Managing Hexavalent Chromium in California Small Drinking Water Systems

Photo Credit: "PG&E Did It, And Always Knew, Since 1952!" by Alison Cassidy 05/31/2015; Edited with cropping and color correction.

In recent years, hexavalent chromium (chromium-6) has become a taxing contaminant for small water systems in California to manage. The contaminant has a complex regulatory and legal history, some of which was made renowned by the 2000 film Erin Brockovich starring Julia Roberts. Presently, an invalidated state drinking water standard, an uncertain regulatory future, and varying positions on the potential drinking water health risks, leave small systems unsure how to proceed. Chromium-6 challenges have only been exacerbated by its history of environmental contamination through industrial sources.

On a federal level, there is currently no drinking water standard. Hexavalent chromium was evaluated under the third round of Unregulated Contaminant Monitoring (UCMR 3). While the U.S. EPA is still evaluating the results and risks of chromium-6, there is no current undertaking to develop a new drinking water standard. A regulation does, however, exist for total chromium which includes all forms of chromium. The total chromium standard of 100 ppb assumes that the chromium sample is composed entirely of its most toxic form, chromium-6, to safeguard against the greatest potential risk. In California the total chromium standard was set at 50 ppb. At the time these total chromium standards were established, ingested hexavalent chromium was not associated with cancer risks. Exposure through drinking water has now been linked to both cancer and skin reactions.

According to a 2018 publication by the Water Research Foundation, the three most reliable water treatment technologies for chromium-6 removal include: reduction, coagulation, and filtration (RCF); adsorption onto regenerable strong base anion (SBA) resin; and adsorption onto disposable weak base anion (WBA) resin. Each technology generates unique waste with different handling and disposal requirements that can be expensive for very small systems to adopt and maintain. In a recent 2019 publication by the American Water Works Association, researchers identified a treatment technique that does not generate concentrated waste by reducing chromium-6 to easily separable and non-toxic chromium-3.

Much of the chromium found in drinking water was introduced from rocks, animals, plants, or volcanic activity. While both chromium-3 and chromium-6 can occur naturally, chromium-6 is more often affiliated with industrial sites that use chrome plating, paints and sprays, leather tanning, or corrosion inhibitors.

Hexavalent chromium was brought to the forefront of public health concerns in 1996 as a result of a class-action lawsuit between Hinkley, CA and Pacific Gas & Electric (PG&E). Prior to 1996 PG&E had released chromium tainted wastewater into unlined spreading ponds around Hinkley, a remote desert community in San Bernardino County. When Hinkley learned of the contamination years later, it filed a lawsuit against PG&E. During this time, legal clerk Erin Brockovich worked to link cancer illnesses to chromium-6 exposure. A convoluted series of legal battles between PG&E and those who developed illnesses from the contamination left the scientific community uncertain about the health risks of chromium-6 in water.

Only in 2008 did the U.S. EPA recognize research by the National Toxicology Program identifying cancerous tumors in rats and mice who ingested heavy doses of hexavalent chromium. By 2013 the growing plume of contamination in Hinkley had spread to over six miles long and two miles wide. Following a long regulatory investigation of the chromium-6 health effects during the PG&E legal battles, California eventually recognized the link between chromium-6 and cancer in 2014, approving a maximum contaminant level (MCL) in drinking water at 10 ppb effective July 1, 2014.

The new standard proved difficult for many small utilities to meet compliance. Senate Bill 385 gave systems with source water above the new MCL until January 1, 2020 to come into compliance without violations. During this time, impacted systems had to submit plans for achieving compliance, obtain approval of the plan, and carry out the plan in a timely manner. Plans could include steps for finding funding, conducting a feasibility study, investigating treatment options, performing an environmental review, acquiring land, facilitating construction, and testing. 

Developing, implementing, and submitting reports for these plans was no small task for any utility. Drinking water systems granted time to meet compliance were also monitoring sources of hexavalent chromium quarterly. As systems notified customers of new exceedances, they took on the burden of managing strong community concerns. It’s estimated that chromium-6 has been detected in 2,475 California drinking water sources spread across 48 out of 51 counties. The Environmental Working Group published a map that includes the average detected chromium-6 concentration by county across the country.

In developing the new MCL, California estimated that costs to implement the rule would increase water bills by $64 per year for customers of large systems and $5,640 per year for customers of small systems. Polluters were not held accountable to assist with compliance costs in areas of industrial contamination. For small drinking water facilities like the Phelan Pinon Hills Community Services District (PPHCSD) or the San Bernadino County Special Districts Department, the sticker price for compliance came at a cost in the millions. Furthermore, these small systems must spread costs over fewer people making the adoption of hexavalent chromium solutions cost prohibitive. In San Bernadino County, PPHCSD opted to take on a water blending project while the San Bernadio County Special Districts began exploring a pilot program for new treatment technology. Ultimately petitioners against the rule claimed that the MCL was too stringent with compliance too expensive. As a result, the rule was invalidated in 2017 by Sacramento Superior Court under grounds that the Department of Health failed to consider the economic feasibility for small water systems. By this time towns like Phelan had already spent $3.7 million toward the mitigation of chromium-6.

Using the data collected during the standard’s three years of implementation, the State Water Resources Control Board intends to develop a new MCL. As regulatory development ensues, impacted systems are left uncertain how to proceed. There is no certainty that a new MCL will in fact be implemented. Yet if the Board successfully passes a new MCL, systems cannot be certain that the standard will remain at 10 ppb. The board developed this FAQ sheet to help systems with ongoing loans and project plans determine their next steps. The PPHCSD in Phelan believes that the 10 ppb standard will be reinstated and has continued to move forward with their $17 million blending project.

Systems that choose to pause or discontinue projects are still left uncertain whether they are providing their community with safe drinking water. While legally facilities must now comply with the total chromium standard of 50 ppb, California did set the chromium-6 public health goal (PHG) at 2 ppb. This PHG conflicts with the U.S. EPA’s total chromium maximum contaminant level goal (MCLG) of 100 ppb and existing research debating that ingestion of chromium-6 can alter its toxicity. For now systems must use their best judgement and remain transparent with their community about all decisions. If the 10 ppb standard is reinstated, operators of nearly 800 groundwater supply wells will be in violation of the rule according to a 2018 publication by Hausladen.

California small water systems are not alone in their challenge to manage drinking water contaminants in the absence of strong regulatory guidance. Water systems across the country have had to make tough decisions about treating unregulated drinking water contaminants, many of which were spread through commercial practices. An example of such contaminants is per- and poly-fluoroalkyl substances (PFAS) and cyanotoxins. Utility decision making to handle these unregulated contaminants must factor in finances, source water conditions, potential project affordability, availability for partnerships, existing infrastructure needs, and more. As we move closer to the new year, water systems and regulatory agencies should take note of the chromium-6 decision-making in California to understand the potential impacts of new regulations on small systems.

Katie Buckley substantially contributed to this article.