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S E C 0 R - ----- - - 7-Eleven Store#21756 Semi-annual Groundwater Monitoring Report (3Q2005) . October 4, 2005 Page 4 An SVE test was conducted on April 24, 2002, by application of vacuum to well SPV-1 Magnehelic gauge measurements of wells MW-1, MW-2, MW-3, and SPV-2 indicated an estimated radius of vapor extraction influence of 25 to 30 feet around the extraction point A second SVE test was conducted on October 17, 2002 Vapor extraction was performed on SPV-2 and MW-1, which resulted in an estimated radius of influence of 25 to 30 feet Influent vapor concentrations, as measured via a flame ionization detector (PID), ranged from 3 to 8 parts per million by volume (ppmv) On December 2, 2003, SECOR submitted a Request for Reduction in Groundwater Sampling with the San Joaquin County Environmental Health Department (SJCEHD) SECOR requested reducing sampling from quarterly to annually The SJCEHD approved a reduction from quarterly to semi-annually in an e-mail dated March 12, 2004 MONITORING AND SAMPLING PROCEDURES The depth to water was measured to within 0 01 feet bgs to four monitoring wells, MW-1 through MW-4, from top of casing (TOC) using a water level indicator Dissolved oxygen concentrations were also measured in MW-1 through MW-4 using a YSI Model 550A dissolved oxygen meter 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 petroleum (LPH) using 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 shown in Attachment A GROUNDWATER SAMPLE ANALYSES AND RESULTS The groundwater samples collected from four monitoring wells, MW-1 through MW-4, were analyzed for the presence of TPHg, BTEX, and fuel oxygenates MtBE, TBA, dnsopropyl ether (DIPE), ethyl-tert-butyl ether (EtBE), and tert-amyl-methyl ether (TAME) 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 TPHg, BTEX, MtBE, TBA, DIPE, EtBE and TAME were not detected above the laboratory reporting limits in groundwater samples from wells MW-1 through MW-4 21756 05-3Q Report doc SECOR Intemabonal Incorporated