SITE INFORMATION AND CORRESPONDENCE_FILE 2

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Mr. Ken Gillies • • Gillies Trucking 3931 Newton Road, Stockton Page 2 of 2 would be appropriate. The EHD considers wells in the core area, near the down-gradient extent of the dissolved plume and sentinel wells to be the most critical for frequent monitoring; wells in the up-gradient and cross-gradient directions that are commonly 'non-detect' can be sampled less frequently. The sampling strategy should be to document concentration trends representative of the dissolved plume mass and to detect expansion and/or contraction of the dissolved plume. Submit a proposed sampling schedule that meets these monitoring goals to the EHD by 17 December 2007. Excavation was dismissed as highly disruptive to your site operation and as unlikely to effectively address impacted soil between 40 and 60 feet below surface grade, where the bulk of the contaminant mass is inferred to reside. SVE, bioventing and injection of oxidizing agents were considered to hold more potential for your site. The EHD recognizes that it is unlikely that your site can be cleaned up to pristine conditions, but the methods discussed (excavation excepted) may individually, or in combination, effectively reduce the contaminant mass, toxicity and mobility sufficiently enough to achieve favorable leach test results and a low-risk closure. Evaluate the remedial methods noted above, and any others you or your consultant believes may be applicable to your site, to address impacted soil and submit a report with recommendations to the EHD by 07 January 2008. Questions or comments may be directed to Nuel Henderson by mail (address on letter head), or by telephone at (209) 468-3436. Donna Heran, REHS, Director Environmental Health Division Nuel C. Henderson, Jr., PG Marg�agorio, REHS Engineering Geologist Program Coordinator Unit IV- Site Mitigation Unit IV— Site Mitigation cc: James L.L. Barton, PG —CVRWQCB Victor Cherven, PG — UEC Clyde Hebbron, PG - UEC