Chromium 6

Chromium 6

Chromium is a naturally occurring metallic element found in rocks, soils, plants and animals. The most common forms are trivalent Chromium (Chromium 3) and hexavalent Chromium (Chromium 6) - the numerals signifying their distinct oxidative state. Chromium 3 is found in foods and is an essential dietary nutrient Chromium 6, on the other hand, can be toxic if ingested in large amounts.

The Chromium 6 detected in our groundwater supply is naturally occurring. There was no industrial spill or discharge. Scientists have estimated that up to 80% of the drinking water sources in the United States could have Chromium 6.

Regulation Requirements on Chromium 6

Since the 1970s until 2014, California enforced a drinking water standard for total Chromium (which includes Chromium 6) of 50 parts per billion (ppb). That level is more stringent than the federal standard of 100 ppb. Note: One part per billion is about one drop in an Olympic-size swimming pool.

California adopted a new drinking water standard of 10 ppb for Chromium 6 in July 2014. On May 31, 2017, the Superior Court of Sacramento County issued a judgment invalidating the Chromium 6 maximum contaminant level (MCL) for drinking water. The court's primary reason for finding the MCL invalid is that the California Department of Public Health (which was responsible for the drinking water program before it was transferred to the State Water Board) failed to comply with one of the requirements in the Safe Drinking Water Act for adopting an MCL. In particular, the department "failed to properly consider the economic feasibility of complying with the MCL." The court also ordered the State Water Board to adopt a new MCL for Chromium 6.

The change became effective with the Office of Administrative Law filing the change with the Secretary of State, on September 11, 2017. Thus, as of September 11, 2017, the maximum contaminant level for Chromium 6 is no longer in effect while the State establishes a new standard. In the interim, Chromium 6 will be regulated under the total Chromium MCL of 50 ppb. The new Chromium 6 MCL could take up to 2 years to set.

All District production wells comply with the total Chromium standard and no treatment is necessary at this time.

For more information on Chromium 6 in drinking water please visit the State Water Board's Division of Drinking Water.

What We've Done to Address Chromium 6

The District has been, and continues to be, very proactive regarding Chromium 6

  • Four wells (Altivo, Seascape, San Andreas, and Bonita) have Chromium 6 levels above 10 ppb. All wells have total Chromium levels below 50 ppb. Altivo Well will be used only for emergency purposes.
  • We conducted a successful pilot treatment project using strong-base anion exchange with grant funding by the Water Research Foundation from April to August 2013.
  • We completed demonstration treatment using strong-base anion exchange from October 2014 to December 2017.
  • We completed demonstration treatment testing using stannous chloride as a reducing agent (to convert Chromium 6 to Chromium 3) with filtration of the precipitate from January to March 2017.
  • Completed environmental permitting for a permanent treatment facility and installed new water transmission mains to treat at a centralized location.

What We're Currently Doing

Design and installation of a permanent, centralized treatment facility to treat water from Seascape, Bonita and San Andreas wells is placed on hold until the new MCL is established by the State. The District can then identify which wells will require treatment, if any, and which treatment alternative will be able to meet the new standard.