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Former Beacon Station No* November 24, 1999 Stockton California Vapor Extraction/Air Sparge Test Report No 2236) The requested analyses were total petroleum hydrocarbons as gasoline (TPHg), the gasoline constituents benzene, toluene, ethylbenzene, and xylenes (BTEX), and the fuel oxygenate methyl tertiary-butyl ether (MTBE) by modified Environmental Protection Agency (EPA) Methods 8015/8020 AIR SPARGE TEST PROCEDURES The AST was performed on October 20, 1999 and consisted of the infection of air into well AS-1 (screened 64 to 70 feet bgs) using a 1-horsepower Gast oilless compressor The injection flowrate and pressure response for wells MW-3 and MW-9 were monitored during the 8-hour test I VAPOR EXTRACTION TEST RESULTS A summary of the VET field data and analytical results are summarized in Table 1 The laboratory report for the air samples is attached TPHg vapor concentrations during the test ranged from 3,800 (VW-2) to 4,600 (VW-1) parts per million (ppm) TPHg was not detected in the effluent sample collected The daily TPHg mass extraction rate ranged from 21 0 to 292 pounds per day (ppd) The maximum flowrate achieved was 91 scfm from VW- 1 at a wellhead vacuum of 60 inches of H2O Vacuum influence ranging from 0 3 to 0 4 inches H2O were observed in well MW-9 Approximately halfway through the VET, a vacuum response ranging from 0 05 to 0 8 was observed in well MW-7 • Based on the favorable field results obtained, (high flowrate at low vacuum and measurable vacuum response up to 56 feet from extraction well) vapor extraction is a feasible remediation alternative for impacted soil beneath the site Horizon estimates a radius of influence of 50 feet while extracting from well VW-1 Well VW-2 exhibited low flow characteristics with a maximum achievable flowrate of 14 scfm The radius of influence for well VW-2 is uncertain, but is estimated as less than 20 feet AIR SPARGE TEST RESULTS The field data obtained dunng the AST is summarized in Table 2 An AS-1 infection flowrate of 13 actual cubic feet per minute (acfm) was established during the 8-hour test Air flow was initially achieved at an infection pressure of I5 psi, with the pressure decreasing to 9 psi The groundwater depth in AS-1 prior to sparging was 48 25 feet bgs, with the AS-1 well screen set at 65 to 70 feet bgs Vadose zone gas pressure responses were measured at wells MW-3 and MW-9 Based on a measured groundwater depth of 48 25 feet bgs, the well screen for MW-3 (65 — 85 feet bgs) was approximately 16 75 feet below the groundwater surface dunng the test The pressure response in well MW-3 appears to be as a result of air migration to the well screen and into the blank portion of the well casing The field data obtained from the AST suggest that air sparging is a feasible remedial alternative from an air flow perspective Pressure response data suggests a radius of influence between 10 and 20 feet 1124Jald Job No 1419 22 2 HORIZON ENVIRONMENTAL INC.