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geofogicaf7ecknics Inc. Page 4 Former Moresco Property 'Report- Remedial Action ` Project No.: 251.3 February 6, 1998 2.4 Gallons of Gasoline Removed to Date `+ Table 2 shows OVM data and air flow rate data. From this data removal rates were calculated and cumulative volumes were tracked. As of January 9, 1998, when the last bimonthly monitoring was conducted, it had removed approximately 85 gallons of gasoline from the subsurface. When the OVM values were compared to the laboratory values for the same sample, the laboratory values were approximately 1.5 times higher. For the calculations, the OVM values were multiplied by a factor of 1.5 to bring them into range of the actual lab data. 3.0 DISCUSSION The VETS was started on November 12, 1997. It has been down three times due to the TO dropping below minimum operating temperature. The dates are as follows: • November 18-19, 1997 '-' • December 15-24, 1997 • January 12, 1998 for about 7 hours L. According to calculations the TO has been meeting the required efficiency standards of: • The TO must destroy VOCs to a minimum of 95% efficiency or • The total VOC emission rate shall not exceed 2.0 pounds in any one day. In order to remove the gasoline in the soil in as short and efficient a time frame as possible, GTI adjusted the passive air recharge wells in the following manner. • Initially all three recharge wells were open. They were balanced so that each was allowing +r equal volumes of recharge to enter the ground. The system was run in that configuration for approximately half a month. • Then two of the three recharge wells were closed at a time and each recharge well was cycled through being opened for one to two weeks at a time. • Finally all the recharge wells were closed in order to pull recharge air vertically from the surface. The bimonthly monitoring indicated a significant decrease in the vapor concentrations being removed from the ground after about two months. The above mentioned configurations showed a marked increase in vapor concentrations being removed from the ground. By the first week in January it became clear that the amount of contamination being pulled for treatment was failing off decidedly. In light of these vapor extraction results, we decided to �. review assumptions used in the mass balance calculations done in October 1996. Mass balance calculations are based on the following parameters: 1. soil density 2. porosity of the soil 3. volume of soil contaminated by the chemicals 4. contaminant concentrations 5. soil pore vapor contaminant concentration �. 6. unit conversion Our review leads us to now believe that the actual gallons of contamination were closer to 200 �. gallons with a possible factor of 2x that amount. This means that since the vapor extraction system has removed approximately 85 gallons (Table 2; approximately 45% of the estimated volume of gasoline), this allows us to accelerate recommendation for closure of this site.