Laserfiche WebLink
geologic structure is such that [he coal seam outcrops at the top of the mountain and dips <br />at approximately 10 to 18 percent, while the overlying surface dips at approximately 18 to • <br />20 pe rcant. ih is does present a fairly constant overburden thickness ranging ', rom <br />approximately 15 to 100 feet, which lends itself to area surface mining. The relatively <br />high angle of dip cn the coal seam and surface requires some modification of what would be <br />considered a conventional area mining pit progression. This modification will be detailed <br />later in this section. <br />A general description of the engineering techniques u[i lized in the development of an area <br />surface mine must begin with the exploratory phase. after the initial discovery of a <br />potential coal field has been made (generally by drilling several "wildcat" test holes), <br />engineers and geologists, utilizing available maps and information, will establish an <br />exploratory drilling pr o9 ram :o "prove up" [he coal reserves. The drill hole pattern is <br />determined and is normally based on sore convenient breakdown of the public land survey <br />system. Additional drilling is conducted where the coal is expected to outs.r op or where <br />faulted conditions are expected. the engineers [hen direct survey crews to es;ablish <br />baseline .c on[rol in order to locate the drill holes and property corners. with this <br />survey ':c on[rof avaitabl e, the area of interest can be contour mapped from aerial <br />photography. Ili th an accurate base map and all of the necessary drilling information, the • <br />engineers can calculate [he various factors necessary to establish a mining plan. In area <br />surface mining, these factors could include acres of coal available, tons of recoverable <br />coal ex petted, cubtc yards of overburden to be removed, antl the ratio of cubic yards of <br />overburden removed per [on of coal produced. These factors and others are exami netl in the <br />light of prevailing market conditions and a determination made as to [he potential <br />economic viability of a mine. Once a positive determination is made and an annual output <br />established for the mine, the er~gineers are required to determine the size, type, and <br />numbers of equipment or facilities needed, includtng topsoil removal equipment, primary <br />stripping machines, drills, tractors, loaders, haulage equipment, reclamation equipment, <br />coal handling facilities, and service facilities. Standard mine engineering practices, <br />including the examination of contour maps, borings, range diagrams, and manufacturer's <br />specifications, are utilized in sizing the major stripy ~; ng machines. Oua nt hies of soils <br />to be moved (as determined by soil surveys) and the distances and travel conditions <br />involved are used [o determine fleet type and size for topsoil handling equipment. <br />Overburden borings, indicating type and amount of rock, as well as expected pr oduc[ion <br />rates are examined in sizing blasthole drills and pit tractors. Ouanti[i es of coal and <br />rate of production are the major determining factors in sizing foade rs and haulage • <br />2 <br />