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5t <br /> `e <br /> Of these wells only MW4 has ever shown a significant amount of <br /> Hydrocarbon contamination. The other wells provide a outer limit <br /> to the hydrocarbon contamination on the site. A ground water <br /> recovery system was placed into operation on May 13 , 1991. The <br /> system was set to pump water from MW4 . <br /> OVERVIEW OF RAHIS PROPOSAL FOR INVESTXGATION OF LATERAL EXTENT <br /> OF SOIL AND GROUND WATER CONTAMINATION <br /> The ground water monitor wells currently on site establish the <br /> maximum possible plume extent, with the exception of the northerly <br /> direction on to the neighboring property. RAH proposes a minimum <br /> of five soil borings be drilled and sampled. <br /> The purpose of these borings will be to: <br /> 1. Establish the northern extent of the hydrocarbon plume <br /> into the neighboring property. <br /> 2 . Further define the extent and nature of the hydrocarbon <br /> plume adjacent to the former tank pit location. <br /> TASK I: CONFIRMATION SOIL BORINGS <br /> Selection of Soil Boring Locations <br /> The first boring will be drilled in the property to the north of <br /> the tanks. If the boring field screens "clean", no further borings <br /> will be drilled on this property. If significant levels of <br /> contamination is discovered in that boring, two further borings <br /> will be drilled. The location of the two further borings will be <br /> determined based on the concentrations observed in the original <br /> boring. <br /> The remaining borings will be drilled inside the arc of the present <br /> "clean" monitor wells, in order to develop a better picture of the <br /> hydrocarbon plume. <br /> One of the borings will be drilled at an angle of 20 degrees next <br /> to the forklift, shop in order to sample under the shop. <br /> The approximate locations of the borings are shown in Figure 3 . <br /> Drilling and Soil Sample Collection <br /> The five soil borings will be drilled by a licensed drilling <br /> contractor using a mobile rig equipped with 8 inch diameter hollow <br /> stem augers. The borings will be drilled to approximately 20 feet. <br /> Representative soil samples will be collected at a minimum of 5 <br /> foot intervals in 2" X 6" brass sleeves with the aid of a 140 lb. <br /> slide hammer and split spoon sampler. A new and clean disposable <br /> bailer will be used to collect a water sample from the inside of <br /> the augers, at the first occurrence of ground water. <br /> 2 <br />