Should Soquel Creek Water District be worried about chromium levels?
While most of the discussions around water in Santa Cruz County have focused on quantity, a new draft report released by a state environmental agency has some local water districts also looking closely at quality.
The California Office of Environmental Health Hazard Assessment released a draft report in April, examining, among other things, contaminants in water supplies throughout the state. The report is essentially a screening methodology to help identify California communities that are “disproportionately burdened by multiple sources of pollution,” according to state officials. Its coverage is highly granular—broken down into more than 8,000 census tracts.
The draft report looked at 12 carcinogenic contaminants, only two of which—arsenic and hexavalent chromium, or chromium-6—are regularly detected in local water sources. Both are considered naturally occurring and aren’t a consequence of man-made activities, according to Taj Dufour, a water engineer with the Soquel Creek Water District.
Four out of 16 of the Soquel Creek Water District’s wells—Altivo, Seascape, San Andreas and Bonita—ranked above California’s public health goal limit of .02 parts per billion (ppb) for chromium-6, and in some cases, above the state’s maximum contaminant level (MCL) standard of 10 ppb, which went into effect on July 1—after an MCL of 50 ppb since the 1970s. (A part per billion is about one drop in an Olympic-size swimming pool.)
The chromium treatment issues represent a different kind of water problem than what the Soquel Creek Water District has been dealing with in recent months as California’s drought worsens to what some scientists are calling historic levels.
Dufour says the chromium is largely traced to the natural geology of the wells—the element leaches out from the ground itself. The SCWD ceased normal pumping operations at Altivo well, which had the highest levels of chromium-6, and reduced pumping at the other affected wells—all of which receive water from the Aromas Red Sands aquifer, which extends from Aptos Creek through the Pajaro Valley. At the Aromas Red Sands aquifer, chromium-6 levels detected ranged from 1.5 ppb to 40 ppb.
Chromium-6, an odorless and tasteless element may be a carcinogen if ingested, according to a long-term study by the Department of Health and Human Services National Toxicology Program. It is much more dangerous when it is airborne, but it wasn’t until 2008 that the EPA began a rigorous ongoing review of the health effects of orally ingested chromium-6. California’s new MCL of 10 ppb is a conservative one, well below the federal standard of 100 ppb.
While the report gave comparatively lower marks to local water supplies than might have been expected, local water officials cautioned that the draft report’s methodology could be misleading. They say our drinking water is safe and the report should be taken with a grain of salt.
The discrepancy, says County Water Resources Director John Ricker, largely boils down to the difference between two existing thresholds when it comes to standards for substances in drinking water.
The U.S. Environmental Protection Agency sets the maximum contaminant levels by determining how much of a particular contaminant can be present with no adverse health effects. MCLs are considered the enforceable drinking water standards that must be met by public water systems.
This draft report, however, used a different standard called public health goals (PHGs), which are set by the California Office of Environmental Health Hazard Assessment, a sub-agency of the California EPA. The MCL for chromium-6 is 500 times higher than the public health goal most recently set in 2011, and the MCL for arsenic is 250 times higher than the public health goal, set in 2004.
Unlike MCLs, PHGs are not enforceable and aren’t required to be met by any public water system. Like their name suggests, they are set as goals based on public health risk considerations and include a wide margin of safety—established at the “one-in-a-million” risk level, meaning not more than one person in a population of one million people drinking water daily for 70 years would be expected to develop cancer as a result of exposure.
A spokesperson for the OEHHA said the agency wouldn’t comment on the report until it’s finalized.
“We’ve not been shown the specific data used,” says Christine Mead, operations and maintenance manager at Soquel Creek Water District. “We’re well within our limits.”
The Association of California Water Agencies (CWA) took umbrage with the report as well, writing to the state agency that the CWA has “significant policy, technical and process concerns” with it. One major concern is that the public agencies and other water departments responsible for providing safe drinking water to the public weren’t consulted for the report.
The district released its own water quality report in April that showed it was within standards set by the U.S. EPA, whose standards are not as strict as California’s.
“The levels we have aren’t a toxic dump or anything like that,” Dufour says. These aren’t new levels, either, he explained. Rather, laboratory testing technology has vastly improved, meaning that smaller and smaller amounts can now be detected.
“Over the last three or so years, we’ve been conducting all sorts of studies to focus on water quality programs—specifically focusing on chromium-6,” Dufour says.
The district is currently working to install a treatment program that’s expected to take care of the chromium as soon as it gets going—and will bring those levels back down to under 10 ppb billion, with a goal of 8 ppb. That’s expected to happen by the end of August, and the new equipment—which is temporary—can treat 1,000 pounds of water per minute. This will get the district through the next 18 months or so that it expects will be needed to install a more permanent treatment system.
Still, Dufour says the district hasn’t had any of its customers reach out to them with concerns about the report, which he emphasizes is still in draft mode.
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