Chromium 6

What is 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.

Are there 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 State Water Board declined to appeal the court’s ruling.  Therefore, there is currently no standard specifically for Chromium 6 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.

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 in the treatment of 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 was switched to standby status for use only in an emergency.
  • We conducted a successful pilot treatment project with grant funding by the Water Research Foundation from April to August 2013 – Read complete report published in September of 2014.
  • We demonstrated our local water could be successfully treated to remove Chromium 6 below 10 ppb. We began operating a temporary Chromium 6 treatment plant in October 2014.

What We're Currently Doing

  • We have been successfully treating Chromium 6 levels to below 10 ppb since 2014, and will continue to treat for Chromium 6 with the temporary treatment plant through the end of 2017.

  • Design and installation of a new 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, and which treatment alternative will be able to meet the new standard.