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I <br /> au <br /> LEEDSMILL•MERNENMOFF. NC. <br /> 'S The entire surface area of the site is covered with either concrete or asphalt. <br /> At a depth of approximately two feet below the surface, 1 ies a concrete layer 0. 5 <br /> to 1 foot thick. This may have been the floor of a warehouse building that <br /> previously occupied this site. Between the asphalt and the concrete is a layer <br /> of clean fill sand with no gravel , and little to no fines . <br /> In the area of the former excavation, the concrete layer is absent. Clean fill <br /> sand occurs from below the surface asphalt to a depth of 4 to 11 feet. The base <br /> of this fill material is believed to be the bottom of the former UST excavation. <br /> Below the concrete layer or below the bottom of the former excavation to a depth <br /> of 42.5 feet, the soils appear to be predominately clay. These clay layers vary <br /> in color from brown to gray to black, and also change from silty clays, to lean <br /> clays to fat clays. Isolated lenses of sand and/or silt were found from 19.0 <br /> feet to 27.5 feet in boring SB3 and S84 within a silty sand layer from 9.0 to <br /> 27.5. These coarser grained sediments were not found in all of the soil borings <br /> and may have controlled the irregular migration path of the soil contamination. <br /> As observed in soil borings SB6, MW1 , and MW3, and illustrated in soil borings <br /> SB1, SB4, and MW2 on the cross-section A-A' (see Figure 5) , the existing clay <br /> layers appear to create a semi -confined aquifer condition. Tight clays with very <br /> little to no sand-sized grains were found to be slightly moist at depths of <br /> approximately 35 to 37 feet in these borings. Below this confining clay, the <br /> sand content increased to as high as 40 percent. This saturated sandy clay is <br /> believeo to be the water bearing aquifer with a potentiometric water surface <br /> depth of approximately 33 feet. <br /> The sea channel directly south of the garage building is lined along the side <br /> with a concrete wail . The bottom of the channel is apparently unlined. The <br /> water surface in the channel is approximately 10 feet below the existing ground <br /> surface. Because the potentiometric water surface level beneath the site is at <br /> a depth of approximately 33 feet; it is apparent that the adjacent sea channel , <br /> with a water surface level at a depth of 10 feet, is not hydraulically connected <br /> to the aquifer beneath the site. Further evidence of this theory is discussed <br /> in Section 4.4 Groundwater Sampling Results. <br /> 3.4 SAMPLE ANALYSIS <br /> The soil samples collected from borings SBI through S68 and monitoring well <br /> borings MW1 through MW3 were analyzed for benzene, toluene, xylene, ethylbenzene <br /> (BTX&E) and for total petroleum hydrocarbons (TPH) as gasoline. In addition, <br /> soil samples collected from soil boring SB6 near the waste oil tank were also' <br /> analyzed for TPH as diesel . <br /> The analytical methods referred to above conform to EPA Test Methods for <br /> Evaluating Solid Waste: Physical/Chemical Methods (SW-846, 2nd Edition) and/or <br /> as specified in the Leaking Underground Fuel Tank Manual (LOFT) , modified EPA SW- <br /> 846 Method 8015. <br /> 13 <br /> 1 <br /> f <br /> 1 <br />