SITE INFORMATION AND CORRESPONDENCE FILE 2

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V Rodger Liston Darpetro Inc. 749 E. Charter Way, Stockton, California Page 2 of 2 • A description of sampling equipment to be utilized ; • A description of the intended sample collection techniques ; and • A description of how the effects of the active air sparging and soil vapor extraction remediation system will be compensated for in the soil gas investigation design and how the soil gas data acquired will then be interpreted . Vapor extraction wells are located near some of the proposed soil gas sampling points. A site conceptual model (SCM), as discussed with you at the 19 June 2002 meeting , should be prepared . All of the proposed investigative and remedial actions should be presented and justified in the context of the SCM . You and CGG have advanced the hypothesis that contamination is migrating onto your site from the west; EHD recommends that this hypothesis be tested by including additional monitoring wells and/or soil .gas sampling points toward the west. The revised work plan , prepared in the context of a site conceptual model and addressing all the issues noted above , should be submitted to PHS/EHD by 15 January 2003 . If there is any confusion on any of these issues , please call the undersigned for clarification . EHD desires to assist you and/or your consultant in this matter as much as possible . Questions or comments may be directed to Nuel Henderson by mail (address on letter head) , by e-mail at nhenderson a sicehd . com , or by telephone at (209) 468-3436 . Donna Heran , REHS , Director Environmental ,Health /Division 00000 Nuel C . Henderson , Jr. , RG Site Mitigation Unit IV cc: Marty Hartzell-CVRWQCB John Cussen — California Geophysical Group , Inc .