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4 r ' 06 April 2005 . AGE-NC Project No 98-0448 Page 4 of 9 In order to monitor the efficiency of hydrocarbon removal, 1) the SVE air flow of the influent stream was monitored routinely utilizing an organic vapor analyzer(OVA)equipped with a photo- ionization detector(PID Thermo Environmental 580B, 10 0 eV, calibrated to isobutylene), and 2) influent air flow vapor stream sample was`collected from sampling ports installed upstream (influent)of the vacuum blower and analyzed Field measurements were recorded at regular intervals and are summarized in Table 6 3 2 IN-SITU AIR SPARGING SYSTEM PROCEDURES ' Between September 2004 and December 2004,the IAS system utilized a 7'/2 horsepower,Westward (model no 52639) electric air compressor 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-4 (screened 25-30 feet),AW-5 (30- 35 feet) and IAS well MW-4B (screened 45-50 feet) A Wilkerson oil filter (model no M18) and tWilkerson air pressure regulator(model no R28)are installed at the outlet of the air compressor for added controls, Wilkerson air pressure regulators (model no RI 8) are installed at each IAS well- head to enable independent control over the varying pressures required to displace water within each air sparge well casing, resulting in continuous air sparging in the IAS network system ' Generally,air pressure was discharged at shallow screened IAS wells AW-1 through AW-5 between 5 and 8 pounds per square inch (psi), and to deeper screened well MW-4B between 13 and 15 psi A liquid-filled, air-guage was installed at each of the above well heads to monitor air pressure 33 COLLECTION AND ANALYSIS OF VAPOR EXTRACTION AIR FLOW SAMPLES A total of three extracted air flow vapor samples were collected on 25 October, 22 November and 22 December 2004 from the influent stream of the regenerative vacuum blower unit to measure ' concentrations of hydrocarbon vapor The samples were collected in Tedlar bags utilizing an electric air-vacuum pump ' Following sample collection, the samples were properly labeled, placed in a covered container and transported under chain of custody to a DHS-certified laboratory for analysis Each sample was analyzed within 72 hours of collection for TPH-g and BTEX/MTBE in accordance with EPA ' Methods 8015M Modified and 8021, respectively ' Advanced GeoEnvironmental,Inc t