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E C 0 R . 7-Eleven Store #14117 Additional Site Assessment Report and Fate and Transport Model February 27, 2004 Page 4 Well Development and Groundwater Sampling On August 20, 2003, Cascade Drilling developed well MW-8 by surging and bailing groundwater from the well Approximately 10 well casing volumes of groundwater were purged from the well, until pH, temperature, and conductivity readings stabilized Parameters monitored during development and well purging included pH, conductivity, and temperature (Appendix C) Purge water from well development and sampling was stored in 55-gallon drums on site, pending offsite disposal Following well development, groundwater samples were collected from the new well during quarterly monitoring and sampling on September 18, 2003 Well purging and sampling equipment was thoroughly cleaned prior to purging and sampling each well The sampling procedure for the 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 The well was 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 sampling event are noted on the field data sheets included in Attachment C During purging, temperature, pH, and electrical conductivity are monitored in order to document that these parameters are stable prior to collecting samples After purging, water levels are 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 The samples were preserved on ice and transported under chain-of-custody manifest to Kiff Analytical LLC, in Davis, California, for analysis of TPHg and BTEX, and fuel oxygenates MtBE, ethyl-tert-butyl ether (EtBE), diisopropyl ether (DIPE), tert-amyl-methyl ether (TAME), tert-butyl alcohol (TBA), and halogenated volatile organic compounds (HVOCs) by EPA Method 82606 Waste Disposal Soil generated during drilling was temporarily stored onsite In properly labeled 55-gallon drums Four discrete soil samples were collected from the drums and transported to Kiff Analytical under chain-of-custody documentation for profiling The four discrete soil samples were combined in the laboratory into one composite sample (SP-1[ABCD]) and analyzed for TPHg, BTEX, and MtBE by EPA 8260B (Table 2) Belshire Environmental Services Inc transported the non-hazardous soil on September 24, 2003, and well development water on October 2, 2003 Six drums of soil were recycled at the TPS Technologies Soil Recycling facility located Adelanto, California and four drums of water were disposed of at the Demenno Kerdoon facility located in Compton, California Copies of the waste disposal documentation are provided in Attachment E RESULTS OF SAMPLING ANALYSIS Soil Sample Analytical Results TPHg and benzene were reported in soil samples collected from MW-8 at maximum concentrations of 11,000 mg/kg and 34 mg/kg at 15 feet bgs, respectively (Figure 2 and Table 2) TPHg and benzene were also reported in soil samples collected from MW-8 to a depth of 45 feet bgs . However, TPHg and benzene were not detected above laboratory reporting limits in the soil sample 14117 Vertical Assessment and Fate and Transport Model doc SECOR Intemational Incorporated