Chromium-6

Chromium-6, also known as hexavalent chromium, occurs naturally in many water sources. In 2014, the Division of Drinking Water (DDW) adopted a new chromium-6 standard of 10 parts per billion (ppb).

Water supplies in our Willows and Dixon Districts, and in our Salinas District’s Las Lomas and Oak Hills systems, exceeded the new maximum contaminant level (MCL). After taking cost, method effectiveness, waste disposal, and raw water quality all into consideration, our crews installed strong base ion-exchange treatment facilities at each affected location. We continue to perform water quality testing quarterly to ensure the water remains in compliance with the standard.

Prior to installing treatment facilities, we investigated treatment methods to meet the new standard as cost-effectively as possible, but because we did 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.

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