Blog: New science informs extent of hexavalent chromium groundwater plumes in Hinkley Valley
The USGS report, commissioned by the Lahontan Regional Water Quality Control Board, showed how the valley’s geology affected background hexavalent chromium concentrations in groundwater. Hexavalent chromium occurs naturally in groundwater in the Mojave Desert. Concentrations increased in Hinkley Valley beginning in 1952 when the Pacific Gas and Electric Company discharged it into unlined ponds. From there, hexavalent chromium entered the aquifer. Once in the ground, a plume of hexavalent chromium traveled with groundwater away from the Hinkley compressor station into Hinkley Valley.