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Groundwater Monitoring Well, CPT,and Ozone Microsparge System Installation Report Tosco(76) Service Station No 11192, Stockton,California May 9 2003 and 0 0053 ppm, respectively The laboratory reported that all other analytes were below the laboratories reporting limits Soil chemical data are summarized in Table 3 5a W2cte_nisposal Approximately 220 gallons of waste water generated by cleaning the drilling equipment and well development and sampling procedures were removed from the site by GR on January 3, 2003, and transported to the Tosco Refinery in Rodeo, California, for disposal On January 8, 2003, Tim Manley Trucking of Sacramento, California transported 19 74 tons of soil (drill cuttings) to the Allied Waste Inc (Allied) Forward Landfill facility in Manteca, California for disposal Copies of the landfill approval letter and waste disposal manifest are included as Appendix G 6.0 CONCLUSIONS AND RECOAMENDATIONS This work was performed to facilitate the installation of a remediation system to address hydrocarbon-impacted groundwater beneath the site The ozone microsparging system will be inspected on a twice monthly schedule to conduct operation and maintenance activities Groundwater samples from select monitoring wells will be collected monthly to monitor the progress of the system The system operation will be enhanced and maintained as needed The progress sampling will be coordinated with the regular scheduled quarterly monitoring and sampling program at the site After the first six months of system operation (3`d quarter, 2003), a progress report will be issued by August 1, 2003, and future progress reports will be prepared on a semi-annual basis The remedial system effectiveness will be evaluated after six months, and further recommendations, if any,will be made at that time GR recommends that the two new monitoring wells be added to the current quarterly monitoring and sampling program The wells should be sampled for a minimum of one hydrologic cycle in order to assist with the ongoing delineation of the dissolved hydrocarbon plume Based on the results of the depth discrete groundwater sampling conducted in the upgradient deep CPT boring (CPT-2), it appears that groundwater beneath this boring location is free of hydrocarbon impact A trace concentration of MtBE was detected in groundwater sample CPT2-75 (2 0 ppb) This MtBE concentration is below the maximum contaminate level (MCL) (13 ppb) This result may not be representative of actual groundwater conditions, and may be due to cross contamination from the drilling and/or sampling procedures Methanol was detected m the groundwater sample collected from boring CPT-2 at 75 feet bgs Methanol is neither currently, nor was historically, a component in gasoline formulated by ConocoPhilhps/Tosco However, methanol is a common chemical utilized by the analytical laboratory, making laboratory contamination a possible source of the methanol detected Based on this, the reported methanol detection is suspect 40 140245 8 10