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. PG&E also prepared and published the draft RFI/RI Report for soil In December 2019. The report is anticipated to be finalized/approved in late 2020.

Soil Risk Assessment Update

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.

The final Soil Risk Assessment Report was published in October 2019 and is anticipated to be approved in March 2020. The report concludes that there is minimal unacceptable risk to human health and wildlife exposed to soil at the site. However, it also identifies nine small and isolated areas that pose unacceptable risk for campers, hikers, OHV riders, and desert shrews if exposed to contaminated soil. These nine areas are located around the PG&E Topock Compressor Station (some on PG&E owned land and some on federal lands) and will be evaluated for corrective action.

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 9,660 pounds (lbs.) of chromium from groundwater (through December 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 1Q groundwater monitoring program sampling event is planned for February 17-28, 2020. Groundwater and surface water monitoring is ongoing.
  • The annual groundwater monitoring program sampling event occurred December 2-21, 2019. 
  • The annual compliance monitoring program sampling event occurred October 1-3, 2019.
  • Biological, archeological, cultural, and paleontological monitoring is conducted as part of the construction activities.
  • Annual Site Conditions Assessment occurred the week of December 4-5, 2019 in accordance with the mitigation measures adopted by DTSC in the 2011 Groundwater Remedy Final EIR and the 2018 Subsequent Final EIR.
  • A biological survey for roosting bats around the Topock remediation site occurred June 24-28, 2019. 

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