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S E C 0 R <br /> 7-Eleven Store#17334 <br /> Quarterly Groundwater Monitoring Report(2Q2003) <br /> August 27, 2003 <br /> Page 3 <br /> On April 3 and 4, 2002, sod boring SB-1 was advanced to a depth of 50 feet bgs where a grab <br /> groundwater sample was collected with a Hydropunch sampler (IT Corporation, 2002) Two double- <br /> nested soil vapor extraction/air sparge SVE/AS wells (SPV-1 and SPV-2) were also installed to 30 <br /> feet bgs Dissolved benzene, TPHg, and MtBE were detected in groundwater samples from SB-1 @ <br /> 50' bgs, at concentrations of 28 ug/L, 7,100 ug/L, and 67 ug/L, respectively <br /> MONITORING AND SAMPLING PROCEDURES <br /> The depth to water was measured in monitoring wells MW-2, MW-3, MW-4, MW-5A, and MW-513, <br /> from top of casing (TOC) using a water level indicator to within 0 01 feet bgs Dissolved oxygen <br /> readings were also collected from each well using a YSI Model 550A dissolved oxygen meter <br /> equipped with a down hole sensor <br /> Well purging and sampling equipment is thoroughly cleaned prior to purging and sampling each well <br /> The sampling procedure for each well includes measuring the water level and checking for the <br /> presence of liquid-phase hydrocarbons (LPH), using either an electronic indicator and a clear <br /> Teflon bailer or an oil-water interface probe Wells not containing LPH are purged of approximately <br /> three casing volumes of water (or to dryness) using a submersible pump or bailer The equipment <br /> and purging methods used for the current sampling event are noted on the field data sheets included <br /> in Attachment A During purging, temperature, pH, and electrical conductivity are monitored in order <br /> to document that these parameters are stable prior to collecting samples After purging, water levels <br /> are allowed to recover to 80% of the original levels prior to collection of the water sample <br /> Groundwater samples are collected using a disposable Teflon bailer, placed into appropriate EPA- <br /> approved containers, labeled, logged onto chain-of-custody documents, and transported on ice to a <br /> California state-certified laboratory Copies of the field notes have been included in Attachment A <br /> GROUNDWATER SAMPLE ANALYSES AND RESULTS <br /> The groundwater samples collected from MW-2, MW-3, MW-4, MW-5A, and MW-513 were analyzed <br /> for the presence of TPHg, benzene, toluene, ethylbenzene, and total xylenes (BTEX), and fuel <br /> oxygenates MtBE, tert-butyl alcohol (TSA), diisopropyl ether (DIPS), ethyl-tert-butyl ether (EtBE), <br /> and tert-amyl-methyl ether (TAME) using EPA Method 8260B The certified laboratory analytical <br /> report and chain-of-custody documentation are presented as Attachment B <br /> Groundwater analytical results are presented on Figure 3 and are summarized in Tables 1 and 2 <br /> Chemical concentrations were generally consistent with historical data <br /> PURGE AND RINSATE WATER DISPOSAL <br /> Water generated during well sampling and equipment cleaning is pumped into a SECOR truck- <br /> mounted water tank The water is transferred into properly labeled 55-gallon drums and stored on- <br /> site The drummed non-hazardous petroleum hydrocarbon contaminated water is transported <br /> quarterly by Belshire Environmental to Demenno Kerdoon in Compton, California, for disposal <br /> ATTACHMENTS <br /> Figures <br /> Tables <br /> Attachment A— Field Notes <br /> Attachment B—Certified Laboratory Analytical Reports and Chain-of-Custody Documentation <br /> cc Mr Harlin Knoll, San Joaquin County Environmental Health Department <br /> Mr James Brathode, RWQCB, Central Valley Region <br /> 17334 43-20 Report doc SECOR Intemat+onal Incorporated <br />