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Total chromium is a naturally occurring element in groundwater supply systems that is made up of chromium 3 and chromium 6 (hexavalent chromium). Chromium is an odorless and tasteless metallic element found naturally in rocks, plants, soil, volcanic dust, humans, and animals. It is also used in several industrial processes. Total chromium is measured by summing up the concentrations of chromium 3 and chromium 6. Chromium 3 has been found to be beneficial and essential for human consumption; chromium 6 has been found to cause cancer if inhaled at high concentrations and to cause cancer in laboratory animals if ingested at high concentration levels.
The hexavalent chromium level in our groundwater supply currently meets the standard set by the United States Environmental Protection Agency MCL for total chromium (100 ppb), which includes hexavalent chromium.
For more information on quarterly hexavalent chromium sampling and public notices, please see the Hexavalent Chromium Update.
The State adopted a new standard that many water agencies in the State cannot meet today. Prior to July 2014, only total chromium was regulated by the California EPA and Federal EPA. The total chromium level in our groundwater currently meets the MCL set by the State set at 50 ppb (parts per billion) and by the U.S. EPA set at 100 ppb, which includes hexavalent chromium.
The City submitted a Corrective Action Plan in August 2015 to the State Water Resources Control Board’s Division of Drinking Water for its review and approval. The compliance plan stated that the City would begin delivery of surface water, which meets all current standards for drinking water constituents, from the Sacramento River in 2016. Delivery of surface water began in June of 2016 and the final connection to the City’s distribution system was made on October 12, 2016.
Since the final connection was made, the City has been optimizing how the water system is operated by limiting use of groundwater wells that exceed the MCL for hexavalent chromium. Over the next few months, groundwater wells that exceed the MCL for hexavalent chromium will be taken out of service permanently or placed in standby mode in case of emergencies.
The City will continue to meet water system demand with surface water as the primary source and supplement with groundwater wells that meet the new hexavalent chromium standard when necessary.
Please contact Water@CityofDavis.org or 530-757-5686 if you have any questions.
For more information on the new regulations please visit: State Water Resources Control Board - Hexavalent Chromium Page or Chromium in Drinking Water - US EPA.