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' 01 October 2004 AGE-NC Project No 95-0173 Page 5 of 10 Between 24 March 2004 and 22 June 2004, an induced vacuum was applied to SVE wells (VW-1 through VW-4)to extract hydrocarbon vapor from the subsurface Wells VW-5 through VW-7 were closed at the well-heads due to only trace levels of petroleum hydrocarbons previously observed from PID field measurements (Table 6) 32 IN-SITU AIR SPARGING SYSTEM PROCEDURES The IAS system consists of a 5 horsepower, Specdaire(model no 5F229B) electric air compressor that Is utilized to infect 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 infected air should volatilize dissolved hydrocarbons in ground water, and force hydrocarbon vapors into the vadose zone,where they can be withdrawn by the aforementioned SVE system . Between 24 March and 22 June 2004, air pressure was continuously discharged from the air compressor to deeper screened well AW-2B between 13 and 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 monitonngwells MW-1,MW-2 and MW-3 were performed to determine j if ground water mounding was occurring as a result of the above IAS activities 33 COLLECTION AND ANALYSIS OF VAPOR EXTRACTION AIR FLOW SAMPLES A total of three sets of extracted air flow vapor samples were collected on 28 April, 26 May and 22 June 2004 from the influent and effluent sampling ports of the regenerative vacuum blower unit to measure concentrations of hydrocarbon vapor The 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 ofcustody to CTEL,aDHS-certified laboratories in California Each sample was analyzed within 72 hours of collection for TPH-g, BTEX and MTBE in accordance with EPA Methods 5030B/8015M and 8021 Advanced GeoEnviron mental,Inc I