Published in the May 2008 Coal USA Magazine
The No. 4 mine, operated by CW Mining, sits among the arid mountainous terrain of central Utah in the Huntington Canyon, just a handful of miles away from neighboring mines Crandall Canyon and Deer Creek.
In relatively short order – mining began at the complex in 1983 – Bear Canyon crews have made outstanding progress. It mined three seams in the No. 1 and No. 2 portals before moving to the No. 3 in February 2003 and then No. 4 in July 2004, where it continued until late last year using only continuous miners from two seams simultaneously (Tank and Blind Canyon).
Then the decision that would be a milestone in CW Mining’s history: a transition from room and pillar mining to longwall on the 7.5ft Tank seam.
“Economically, room and pillar was not going to be good for us in the long term,” said mine engineer Miles Stephens. “It was not going to give us the ability to continue productively enough.”
It was a decision the company thought about for some time; discussions about the potential transition began in 1997 and more serious plans for the move would come about six years later in 2002. The company spoke at length with a consultant about the unique issues of the mine and the benefits of longwalling the seam, and in 2004 began developing the longwall panels.
“It was an obvious decision for management,” Stephens said. “The consultant verified that the reserves were sufficient for a longwall.”
The top concern for the company and the advisor at the time was the short length of the panels at Bear Canyon, which were slated to vary between 3300ft and 6500ft. The level of recovery and productivity that would be attained through longwall mining, however, could not be ignored.
“When No. 4 opened it was already known it would be for longwall,” Stephens noted, as the volume of coal the operation was getting at the time did not meet expectations and associated costs were rising up against the shortage in output. “Our choices were to either go to three or four room and pillar sections or go longwall … [we found] longwall, long term, would be more profitable.”
Incidentally, that was one of the mine’s most significant obstacles at that point – the capital cost involved in obtaining the needed equipment for the face. Stephens noted that they were able to secure much of the equipment rebuilt or overhauled, which was positive news for the small company.
CW Mining considers the transition to a more productive method to be phase one of a three-tiered unprecedented expansion plan for the Bear Canyon complex. After mining out the planned panels, which management estimates will take about five years, the reserves exist to return to room and pillar for another few years. At completion, it will return to the lower Blind Canyon seam to room and pillar and longwall those reserves.
“After completing the Blind Canyon seam, [we] will move to the more lucrative Hiawatha seam, where larger panels, a thicker seam, and many more tons remain to be mined. This would have to be mined from separate portals,” Stephens noted, adding that those plans are about a decade away.
At press time, crews at the operation were on target to complete the first longwall panel they began cutting late last year. As progress in the inaugural block kicked off, management quickly realized a significant logistical issue – geological issues slowed progress on the development of the second panel, leaving the potential for incomplete gate entries when crews were ready for their first longwall move.
Bear Canyon is not one to stop in its tracks and hibernate, however – plans are to barrel on with the development of other panels while the situation is rectified and the second panel’s set-up is completed.
With total remaining reserves topping 52Mt, there is still much life left in this complex as it claws its way forward. Management also recognizes that it is in a unique geological position as well, as there are three mineable seams from which to pull within the Blackhawk Formation.
“Massive sandstone formations occur both above (Castlegate SS) and below (Star Point SS) the coal seams,” Stephens noted of the layout made up of the uppermost line, Tank, under 1400ft of cover, Blind Canyon 210ft below it, and Hiawatha, which is approximately 50ft below that.
“A major fault [Bear Canyon Fault] creates an offset of 200 feet from one side of the canyon to the other. Sandstone channels located within the seam are common and typically not found until they are encountered during mining [while] the coal seam dips slightly toward the south.”
The Bear Canyon unit line-up for development includes a Joy 14CM-15 continuous miner, two electric shuttle cars, a battery-powered scoop and a Fletcher roof bolter.
The mine’s longwall equipment fleet includes a Joy 4LS9 370T shearer which will cut away from its panels measuring between 500ft and 800ft in width, and between 3300ft and 6800ft in length. Rebuilt Hemscheidt two-leg shields, each of the 92 bearing an 850t load yield and 6–9ft working range, will support the roof with the panel’s advancement.
The shearer will cut full seam from the face unless it encounters an area of greater than 10ft, noted management; Stephens said it would most likely leave a little floor coal.
It may be a new kid on the longwall block, but...click here to read on.
