Abstract
This report examines the technical and economic feasibility of hydraulically mining the 12- to 20-ft-thick middle bed coal seam at Mid-Continent Resources, Inc., near Carbondale, Colorado. The mining system permits the safe recovery of a seam that is too thick to be recovered by longwall methods. Dual rooms are developed straight up the 8 deg to 13 deg pitch. The bottom room, under top coal and supported by yieldable arches, serves as an intake and fluming room. The parallel room against the roof, supported by roof bolts, serves as a return air course and bleeder. The top coal and pillars are extracted by a jet of water directed by a monitor, eliminating the need for miners or machinery to work beyond a roof supported by yieldable arches. Safety is markedly enhanced by roof control with yieldable arches, remote control extraction of the top coal and pillars, elimination of electricity from the vicinity of the working face, and positive ventilation of the area being pillared. The study shows that it is highly feasible to produce 1.2 Mmtpy clean coal by hydraulic mining with internal rates of return from 23% to 92%, based on a range of selling prices from $30 to $40 per ton and on the extent to which existing capital for shared facilities is charged against the hydraulic mine. Capital expenditures required for the hydraulic mine, including interest during construction, are estimated to be $18 million, and overall productivity is estimated to be 28 clean tons of coal per employee per shift.
