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S E C 0 R • 7-Eleven Store#32262 Extended Groundwater Pumping Test and Oxygen Injection Feasibility Study November 15, 2005 Page 3 MW-3, MW-5, and MW-6D at concentrations ranging from 0 0079 mg/kg to 9 5 mg/kg TBA was detected in MW-5 and MW-60 at concentrations ranging from 0 010 mg/kg to 2 2 mg/kg Soil samples collected from MW-1 through MW-5, and MW-6D, did not contain TPHg, BTEX, dllsopropyl ether (DIPE), ethyl-tert-butyl ether (EtBE), 1,2-dichloroethane (1,2-DCA), or 1,2-dibromoethane (EDB) above laboratory reporting limits On June 2, 2004, SECOR supervised the drilling of one onsite groundwater monitoring well (MW-7), one oxygen Injection test well (S-1), and one groundwater extraction test well (EX- 1) The purpose of this work was to delineate the vertical and lateral extent of petroleum hydrocarbons In soil and groundwater at the site Analytical results indicated that the majority of hydrocarbons in soil are located in the area of the former USTs and dispensers to depths of approximately 20 feet On June 21, 2004, SECOR conducted an oxygen Injection test on oxygen injection well S- 1 Approximately 150 cubic feet (ft) of oxygen was injected into well S-1 over approximately a 30 minute interval Dissolved oxygen (DO) concentrations were measured with a DO meter equipped with a down hole probe in well S-1 before and immediately following completion of the injection test During the test, Injection pressures and flow rates were recorded from the injection well and lower explosive limit (LEL) oxygen measurements were collected in S-1 and in adjacent wells EX-1 and MW-5 After the oxygen injection feasibility test, it was determined that the radius of influence for oxygen injection is less than five feet, therefore, oxygen injection was not considered a feasible remedial alternative for this site On July 26, 2004 SECOR supervised the drilling of two offsite groundwater monitoring wells (MW-8 and MW-9) at the Shell property north of the site These wells were installed for the purposes of monitoring the hydrocarbon concentrations offsite, and to assess the feasibility of remedial techniques On July 30, 2004, MW-8 and MW-9 reported MtBE concentrations of 210 ug/L and 420 ug/L respectively On August 2, 2004 SECOR supervised the advancement of two CPT borings (CPT-1 and CPT-2) to approximately 83 feet bgs This work was done for the purpose of hydrocarbon assessment, and to investigate sub-surface lithology A grab groundwater sample collected at 60 feet bgs from CPT-1 contained 69 ug/L TPHg and 0 74 ug/L MtBE BTEX, TBA, DIPS, ETBE, and TAME were not detected above the laboratory reporting limits No detectable concentrations of BTEX, TPHg, MtBE, TBA, DIPE, ETBE, or TAME were reported in the water sample collected from CPT-1 at 82 feet bgs or from CPT-2 at 65 and 81 feet bgs A step-drawdown test was conducted on August 11, 2004 using a submersible pump in well EX-1 Based on the analysis of the step-drawdown test the constant-rate test was initiated on August 12, 2004 by pumping EX-1 at 0 8 gallons per minute (gpm) The objective of the test was to create hydraulic stress in the aquifer by pumping from well EX-1 at a constant pumping rate while monitoring drawdown in observation wells S-1 and MW-5 During the 17-Elevenl7-11 Stores1322621Reports132262 Pump Test and 02 Feasibility 11-10-05 doc SECOR International Incorporated 1