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f , ' L 1 f t r 15 October 2002 AGE-NC Project No 97-0333 Page 4 of 8 ' 2 6 MASS-VOLUME REMOVAL CALCULATIONS , Between'OlApnl and 06 June 2002,an estimated 33 85 pounds of MTBE was extracted from ground ' water(Table 1), since the system was initiated on 21 January 2002, a total mass of 146 77 pounds of MTBE has been, removed April, May and June 2002 mass-volume calculations of MTBE- impacted ground water extracted from the ground water pump-and-treat system are presented in Appendix B Plots of cumulative ground water pump and treat mass removal trends and influent ground water MTBE concentrations versus time are in Appendix C r I 3.4: GROUND WATER MONITORING AND SAMPLING I ' On 29'May 2002, ground water monitoring was performed at the site on wells MW-1 through MW-6, as-built monitoring well constriction details are summarized in Table 4 Ground water monitoring procedures for the site were outlined in the AGE-prepared Work Plan Addendum - ' August 1999, dated 10 August 1999 and approved by the San Joaquin County Environmental Health Department (EHD)by letter dated 25 August 1999 3 1 WELL MONITORING AND EVACUATION Depth'to ground water was measured in each well from the top of the well casing to the nearest 0 01-foot utilizing a Solinst water level meter The ground water elevation in each well was calculated by subtracting the measured depth to ground water from the surveyed casing elevation ' I I (Table 5) Ground water elevations were plotted and contoured on a scaled site map (Figure 3) ! After water'levels were measured, approximately,7 gallons of ground water,(a minimum of three I' i ' i casing ,water-volumes per well) were evacuated (purged) from wells MW-I through MW-5 and 13 gallons-of water were evacuated'from'well MW-6 utilizing'polyethylene disposable bailers 'I ' Temperature,pH and conductivity were measured for stabilization at regular purge-volume intervals from each well using an Oakton water analyzer Copies of field data and logs are in Appendix D Purged ground water Was contamenzed in 5 5-gallon drums and was stored'on-site in an area lacking general public access , ! 3 2 GROUND WATER SAMPLING ' I I Following well purging, ground water levels in the monitoring wells were allowed to achieve a I minimum of 80 percent recharge prior to sample collection Ground water samples were collected from,each of the purged wells'utilising new, disposable polyethylene bailers and transferred into r , r I I ! I f 1 Advanced GeoEnvrronmental,IncII II'I ` V II' I I !, {