Activities at a Glance

Soil Investigation Update

The soil Investigation was completed in the second quarter of 2017. Soil sampling and related Soil Investigation field work was conducted between December 2015 and March 2016, January through March 2017, and the latter part of April 2017. That work fulfilled the requirements of the Topock Soil Facility Investigation/ Remedial Investigation (RFI/RI) Work Plan and Data Gap Work Plans #1, #2, and #3. Field Work included:

  • Collection of soil samples at 364 locations.
  • Trenching of 15 locations to evaluate possible contamination.
  • Collection of sediment and pore water samples from 10 locations at the edge of the Colorado River by the East Ravine.

After sample collection was completed, results were evaluated by the Department of Toxic Substances Control (DTSC), the U.S. Department of the Interior (DOI), and PG&E to determine if additional data collection is needed to complete the Soil Investigation and evaluate potential next steps. The agencies and PG&E balanced the data collection necessary with Tribes request to minimize site intrusion by maximizing the use of archived samples and collection of samples from previously disturbed locations.

On June 20, 2017, DTSC and DOI determined that the Soil RFI/RI field work was completed and concurred with PG&E to move forward with the risk evaluation process per the approved Risk Assessment Work Plan and addendum. In addition, PG&E has commenced the preparation of the Soil RFI/RI report.

Soil Risk Assessment Update

The Soil Risk Assessment Report is anticipated to be completed in 2019. A Final Risk Assessment Work Plan Addendum II was submitted June 29, 2015, and contains updated information relevant to soil risk assessment activities and evaluation based on comments received by Tribal Nations, agencies, and stakeholders. DTSC approved the Soil Risk Assessment Work Plan (submitted August 25, 2008) and the Risk Assessment Work Plan Addendum (submitted February 4, 2009) together referred to as the Final Risk Assessment Work Plan (RAWP). DTSC conditionally approved the Soil Risk Assessment Addendum II on August 31, 2015 (clarified on September 15, 2015) and DOI conditionally approved the Soil Risk Assessment Addendum II on September 8, 2015. On June 20, 2017, DTSC and DOI determined that the Soil RFI/RI field work was completed, and concurred with PG&E to move forward with the risk evaluation process according to the approved Risk Assessment Work Plan and Addendum.

Interim Measures

Since 2005, the Interim Measures' goal of maintaining contaminated groundwater flow away from the Colorado River continues to be met, as reported in the Quarterly Performance Monitoring/Groundwater Monitoring Reports. Through its operation, the Interim Measures system has removed approximately 9,570 pounds (lbs.) of chromium from groundwater (through September 2019). After chromium is removed from the groundwater, the groundwater is injected back underground to maintain this valuable resource within the project area.

Mitigation Measures

Mitigation measures were adopted as part of the January 31, 2011 certified final groundwater EIR and 2013 addendum groundwater EIR. Additional or revised mitigation measures were adopted from the certified Subsequent EIR for the groundwater remedy in April 2018. These mitigation measures were adopted to reduce potential impacts to the environment during the proposed groundwater cleanup. Implementation of these mitigation measures are in progress.

Mitigation measures were also adopted as part of the August 24, 2015 certified Soil Investigation EIR. Although they are similiar to groundwater measures, they remain in effect for soil investigation activities such as potential bench scale tests, pilot studies, and geotechnical evaluations to support, inform, and enable, if necessary, the evaluation and selection of corrective measures in a future Soil CMS/FS.

Monitoring and Survey Activities

The following monitoring and survey activities were conducted or are planned:

  • The annual groundwater monitoring program sampling event is planned for December 3-14, 2018. Groundwater and surface water monitoring is ongoing.
  • The annual compliance monitoring program sampling event is planned for December 3 - 5, 2018.
  • Biological, archeological, cultural, and paleontological monitoring is conducted as part of the construction activities.
  • Annual Site Conditions Assessment occurred the week of November 5, 2018 in accordance with the mitigation measures adopted by DTSC in the 2011 Groundwater Remedy Final EIR and the 2018 Subsequent Final EIR.
  • The Western Yellow-Billed Cuckoo presence/absence surveys occurred June 20 - 22, July 3 - 4, July 18 - 19, and August 1 - 2, 2018.

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