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CLEARWATER • G R O U P Envrron mrnlol Srrurcrs Groundwater Gradient The new monitoring wells were surveyed to the existing wells in June 2001 The top of casing data for the new and existing wells are presented on Table 2 Clearwater calculated the groundwater elevations, groundwater flow direction and groundwater gradient using this data The groundwater contour and gradient are shown on Figure 4 As indicated,the groundwater flow direction is shown to be southwest at a gradient of 0 003 ft/ft This is consistent with results generated from previous investigations Conclusions Results from the recent phase of site investigation and monitoring well installation indicate the following 1 Contaminant impact is concentrated in the dissolved-phase on-site in areas beneath and proximal to the former UST area, 2 Contaminants of concern appear to be primarily TPH-G,benzene and to a lesser extent MtBE, • 3 Groundwater on-site appears to flow at a shallow gradient towards the southwest, 4 Groundwater quality data collected from the wells with submerged screens (MW-1 through MW-8) are not consistent with data collected from adjacent appropriately screened wells and therefore are not representative of actual groundwater quality conditions, 5 The groundwater plume as tested in properly screened wells is undelineated in all directions Recommendations Given the results of this most recent phase of site investigation and the analysis of contaminant concentration trends over time, Clearwater has prepared the following recommendations 1 Conduct additional plume delineation work with new wells installed off-site to the west (north of MW-6) and to the east (northwest of MW-8), 2 Install three replacement wells proximal to wells MW-6, MW-7, and MW-8 which currently have submerged screens, 3 Continue quarterly sampling, but remove wells MW-1 through MW-8 from the sampling program, as the collection of representative groundwater samples from these wells is not feasible However, we do not yet recommend the destruction of these wells as they may useful for air sparging or in the • event that the water table will again drop in elevation Page 7