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Cieolog"(Technkslac Page 11 ' Additional Site Characterization Report Project No 662 2 • February 20,2004 ' Figure 3 and 5 are fine grained silt and clay units In the lower fine units several discontinuous sand layers are present ' Hydrogeology The geotechnical data obtained from boring EW-i (section 3 3 above) further confirm the site lithology This borehole is within ten feet of the CPT-4 and MW-104 locations (see Figure 2) and the data indicate that a higher permeability unit of 3x 10 a cm/sec (sand) is ' present in the 38 feet bgs sample, while low permeability units (clayey) are present at 28, 32 and 50 feet bgs with values of 2x10' to 4x10' cm/sec This suggests that contaminant migration downward would tend to be retarded by the fine layers and that lateral dispersion ' by groundwater in the coarse sand units would occur This situation will be examined in the next section that discusses the contaminant distribution in soil and groundwater at the site Groundwater elevation has ranged from approximately 20 —29 feet bgs during the course of this investigation and has historically flowed to the east 4.2 Chemical Distribution Figures 4 and 6 show the site lithology with the results of the CPT borehole soil and water data superimposed on the geology The groundwater data from the November 2003 monitoring event is indicated where monitoring well screens are shown on the sections Soil data from well boreholes is also shown on the section Borehole CPT-2 was located on the western (up gradient) side of the site near MW-2 In Figure 4 it can be seen that all four soil samples and all five groundwater samples from ' CPT-2 did not contain contaminant concentrations above the laboratory reporting limits This situation is expected because well MW-2 has been non-detect since its initial sampling ' in January 2000 To the east of CPT-2 lies the former UST excavation Wells MW-104, EW-I and borehole ' CPT-4 were placed in this general location High levels of contamination are present in first encountered groundwater at a depth of 29 feet bgs in CPT-4 22,000 ug/l TPH-G and 19,000 ug/1 MTBE Samples taken from below this elevation show that the contamination ' attenuates with depth to 9 6 and 33 ug/l MTBE at 62 and 68 feet respectively The screened portion of MW-104 lies at 48 — 53 feet bgs and the well contained 2 8 ug/l MTBE in November 2003 The soil data in this location is localized with a high of 1 2 mg/kg MTBE ' at a depth of 35 feet in CPT-4 Soil samples from above and below this depth did not contain contaminant concentrations above the laboratory reporting limits Boreholes CPT-8 and GP-6 lie on the eastern edge of the site (alley) and the data from these boreholes was non-detect for both soil and groundwater 1