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3 <br /> S E C 0 R <br /> 7-Eleven Store#21756 <br /> . Semi-annual Groundwater Monitoring Report (102005) <br /> May 2, 2005 <br /> Page 3 <br /> and MW-4, and a grab groundwater sample from GP-6, did not contain BTEX, TPHg, and <br /> fuelloxygenates above laboratory reporting limits <br /> An SVE test was conducted on April 24, 2002, by application of vacuum to well SPV-1 <br /> Magnehelic gauge measurements of wells MW-1, MW-2, MW-3, and SPV-2 indicated an <br /> estimated radius of vapor extraction influence of 25 to 30 feet around the extraction point <br /> A second SVE test was conducted on October 17, 2002 Vapor extraction was performed <br /> on SPV-2 and MWA, which resulted in an estimated radius of influence of 25 to 30 feet <br /> Influent vapor concentrations, as measured via a flame ionization detector (FID), ranged <br /> from 3 to 8 parts per million by volume (ppmv) <br /> On December 2, 2003, SECOR submitted a Request for Reduction in Groundwater <br /> Sampling with the San Joaquin County Environmental Health Department (SJCEHD) <br /> SECOR requested reducing sampling from quarterly to annually The SJCEHD approved a <br /> reduction from quarterly to semi-annually in an e-mail dated March 12, 2004 <br /> MONITORING AND SAMPLING PROCEDURES <br /> The depth to water was measured to within 0 01 feet bgs in four monitoring wells, MWA <br /> through MW-4, from top of casing (TOC) using a water level indicator Dissolved oxygen <br /> • concentrations were also measured in four wells (MW-1 through MW-4) using a YSI Model <br /> 550A dissolved oxygen meter equipped with a down hole sensor <br /> Well purging and sampling equipment was thoroughly cleaned prior to purging and <br /> sampling each well The sampling procedure for each well included measuring the water <br /> level and checking for the presence of liquid-phase petroleum (LPH) using a clear Teflon® <br /> bailer or an oil-water interface probe Wells not containing LPH were purged of <br /> approximately three casing volumes of water (or to dryness) using a submersible pump or <br /> bailer The equipment and purging methods used for the current sampling event are noted <br /> on the field data sheets in Attachment A During purging, temperature, pH, and electrical <br /> conductivity were monitored After purging, water levels were allowed to recover to 80% of <br /> the original levels prior to collection of the water sample Groundwater samples were <br /> collected using a disposable Teflon`s bailer, placed into appropriate Environmental <br /> Protection Agency (EPA) approved containers, labeled, logged onto chain-of-custody <br /> documents, and transported on ice to a California state-certified laboratory Copies of the <br /> field notes have are shown in Attachment A <br /> GROUNDWATER SAMPLE ANALYSES AND RESULTS <br /> The groundwater samples collected from four monitoring wells, MWA through MW-4, were <br /> analyzed for the presence of TPHg, BTEX, and fuel oxygenates MtBE, TBA, dnsopropyl <br /> ether (DIPS), ethyl-tert-butyl ether (EtBE), and tert-a myl-m ethyl ether (TAME) by EPA <br /> Method 8260B The certified laboratory analytical report and chain-of-custody <br /> documentation are presented as Attachment B <br /> Groundwater analytical results are presented on Figure 3, and are summarized in Tables 1 <br /> and 2 Hydrocarbon concentrations were generally consistent with historical data <br /> 21756 05-1 Q Report doc SECOR lntemationa!incorporated <br />