Chromium-6, also known as hexavalent chromium, occurs naturally in many water sources.
The Division of Drinking Water (DDW) adopted a new chromium-6 standard of 10 parts per billion (ppb); it has been finalized by the California Office of Administrative Law and became effective July 1, 2014.
Cal Water formally tested all water sources by the end of 2014 for chromium-6. In those sources where test results exceed the standard, also known as a Maximum Contaminant Level (MCL), of 10 ppb, water suppliers must begin quarterly monitoring for compliance. Water supplies in our Willows and Dixon Districts, and in our Salinas District’s Las Lomas and Oak Hills systems, exceed this MCL.
We have been diligently investigating treatment methods to meet the new standard as cost-effectively as possible, but because we do not have a more reasonable timeline for compliance nor enough time to allow technological methods to become more cost-effective, we expect this to have a significant impact on future water rates. We remain committed, however, to meeting all federal and state water quality standards, because protecting our customers’ health and safety is our highest priority.
California is the first state to set a limit for chromium-6, which is a subset of total chromium. The state has had an MCL of 50 ppb for total chromium since the 1970s. The Environmental Protection Agency has a federal limit of 100 ppb for total chromium and no standard for chromium-6.