2018 - Present

The Pacific Gas and Electric Company (PG&E) Topock Compressor Station (Station) compresses natural gas so it can be transported through pipelines to PG&E's customers in northern and central California. Historical waste management practices have resulted in potential contamination to both soil and groundwater. From 1951 to 1985, PG&E used hexavalent chromiumHexavalent chromium is a form of chromium. Chromium is a metal naturally found in rocks, soil, and the tissue of plants and animals. Hexavalent chromium can be found naturally at low concentrations, but it is also used in industrial products and processes and is a known carcinogen. On May 28, 2014, the California Department of Public Health adopted a new California drinking water standard at 10 parts per billion for hexavalent chromium. to prevent rust in its cooling towers. From 1951 to 1964, untreated wastewater from the cooling towers was discharged into percolation beds in Bat Cave Wash, a normally dry wash next to the Station. Beginning in 1964, PG&E treated the wastewater to remove hexavalent chromium. The treated wastewater was discharged into Bat Cave Wash until 1968, and subsequently was discharged into an onsite injection well. Over time, PG&E installed a series of lined evaporation ponds for wastewater disposal. In 1985, PG&E stopped using the chromium-based additive and switched to a phosphate-based solution.

  • Phase 2 construction of the groundwater remedy began on March 2, 2022 and is ongoing.
  • PG&E has submitted quarterly remedy progress reports to the agencies since March 2022. The latest quarterly report can be found here.
  • Phase 1 construction of the groundwater remedy began October 2, 2018 and was completed in December 2021. Phase 1 systems and components were integrated and tested to make sure they function properly. On December 22, 2021, PG&E initiated injection of ethanol into the groundwater at select NTH IRZ wells.
  • Concurrently, after receipt of DTSC’s and DOI’s approvals, PG&E turned off the Interim Measure No. 3 (IM-3) on December 21, 2021 and started to prepare IM-3 for layup. The preparation for lay-up was completed on March 21, 2022. When the IM-3 system is in a lay-up condition, the system will be left in a safe, secure, and preserved state and will not operate again until agency approval is received for decommissioning and removal of the system.
  • PG&E began to collect native seeds for use in mitigation planting in June 2021and continued into fourth quarter 2021. Seeds were propagated at a nursery and grown into container plants. In December 2021, PG&E began to prepare the mitigation planting areas in the floodplain, south of BNSF Railroad bridge for future mitigation planting. Site preparation activities included the removal of tamarisk debris and root balls, off-site disposal of debris, installation of an irrigation system, leaching of soluble salts from the soil for the establishment of the new plants, and installation of fences to protect plants. After fence installation, plants grown from the collected seeds were placed into the ground in March 2022. In addition, fence installation and cactus and shrub planting at an uplands mitigation planting area occurred in April 2022.
    PG&E is conducting O&M activities in the mitigation planting areas which include weed abatement (e.g., manual weed removal, herbicide application, etc.), drip irrigation and maintenance of system, plant health monitoring and census, and soil sampling.
  • The Soil RFI/RI reporting began concurrently with the soil Risk Assessment. The revised RFI/RI report was submitted on May 31, 2021 for review and comment. Revision based on comments received are in progress. A final RFI/RI report is anticipated in early 2023.
  • The DTSC January 2022 Fact Sheet - Community Update: Pacific Gas & Electric Company (PG&E) Topock Compressor Station, Cleanup Program Update is available to view here.
  • PG&E has submitted monthly groundwater construction progress reports to the agencies since November 2018. The latest monthly report can be found here. 
  • A tracer study and a pumping test were initiated in mid-June 2021 to obtain additional information about the subsurface in the vicinity of the Topock Compressor Station. The information gathered will assist in refining the groundwater model used to assess the performance of the groundwater remedy. DTSC conducted a CEQA review of the proposed study, and prepared/adopted an addendum to the groundwater SEIR on April 8, 2021.
  • Due to the COVID-19 pandemic, a temporary shutdown of the groundwater remedy construction activities occurred from April 1, 2020 to May 11, 2020. Agencies' direction to PG&E to shut down can be found here.
  • As required by the Land Use Covenant entered by PG&E and DTSC, a Soil Management Plan (SMP) for the Compressor Station was submitted on November 1, 2019. The Land Use Covenant requires PG&E to provide DTSC notification of any on-site excavation and the SMP defines sampling and management of any soil excavated on the Station in a manner that is protective of human health and the environment consistent with appropriate federal, state, and local requirements.
  • On October 30, 2018, DOI directed PG&E to prepare a Draft Engineering Evaluation/ Cost Analysis (EE/CA). The purpose of an EE/CA is to evaluate the need for a non-time critical removal action (NTCRA) on federal lands or at locations where contamination has the potential to migrate to federal lands. The public comment period for the EE/CA occurred from June 3, 2020 to August 5, 2020. The draft EE/CA can be found here. The DOI has responded to comments received and issued responses to comments on April 23, 2021. DOI prepared and approved a decision document, called an Action Memorandum, for the NTCRA on October 12, 2021. The Action Memorandum, along with a Responsiveness Summary and the Final EE/CA can be found here. A fact sheet on the EE/CA can be found here. 
  • Based on the Final Design, the 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. prepared a Subsequent Groundwater Remedy Environmental Impact Report (SEIR). The April 24, 2018 certified Final SEIR evaluated potential environmental impacts resulting from design details of the selected groundwater remedy (in situ TreatmentTreatment of contamination in place. with Freshwater FlushingMoving of fresh water through the well system to push the plume through an In-Situ Reduction Zone located along National Trails Highway.) that were modified since the approval of the conceptual Groundwater Remediation Project in the 2011 Final Groundwater Remedy EIR and the 2013 Addendum to the EIR.
  • The DTSC certified the Final SEIR on April 24, 2018, and conditionally approved the groundwater remedy design on April 24, 2018. Construction of the final groundwater remedy system began October 2, 2018.
  • The First Addendum to the Corrective Action Consent Agreement (CACA) was completed on January 25, 2018.
  • On June 20, 2017, DTSC and DOI determined that the Soil RFI/RI field work was completed. PG&E proceeded in preparing the Soil Human Health and Ecological Risk Assessment (HHERA) in accordance with the approved work plan and addendum. The Final Soil HERRA Report was published in October 2019. An Errata was submitted on February 19, 2020. The Soil HERRA and Errata were accepted on May 29, 2020 by DTSC and DOI. 
  • The Basis of Design/Final (100%) Design Report was submitted by PG&E on November 18, 2015. An errata was submitted on November 18, 2016 and an addendum to the flow and solute transport model was submitted on January 9, 2017. An addendum to the SMP was submitted on May 28, 2019. In April 2022, PG&E submitted, and DTSC approved, an updated Table to the SMP that incorporated revised values from the Soil HHERA.