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GeofogicafTechnics inc. Page 6 Pilot Test report COE-Arco Project No.750.2 August 8,2000 �I The vapor stream was slightly moist; indicating the soil below the site is moist. It would be expected that during the winter and spring months the extraction system would remove enough moisture that would need to be addressed with a water knockout drum. The PID readings of the emissions do not corroborate with the laboratory data. Laboratory data was higher then the PID readings by a factor of 3 to 6 times. This may be due in part to the fact that PIDs have a relatively small window of compounds they detect, primarily lighter compounds such as benzene and toluene. If the vapor stream is low in these compounds but �. high in TPH then the PID will not give a good indication of TPH concentrations. 4.2 Pilot Test Conclusions Data obtained from this pilot test suggests the following conclusions: • The site exhibits measurable pneumatic conductivity from VEW-I and VEW-4 out to at least the monitoring wells. • VEW-2 and VEW 3 appear to have less lateral vacuum influence, which may be due to being screened in tighter geologic units then VEW I & 4. • The soil pore spaces are currently full of gasoline vapors with little to no oxygen in the subsurface. This will require that the extraction equipment installed at the site for remediation purposes, will need to be run at low flow rates until oxygen is introduced into the subsurface. From experience at other sites, GTI estimates this may take up to a month. • �Jf ven though. the pilot test was run at low flow rates, 28 to 45 CFM, respectable volumes contaminants were being removed from the subsurface. When a full extraction system is put into operation with extraction rates of 150 to 200 CFM, removal volumes are L.rol estimated to be several hundred pounds per day. • The soil appears to contain some water vapor, however the amount would be expected to increase in the winter and spring months. A water knockout drum will need to be used to remove water vapor prior to it entering the emission treatment unit. In the case of heavy precipitation years, it may be necessary to run the extraction system only during the summer and fall months. • The four vapor extraction wells currently on site should adequately address the vadose �- zone contamination at the site. 4.3 Recommendations It is recommended that a Soil Vapor Extraction and Treatment System be installed to accomplish the following goals: LN 0 Remove the elevated concentrations of BTEX, MTBE and TPH-G in the vadose zone soils. • Stop the continued leaching of these contaminants from the soil into the groundwater. • Increase the oxygen content in the subsurface so that the rate of biodegradation of these ti. hydrocarbons will increase. To prepare for this remedial work, GTI will prepare a Remedial Design Plan based on the approved Corrective Action Plan submitted on March 31 20OQ and on the results of this Pilot Test. This plan can e used as the basis or o tciting bids and obtaining approval from the USTCFP {Fund) on the cost for remediation. Z � ho