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' • 28 May 2003 AGE-NC Project No 95-0173 ' Page 2of8 ' at regular purge-volume intervals using an Oakton water analyzer Field data and logs are included in Appendix A Purged ground water was containerized in 55-gallon drums and was stored on-site in an area lacking general public access Multi-level monitoring well MW-13 (A-C) and the deep (screen interval B) air sparge wells were purged by lowering and raising a 318-inch outer diameter,length-discrete polyethylene hose equipped ' with a ball-valve water tip through the top chambers into the specific water-charged screened section, a Watera-Hydro-Lift H pump equipped with a mechanical arm was utilized to surge the polyethylene hose Approximately 2 25 to 4 gallons of ground water (a minimum of three casing- water volumes per well) were purged from each multi-level well chamber and between 14 and 20 gallons purged from air sparge wells AW-1B and AW-2B Temperature, pH and conductivity were measured for stabilization at regular purge-volume intervals from each well using the Oakton water ' analyzer Field data and logs are in Appendix A Multi-level well purged ground water was transferred to 55-gallon drums and stored on-site in an area lacking general public access 2 2 GROUND WATER SAMPLING ' Following well purging,ground water levels in the wells achieved a minimum of 80 percent recharge prior to sample collection, except for well MW-11 which was purged `dry' Subsequently, ground ' water samples were collected from the single-level monitoring wells and shallow air sparge wells utilizing new,disposable polyethylene bailers and transferred into 40-m1 EPA-approved VOA vials containing 0 5 ml 18%hydrochloric acid as a sample preservative, ground water samples from the ' multi-level well and deep air sparge wells were collected directly into the 40-m1 VOA vials utilizing the Watera hose bailer Care was taken to ensure that visible air bubbles were not present in the vials after filling and capping Ground water sample containers were labeled with the well designation, ' date, time, and sampler's initials ' 2 3 LABORATORY ANALYSIS OF GROUND WATER SAMPLES After labeling,each ground water sample was logged on a chain-of-custody form,placed in a chilled container and transported to Castle Analytical Laboratory, a California Department of Health Services (DHS)-certified laboratory to be analyzed for ' • Total petroleum hydrocarbons quantified as gasoline(TPH-g)by EPA Method 5030/8015M, • Benzene,toluene,ethylbenzene and xylene(BTEX)and methyl tertiary-butyl ether(MTBE) 10 by EPA Method 8020, and ' Advanced GeoEnviron mental,Inc