CORRESPONDENCE_2025 - Laserfiche WebLink

Home Browse Search

Brendan Kenny Central Valley Regional Water Quality Control Board July 15, 2025 Remediation Systems Operations and Performance Summary CAO Task 9.a indicates that quarterly program updates shall include information on remedial systems during each reporting period. A summary of the Site's GWTS, residential GWTSs, and the facility's landfill GCCS are provided in this Program Update. Additional details regarding the Site's GWTS (submitted by July 30, 2025) and the residential GWTSs (submitted by August 1, 2025) are provided under separate cover in the following reports: • Second Quarter 2025 Groundwater Treatment System Monitoring Report; and • Second Quarter 2025 Residential Groundwater Treatment Systems Monitoring Report. Groundwater Extraction and Treatment System A GWTS is operated at the Site to address detections of volatile organic compounds (VOCs) in groundwater in accordance with the WDRs outlined in the Order. The California State Water Resources Control Board Monitoring and Reporting Program (MRP) Table 19 lists six groundwater extraction wells as part of the GWTS (EW -1, EW -2, EW -3R, EW -4, EW -5, and CDCR-EW-1). Five of the six groundwater extraction wells listed in Table 19 of the MRP (EW -1, EW -2, EW -3R, EW -4, and EW -5) are monitored monthly as they are the only extraction wells part of an operational system. Extraction well CDCR-EW-1 is currently not part of an operational remedial system and therefore is not monitored monthly. Additional offsite extraction wells (CDCR-EW-2, CDCR-EW-3, CDCR-EW-4, and CDCR-EW-5) are not included in the MRP and not connected to an operational remedial system and, therefore, are not monitored monthly as part of the corrective action program. However, these five offsite extraction wells were added to the routine quarterly monitoring program in the second quarter of 2025. The extracted groundwater is treated by two 10,000 -pound granulated activated carbon (GAC) vessels that were installed in January 2020. During the reporting period, the GWTS was inspected and monitored bi-weekly during April and May and monthly in June by Del -Tech Geotechnical Support (Del -Tech) of Oakdale, California. Flow rates from the extraction wells were routinely monitored and adjusted, if needed, to confirm groundwater capture within the treatment area. Del- Tech's field inspection forms are included in Attachment 1. During the second quarter, the GWTS treated approximately 47,674,807 gallons of extracted groundwater, which represents an average total flow rate of approximately 512,632 gallons per day. Based on the extracted volumes and analytical VOC concentrations, the GWTS removed approximately 0.40 pounds of total VOCs during the reporting period. Del-Tech's downtime log for the reporting period is included in Attachment 1. The GWTS was operational throughout the reporting period, except for the following downtime events, which indicates the system was operational for 97 percent of the time (a total of 2,160 hours of system operation): • On May 7, 2025, all extraction wells were momentarily turned off to remove and calibrate flow meters as part of annual operation and maintenance tasks. All extraction wells were restarted on the same day. • On June 24, 2025, all extraction wells were turned off to perform GAC changeout in the lead GAC vessel. After the GAC changeout occurred, the lead/lag vessel order was switched. All extraction wells were restarted on June 27, 2025. Flow meters were reinstalled on June 25, 2025, during the GAC changeout process. Low concentrations of total VOCs (up to 1.63 micrograms per liter of total VOCs) were detected in the five system influent samples collected. No VOCs were detected above the practical quantitation limit in any of the system effluent samples collected at the point of compliance, satisfying the discharge requirements of the Order. www.arcadis.com 2/4 Forward Landfill 2Q25 CAP Update_ 07152025_ draft OFC Comment