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Page 2 evaluated the effectiveness of injecting granular zero-valent iron(GZVI) into the affected intermediate (primarily screened between 60 to 82 feet bgs) groundwater system. A total of 18,260 pounds of GZVI has been injected into the subsurface along fractures generated by the injection process. As groundwater passes through this iron filled fracture zone, carbon tetrachloride is degraded or oxidized with a theoretical 18 percent (molar basis) going to methylene chloride, which is then biologically degraded. Overall, an approximate 50 percent reduction in carbon tetrachloride concentrations has been achieved downgradient of the GZVI, which is clear evidence that the GZVI is providing treatment for the surrounding groundwater. A greater reduction has not been achieved as only a portion of groundwater reaching the monitoring wells is currently flowing through the GZVI treatment zone. Consequently, this work plan proposes to install two pairs of wells (an extraction well and a complementary injection well) at the site to increase the physical contact between the contaminated groundwater and the GZVI treatment zone. The work plan also proposes to install an additional monitoring well to monitor the progress of remediation. 2. Pre-Field Activities Huff & Huff will obtain well-installation permits from the San Joaquin County Environmental Health Department for the installation of five wells (two extraction well/injection well pairs, and one additional monitoring well). Huff & Huff will notify Underground Service Alert at least 48 hours prior to breaking ground, as required by law. The existing site Health and Safety Plan will be updated to review emergency contact information and activities related to installation and operation of the system. 3. Scone of Work The proposed system layout for the groundwater recirculation system is presented in Figure 2. Groundwater will be pumped from new extraction well EW-11B, which will be installed up gradient of MW-413. Well EW-11B will be screened between 60 and 80 feet below ground surface (bgs); its location relative to the other monitoring wells on site is depicted in Figure 2. The groundwater extracted from well EW-11B will be injected into the new injection well IW-BH2A. This injection well will be installed in the center of the previous GZVI injection boring, BH-2A, which was selected based on where the most GZVI was injected during the fracturing process conducted in May 2005. Installation of a second pair of extraction/injection wells (EW-12B and IW-BHI) will be conducted at the same time. The groundwater from the extraction well will be pumped at a nominal flow rate between 0.5 and 1.0 gallon per minute (gpm) using Grundfos RediF1o3 well pumps; this pumping rate is expected to accelerate the remedial process and maintain the capture zone. The pumps will be operated from CU300 operating consoles, which will provide a variable pump speed range of 3,000 to 10,700 rotations per minute. Each pump will have an adjustable pumping rate range from 0 to 10 gpm. R:IC0NTGRANMCCl4Cargi111Ftcnch Camp1GW Recirculation Pilot Study Work Plan October 2007\Well Inatellation Work Plan-French Camp Grain Elevator 0125 08,doc