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i <br /> 7-Eleven Store#19976 <br /> Quarterly Groundwater Monitoring and Remediation Progress Report (1Q2005) <br /> May 4, 2005 <br /> . Page 4 <br /> conducted using well MW-2 for vapor extraction, and double-nested sparge well SP-1 for air <br /> infection Pre-sparging extracted vapor levels ranged up 1,000 ppmv, with dissolved <br /> oxygen (DO) levels of up to 0 72 mg/L Air was then infected into the deeper section of well <br /> SP-1 using an oil-less air compressor Vapor levels in well MW-2 increased to 1,600 ppmv, <br /> and DO levels to 8 mg/L, after 30 minutes of sparging The data indicated the area of <br /> sparging influence in SP-1 included the region of MW-2, and that treatment using well SP-1 <br /> should be successful at reducing dissolved hydrocarbons/oxygenates in well MW-2 and the <br /> surrounding area Air sparge testing was repeated on May 23, 2002, using well MW-1A as <br /> the injection point, and the horizontal wells as the SVE point Results indicated no <br /> breakthrough of sparged air into the vadose zone accessible by the horizontal wells <br /> On May 27, 2003, one soil sample was collected under the northern fuel dispenser, and a <br /> second sample was collected beneath the product line during a fuel system upgrade The <br /> soil samples collected beneath the dispenser and fuel delivery piping did not contain <br /> concentrations of TPHg, BTEX, or fuel oxygenates above laboratory detection limits On <br /> June 9, 2003, three 10,000-gallon double-walled fiberglass USTs were removed from the <br /> excavation and hauled offsite <br /> On June 9 and 19, 2003, a total of six UST confirmation soil samples (T1 N-15' through <br /> T3S-13') were collected in native soil underlying the ends of the three USTs (Figure 2) at <br /> approximate depths of 12 to 15 feet bgs during the second UST replacement event at the <br /> site TPHg, BTEX, and fuel oxygenates were not detected at concentrations above <br /> laboratory detection limits in two of the six soil samples collected beneath the USTs <br /> Benzene and TPHg were reported in the soil samples collected beneath the north ends of <br /> two USTs (T1 N, T2N) at maximum concentrations of 0 0087 mg/kg and 9 3 mg/kg, <br /> respectively MtBE and TBA were reported at maximum concentrations of 3 3 mg/kg <br /> (T1N@13') and 18 mg/kg (T3N@13'), respectively <br /> Between June 23 and July 7, 2003, Glacier Environmental Services installed two new <br /> double-walled fiberglass USTs one 10,000-gallon premium unleaded gasoline UST, and <br /> one 15,000-gallon regular unleaded gasoline UST, and associated piping and dispensers <br /> (Figure 2) In order to accommodate the new 15,000-gallon UST, Glacier excavated <br /> approximately 288 cubic yards of soil, expanding the UST pit to the west The excavated <br /> soil was disposed of at Forward Inc landfill <br /> During the installation of the new UST's in July 2003, SECOR personnel extended the <br /> horizontal extraction line in the tank pit to the east to terminate in the well box of SP-1 Half <br /> inch tubing was run from the function box in the planter to SP-1 to facilitate oxygen injection <br /> away from the dispenser islands <br /> On April 9, 2004, SECOR submitted a request with the SJCEHD to reduce sampling of <br /> MW-4 and MW-4A from quarterly to annually Approval was received in a letter from the <br /> SJCEHD dated July 28, 2004 <br /> On June 2, 2004 a 22-hour SVE event was conducted on the horizontal tank pit wells <br /> . Based on soil vapor samples collected during the test it is estimated that approximately <br /> 19976 05-10 Report doc SECOR International Incorporated <br />