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

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WELL INSTALLATION AND INTERIM REMEDIAL ACTION REPORT www.arcadis.com FINAL_Forward CHCF (CDCR) Well Installation Report_10182024 23 Performance monitoring data recorded during routine site visits will include the following: • System runtime; • Individual extraction well flow rates and totalizer readings (weekly as required by Item 3d of the CAO [RWQCB 2017]); • Total influent system flow rates and totalizer readings; • Water level readings from the extraction wells; • Influent and effluent tank water level readings; • Pressure at the influent and effluent of the particulate filtration system; • Pressure at the influent, midpoint, and effluent of the GAC system; • Analytical data from in the influent, midpoint, and effluent locations of the GAC treatment train; • Flow and totalizer readings at the effluent of the system; and, • Timing and cause for any system shutdowns. These observations will be used to optimize the GWET system operation. Controls will shut down the GWETS should critical operating parameters (e.g., pressure readings, equalization tank water levels) fall outside operational setpoints during non-supervised periods. System components will be operated and maintained in accordance with the manufacturer’s guidance and equipment manuals. System monitoring will be conducted in person. Remote monitoring will be performed as the GWET system will be constructed with a supervisory control and data acquisition platform. 7.2.3 Routine Sampling Groundwater samples will be collected periodically from the individual extraction wells to evaluate mass loading entering the system from each well, as well as from the GAC influent, GAC midpoint, and GAC effluent sample ports to evaluate VOC mass recovery and treatment, to determine the timing of GAC media changeout. Samples will be collected and analyzed for VOCs by USEPA Method 8260B. Samples initially will be collected weekly; however, sampling frequency may be reduced once the rate of media exhaustion is understood. GAC media changeout will occur when COCs are detected at the midpoint of the GAC vessel treatment train when breakthrough has occurred. Changeouts will include replacement of spent media (defined as media upstream of the sample location where COCs were detected) and moving the lag vessel to the lead position. Additional samples may be collected as required by the discharge permit. 7.2.4 Routine Monitoring System optimization efforts for remedial treatment will be conducted as treatment progresses, which may include changing extraction well flow rates to improve mass removal rates and/or alter flow paths in the subsurface. Per item 3c of the CAO (RWQCB 2017), this report must “…propose a monitoring plan for the system which will demonstrate the areal radius of influence for each pumping well…” The existing groundwater monitoring program includes quarterly gauging of several monitoring wells within the TVOC plume that is greater than 25 µg/L, in addition to other monitoring wells that are outside of the active treatment area but are likely to demonstrate water level influence from the GWET system. Table 18 below highlights tho se monitoring wells, their WBZ, and the frequency of gauging activities. There are no changes proposed to the existing monitoring program at the CDCR Facility.