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C'"togualrahwasInc Page S Morita Additional Site Characterization Report Project No 724 2 April 19,2004 ' Wells MW-1101210 Intermediate and deep well pair N4W-1101210 was installed approximately 40 feet southeast ' of the site This is a down gradient position and the subsurface in this location is characterized as follows ❑ The subsurface contained alternating layers of sands, silts and clays ❑ Shallow samples contained both live roots and root tubes ❑ Sand intervals occur at 0— 5, 20, 35, 45, 70—75 feet bgs ❑ The sands ranged from very fine to coarse in grain size and brown to grey in color CaCO3 nodules, iron oxide staining and black organic detritus or magnetite were ' occasionally present ❑ Fine grain units- silts and clays were found at depths of approximately 10 - 15, 25 - 35, 40, 50—70 feet bgs ❑ The silts and clays ranged from light brown, light grey to blue/green-grey or grey in color with some CaCO3 nodules and black organic detritus or magnetite ❑ Groundwater was encountered at approximately 38 feet bgs ❑ No field evidence of contamination was noted in samples from these borings Figure 3 indicates the locations of geological cross sections presented in Figures 4 and 5 The site exhibits little correlation between boreholes and this situation is exacerbated by the ' fact that different geologists logged the boreholes For this reason the cross sections have coarse grained units combined (sands, clayey sands, silty sands) and fine grained units combined (clays, silts, sandy clays) This serves to identify the preferential pathways for contaminant migration through units of greater hydraulic conductivity Note The cross sections were developed using data gathered by different individuals utilizing different methodologies Therefore, they need to be looked at as one of several possible interpretations of actual site conditions) Figure 4 Cross Section A — A' illustrates the geology trending from the northwest to the ' east side of the site The diagram indicates that more sands are present below 65 feet bgs on site and below 50 feet bgs in the off-site location of MW-1091209 GTI's interpretation of the geology has shown sand units at 25 and 50 feet bgs as laterally continuous These units were not uniformly identified in the original boring logs for wells MW-1 through MW-5, ' however, these boreholes were sampled at 5 foot intervals by different geologists Figure 5 Cross Section B — B' illustrates the geology trending from southwest to the northeast off site The geology is similar to that present in Figure 4 5.0 CONCLUSIONS & RECOMMENDATIONS Based on our interpretation of the data collected over the course of this subsurface investigation, GTI have reached several conclusions These conclusions are based on the ' premise that the data we considered, although incomplete, are representative of actual site conditions We acknowledge that there may be undiscovered conditions, which would upon their consideration, change our interpretation and thus our conclusions Our recommendations are based on our knowledge of site conditions, and on the state and limitations of subsurface investigative technology