SITE INFORMATION AND CORRESPONDENCE

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Mr. James Taylor - 4 - 4 October 2007 The quarterly reports should include laboratory data sheets, which may be provided on electronic media. A well installation report shall be provided within 60 days of well installation and needs to include well logs, construction diagrams, and a figure. A Recirculation Status Report shall be provided within 120 days of starting the recirculation system. The Recirculation Status Report should provide an estimate of the extent of the groundwater mound, if any, at injection well IW-BH2A, an estimate of the hydraulic conductivity at the injection area, an estimate of the radius of influence of the extraction well, and an estimate of the hydraulic conductivity in the extraction area. Within 14 months of starting the recirculation system, a Pilot Study Evaluation Report shall be provided to Regional Water Board staff. The Pilot Study Evaluation Report should provide an assessment of the effectiveness of the recirculation on contaminant reduction. The Pilot Study Evaluation should update the groundwater model and assess the potential for an expanded groundwater recirculation system to accelerate the rate that site pollutants are degraded. Summary Thank you for suggesting a means to accelerate the treatment of carbon tetrachloride observed as a result of the zero-valent iron injections. The proposed recirculation pilot study should refine the groundwater model and evaluate the potential to treat a greater volume of groundwater by forcing it through the existing iron. If injection into IW-BH2A causes an increase in water surface in MW-3B, about 90 feet away, ContiGroup shall notify Regional Water Board staff and decrease the injection rate. By 30 October 2007, please provide a work plan and schedule for installation and development of injection wells, extraction wells, and monitoring well MW-13 to Regional Water Board staff and a copy to San Joaquin County Environmental Health Department. The attached draft Monitoring and Reporting Program proposes a monitoring program for the recirculation pilot study and for groundwater plume monitoring. Please review the draft monitoring program and provide comments by 30 October 2007. If you have any questions or comments, you may contact me by telephone at (916) 464-4680, by/ mail at rrell waterboards.ca. ov, or by regular mail at the letterhead address. l *41 AMY;ERRELL Private Sites Cleanup Unit Enclosure cc: Mr. Michael Infurna, San Joaquin County EHD, Stockton Ms. Linda Huff, Huff & Huff Inc., Oak Brook IL (with enclosure)