SITE INFORMATION AND CORRESPONDENCE FILE 2

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Stantec 76(Former BP)Service Station No. 11192 December 7,2010 Page 2 gradient of Shell wells S-15 and S-6, near the intersection of Elmwood Avenue and Argonaut Street. In a correspondence dated July 6, 2009, the San Joaquin County Environmental Health Division (SJCEHD) approved the March 26, 2009 work plan proposing the installation of intermediate 13- zone well MW-14, but also requested the submittal of another work plan to address additional issues. A summary of the July 6, 2009 regulatory letter(in italics) and the proposed scope of work presented in the April 26, 2010 Revised Work Plan Addendum for Additional Site Assessment is presented below: 1. Further on-site vertical delineation is needed of tert-butyl alcohol (TBA) impacts to the groundwater at depths deeper than 78 ft bgs in the vicinity of MW-11. To address this concern, Stantec proposed the installation of an on-site deep D-zone groundwater monitoring well (MW-16) down-gradient of deep C-zone well MW-11. The purpose of MW-16 is to provide vertical delineation of the dissolved oxygenate plume in the groundwater beneath the site (Figure 1). 2. Further lateral delineation is needed for TBA impacts to the groundwater off-site to the northeast(down-gradient of Shell well S-15). To address this concern, Stantec proposed the installation of an off-site shallow A-zone groundwater monitoring well (MW-15) in the immediate vicinity of the previously proposed and approved intermediate B-zone monitoring well (MW-14). The locations of B-zone well MW-14 and A-zone well MW-15 will provide additional vertical and lateral delineation of the dissolved oxygenate plume in the groundwater further down-gradient of the site(Figure 1). 3. Further lateral delineation is needed for the TBA impacts to the groundwater beneath the Shell Station. To address this concern, Stantec recommended the collection of split groundwater samples from Shell wells for the analysis of methyl tert-butyl ether (MTBE) and TBA during coordinated semiannual sampling. In a letter correspondence dated May 28, 2010 (Attachment A), the SJCEHD stated that the work plan was not adequate to provide a sufficient understanding of the lateral extent of the TBA- impacted groundwater, and requested the submittal of a second revised work plan addendum that should include an additional C-zone groundwater investigation along Elmwood Avenue and west of Pershing Avenue. This second revision of the work plan addendum has been prepared to address this concern. 11192 Second Revision WP Add rewrite 12-10.doc