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} Morita Brothers <br /> 814 E. Charter Way, Stockton <br /> Page 3 of 3 <br /> Environmental Screening Levels (ESLs) and the California Human Health <br /> Screening Levels (CHHSLs) for soil and soil gas',i,pmay be. used as a first tier <br /> criteria to evaluate residual contamination for vapor intrusion into structures, <br /> direct exposure and gross contamination. <br /> The SCM indicates that all significantly impacted soil has been removed from the <br /> site, but it is not clear to the EHD that impacted soil!!west of the over-excavation <br /> was removed. Excavation wall sample W-1 @ 20 feet was significantly impacted <br /> as were soil samples collected from boring TH-4, which appears to have been <br /> west of the over-excavation. Data from this area should be evaluated according <br /> to the criteria required by the CVRWQCB. <br /> Impacted groundwater encountered in monitoring well MW-208 was modeled to <br /> represent an intruding, migrating plume from the 749 East Charter Way site. The <br /> model appears to be supported by the evidence cited in the SCM. If the model is <br /> correct, the model could be validated by collecting,: groundwater samples at a <br /> j position between the 749 East Charter Way-site and MW-208. <br /> Please submit a work plan to the EHD .by 05 December 2006 to validate the <br /> model for the impact to MW-208 and any data collection deemed necessary to <br /> properly address the issue with the SFBRWQCB's 'ESLs and CHHSLs, and to <br /> evaluate the potential for vapor intrusion of structures,'; If any or all of these issues <br /> can be addressed without additional data'.collection, submit a report rather than a <br /> work plan. <br /> Questions or comments may be directed to Nuel Henderson by mail (address on <br /> letter head), by e-mail at nhenderson(csicehd.com, or by telephone at <br /> (209) 468-3436. <br /> Donna Heran, RENS, Director <br /> Environmental Health Department <br /> Nuel C. Henderson, Jr., PG 'Margaret Lagorio, REHS <br /> Engineering Geologist Program Coordinator <br /> LOP/ Site Mitigation Unit IV LOP/Site Mitigation Unit IV <br /> I <br /> cc: James L.L. Barton, PG - CVRWQCB <br /> Dr. Raynold I. Kablanow II, PG-Geological Technics. Inc. <br />