Revised On: Jan. 4, 2024 - 10:00 p.m.

In 1996, the California Department of Toxic Substances Control (DTSC) entered into an agreement with PG&E to investigate the nature and extent of hexavalent and total chromium contamination resulting from releases from the PG&E Topock Compressor Station in Needles. Under the terms of the agreement, PG&E is following an investigation and cleanup process governed by a federal law known as the Resource Conservation and Recovery Act (RCRA). Additionally, because some of the property affected by operations at the compressor station is owned by the U.S. Department of the Interior (DOI), DOI is overseeing remedial actions at the site pursuant to the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA). Due to the Topock Compressor Station's proximity to the Colorado River, ADEQ participates in investigation activities as they relate to the Colorado River and potential future impacts to Arizona's groundwater.

In 2005, ADEQ initiated a yearlong groundwater study in Arizona to assess whether there was a potential threat to human health from hexavalent chromium in the drinking water supplies for the Arizona communities of Topock and Golden Shores. At the time of the document review, the study concluded that there was no immediate threat to human health from use of groundwater for drinking water in Arizona. However, available information at the time did not allow ADEQ to completely assess potential long-term threats to the future water supply because the eastern extent of hexavalent chromium contamination in groundwater was not defined. As such, the study recommended the installation of groundwater monitoring wells in Arizona. The final report is available at ADEQ's Phoenix office and at the document repositories listed below.

In December 2006, PG&E entered ADEQ's Voluntary Remediation Program (VRP) in order to initiate a Colorado River investigation that would include the Arizona side of the river. PG&E submitted a work plan in March 2007 with the primary goal to define the eastern extent of the hexavalent chromium plume emanating from the Topock Compressor Station. The VRP approved the work plan in May 2007.

The well installations proposed in the work plan were completed in spring 2008. Three wells were installed, including a slant well beneath the Colorado River, a vertical well at the Havasu National Wildlife Refuge (HNWR), and a vertical well at the Topock Marina.