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  Welcome to the California Department of Toxic Substances Control (DTSC) website for the Topock site. Environmental investigation and cleanup activities have been under way in the vicinity of Pacific Gas and Electric Company (PG&E)’s Topock Compressor Station since 1997 as a part of a process known as Corrective Action.

Protection of the groundwater resources of California, including the Colorado River, is one of DTSC's highest priorities. DTSC has directed PG&E to take actions, known as Interim Measures, to control the plume and protect the river. DTSC's goal is to quickly move forward to select an environmentally appropriate cleanup remedy. Under DTSC's direction, PG&E will evaluate options and propose a final remedy for the site. The proposed final remedy will be fully evaluated in accordance with the California Environmental Quality Act, with input from and review by all stakeholders, including tribal governments.

This website provides an overview of current site activities and other site-related information. Information on this website includes: Topock site location and history, investigation and cleanup activities, the corrective action process and other regulations governing the cleanup, nearby communities, future plans and who to contact for information.
To visit DTSC on our main website go to www.dtsc.ca.gov.
 
  • The website Document Library is being revised and will be unavailable until late Thursday the 20th.
  • DTSC held a Public Comment Period and a series of five Public Meetings in May and June, 2008, to take Public Comment on the proposed scope of the Environmental Impact Report (EIR) and the EIR Notice of Preparation (NOP). The NOP and other CEQA documents can be viewed in the online Document Library, and in the Information Repositories.
  • The Topock Project Schedule is available for review.
  • DTSC held a Consultative Workgroup (CWG) meeting on April 2, 2008. The CWG will continue to meet quarterly in 2008; the next CWG meeting will be held on June 18, 2008 in Bullhead City, NV.

    2008 Activities
  • Over 220 million gallons of groundwater have been treated by the Interim Measures (IM2 and IM3) from March 2004 through May 2008. The IM3 Groundwater Treatment System continues operation, removing 3-4 lbs of chromium per day, for a total of 3,145 lbs removed through May 2008.
  • New vertical and slant monitoring wells were installed on the Arizona shoreline in March and April 2008. The slant wells allow for monitoring the groundwater underneath the Colorado River.
  • A Draft Risk Assessment Work Plan (RAWP) was submitted to DTSC and the federal agencies on February 21, 2008. The RAWP will cover both human health and ecological risk assessments for soil and groundwater. Agency comments will be incorporated into the final RAWP due in August 2008.
  • A draft of RFI Volume 2 - Groundwater and Surface Water Characterization Results will be submitted to DTSC in the summer of 2008 and the final version will be completed in late 2008.
  • Supplemental RFI soil investigations are being planned for mid- and late-2008.
  • Data from hydraulic testing of bedrock wells from 2007 will be utilized to complete a Summary of Evaluation of Hydraulic Conditions report. Additional bedrock wells are being considered in the East Ravine (east of the Station) to conduct additional hydraulic analyses. If approved, the wells will be installed in mid-2008.
  • A Final Draft Corrective Measures Study (CMS)/Feasibility Study (FS) Work Plan was approved by DTSC on June 13, 2008.
  • The Chromium Isotope Study Report was completed in May 2008 and is under DTSC review.
  • The Groundwater Background Study report has been reviewed by DTSC and is being reviewed by DOI.
  • Biological and cultural resources surveys and monitoring of field activities will continue to be a priority in 2008.

    2006 - 2007 Accomplishments
  • PG&E has consistently met the goal for maintaining groundwater flow away from the Colorado River, as shown in the Monthly Performance Monitoring Reports.
  • The Final RFI Volume 1: Site Background and History was approved by DTSC in August 2007.
  • The Floodplain In-situ Pilot Study was completed in November 2007. Initial results show in-situ to be a successful remediation technique for hexavalent chromium; three out of four pilot test wells had reductions of Cr6 from thousands of parts per billion (ppb) to less than 0.2 ppb in just six months . An upland in-situ pilot study is currently underway.
  • Over 290 samples were collected from the Colorado River, and over 550 groundwater samples were collected from wells during 2007. Installation of 14 additional groundwater monitoring wells was completed in 2007, bringing the total number of wells to more than 100. And addition of a new shoreline monitoring location added brings the total surface (river) water sampling points to 10 shoreline and 9 river locations.
  • Five slant wells (in 2 well casings) were installed on the California shoreline in spring 2007. These angled wells allow for samples to be collected from groundwater in soils below the bottom of the Colorado River. Sampling results to date show no detectable hexavalent chromium, and highly reducing soil conditions.
  • A programmatic (overarching) Biological Assessment was completed in January 2007 to cover remediation and investigation projects at Topock up to the final remedy. For habitat improvement, approximately 400 mesquite trees were planted on the Havasu National Wildlife Refuge, and a drip irrigation system was installed to maintain the development of the young mesquite.
  • Annual monitoring determined that no archaeological or historical sites were affected by field activities in 2007. A nomination for Rte. 66 to be listed on the National Register of Historic Places was completed, and the protective covering over Rte. 66 continues to be monitored and maintained throughout all field activity.