Laserfiche WebLink
Sttnon - 2.05.3 <br />have to improve significantly to justify resumption of mining operations in the C Seam since poor <br />roof conditions and resulting dilution are the primary limiting factors. The limiting roof conditions <br />• could improve with progressive mine advance, although initial indications are not favorable. Further <br />mining m the C Seam is currently infeasible due to marginal coal quality. <br />The B Seam mine plan was revised [o reflect additional utfom~ation gained through ongoing mining <br />and consideration of development and operational requiremenu for the longwall mining system <br />Muting progressed from the initial development area in private coal with development of entries and <br />mining sections to the east in the Federal coal. OMI pursued acquisition of a lease modification <br />adding 160 acres to the reserve along the eastern edge of the lease tract, however, initial mine <br />development in this area indicated unfavorable mining conditions and the lease modification <br />application was withdrawn. In preparation for initiation of longwall mining operations in August <br />1998, development of longwall panels began in August 1997. the Mute Plan Map, (Map 2.05-M2), <br />shows the modified B Seam mine plan reflecting longwall operations, including the projected mining <br />sequence and duration. The C Seam mine plan was not revised because of the uncertainty regarding <br />any future mining of the C Seam in this area. Areas previously mined in the B and C Coal Seams in <br />the Sanbom Creek Mine are shown on both the Coal Seam Isopach Maps, (Maps 2.04-M4A through <br />2.04-M4D), and the Mine Plan Map, (Map 2.05-M2). <br />Longwall operations involve the use of one or more rotating shearer dnrms mounted on a ranging <br />arm which travels the full width of the longwall face, cueing coal with each successive pass. The coal <br />drops to the armored face conveyor, which tames it to the stage loader at the headgate where it <br />transfers to a panel conveyor belt for transport to the mine conveyor haulage system The shearer <br />and face conveyor operate under a protective canopy formed by a series of hydraulically-operated <br />roof support shields. The roof supports are attached to the face conveyor pan-line and are aligned in <br />parallel and immediately adjacent to each other to form a full protective bamer between the working <br />. face and the gob area behind the shields. As each successive cut along the width of the longwall face <br />u completed, venical pressure u released on each shield support behind the shearer and each shield u <br />advanced by hydraulic ram and extended to support the roof in its new position in preparation for the <br />next cut. As the longwall system advances with each successive cut, the roof behind caves, effectively <br />releasing the roof stresses created by removal of the coal seam <br />Longwall development activities are scheduled to provide one or more developed panek ahead of the <br />active longwall panel When the longwall reaches the limit of the bamer pillar adjacent to the main or <br />sub-main 6aulageway, the longwall is dismantled and moved to the far end of the next developed <br />longwall panel. For longwall opetatiotu, coal from the active longwall panel feeds to the mine <br />haulage conveyor system, which tames the coal to the surface. From the portals, the coal is <br />transferred to either the East Yatd or E(k.Creek coal stockpile by the Sanbom Creek Mine overland <br />conveyor. <br />The B Seam mine plan projects mining under overburden that exceeds 2,000 feet in many areas. <br />Longwall operations increase the potential for recovery of coal reserves under deep cover by <br />providing continuous stress release. Recovery factors for room and pillar operations in the high <br />cover areas were previously assumed to be 50 percent of the upper 11-feet of the seam In low cover <br />areas it was assumed that recovery would increase by 10 to 15 percent. Given that the longwall <br />mitring method eliminates the need for temporary or permanent support pillars except adjacent to <br />main haulageways, coal recovery factors of 75 percent or greater are anticipated. Previous subsidence <br />projections for conventional room and pillar mining operations in the B Seam were based on an angle <br />of draw of 25 degrees. Given the projected mining depth, typical draw angles for longwall operations <br />of 15 [0 30 degrees are approximately the same. During initial longwall mitring, OMI is visually <br />inspecting overlying surface areas for anysignificant variance from previous subsidence projections. <br />. Muting in much of the Sanbom East Tray will be performed under old mine workings. Portions <br />of the old mine workings are known to be flooded. These old mine workings are shown on the <br />Mme Plan Map, (Map 2.05-MZ). A detailed report titled, Water Communication Potential from <br />Overlying Workings a[ the Sanbom Creek Mute, included in Exhibit 2.04-E4, Hydrologic <br />PR04 2.05-5 Revised August 2000 <br />