SITE INFORMATION AND CORRESPONDENCE FILE 1

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TERRA VAC removed from the vapor stream in the vapor/liquid separator. Soil vapors were discharged directly to the atmosphere with the permission of the Central Valley Air Quality Control District. Groundwater was pumped out the vapor/liquid separator into storage drums pending disposal. During the test, Terra Vac monitored the amount of drawdown and water production rates, vapor flowrates and concentration, and the amount of vacuum applied to each wellhead. Test data collected for each well is shown in the attached table. A summary of test results follows: • Well MW-1 appears to be amenable to DVE. Approximately twelve feet of drawdown was achieved with a water removal rate of one gallon per minute. However, the performance of this well appears to be anomalous and may not be representative of overall site conditions. • Wells MW-2 and MW-3 do not appear to be amenable to DVE. Water removal rates of about five gallons per minute achieved only two feet of drawdown. The performance of these two wells is likely to be indicative of high water yield across the site. • Vadose zone soil in the area of MW-1 appear to be amenable to vapor extraction. A relatively high flow rate of 47 cubic feet per minute was induced with a vacuum of five inches of mercury. While this vacuum was being applied to MW-1, an induced vacuum of 0.09 inches of mercury was observed in well MW-2. • Although vapor concentration in MW-2 and MW-3 were lower than MW-1, a large amount of bleed air was introduced at the wellheads to promote groundwater entrainment. Actual soil vapor concentrations are likely to be similar to those observed in MW-1. With these concentrations, soil vapor extraction has the potential to remove significant amounts of hydrocarbons from vadose zone soils. During long term dual vapor extraction, water yield rates are likely to drop. However, given a production rate of two gallons per minute per well, in a field of twenty extraction wells, the water treatment capacity of a DVE system would have to be greater that forty gallons per minute. Since the installation of such a system would not be practical, Terra Vac has considered air sparging of the saturated zone as an alternative. Recent assessment data from the site indicates that soil in the saturated zone consist of clay with interlaced sand lenses. This lithology is not ideal for the application of air sparging. Low permeability clay would respond more slowly to insitu bioremediation as compared to sandy soils, and air dispersion within the saturated zone may not be uniform. Although these factors dictate a longer period of active remediation, it is reasonable to assume that air sparging would remediate saturated zone soils without pumping and treating impacted groundwater. Therefore, Terra Vac recommends installation of a combined soil vapor extraction/air sparging system for full scale remediation of this site. 2