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1 ' 08 April 2005 AGE-NC Project No 95-0173 ' Page 2 of 10 ' the San Joaquin County Environmental Health Department(EHD) As-built construction details of all monitoring wells are summarized in Table 1 2 1 WELL MONITORING AND EVACUATION PROCEDURES On 30 November 2004, the depth to ground water was measured at each well from the tops of the well casings to the nearest 0 01-foot utilizing a Solinst water level meter Ground water elevation at the site was calculated by subtracting the measured depth to ground water from the surveyed well ' casing elevations (Table 2) After water levels were measured, approximately 2'/z to 8 gallons of ground water(a minimum of ' three casing-water volumes per well) were evacuated(purged) from single-level monitoring wells MW-1 through MW-10, MW-12 (well MW-11 was dry) and air sparge wells AW-lA and AW-2A utilizing disposable polyethylene bailers, approximately 21/4 to 18 gallons of ground water were purged from multi-level monitoring well MW-13 (A-C) and air sparge wells AW-1B and AW-2B by lowering and raising a 3/8-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 Waterra Hydro-Lift II pump equipped with a mechanical arm was utilized to surge the polyethylene hose Temperature,pH,and conductivity were measured for stabilization at regular purge-volume intervals in each well using an Oakton water analyzer Field data and logs are provided in Appendix A Purged ground water was transferred into properly labeled,Department of Transportation(DOT)-approved 55-gallon drums and stored on-site in an area lacking general public access E2 2 GROUND WATER SAMPLING Following well purging, ground water levels in the wells achieved a minimum 80%recharge prior to sample collection Subsequently, ground water samples were collected from each purged well utilizing new, disposable polyethylene bailers and transferred into three, 40-milliliter (ml) EPA- approved volatile organic analysis (VOA) vials containing 0 5 ml 18% hydrochloric acid solution as a sample preservative,ground water samples were collected from multi-level well MW-13 (A-C) and air sparge wells AW-1 B and AW-211 and poured directly into the 40-m1 VOA vials utilizing the Waterra 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 Advanced GeoEnvironmental,Inc