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lie 15 December 2003 AGE-NC Project No 95-0173 - Page 4 of 9 32 IN-SITU AIR SPARGING SYSTEM PROCEDURES The IAS system utilizes a 5 horsepower, Speedaire (model no 5F229B) electric air compressor to inj ect air beneath the water table From the outlet of the air compressor, a manifold network of one- inch diameter, schedule 80 PVC piping was installed underground to the well heads at IAS wells AW-1 through AW-7 and ground water monitoring wells MW-1 through MW-3 A Wilkerson oil ' filter (model no M18) and Wilkerson air pressure regulator (model no R28) are installed at the outlet of the air compressor for added controls The injected air should volatilize dissolved hydrocarbons in ground water, and force hydrocarbon vapors into the vadose zone,where they can ' be withdrawn by the above SVE system Generally,air pressure was discharged from the air compressor to shallow screened IAS wells AW-3 ' through AW-7 and MW-1 through MW-3 at 5 to 7 pounds per square inch (psi), or alternatively discharged to deeper screened well AW-1B at 13 to 15 psi Utilizing a Solinst water level indicator and a YSI-50 dissolved oxygen meter, measurements of ground water depth and dissolved oxygen ' from ground water monitoring wells MW-1, MW-2 and MW-3 were performed to determine if ground water mounding was occurring as a result of the above IAS activities (Table 6) 32 COLLECTION AND ANALYSIS OF VAPOR EXTRACTION AIR FLOW SAMPLES Between 23 June 2003 and 09 September 2003, a total of four pairs of extracted air flow vapor samples were collected from the influent and effluent of the SVE unit to measure concentrations of hydrocarbon vapor The air flow vapor samples were collected in Tedlar bags using a hand air- vacuum pump Following sample collection,the samples were properly labeled,placed in a covered container and transported under chain-of-custody to McCampbell Analytical Inc (MAI)in Pacheco. California Each sample was analyzed within 72 hours of collection for TPH-g,BTEX and MTBE ' in accordance with EPA Methods 5030B/8015Cm Modified and 8021B r4.0. FINDINGS Ground water elevation, flow direction and gradient were determined from field data collected on 23 September 2003, the contaminant impact to ground water was quantified trom the laboratory analysis From field and laboratory data collected at the SVE remediation system between 23 June 2003 and 09 September 2003, AGE determined the average TPH--g concentration, the average flow rate and ' calculated the approximate mass and volume of hydrocarbons removed ' Advanced GeoEnvironmental,Inc