Location: 

• Pacific Gas and Electric Company's (PG&E) Topock Compressor Station is located in San Bernardino County, California, approximately 12 miles southeast of Needles, California, along the Colorado River. Moabi Regional Park, California, is one mile northwest of the station; Topock, Arizona, is one-half mile east, across the Colorado River; and Golden Shores, Arizona, is five miles to the north, across the Colorado River.

Acceptance Into Voluntary Remediation Program (VRP):

Contaminants of Concern (COCs):

• Hexavalent chromium

Affected Media:

• Soil (Soil affected in California only)
• Groundwater (Groundwater affected in California only)

What are My Health Risks:

For Soil | There is little to no health risk unless there is contact with skin or ingestion of contaminated soil. (Soil affected in California only.)

For Groundwater | To date, sampling results consistently indicate that Arizona groundwater is not impacted by chromium.

If you have a private well in the vicinity of the exceedance, we encourage you to test the well water

Not sure what to test for? |Learn More >

Site Summary:

• 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
• Remediation of the site is being overseen by the California Department of Toxic Substances Control (DTSC) and the U.S. Department of the Interior (DOI)
• In Situ Treatment with Freshwater Flushing has been selected as the final remedy
  • The plan includes a network of injection and extraction wells along the National Trails Highway (NTH) approximately 600 feet west of the Colorado River. This network of wells forms the in-situ reactive zone (IRZ).
  • Ethanol is added to the contaminated groundwater to stimulate the growth of naturally occurring, harmless and helpful bacteria. The bacteria temporarily alters the geochemical conditions in the groundwater and helps convert hexavalent chromium to non-soluble trivalent chromium. Injection wells located around the hexavalent chromium groundwater plume will pump freshwater into the groundwater aquifer to push the contaminated water toward the reactive zone.
  • Construction, startup, and initial operation are separated into two phases with Phase 2 split into two sub-phases.
  • Phase 1, which began on Oct. 2, 2018, is now complete. It includes the NTH IRZ with 22 remediation wells (for injection and/or extraction) and a robust network of 75 monitoring wells (for measuring water levels and quality), as well as a network of over 74,000 linear feet of water conveyance piping and 41,000 feet of electrical conduits that connect the remediation wells to the power supply system, the carbon amendment building, and the produced water conditioning system.
  • All systems and components were integrated and tested to make sure they function properly. On Dec. 22, 2021, PG&E turned on the NTH IRZ remedy treatment system.
  • In March 2022, PG&E began Phase 2 of the remedy construction, which is a continuation of construction for remaining components, including freshwater injection wells and additional pipelines for water conveyance.
• Visit the Topock Remediation website for the latest information | Visit Site >