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a= �.r LEEDSHILL-MEAKEW4OFF,IMC. The entire surface area of the site is covered with either concrete or asphalt. At a depth of approximately two feet below the surface, lies a concrete layer 0.5 to I foot thick. This may have been the flour of a warehouse building that previously occupied this site. Between the asphalt and the concrete is a layer of clean fill sand with no gravel, and little to no fines. In the area of the former excavation, the concrete layer is absent. Clean fill sand occurs from below the surface asphalt to a depth of 9 to 11 feet. The base of this fill material is believed to be the bottom of the former UST excavation. WA Below the concrete layer or below the bottom of the former excavation to a depth of 42.5 feet, the soils appear to be predominately clay. These clay layers vary -- in color from brown to gray to black, and also change From silty clays, to lean clays to fat clays. Isolated lenses of sand and/or silt were found from 19.0 feet to 27.5 feet in Goring SB3 and SB4 within a silty sand layer from 9.0 to 27.5. These coarser grained sediments were not found in all of the soil borings and may have controlled the irregular migration path of the soil contamination. As observed in soil borings SB6, MWI, and MW3, and illustrated in soil borings SBI, S64, and MW2 on the cross-section A-A' (see Figure 5), the existing clay layers appear to create a semi-confined aquifer condition. Tight clays with very little to no sand-sized grains were found to be slightly moist at depths of approximately 35 to 37 feet in these borings. Below this confining clay, the sand content increased to as high as 40 percent. This saturated sandy clay is believed to be the water bearing aquifer with..a potentiometric water surface depth of approximately 33 feet. The sea channel directly south of the garage building is lined along the side with a concrete wall. The bottom of the channel is apparently unlined. The s water surface in the channel is approximately 10 feet below the existing ground E surface. Because the patentiometric water surface level beneath the site is at a depth of approximately 33 feet; it is apparent that the adjacent sea channel, with a water surface level at a depth of 10 feet, is not hydraulically connected to the aquifer beneath the site. Further evidence of this theory is discussed in Section 4.4 Groundwater Sampling Results. s, 3.4 SAMPLE ANALYSIS €.. The soil samples collected from borings S81 through SB8 and monitoring well borings MWI through MW3 were analyzed for benzene, toluene, xylene, ethylbenzene r; (BTX&E) and for total petroleum hydrocarbons (TPN) as gasoline. In addition, soil samples collected from soil boring SB6 near the waste oil tank were also J analyzed for TPH as diesel.. The analytical methods referred to above conform to EPA Test Methods for { '' Evaluating Solid Waste: Physical/Chemical Methods (SW-846, 2nd Edition) and/or c� as specified in the leaking Underground Fuel_Tanl Manual (LUFT), modified EPA SW- 846 Method 8015. ,.� I3 'sa