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25 May 2001 AGE-NC Project No. 95-0118 Page 2 of 6 During the 18 months of the remediation system operation (soil vapor extraction), an estimated 134 gallons of petroleum as gasoline were extracted. 2.0. PROCEDURES On 27 April 2001, around water monitoring and sampling was performed at the site on wells MW-1 through MW-6 and air-sparge wells IAS-1 through 1AS-3. Monitoring and sampling were performed in accordance with guidelines .established by the Central Valley Regional Water Quality Control i Board (CVRWQCB) for subsurface investigation of underground storage tank ,sites and in accordance with the PHS-EHD--approved Remedial Action Work Plan Addenduln prepared by AGE, 3 dated 14 January 1998. , 2.1. MONITORING WELL PURGE PROCEDURES J Depths to around water were measured in each well from the tops of the well casings at the site to the nearest 0,01-foot utilizing a Solinst water level meter. Ground water elevation in each well at the site was calculated by subtracting the measured depth to ground water fi•om the surveyed casing elevations (Table 1). Ground water elevations were plotted and contoured on a scaled site map .=_ (Figure 3). . After water levels were measured, approximately 6 to 10.6 gallons of ground water (a n 'muzxr of three casing'water-volumes per well) were removed from wells MW-1 through MW-6 and.IAS-1. through 1AS-3 utilizing a new disposable bailers. Temperature, pH and conductivity were measured for stabilization at regular purge-volume intervals from each well using a Hydac water analyzer. Field data and logs are in Appendix A. Purged ground water was containerized in 55-gallon drums and stored at the site. L 2.2. GROUND WATER SAMPLING -= Following well purging, ground water levels in the monitoring wells were allowed to achieve a minimurn of 80 percent recharge of the initial ground water level, prior to sample collection. Ground water samples were collected from the purged wells utilizing new, disposable polyethylene bailers, one I-liter amber bottle without a preservative and three 40-m1 EPA-approved volatile organic _ analysis (VOA) vials containing 0.5 ml 18% hydrochloric acid as a sample preservative. 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 GeoEnvironmentu4 Inc.