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AW Mr. Michael Infuma October 16, 2008 CONESTO3A-ROVERS & ASSOCIATES implement this remedial approach (discussed further below), but in the mean time we have evaluated interim GWE via batch discharge while we prepare for ISCO. The only way to operate the existing GWE system and guarantee compliance with the discharge permit conditions is to perform batch discharge . Batch discharge involves operating the GWE system and routing the treated groundwater to onsite storage tanks, which are sampled, and when the water is determined to be clean it is then discharged to the sanitary sewer. While this option first seemed feasible, after a thorough review we found some limiting factors that lead us to conclude this is not a viable option. We contacted the City of Stockton to advise them we wanted to operate the existing GWE system under a batch discharge arrangement. City of Stockton staff informed us that we were not allowed to do batch discharge under the existing discharge permit and we would need to apply for a new discharge permit to perform batch discharge. The quickest turn around time the City of Stockton could provide for the new permit is approximately one month. Water storage capacity is another limiting factor for batch discharge. To operate under the batch discharge scenario we need to place as many storage tanks as possible onsite to maximize run time and the groundwater extraction rate. Since the site is an operating gas station, the space available for storage tanks is limited to the area behind the station building. In addition, access to the area behind the station building is limited and we are not able to place 20,000-gallon Baker tanks there. So we are limited to using the 6,500-gallon poly tanks. Only three of these poly tanks will fit behind the station building and still allow access to the carbon beds for carbon change outs. Three poly tanks will give us approximately 18,000-gallons of storage capacity. Considering the time (under various groundwater extraction rates) to fill the tanks, sample, get results, empty the tanks, and restart groundwater extraction, the best we could achieve would be approximately 18,000 gallons (1 batch) per week. This would involve 3 to 4 technician visits to the site per week to manage this system. For comparison purposes, this is approximately 18% of the yield of the original GWE system with a 3 to 4 fold increase in technician site visits. Due to the limited water storage capacity available at this site the GWE system (under a batch discharge scenario) could only be operated within the 1 to 3 gallon per minute range and it could not be operated continuously. The system would be shut down for several days during each batch cycle for sample laboratory analysis and to drain the tanks. The low groundwater extraction rate combined with the intermittent operation would not be able to provide hydraulic control for the site. 240783 2 Worldwide Engineering, Environmental, Construction, and IT Services