A search for new sources of water by the Rio Linda-Elverta Community Water District has found that wells closest to the former McClellan Air Force Base have the highest levels of hexavalent chromium, or chromium-6, a known carcinogen.
That finding was an unintended offshoot of the search by the small water district, which serves 4,600 customers. It suggests that onetime military activity at McClellan, which closed as a base in 2001 and now operates as a business park, may still affect the community.
“Looking at the broader picture, and the data from the well siting study, suggests that the chromium levels are coming from the contamination from the Air Force base to the southeast,” said Larry Ernst, a hydrogeologist with Wood Rodgers and author of the report.
That assessment found that water from six of 11 wells in the Rio Linda-Elverta district tested above the state’s maximum contaminant levels for chromium-6. The state standard is 10 parts per billion. All of the wells above the state standard are either in the east or south areas of the water district, near the 3,452-acre former air force base just northeast of Sacramento city limits.
His research found detectable amounts of chromium-6 in the shallow aquifers near the base and that levels decrease the farther away wells are from the base. Groundwater contamination with hexavalent chromium is often the result of chrome plating of aircraft and equipment, which was conducted at the base for decades.
McClellan qualifies as a Superfund site because of the 326 waste areas the Environmental Protection Agency has identified on the base. Superfund is the primary federal program to clean up the nation’s uncontrolled hazardous waste sites.
The Air Force disagrees with Ernst’s contention that chromium levels in the Rio Linda-Elverta district are due to contamination from the McClellan property, said Steve Mayer, radiation safety officer at McClellan.
The Air Force has tested its groundwater for hexavalent chromium at McClellan since the 1980s and has identified two chromium plumes there, Mayer said. The Air Force is responsible for cleanup of soil deeper than 15 feet, as well as groundwater at McClellan, according to the EPA.
“Extraction wells are actively removing and treating the groundwater associated with those two plumes at this time,” said Mayer. “Both of those are within base boundaries.”
Rob Swartz, manager with the Sacramento Groundwater Authority, said he was surprised by the results of Ernst’s findings. He said more research is necessary to determine why wells closest to McClellan have the highest chromium-6 levels.
“I think it’s premature to reach any conclusion,” Swartz said. “I don’t think we can rule out that there are potential natural sources of the chromium.”
Exposure to chromium-6 can lead to skin irritation, occupational asthma, and kidney and liver damage, according to the National Institute for Occupational Safety and Health. The carcinogen came into the limelight in 2000 with the film “Erin Brockovich,” in which the title character, played by Julia Roberts, sued Pacific Gas and Electric Co. over chromium-6 found in a Mojave Desert community’s drinking water.
On the western side of the Sacramento Valley, several wells in Davis, Woodland and Dixon have recorded high levels of chromium-6. Those areas may be affected by the Coast Ranges, which contain marine-based sediments that typically are sources of naturally occurring chromium, Swartz said.
Some of the highest well readings have been found at the former Department of Energy Laboratory for Energy-Related Health Research in southwestern Davis. UC Davis environmental scientist Sue Fields has said it is not known why the chromium-6 levels are rising at wells at that site. Unlike military activities at McClellan, no chrome plating occurred there.
It is also not well understood why chromium levels are high in the Rio Linda area, which is farther from the Coastal Ranges than communities in Yolo County. But Ernst does not believe high chromium-6 levels in the Rio Linda and Elverta area are naturally occurring.
“If the levels are lower the farther you get away from the site, the likelihood is that the high levels are due to contaminants at the McClellan site,” he said.
Ernst sees the high chromium levels within the Rio Linda-Elverta district as a budgetary concern for small water agencies. Mary Henrici, the district’s general manager, estimated costs for three new wells at $10 million to $13 million, plus $1 million yearly in operational and maintenance costs for wells now in use that can be treated for chromium-6.
“When you have to find a new supply of water or treat the current supply – that’s always expensive,” Henrici said.
She said any new wells will likely be in the northern part of the water district, closer to Placer County than to McClellan.
Edward Ortiz: (916) 321-1071, @edwardortiz