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7-Eleven Store#20632 Quarterly Groundwater Monitoring Report(2Q2005) • August 12, 2005 Page 3 indicator Dissolved oxygen concentrations were also measured in 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 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 presented in Attachment A GROUNDWATER SAMPLE ANALYSES AND RESULTS The groundwater samples collected from MW-2, MW-3, MW-4R, MW-5, MW-6, and MW-7 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) 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 Hydrocarbon 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 ATTACHMENTS Figures Tables Attachment A— Field Notes Attachment B—Certified Laboratory Analytical Reports and Chain-of-Custody Documentation cc Mr Harlin Knoll, San Joaquin County Environmental Health Department Mr James Brathovde, Regional Water Quality Control Board, Central Valley Region • 20632 05-2Q Report doc SECOR International Incorporated