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Stantec August 15,2013 Page 3 of 8 Onsite oxygen injection wells (1-2 through 1-5) were installed on December 30 and 31, 2008 and January 8, 2009. Between March 9 and 31, 2009, conveyance conduits were installed, leading from oxygen injection wells 1-2 through 1-5 to a single subsurface well vault. On April 16, 2009, Stantec submitted a Well Installation and Subsurface Trenching Report to the SJCEHD. On April 17, 2009, all of the site groundwater monitoring and newly installed remediation wells were professionally surveyed in relation to existing site features. On April 27, 2009, Stantec conducted the initial oxygen injection event using the newly installed subsurface conveyance trenching and lines. The initial injection event was observed by Mr. Phil Simmons of the local fire department as required by the City of Stockton Public Works Department. Oxygen injection continued on a biweekly to monthly basis. In a letter dated July 17, 2009, the SJCEHD requested the reduction-9f groundwater monitoring and sampling fre ue -c_y_fr_om quarte oto+semi=annually_as_require�i under the State Water Resources Control Board (SWRCB) Resolution 2009-0042. However, because this site was in remediation at that time, 7-Eleven continued to conduct quarterly groundwater monitoring and sampling activities in order to monitor the effectiveness of the remedial approach On April 9, 2013, Stantec submitted a request to cease oxygen injections at the site and to evaluate the site for case closure. On April 30, 2013 the SJCEHD concurred with Stantec's request via email. On June 19, 2013, the two 10,000-gallon single walled steel USTs were removed f grn the site. No hydrocarbon impacts to the surrounding soil was observed during the UST removal. As part of the UST removal, on June 17, 2013, monitoring w--eILMW-2 wasAestLoje—(Lby_ overdrillin9 due to the well location t.et-ween b-e two_t.�STa• In addition, monitoring well MW-4 was damaged during the UST removal activities. Based on conversations with the SJCEHD, the well was not repaired at that time based on the pending site closure request and subsequent well destruction requirements. iThe_UST Closure Report and_Moniforing Wel/ Destruction Report will be submitted to the SJCEHD under separate cover. Summaries of soil and groundwater analytical results are presented in Tables 1 and 2, respectively. A soil boring and well construction detail summary is presented in Table 3. The locations of soil borings are presented on Figure 3. REQUEST FOR CASE CLOSURE PURSUANT TO THE LOW-THREAT UNDERGROUND STORAGE TANK CASE CLOSURE POLICY The SWRCB adopted the LTCP on May 1, 2012. The SWRCB provided notification that the LTCP had become effective on August 17, 2012 as outlined in their August 24, 2012 announcement. The announcement also provided a checklist to be used by regulatory agencies and responsible parties to evaluate the applicability of the LTCP to UST sites; this checklist is included in Attachment A. V:\1857\active\7- Eleven\active\185750063_711_14117\05_report_del iv\reports\14117_2013_08_15_closure_report.doc