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WELL INSTALLATION AND INTERIM REMEDIAL ACTION REPORT <br />www.arcadis.com <br />FINAL_Forward CHCF (CDCR) Well Installation Report_10182024 <br /> <br />19 <br />• Extraction of groundwater from the intermediate WBZ from extraction wells CDCR-EW-2 through CDCR-EW- <br />5 to hydraulically capture the TVOC plume with concentrations greater than 25 µg/L beneath the CDCR <br />property; <br />• Use of existing extraction and monitoring wells and piezometers to monitor remedial performance; <br />• Use of GAC adsorption vessels to remove VOCs from extracted groundwater prior to disposal; <br />• Variations to groundwater extraction well flow rates over the course of treatment to ensure hydraulic capture; <br />and <br />• Implementation of a groundwater monitoring program designed to provide sufficient information for remedy <br />optimization (e.g., adaptive operation strategy). <br />6.4 Groundwater Extraction and Treatment System <br />This section describes the implementation details for the IRA outlined in this Report. <br />6.4.1 System Operation <br />The implementation approach summarized herein will include automated, partially supervised, continuous <br />groundwater extraction, treatment, and disposal. This approach will achieve the objectives for groundwater <br />outlined in CAO R5-2017-0703 (RWQCB 2017) by maintaining hydraulic containment of the TVOC plume with <br />concentrations greater than 25 µg/L beneath the CDCR property. The proposed GWETS layout, process flow <br />diagram, and piping and instrumentation diagram are presented on Figures 8, 9, and 10 respectively. <br />6.4.2 Groundwater Extraction <br />Extraction wellheads will be outfitted with flow totalizers and pressure gauges. Groundwater extraction will be <br />conducted using pumps with intakes installed near the bottom of well screen intervals in existing extraction wells <br />(CDCR-EW-2, CDCR-EW-3, and CDCR-EW-4) and proposed extraction well (CDCR-EW-5). Submersible <br />groundwater pumps will be installed in the extraction wells and connected to conveyance piping that will transport <br />the extracted groundwater to the system compound. Extracted groundwater will be conveyed to the ex-situ <br />groundwater treatment system via belowground piping. <br />6.4.3 Ex-Situ Groundwater Processes, Treatment, and Disposal <br />A groundwater extraction system is proposed to be built on the CDCR property within facility, and GAC adsorption <br />has been selected for the ex-situ treatment of extracted groundwater. The treatment system will consist of two <br />GAC vessels, each filled with approximately 6,000 pounds of media, connected in series. Pressure gauges and <br />sample ports will be installed before the first vessel, between the two vessels, and after the second vessel to <br />monitor system operating pressures and to allow for collection of process water samples for COC breakthrough <br />monitoring. <br />Before GAC treatment, extracted groundwater will be discharged to a 5,000-gallon influent equalization tank. A <br />transfer pump will be utilized to pump groundwater from the influent equalization tank through a series of <br />particulate bag filters, followed by the two 6,000-lb GAC vessels. Post-GAC treatment, treated groundwater will <br />enter a 5,000-gallon effluent equalization tank and a transfer pump will convey treated groundwater, via <br />aboveground piping, to the infiltration basin south of the CDCR property. The infiltration basin currently receives