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I31 August 2000 AGE Project No 96-0232 IPage 16 of 25 ' believes that with the abandonment of the domestic water wells RDW-1 and DW-1, the closest sensitive receptors and vertical conduits for the site area will have been effectively removed, thus warranting greater-than- MCL clean-up goals for the site 4 3 ON-SITE REMEDIATION Initially, on-site ground water extraction is proposed utilizing existing well EW-2 and seven newly installed ground water extraction wells (Figure 9), placement of ground water extraction wells is proposed within the core of the dissolved TPH-g, TPH-d and MTBE plumes (Figures 25, 26, 27- Problem Assessment Report, dated 19 June 2000) Extracted ground water will be treated on-site in a southwest section of the site (Figure 10) and discharged into a conveyance ditch located some 500 ' feet south of the site (Figure 11) AGE proposes to continuously extract ground water from EW-2 and the newly installed ground water extraction wells at a total flow rate between 20 and 25 GPM, however it will be necessary to implement a ground water extraction surging method to manage the total water volume treated and discharged into the conveyance ditch Therefore, AGE proposes to extract ground water from four of the eight wells in 12-hour shifts and at individual pump flow rates between 5 and 6 GPM ' 44 OFF-SITE REMEDIATION As previously mentioned in the RWQCB letter Review of Problem Assessment Report, dated 24 July I 2000, off-site investigation activities beyond the property limits are in the process of being completed, and off-site remediation may be warranted at a later date However, upon being annexed into the San Joaquin County Utility Maintenance District, efforts will be made to abandon the domestic water wells located at Rocky's Restaurant and Three B's Truck Plaza (domestic water wells RDW-1 and DW-1, respectively)thereby removing the nearest off-site sensitive receptors and vertical conduits from the Flag City Chevron site thereby reducing the potential necessity for off-site, Iremediation 4 5 SECOND ZONE AQUIFER GROUND WATER EXTRACTION AND TREATMENT Initially, AGE does not recommend ground water extraction from the Second Zone Aquifer until ground water remediation efforts from the First Zone Aquifer have met with the RWQCB's satisfaction AGE believes that ground water extraction from the Second Zone Aquifer could potentially enhance the vertical and horizontal migration of MTBE-impact from the First Zone Aquifer to the Second Zone Aquifer, therefore, remedial efforts in the Second Zone Aquifer should be re-evaluated following clean-up efforts of the First Zone Aquifer Advanced GeoEnvironmentai„inc