Published in the May 2008 Coal USA Magazine
It's not an easy drive – about two-and-a-half hours by car from capital Salt Lake City into the Huntington Canyon sprawled across the desert of central Utah – but one look at the well-developed, clean and immense Deer Creek complex and the area adjacent the company’s Huntington Plant and its evident the miners are a proud bunch who are committed to the success of their mine.
The Wasatch Plateau Coal Field outside the town of Huntington is laid out like a starburst with an arterial map of transportation paths cut into the Utah mountainsides, and the flow of the mine's diesel trucks filled with crew, equipment haulers and coal transport units is fluid and constant. It seems old hat to Deer Creek's workers because it is: the complex commenced that portion in 1978 (after purchasing the property from Peabody in 1977) while the now-closed Wilberg mine cut its first coal one year later.
Deer Creek is owned by PacifiCorp, which serves 1.7 million customers in six western states through business units, Rocky Mountain Power and Pacific Power. The PacifiCorp Energy business unit operates the company’s coal mines and generating plants.
Not unlike its neighboring mines, such as the Bear Canyon operation and the Crandall Canyon complex that was closed last year, Deer Creek is a deep mine with overburden ranging from 1200-2600ft. It mines from two seams, Blind Canyon and Hiawatha, thick and rich by reputation and separated by approximately 85-100ft of interburden at the site.
While the longwall is active in the former of the two, crews can easily access both as needed through the use of rock slopes constructed specifically for that purpose. According to officials, the sheer breadth of the complex made the decision to construct it easy from both a productivity and efficiency standpoint.
Deer Creek is currently mining its first panel in the Blind Canyon seam of the Mill Fork area with steady mining from Blind Canyon until 2012 before returning to Hiawatha where it will remain until about 2019. It will continue to be a longwall operation through the remainder of the life of the lease.
Despite the vastness of the operation, it does deal with some fairly complex geology which routinely brings surprises and presents challenges to manage the extent and conditions of mining. The Hiawatha seam (lower) ranges from 8-18.7ft (average 11.2ft), and the Blind Canyon seam varies from 8.8-13.25ft (average 10.8ft), bringing with them a set of unique circumstances for management.
The roof above the seams generally consists of layered mudstones several feet thick, with overlying sandstones. In preparation for mining, the company does exploratory helicopter-aided core drilling due to the rugged terrain as well as small underground core rigs for inter-seam core drilling in overlapping seam areas.
As longwall panels are developed, extensive in-mine geology mapping is conducted to characterize the geology and anomalous features that might affect panel mineability and coal quality. Horizontal directional drilling is used for special exploration problems and occasional utility work.
Besides the complicated geology of the region, other issues that concern Deer Creek officials include the mining horizon and gate entry roof control under the mine's deep cover.
One area management is happy to report on is gas, as it is not an issue at the mine and is not prevalent on the Wasatch Plateau. Other Utah mines on the Book Cliffs range and most of the other western mines as well as other regions of the country contend with the methane issues, which bring unique considerations.
The staff at Deer Creek travels both above and below ground via diesel pick-ups and mantrips such as Getman's TerraPro. The operation originally utilized track haulage, but diesel haulage was introduced in 1982, providing tremendous flexibility for mine activities over the years.
While diesel technology, particularly passenger trucks, tends to be a more comfortable and quicker ride than the personnel carriers found in the eastern states, a rapid trip to the active sections is not on the cards for visitors or workers at Deer Creek. The portal to the longwall face is about 11.2 miles, or about 45 minutes long.
The trip underground may be lengthy, but Deer Creek crews have ensured every foot of travel can be done so safely through an extensive network of roof and rib control technologies. Wire mesh, steel mats and rib bolting are all used in addition to the primary roof bolting. Additional supplemental roof control is installed as needed to ensure stability for ground control in its deep and dynamic surroundings.
The longwall face cuts an average 84-120in from the Hiawatha seam which, at press time, averaged 9.5ft. Longwall panels are generally about 730ft wide with lengths stretching from 1500ft to 10,000ft.
A Joy 7LS shearer cuts from Deer Creek's longwall face, outfitted with 72in drums and a web width of 38.5in under an installed power drive of 1030hp. Providing roof support are 129 shields – 123 line shields and three at each gate – each with a yield load of 1170 tons, operating range of 56in to 132in and working range of 84in to 120in.
The Joy face conveyor employs, dual 600hp motors at 2300VAC. It is a 940mm-wide conveyor with twin 34mm links traveling at 253 feet per minute.
The mine's stageloader and crusher work in tandem to keep the outgoing coal fluidly on the move. Both are Joy models with the stageloader measuring 1154mm, working with dual 250hp drives at 2300VAC to move 3500 tons per hour at an average 456ft per minute and the crusher also housing a 250hp motor.
Average daily retreat for the longwall is about 65ft/19.8m, which equates to a monthly total of about 1040ft/318m. Typical tonnage will round up to approximately 17,000 tons per day or 275,000-300,000 tons per month, which takes longwall move delays into consideration.
Overall, management at Deer Creek is happy with...click here to read on.
