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f� E C 0 R 7-Eleven Store#14117 Quarterly Groundwater Monitoring Report (4Q2004) February 16, 2005 . Page 3 Per the request of the SJCEHD, groundwater monitoring and sampling is coordinated with a former Exxon site (currently a USA Gasoline station) immediately east of the 7-Eleven site On July 22, 2004 , SECOR submitted a proposal for a Field Test Program for Evaluation of Oxidation Capacity of Groundwater to the RWQCB The RWQCB conditionally approved the proposal in a letter dated October 4, 2004 On July 27, 2004, SECOR submitted a Work Plan for Additional Offsite Assessment to the SJCEHD The work plan was approved by the SJCEHD in a letter dated August 23, 2004 The work plan proposed the installation of two offsite groundwater monitoring wells (MW-9 and MW- 10), advancing three offsite soil borings (GP1 through GP-3) and three offsite CPT borings (CPT-1 through CPT-3) Submitted proposal for Field Test Program for Evaluation of Oxidation Capacity of Groundwater dated July 22, 2004 to the RWQCB The work plan for pilot study was approved by the RWQCB on October 4, 2004 MONITORING AND SAMPLING PROCEDURES The depth to water was measured to within 0 01 feet bgs in monitoring wells MW-1 through MW-8 from top of casing (TOC) using a water level indicator Dissolved oxygen concentrations were also measured in each well using a YSI Model 550A dissolved oxygen Smeter equipped with a down hole sensor Well purging and sampling equipment was thoroughly cleaned prior to purging and sampling each well The sampling procedure for each well included measuring the water level and checking for the presence of liquid-phase hydrocarbons (LPH), using either an electronic indicator and a clear Teflon® bailer or an oil-water interface probe Wells not containing LPH were purged of approximately three casing volumes of water (or to dryness) using a submersible pump or bailer The equipment and purging methods used for the current sampling event are noted on the field data sheets in Attachment A During purging, temperature, pH, and electrical conductivity were monitored After purging, water levels were allowed to recover to 80% of the original levels prior to collection of the water sample Groundwater samples were collected using a disposable Teflon® bailer, placed into appropriate Environmental Protection Agency EPA approved containers, labeled, logged onto chain-of-custody documents, and transported on ice to a California state-certified laboratory Copies of the field notes are presented in Attachment A GROUNDWATER SAMPLE ANALYSES AND RESULTS The groundwater samples collected from MW-1 through MW-8 were analyzed for TPHg, BTEX, and the fuel oxygenates MtBE, tert-butyl alcohol (TBA), dnsopropyl ether (DIPE), ethyl-tert-butyl ether (EtBE), tert-amyl-methyl ether (TAME), 1,2-dichloroethane (1,2-DCA), and 1,2-dibromoethane (EDB) by EPA Method 8260B The certified laboratory analytical report and chain-of-custody documentation are presented as Attachment B Groundwater analytical results are presented on Figure 3, and are summarized in Tables 1 and 2 Hydrocarbon concentrations were generally consistent with historical data 14117 04-4Q Report doc SECOR Intemational Incorporated