SITE INFORMATION AND CORRESPONDENCE

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Ken and Ed Enditch . • 101 S.Wilson Way Page 2 of 2 impacted ground water in the predominantly poorly graded sand and silty sand of Hydrologic Unit 1, as defined by AGE. Implementing interim remediation of impacted ground water appears to be a prudent action to take to reduce contaminant mass and to establish hydraulic control of the plume. Vadose zone soil is also impacted by fuel hydrocarbons and additives, such as TPH-g, BETX, and MTBE. Significantly impacted soil extends to at least 65 feet bsg (64-65) with 730 milligrams per kilogram (mg/kg) TPH-g and 7.3 mg/kg benzene. Less intensely impacted soil extends to depths as great as 86 feet bsg. Vadose zone soil, approximately surface grade to 40 feet bsg, is impacted by as much as 6,200 mg/kg TPH-g, 70 mg/kg benzene (132-40) and 13 mg/kg MTBE (tank pull samples TK2-W and TK6). Most soil analyses predated routine MTBE and other oxygenate analyses. With significantly impacted soil directly overlying and in contact with the saturated zone, interim remediation of soil to reduce the adsorbed contaminant mass also appears to be a prudent measure to be taken at this time. The soil vapor extraction test conducted in January 1996 indicated an effective radius of influence of 30 feet. The proposed design for the SVE system, utilizing existing vapor wells appears to be adequate. The proposed interim remediation for ground water extraction and soil vapor extraction is approved as necessary and adequate. Please proceed immediately with implementation of the work plan. Acquire all necessary and appropriate permits. Please submit a drilling permit application and $89.00 fee to EHD for the extraction wells to be installed in the subject property. Notify EHD at least 72 hours prior to commencing each phase of fieldwork. Questions or comments may be directed to the undersigned at (209) 468-3436 or by mail (address on the letterhead). Donna Hergn, REHS, Director Environmental Health Division.-- - Nuel C. Henderson, Jr., RG Margare agorio, REHS Site Mitigation, Unit IV Supervisor, Unit IV C: Tim Cuellar- AGE James L.L. Barton - CVRWQCB