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I 19 June 2001 AGE-NC Project No 97-0326 Page 3 of 7 • Ethylene dibromide (EDB) and 1,2 dichloroethane (1,2 DCA) in accordance with EPA Method 8260 • Volatile orgarucs (vocs) by GUMS (full-scan 8260) ' 3.0. RESULTS The CPT lithologic data interpretation was integrated with previous subsurface soil descriptions to ' refine the subsurface geological model, the hydrocarbon impact to ground water and soli were assessed by laboratory analysis of the grab ground water and soil samples, as presented below ' 31 STRATIGRAPHY ' Based on the findings from the CPT soil borings and soil composition data acquired in previous borings (Figure 2), cross sections A-A' and B-B' were constructed,which depict general lrthology beneath the site (Figures 3 and 4) The sediments above 70 feet below surface grade (bsg) tend to be fine-grained, predominantly consisting of alternating clayey silts, silty clays and clays In cross- section AA' a 10-foot thick silt and sand wedge is shown near the western edge of the site which lenses out eastwards Beneath the wedge at a depth of about 28 feet is approximately 2 feet of stiff ' fine-grained or hard silt,which appears to continue eastward, however, this layer is not observed in more southernly bonngs (see Figure 4) ' Below 70 feet bsg is a vertical sequence of CPT-defined sediment types beginning with approximately 2 feet of clay, followed by 3 feet of stiff fine-grained sediment, 1 foot of cemented sand, 2 feet of sand, and 1 to 2 feet of sandy silt, this sequence appears In all of the CPT borings, ' suggesting a high degree of lateral continuity In this sequence As mapped, the sequence appears to be nearly horizontal from north to south, with a slight westward dip from east to west (see Figures ' 3 and 4) Based on CPT data from the deepest boring (CPT-03), the sediment types below 100 feet include ' a 2-foot silt interval, a 7-foot"stiff fine-grained"interval,underlain by a minimum 12-foot coarse- grained interval consisting of sands and gravelly sands to total depth at 121 feet bsg ' AGE interprets the CPT data to tentatively identify four hydrostratigrapluc units (HSUs - after Sanders, 1998) informally identified as, 1) HSU-1, from the depth of the water table to approximately 78 feet bsg, 2) HSU-2, from 78 to 82 feet bsg, 3) HSU-3, from approximately 82 to t109 feet bsg and 4) HSU-4, from about 109 to 121 feet bsg HSU-2 and HSU-4, which are sand advanced GeoEnvervnmental,Inc 1