns. He established ChemRisk and served as its director, with senior scientist Brent Kerger among his team members. Their clientele included PG&E and BP.

Paustenbach was connected to controversy surrounding research by Chinese scientist Jian Dong Zhang, who in 1987 linked chromium contamination in drinking water to higher stomach cancer rates near a chromium smelter in Liaoning Province. CalEPA’s 2008 evaluation supported Zhang’s findings of increased cancer incidence. PG&E retained ChemRisk, a commercial scientific consulting firm, to counter these claims.

The Center for Public Integrity reported that Zhang’s revised 1997 study—published without disclosing PG&E’s involvement—contributed to delaying California’s enforcement of tougher chromium drinking water regulations. The EPA cited this revision when approving chromium use in wood preservatives and discounted chromium-6 as an oral carcinogen.

In 2006, the Journal of Occupational and Environmental Medicine retracted Zhang’s 1997 article due to undisclosed financial backing and intellectual input from external parties, including ChemRisk acting as consultants for PG&E amid litigation over chromium contamination. Paustenbach later collaborated with Exponent and has been scrutinized by investigative journalists regarding these consulting roles.

Steven Patierno

In September 2010, scientists at the EPA determined that "even minimal exposure to a chemical frequently present in tap water might lead to cancer." Steven Patierno, who served as a defense expert witness in seven chromium-6 legal cases, was appointed by the EPA to participate in the peer-review panel evaluating the agency's chromium-6 research, which sparked concerns regarding potential conflicts of interest. These connections were uncovered by investigative reporters from the Center for Public Integrity in their Toxic Clout series.

Patierno, who holds the position of deputy director at the Duke Cancer Institute and formerly taught pharmacology at George Washington University, conducted research claiming that "consuming low levels of chromium (VI) does not induce cancer." He collaborated on publications with ChemRisk's Paustenbach, another expert witness for PG&E. In 1996, they jointly authored a study concluding that chromium 6 is not genotoxic.

Film

The contamination event and ensuing litigation served as the basis for the 2000 biographical movie Erin Brockovich, featuring Julia Roberts in the lead role. The film received widespread critical praise, with Roberts winning both a Golden Globe Award for Best Actress in a Motion Picture – Drama and an Academy Award for Best Actress. Erin Brockovich herself remarked that the film was approximately 98 percent accurate and made a brief cameo appearance.

External links

Hinkley Groundwater Remediation Program