California Water Science Center

Cooperating Agency: Lahontan Regional Water Quality Control Board
Project Chief: John A. Izbicki
Phone: 619-225-6131
Email: jaizbick@usgs.gov

Occurrence of natural and anthropogenic hexavalent chromium (Cr VI) in groundwater near a mapped plume, Hinkley, CA

Mojave River Groundwater Basin

Mojave River Groundwater Basin


Study area location

Study area location

Full Proposal

Cooperating Agency: Lahontan Regional Water Quality Control Board
Project Chief: John A. Izbicki
Phone: 619-225-6131
Email: jaizbick@usgs.gov

The Pacific Gas and Electric Company (PG&E) Hinkley Compressor Station, 3 miles southeast of Hinkley, CA and 80 miles northeast of Los Angeles, is used to compress natural gas as the gas is transported through pipelines from Texas to California. Between 1952 and 1964, cooling water was treated with a compound containing chromium to prevent corrosion within the compressor station. This water was discharged to unlined ponds, resulting in contamination of soil and groundwater within the underlying alluvial aquifer. In 2007, a study intended to characterize naturally-occurring background concentrations estimated average Cr VI concentrations in the area of 1.2 micrograms per liter (µg/L). The normal 95 percent upper tolerance limit of 3.1 µg/L from the 2007 background study was adopted as the cleanup level for remediation at the site. The Regional Water Quality Control Board subsequently agreed to revisit the 2007 background study in response to criticism of the study's methodology and the increase in mapped extent of the plume between 2008 and 2011.

The purpose of this study is to evaluate the occurrence of natural and anthropogenic Cr VI, and estimate naturally-occurring background Cr VI concentrations upgradient, near the plume margins, and downgradient from a mapped Cr VI contamination plume near Hinkley, CA.

The cooperator for this study is the Lahontan Regional Water Quality Control Board. The scope of the study was developed by the U.S. Geological Survey in collaboration with the Technical Working Group (TWG) composed of local stakeholders (the Hinkley Community Advisory Committee, CAC), community advisors (Project Navigator, Inc.), State regulatory agencies (Lahontan Regional Water Quality Control Board), and Pacific Gas and Electric and their consultants. The scope of the study includes the following tasks: 1) evaluation of existing data; 2) sample collection and analyses of rock and alluvium; 3) sample collection and analysis for water chemistry and multiple tracers, 4) evaluation of geologic, hydrologic, and geochemical conditions in western, northern, and eastern subareas within the study area; 5) evaluation of historic and present-day groundwater movement, 6) evaluation of the occurrence of natural and anthropogenic chromium; 7) determination of background Cr VI concentrations; and 8) assessment of the fate of chromium following in-situ reduction. The study will begin in Federal Fiscal Year 2014 and end in 2018. An initial fact-sheet style report describing the study approach, an interim report describing selected preliminary results, and a final report will be produced.

This proposal will contribute to the U.S. Geological Survey's ability to "ensure adequate quantity and quality of water to meet human and ecological needs in the face of growing competition among domestic, industrial-commercial, agricultural, and environmental uses" as described in the U.S. Geological Survey Science Strategy (U.S. Geological Survey, 2007; Evenson and others, 2013). The proposal is within the U.S. Geological Survey Water Resources Mission Areas to "define and better protect the quality of the Nation's water resources."

Project Update (2016)

All major project tasks (with the exception of Task 7) are active and moving forward on schedule and on budget. A scheduled report was published on time in January 2016. Most major work elements related to sample collection have been completed or have significant progress. After a year of design and development, experimental work to be done as part of Task 8 has been started. At this point, the project is in a data evaluation, review, and preliminary interpretation phase with the aim of moving toward a "data gap" analyses.

The project is being coordinated closely with similar work being done with Mojave Water Agency (Task 5: Geochemistry)

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