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y[1T EC ® R 7-Eleven Store#21756 ;x Quarterly Groundwater Monitoring Report(3Q2004) • October 28, 2004 1 Page 3 f (SVE) wells, and also screened from 24 to 29 feet bgs as sparge wells A Geoprobe soil h , boring (GP-6) was advanced to a depth of 40 feet bgs Soil samples collected from GP-6 and MW-4, and a grab groundwater sample from GP-6, did not contain BTEX, TPHg, and fuel/oxygenates above laboratory reporting limits < r 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 f 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 feety Influent vapor concentrations, as measured via a flame ionization detector (FID), ranged g p 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 in four monitoring wells, MWA through MW-4, from top of casing (TOC) using a water level indicator Dissolved oxygen concentrations were also collected from three wells (MW-1, MW-3 & MW-4) using a YSI Model 550A dissolved oxygen meter equipped with a down hole sensor During the third quarter monitoring and sampling event, grab samples were taken from MWA and MW-3 MW-2 was defined as "dry" and not sampled because the measured water column elevation was observed to be below the screened interval of the well 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 (!_PH) 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 b 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 have are shown in Attachment A GROUNDWATER SAMPLE ANALYSES AND RESULTS The groundwater samples collected from three monitoring wells MWA, MW-3 & MW-4 were ' analyzed for the presence of TPHg, BTEX, and fuel oxygenates MtBE, TBA, diisopropyl 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 �a 21756 04-30 Report doc SECOR rntemational Incorporated ~