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GEORGE AND MEI TERANISHI • <br /> 1600 Durham Ferry Rd. <br /> Page 2 of 2 <br /> The current data suggests that impacted groundwater does not penetrate to the second <br /> sand interval in the former UST area, but may either penetrate deeper or is being drawn <br /> down in the former dispenser area and toward the domestic well north of the site. If the <br /> groundwater in the second and/or third sand 'cleans up', then EHD will consider vertical <br /> assessment of impacted groundwater for this site to be completed. Of concern at this <br /> time is the impacted groundwater encountered in monitor well MW-106 in the second <br /> sand interval, as this groundwater may be migrating toward the domestic well toward the <br /> north. <br /> The FS analyzed several potential remedial alternatives for the site including air <br /> sparging, vapor extraction, monitored natural attenuation, enhanced bioremediation, <br /> pump and treat, dual-phase extraction, soil excavation, and in situ chemical treatment. <br /> After analyzing applicability to the site and cost effectiveness, GTI selected in situ <br /> advanced oxidation as the preferred method of remediation, and propose to install <br /> and/or modify 30 wells to construct the system. <br /> EHD concurs that in situ oxidation may be the most effective remedial method of this <br /> site; however, the Central Valley Regional Water Quality Control Board (CVRWQCB) is <br /> currently requiring bench-scale tests of the selected oxidants reacting with soil and <br /> ground water from the zone of anticipated application to evaluate the necessity to issue <br /> a waste discharge requirement (WDR) permit. EHD recommends you contact Mr. James <br /> Barton,•R.G. of the CVRWQCB at (916) 464-4615 to obtain guidance on the test design <br /> and objectives. In general, the testing should detect mobilization of metals, formation of <br /> insoluble precipitates, generation of large biomasses, changes in soil porosity or <br /> permeability, and/or degradation to other toxic compounds. Please provide EHD with a <br /> work plan to acquire soil and impacted ground water samples from the intervals of <br /> intended application and to conduct the bench-scale test by 15 August 2004. Also, <br /> please provide a copy of the work plan to the CVRWQCB. <br /> Questions or comments may be directed to Nuel Henderson at (209)468-3436. <br /> Donna Heran, RENS, Director <br /> Environmental Health Division <br /> Nuel C. Henderson, Jr., RG Margareagorio, R <br /> Unit IV- Site Mitigation Supervisor, Unit IV <br /> C: James L.L. Barton—CVRWQCB <br /> Ray Kablanow, Eric Price — Geological Technics Inc. <br />