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. ' �u n 6 1996 4 1 1,P11 1 EG lEGuNOLOG I r S No 2615 P 9/31 95-WP 103 05 RESULTS AND DISCUSSION Pilot Boring and Soil Sampling The most significant results of the pilot boring and soil sampling was the hthologic logging The identification of very low permeability sediments below approximately 85 feet bgs within what is still considered the upper water zone influenced the well construction The ability of the UVB to drive vertical circulation through a thick tmterval of low hydraulic conductivity sediments is limited Therefore, the well was constructed above 85 feet to ensure that a circulation cell would be created Although the results of the geotechnical and chemical analyses assisted in further defining site soil charactenmes, these results did not contribute significantly to the evaluation of the UVB groundwater treatment and are not presented here Baseline Groundwater Sampling The VOC analyses showed WE concentrations ranging from 3.4 µg/1 to 1,000 µg/1 in samples obtained from the perimeter wells Except for monitoring well 31MW1 (3 4µg11), the TCE concentrations ranged between 160 µg/1 and 940 pgll (Table 1) The presence of a relatively lower TCE concentration in monitoring well 31MW1 supports the earlier finding that the groundwater within the alluvial aquifer at Site 31 occurs in two zones TCE concentrations of 6 4 µg/1 and 33 0 ILA respectively, were found in the groundwater samples collected from the monitoring wells attached to the treatment well (WI and W3) A possible explanation for relatively low TCE concentrations (compared to penmeter wells) in these samples is that water was used during well installation, which may have contributed to temporary dilution of actual groundwater concentrations Operational Monitoring - Air Monitoring and Sampling System Operating Parameters. Figure 5 is a graphical representation of the airstream flow data measured at sample ports INTAKE and V2 as a function of time These points represent the volume of air entering the treatment well and used in aur stripping (INTAKE), and the volume of air being discharged by the blower (V21 which is a combination of intake air and air removed from the unsaturated zone through soil vapor extraction The fluctuation in flow rates recorded in a few rounds in the first few days after start-up is attributed to equipment malfunction or operator error and are not considered to represent actual flow conditions The very low flow rates measured at the INTAKE in the initial seven weeks is attributed to the method used for measuring air flow Following modification to the INTAKE air monitoring port as shown on Figure 5, the air flows at port V2 correlate very closely with aur flows at the INTAKE port, indicatmg that little to no air flow was occurring from the vadose zone Since the UVE well is not located within an area of soul contamination, soil vapor extraction was not performed during this pilot study Air Sampling Results. Aar samples were collected from the four sample ports located on the aboveground components of the system The compounds detected in the air samples included acetone, benzene, 2-butanone, carbon disuifde, carbon tetrachloride, chloroethane, chloromethane, dichloromethane, ethylbenzene, styrene, toluene, trichloroethane, trichloroethene, tetrachloroethene, tetrachlorofluoromedme (F-11), and xylenes The following trends were observed in the air analytical . data Total VOC concentrations in the airstream peaked at 825 6µg/cu m a few days following startup, 7