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SIEC ® R 7-Eleven Store#17334 Quarterly Groundwater Monitoring Report (4Q2003) • March 11, 2004 Page 3 On April 3 and 4, 2002, soil boring SB-1 was advanced to a depth of 50 feet bgs, where a grab groundwater sample was collected with a Hydropunch sampler (IT Corporation, 2002) Two double- nested soil vapor extraction/air sparge SVEIAS wells (SPV-1 and SPV-2) were also installed to 30 feet bgs Dissolved benzene, TPHg, and MtBE were detected in groundwater samples from SB-1 @ 50' bgs, at concentrations of 28 ug/L, 7,100 ug/L, and 67 ug/L, respectively On April 4, 2003, two soil samples were collected under the fuel dispensers and two soil samples were collected under the fuel lines northeast of the UST pit Soil sample 1_2-5 0' contained MtBE at a concentration of 0 012 mg/kg MONITORING AND SAMPLING PROCEDURES The depth to water was measured in monitoring wells MW-2, MW-3, MW-4, MW-5A, and MW-513, from top of casing (TOC) using a water level indicator to within 0 01 feet bgs Dissolved oxygen readings were also collected from each well 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 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 included in Attachment A During purging, temperature, pH, and electrical conductivity were monitored in order to document that these parameters were stable prior to collecting samples 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 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 been , included in Attachment A 3 GROUNDWATER SAMPLE ANALYSES AND RESULTS The groundwater samples collected from MW-2, MW-3, MW-4, MW-5A, and MW-5B were analyzed for the presence of TPHg, benzene, toluene, ethylbenzene, and total xylenes (BTEX), and fuel oxygenates MtBE, tert-butyl alcohol (TBA), diisopropyl ether (DIPE), ethyl-tert-butyl ether (EtBE), and tert-amyl-methyl ether (TAME) using 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 Chemical concentrations were generally consistent with historical data PURGE AND RINSATE WATER DISPOSAL Water generated during well sampling and equipment cleaning was pumped into a SECOR truck- mounted water tank The water was transferred into properly labeled 55-gallon drums and stored on-site The drummed non-hazardous petroleum hydrocarbon contaminated water is transported quarterly by Belshire Environmental to Demenno Kerdoon in Compton, California, for disposal ) i 17334 03-4Q Report SECOR lntemational Incorporated