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/ 2/ 323—� <br /> A TERRA <br /> Environmental Consultants <br /> August 3, 1992 . .,�3� fp Jr! <br /> A 0 5 1992 r <br /> Mr. Reginald Gillespie 110. <br /> Faison, Fletcher, Barber & Gillespie <br /> University Tower, Suite 1400 <br /> 3101 Petty Road <br /> Durham, North Carolina 27717-1729 <br /> Reference: Use of Geophysical Methods <br /> Reconnaissance for Sanitary Landfill Evaluations <br /> Orange County Sites, North Carolina <br /> Aquaterra Job No. 598 <br /> Dear Mr. Gillespie: <br /> As you requested during a July 28, 1992, conversation with Mr. David Duncklee, <br /> Aquaterra has prepared the following information concerning the merit of <br /> geophysical evaluations in siting suitable tracts of land for sanitary landfills. The <br /> possibility of using geophysical techniques such as a seismic or magnetic method was <br /> originally recommended in our March 2, 1992, correspondence (L2434-92). <br /> Prospective Geophysical Methods <br /> Magnetic Prospecting Method <br /> The presence of a diabase dike is a major limitation for a potential site Magnetic <br /> prospecting techniques such as a magnetometer can be used to determine whether a <br /> diabase dike underlies a site These instruments detect variations in the earth's <br /> magnetic field, which indicates the potential presence of near surface objects. <br /> The presence of ferrous minerals in the geologic features account for the features' <br /> magnetic properties. The order of magnetic properties are from the basic igneous <br /> rocks (ie. gabbros, diabase), acid igneous rocks (granites), metamorphic rocks, shale, <br /> sandstone and sediment, and dolomite. <br /> Corporate Office Charlotte Office Greensboro Office <br /> P. O. Box 50328 P. O. Box 668107 P. O. Box 16241 <br /> Raleigh,NC 27650 Charlotte,NC 28266-8107 Greensboro,NC 27416-0241 <br /> (919)859-9987 (704)525-8680 (919)273-5003 <br /> FAX(919)859-9930 FAX(704) 527-2792 FAX(919)271-8138 <br />