COMPLIANCE INFO_EW-5 INSTALL PERMIT PACKAGE 2/14/25

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9999 S. Austin Road Manteca, CA 95336 P: (209) 982-4298 F: (209) 982-1009 Brendan Kenny Engineering Geologist Central Valley Regional Water Quality Control Board 11020 Sun Center Drive, Suite 200 Rancho Cordova, CA 95670 October 18, 2024 RE: Well Installation and Interim Remedial Action Design Report Dear Brendan Kenny: Forward, Inc. (Forward) is pleased to submit this Well Installation and Interim Remedial Action Report (Report) for the installation of additional groundwater monitoring points and remedial wells for the design of the interim remedial action (IRA) associated with the California Department of Corrections and Rehabilitation (CDCR) property located on South Austin Road in Stockton, California. Two groundwater extraction wells (CDCR-EW-3 and CDCR-EW-4) and four monitoring wells (AMW-60S, AMW-60M, AMW-61S, and AMW- 61M) were installed at the CDCR property between May and August 2024 as part of the remedial scope to address the requirement in the Cleanup and Abatement Order (CAO) R5-2017-0703, Item 3c, for an IRA to address the total volatile organic compounds (VOC) plume mass with concentrations of 25 micrograms per liter (µg/L) or greater beneath the CDCR property. Hydraulic testing was performed at the CDCR property on the extraction wells to assess groundwater capture of the total VOC (TVOC) plume with concentrations of 25 µg/L or greater. The results indicated that combined extraction from CDCR-EW-2, -3, and -4 was inadequate to fully capture the greater than 25 ug/L TVOC plume at the CDCR Property. Therefore, an additional extraction well, CDCR- EW-5, is proposed to be installed approximately 70 feet to the northeast of monitoring well AMW -50M. With the addition of CDCR-EW-5, we believe this will adequately capture the greater than 25 ug/L TVOC plume at the CDCR Property. Extraction wells CDCR-EW-2 through - 5 will be connected to a proposed groundwater extraction and treatment (GWET) system. The attached Report includes a summary of the installation of the monitoring and extraction wells, hydraulic testing of the extraction wells, evaluation of hydraulic capture of the greater than 25 ug/L TVOC plume, the proposed installation of CDCR-EW-5, and the proposed interim remedial GWET system at the CDCR property. Forward is requesting your approval of the additional extraction well, CDCR-EW-5, and the proposed design elements for the interim remedial GWET system at the CDCR property. Since issuance of the CAO, additional investigation and testing activities conducted at CDCR property north of the landfill have indicated the presence of differing and distinct VOC concentrations and chemical signatures compared to those associated with the Landfill’s Point of Compliance. This information is also detailed in the Remedial Investigation Update and Revised Feasibility Addendum submitted on June 30, 2023, and the CDCR Site Investigation and Remedial Design Work Plan Second Addendum submitted on February 1, 2023. However, Forward is still committed to complying with the requirements set forth in the 2017 CAO R5-2017-0703 and will move forward with the installation of the IRA. Certification Statement I certify under penalty of law, that I have personally examined and am familiar with the information submitted in this document and all attachments, and that based on my inquiry of those individuals immediately responsible for obtaining this information, I beli eve that the information is true, accurate, and complete. I am aware that there are significant penalties for subm itting false information, including the possibility of fine and imprisonment. If you have questions or comments regarding the above information, please contact me at (209) 601-2274. Regards, Osvaldo Cordero Environmental Manager