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CRC Environmental Risk Management, Inc. <br /> May 9, 1995 <br /> Page 4 <br /> 1 ,400 g/m (shaded on Plate 2). Although these values are large enough to represent <br /> a UST, the contours do not exhibit the characteristic shape or dimensions of a UST. <br /> This could be due to interference from the overhead powerlines and underground <br /> utilities that traverse this area. Also, it is not known to what extent these facilities <br /> contribute to the high VMAG values. <br /> The distribution of VMAG contours indicates a distinct difference between the <br /> northern and southern portions of the survey area. The general lack of contours in <br /> the north indicate uniform magnetic gradient values. The one exception is closely <br /> spaced contours at the extreme northern end of the site. This anomalous zone can <br /> be explained by the presence of the ASB sign, and the electric lines inside the planter <br /> (Plate 1 ). <br /> The southern portion of the site (ON-100N, Plate 2) is characterized by closely spaced <br /> contours and numerous contour closures. These features may be caused by <br /> underground utilities and overhead lines. In addition, the closely spaced contours <br /> along the perimeter of the site are probably caused by the light poles, the building, <br /> and the canopy support structure. <br /> GPR Survey <br /> The results of the GPR investigation were limited by the minimal depth of penetration <br /> (1 -2 feet) throughout the site. As a result, the GPR data does not show any <br /> indication of UST's or their associate backfill or piping. <br /> Borehole Investigations <br /> The final locations of the five borings we investigated are shown on the Site Location <br /> Map, Plate 1 . The locations of anomalous conditions detected with the EMLL and <br /> GPR techniques were marked on the ground surface with spray paint at the time of <br /> the investigation. When necessary, the location of the proposed borehole was moved <br /> to avoid potential obstructions. <br /> RECOMMENDATIONS <br /> Since all geophysical methods are interpretive and may be limited by varying <br /> subsurface conditions, we always recommend using due caution when drilling. In <br />