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 later 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 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 existing locations.

On June 20, 2017, DTSC and DOI determined that the Soil RFI/RI field work was completed and directed PG&E to move forward with the risk evalution process per the approved Risk Assessment Work Plan and addendum. In addition, PG&E will commence the preparation of the RFI/RI Volume 3 report.

Soil Risk Assessment Update

A Risk Assessment Work Plan Addendum II was submitted May 7, 2014, and contains updated information relevant to soil risk assessment activities and evaluation based on comments received by Tribal Nations, agencies, and stakeholders. Comments were received from DTSC, DOI, and Tribes. DTSC approved the Work Plan on August 24, 2015. On June 20, 2017, DTSC and DOI determined that the Soil RFI/RI field work was completed, and directed PG&E to move forward with the risk evaluation process according to the approved Risk Assessment Work Plan and Addendum.

Old Well/TCS Well No. 4

A surface geophysical survey and excavation were conducted in April and July 2013 to locate an old well in Bat Cave Wash several feet below the ground. The well was located, and in September 2013, modifications were made to bring the well casing up to the existing ground surface, and soil samples were collected near the wellhead. Archeological monitoring and biological monitoring were conducted during all stages of the field work. This well is referred to as TCS Well No. 4 (TCS-4). PG&E submitted a final Decommissioning Plan to DTSC and DOI on December 7, 2015. DOI approved and DTSC concurred with the final Decommissioning Plan on December 15, 2015. Decommissioning activities began on February 24, 2016 and were completed on March 9, 2016. A Decommissioning Report was submitted to agencies on June 7, 2016.

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 also removed approximately 8,930 pounds (lbs.) of chromium from groundwater (through May 2017). Once the groundwater is treated, 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 are adopted to reduce potential impacts to the environment during the proposed groundwater cleanup. 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.

Monitoring and Survey Activities

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

  • The Southwestern Willow Flycatcher (SWFL) protocol bird surveys occurred on May 15 - 19, June 5 - 9, and June 19 - 23, 2017.
  • Biological (plant and wildlife) surveys were conducted on May 24 and 25 and July 7 and 8, 2016, for the additional areas that are proposed to be added to the groundwater cleanup SEIR Project Area.
  • Archaeological and historical resources field surveys were conducted on June 29-30, 2016 for the additional areas that are proposed to be added to the groundwater cleanup SEIR Project Area.
  • Annual cultural resources monitoring field event was conducted on October 24-28, 2016 in accordance with the mitigation measures adopted by DTSC in the 2011 Groundwater Remedy Final EIR.
  • Groundwater and surface water monitoring is ongoing.