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Exploratory soil borings were drilled at five locations within the LNPA during the Phase I RI to further characterize the subsurface stratigraphy and to evaluate the lateral and vertical extent of VOC impacts in groundwater. The boring locations are referred to as investigation locations B-1 through B-5 (Figure 5). Two borings were drilled at each investigation location using mud rotary drilling technology. The first boring at each location was used to conduct geophysical logging to evaluate subsurface stratigraphy and identify water bearing intervals to be targeted during depth discrete groundwater sampling. The second boring was used to collect depth discrete groundwater samples. The findings of the LNPA RI were consistent with the findings of earlier subsurface work conducted at the LNC site that is contained within the greater LNPA and adjacent areas. Data collected during the Phase I RI indicated that the LNPA is underlain by a heterogeneous mix of interbedded gravels, sands, silty sands, sandy silts, sandy clay typical of low alluvial fan and stream deposits. Sediments beneath the LNC appear to also be present as laterally discontinuous lenses to a depth of at least sixty feet bgs. Results of lithologic and geophysical logging conducted during the Phase I RI and earlier work conducted within the LNPA suggest that lithology at the northern portion of the Site (toward the Mokelumne River)may be more permeable than other areas of the Site due to highly interbedded sequences of sands and silty sands localized at this portion of the Site (Figure 6). Gravel and gravelly sand lenses were encountered at the northern and southern extent of the LNPA boundary at depths of approximately 140 ft bgs and 180 ft bgs in investigation locations B-1 and B-5. Such lenses have been documented at the northern portion of the LNPA from earlier investigations conducted at the LNC site and have been theorized as being channel deposits (NERI, 1996). Analytical results from depth discrete groundwater sampling indicated VOCs are present in groundwater beneath the southern and eastern portions of the LNPA. The predominant VOCs M ain\D:AEnvironmentaI\LN CV\10152007.wpd 23