Welcome to the California Department of Toxic Substances Control (DTSC) The department within the California Environmental Protection Agency in charge of the regulation of hazardous waste from generation to final disposal. DTSC oversees the investigation and cleanup of hazardous waste sites.website for the Pacific Gas and Electric Company (PG&E) Topock Environmental Investigation and Remediation Project (Project) at the Topock Compressor Station (Station) and adjacent land, collectively known as the Topock Project Site (Site). Topock Environmental investigation and remediation activities have been under way at the Site since 1997.

Protection of California's groundwater Water beneath the Earth’s surface that flows through soil and rock openings (aquifers).and surface waterWater collecting on the ground or in a stream, river, lake, wetland, or ocean. resources, including the Colorado River, as well as lands surrounding the Station, is one of DTSC's highest priorities. In 2004, DTSC directed PG&E to take immediate, stopgap actions, known as Interim MeasuresCleanup actions taken to protect public health and the environment while long-term solutions are being developed., to ensure that the chromium plumeA body of contaminated groundwater. The movement of a groundwater plume can be influenced by such factors as local groundwater flow patterns, the character of the aquifer in which the groundwater is contained, and the density of contaminants. beneath the Site flows away from the Colorado River while additional investigation and final cleanup options were evaluated. DTSC adopted a Final Remedy approach for the groundwater contamination based on PG&E's study of the Site and certified the Final Environmental Impact Report (EIR) in January 2011. The U.S. Department of the Interior (DOI), as a co-regulatory agency overseeing the Site, also adopted a Groundwater Record of Decision in December 2010, and selected the same remedy for the groundwater cleanup. After remedy selection, DTSC worked with PG&E, Federal Agencies, interested Tribes, and other key project stakeholders in the design of the remedy. Because of the specificity of the design details and additional knowledge of the anticipated site impacts, DTSC prepared a Subsequent EIR (SEIR) for the groundwater remedy. The Final SEIR was certified in April 2018. DTSC and DOI subsequently also approved the final Groundwater Remedy Design in April 2018. Phase 1 construction of the remedy began in October 2018 and is anticipated to continue through 2021; the end of heavy construction is anticipated in the Spring of 2021. System integration and functional testing is planned for the second and third quarters of 2021, with remedy startup in Fall of 2021. For the current schedule of construction activities click here.

This website provides an overview of current Site activities and other Site-related information. Information on this website includes:

  • PG&E Topock Compressor Station Site location and history
  • Investigation and cleanup activities: past, present, and future
  • Groundwater remedy construction activities
  • Public involvement information
  • Cleanup-related technical reports and work plans

To visit DTSC on our main website, go to www.dtsc.ca.gov.

Difficulty Accessing Material?

If you have a disability and have difficulty accessing material on this site please contact us in writing, via email or via telephone and we will work with you to make the information available. Please indicate the nature of the accessibility need, your preferred format (Braille, large print, etc.), what material you are trying to access including where it's located on this site, and how to reach you if questions arise while fulfilling your request. You can direct your requests to:


Written Requests

The Office of Civil Rights
Department of Toxic Substances Control
P.O. Box 806
Sacramento, CA 95812-0806

Email Requests


Telephone Requests

+1 916 324-3095
+1 800 728-6942 - Toll Free