The now-demolished River City Metal Finishing is located at 12040 Potranco Rd. on San Antonio's far-Westside. Credit: Courtesy / Google Maps

A toxic and potentially carcinogenic chemical has been found in two water supply wells on San Antonio’s far-Westside, though in levels that do not exceed federal drinking water standards, according to the U.S. Environmental Protection Agency.

Hexavalent chromium, or chromium-6, left over from metal plating work at the now-demolished River City Metal Finishing has been detected in two wells that serve more than 900 people in the Coolcrest neighborhood south of the former industrial site at 12040 Potranco Rd.

The former metal plating site has cleared an initial hurdle for further investigation and cleanup under the EPA’s Superfund program, with officials announcing on Tuesday its addition to the agency’s National Priorities List.

Hexavalent chromium is best known as the focus of environmental campaigner Erin Brockovich, who worked to expose hazardous levels of the chemical in the drinking water of Hinkley, California.

The Coolcrest wells where contamination was detected provide drinking water from the Edwards Aquifer to 909 people in the neighborhood, according to an EPA report from January.

Levels of hexavalent chromium detected in the wells were 0.232 micrograms per liter and 0.194 micrograms per liter, respectively – above the EPA’s cancer risk screening benchmark of 0.05 micrograms per liter, the report states.

Despite the use of the cancer risk screening benchmark, the concentrations are extremely low compared to the EPA’s enforceable drinking water standard known as the maximum contaminant level. For total chromium, that level is 0.1 milligrams, or 100 micrograms, per liter.

An EPA webpage states that hexavalent chromium poses long-term health risks when consumed in levels greater than the maximum over many years. These risks include allergic dermatitis, a skin rash that forms after contact with allergens.

In 2010, the EPA also proposed classifying the chemical as a carcinogen when ingested, though that was never finalized. The EPA does classify it as a carcinogen when inhaled.

The chemical shows up in low levels in drinking water all over the United States, affecting more than 200 million Americans, according to pollution watchdog Environmental Working Group.

The report did not mention any detection of hexavalent chromium in nearby San Antonio Water System wells. None of SAWS’ wells had any hexavalent chromium detections in 2017, spokeswoman Anne Hayden said.

Besides hexavalent chromium, River City Metal Plating left behind cyanide, lead, cadmium, copper, selenium, zinc, and another form of chromium in soil and shallow groundwater below the site, according to the EPA.

The Texas Commission on Environmental Quality, the State’s version of the EPA, did some cleanup work at the site in August 2013, removing drums and containers of waste and demolishing the building, carport, and concrete foundations, according to the EPA.

The commission referred the site to the federal agency due to contamination in the Edwards Aquifer, the EPA document states. 

“Without investigation and remediation of the contaminated ground water plume, contamination may migrate to additional public water supply wells and private wells,” it states.

Twenty water supply wells lie within four miles of the site, according to the EPA.

The National Priorities List contains some of the country’s most polluted sites targeted for cleanup. The EPA first proposed adding River City Metal Finishing, which operated from 1994 until approximately 2002, to the list in January.

Brendan Gibbons is a former senior reporter at the San Antonio Report. He is an environmental journalist for Oil & Gas Watch.