USGS Scientists and the Hinkley Community Work to Define Natural Background Concentrations of Hexavalent Chromium in Groundwater
Hinkley, California is a small town of about 1,900 people in the Mojave Desert that is dependent on local groundwater supplies. Most of the groundwater system is naturally low in hexavalent chromium "Cr(VI)," but there are differences depending on geology.
Pacific Gas and Electric discharged Cr(VI) from its compressor station into unlined ponds and created a plume in the aquifer. Determining what is “background” is an important part of the Lahontan Regional Water Quality Control Board’s process for defining what PG&E must do to rectify the situation.
The USGS was asked to answer the question: “What are the natural background concentration of Cr(VI) in Hinkley’s groundwater?" To address this issue, the USGS worked with community members as part of the scientific project. The goal was to make the scientific process transparent and reduce the level of conflict over background values.
The lead scientist, Dr. John Izbicki, understood that “background” meant different things to different stakeholders and created a “summative scale” tool everyone could use to determine which wells could be labelled as “background.” This tool was based on how geochemistry in the aquifer works and new data sets were collected that included measurements that indicated aquifer condition such as grain size of minerals and oxygen levels.
Working with the Community of Hinkley
Map of Results
![Final Cr(VI) results map - Hinkley, CA](https://d9-wret.s3.us-west-2.amazonaws.com/assets/palladium/production/s3fs-public/styles/full_width/public/media/images/sac17-0650_figG.9_simplified.jpg?itok=6xxTxoJw)
VIDEO
View presentation of final results to the Lahontan Regional Water Quality Control Board.
Related Content
Below are science project pages related to this study.
Results of Hexavalent Chromium Background Study in Hinkley, California
Below are data reports related to this study.
Aqueous and Solid Phase Chemistry of Sequestration and Re-oxidation of Chromium in Experimental Microcosms with Sand and Sediment from Hinkley, CA
Grain size, mineralogic, and trace-element data from field samples near Hinkley, California
Hydrologic data in Hinkley and Water Valleys, San Bernardino County, California, 2015-2018
Gravity data of the Hinkley area, southern California
Geologic map and borehole stratigraphy of Hinkley Valley and vicinity, San Bernardino County, California
Below are publications related to this study.
Natural and anthropogenic hexavalent chromium, Cr(VI), in groundwater near a mapped plume, Hinkley, California
Natural and anthropogenic (human-made) hexavalent chromium, Cr(VI), in groundwater near a mapped plume, Hinkley, California
Predevelopment water levels, groundwater recharge, and selected hydrologic properties of aquifer materials, Hinkley and Water Valleys, California
Middle Pleistocene infill of Hinkley Valley by Mojave River sediment and associated lake sediment: Depositional architecture and deformation by strike-slip faults
Natural and man-made hexavalent chromium, Cr(VI), in groundwater near a mapped plume, Hinkley, California—study progress as of May 2017, and a summative-scale approach to estimate background Cr(VI) concentrations
A plan for study of hexavalent chromium, CR(VI) in groundwater near a mapped plume, Hinkley, California, 2016
Below are news items related to this study.
Related Content
Below are science project pages related to this study.
Results of Hexavalent Chromium Background Study in Hinkley, California
Below are data reports related to this study.
Aqueous and Solid Phase Chemistry of Sequestration and Re-oxidation of Chromium in Experimental Microcosms with Sand and Sediment from Hinkley, CA
Grain size, mineralogic, and trace-element data from field samples near Hinkley, California
Hydrologic data in Hinkley and Water Valleys, San Bernardino County, California, 2015-2018
Gravity data of the Hinkley area, southern California
Geologic map and borehole stratigraphy of Hinkley Valley and vicinity, San Bernardino County, California
Below are publications related to this study.
Natural and anthropogenic hexavalent chromium, Cr(VI), in groundwater near a mapped plume, Hinkley, California
Natural and anthropogenic (human-made) hexavalent chromium, Cr(VI), in groundwater near a mapped plume, Hinkley, California
Predevelopment water levels, groundwater recharge, and selected hydrologic properties of aquifer materials, Hinkley and Water Valleys, California
Middle Pleistocene infill of Hinkley Valley by Mojave River sediment and associated lake sediment: Depositional architecture and deformation by strike-slip faults
Natural and man-made hexavalent chromium, Cr(VI), in groundwater near a mapped plume, Hinkley, California—study progress as of May 2017, and a summative-scale approach to estimate background Cr(VI) concentrations
A plan for study of hexavalent chromium, CR(VI) in groundwater near a mapped plume, Hinkley, California, 2016
Below are news items related to this study.