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In answer to a question from Commissioner Gordon, Mr. Scarlett <br />stated that an ideal site is one where ground water is 1,000 feet below the <br />surface with deep soil and with a high enough clay content so that water is <br />not going anywhere when it leaks out. He noted that magnetic testing will not <br />give any information in the quantitative sense on groundwater or depth or type <br />of rock or soil types. It will tell if there is a diabase dike. If there is <br />not a system of dikes which. are extensive over the area and extending outside <br />of the landfill itself, then it is not going to be of great consequence in <br />developing the landfill. Diabase dike sometimes run for miles. <br />Mr. Joyce stated that the size of the site is a function of the <br />depth of soil and a function of depth to ground water. The features of a site <br />they want for a landfill includes deep soil, soil with special <br />characteristics, deep ground water, tight geology and the ability to predict <br />the direction and flow of groundwater from the site. <br />In answer to a question from Commissioner Gordon about the minimum <br />amount of area that is needed for the actual landfill, Mr. Joyce stated that <br />the size of the lot is the function of the depth of soil and the depth of <br />groundwater -- how much soil can be excavated before reaching the material <br />that can be excavated. A perfect site has very deep soil with some having a <br />high clay content. From an engineering standpoint they want deep soil and <br />soil with certain characteristics and a deep water table with information <br />about the direction and flow of the groundwater. They have to understand the <br />subsurface conditions before they can determine the volume and thus the size <br />of the lot. <br />SEISMIC REFRACTION can sometimes detect depth to ground water. In <br />this area, the soil characteristics are hard to determine. Because ground <br />water does not sit in the soil as it does with sand, it is difficult to <br />distinguish depth to ground water on seismic records. This will provide an <br />average feel for determining depth to bedrock.. He does not like to do this <br />type of testing unsupported by other techniques. <br />Commissioner Willhoit referred to the four sites in the Piedmont <br />and asked about the likelihood of eliminating a site with the use of <br />geophysical methods which would identify fatal flaws or undesirable <br />characteristics without proceeding to the trenching. Mr. Scarlett noted there <br />are no techniques that take the place of trenching. Trenching is done to gain <br />soil samples to take to the lab to get real numbers. None of these techniques <br />are going to give this information. One alternative is to do all these <br />techniques and do an additional ranking from that data. It would not tell <br />which sites to keep on the list and which to eliminate. He explained that <br />enough investigation needs to be done on each site to determine if one is <br />better than another. <br />Mr. Joyce addressed this same question of whether or not sites can <br />be eliminated by using geophysical techniques only. He explained it is very <br />complicated to get reliable data purely on geophysical work. His firm feels <br />it is much more reliable to have invasive drilling on the site and in some <br />cases to compliment the type of geophysical work and confirm what Mr. Scarlett <br />is talking about. He stated that it may be possible to eliminate a site <br />