Activities at a Glance

Soil Investigation Update

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

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 Soil Risk Assessment is anticipated to be completed in 2018.

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 9,100 pounds (lbs.) of chromium from groundwater (through December 2017). After chromium is removed from the groundwater, it 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. These mitigation measures were adopted to reduce potential impacts to the environment during the proposed groundwater cleanup. Several of these measures were completed during the design of the groundwater remedy, and are no longer applicable. Mitigation measures to reduce potential impacts to the environment during the soils investigation were also adopted as part of the August 24, 2015 certified Final EIR for Soils Investigation. 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 occurred from December 4-15, 2017. Groundwater and surface water monitoring is ongoing.
  • Annual site condition assessment of cultural resources was conducted on November 6-9, 2017 in accordance with the mitigation measures adopted by DTSC in the 2011 Groundwater Remedy Final EIR.
  • The annual compliance monitoring program sampling event occurred from October 23-25, 2017.
  • A late season botanical survey of the Final Topock Groundwater Remedy construction footprint was conducted from September 13-14, 2017. In 2017, another botanical survey was conducted in March 2017 of the same construction footprint.
  • The Southwestern Willow Flycatcher protocol bird surveys occurred on May 15 - 19, June 5 - 9, June 19 - 23, and July 10-14, 2017.