General Stratigraphy of the Usibelli Coal Mine, Healy, Alaska
The Central Alaska-Nenana Coal Province
Compiled By Jean M. Neubeck, CPG-11438
Editor’s note: The 2015 AIPG annual meeting in Anchorage featured several field trips including an excursion to the Usibelli Coal Mine on September 20, 2015. The following information was provided through Usibelli Coal Mine, Inc. (UCM) where not otherwise cited. The abbreviated descriptions of the geologic formations are based on a 2004 USGS report that was excerpted and modified for the AIPG field trip and further edited for TPG. We thank Bill Brophy, V.P. Customer Relation, and Justin Seavey, Sr. Mining Engineer for their guidance on the field trip, and UCM geologist Mitch Usibelli, who is a member of the Usibelli family that owns and operates the mine. Additional sources are cited within the corresponding text, as applicable.
Coal is the most abundant fossil fuel in the U.S., which produces about 1 billion tons of coal annually, based on 2009 data. Twenty-seven percent (27%) of the world’s coal is located in the U.S. and half of all U.S. coal resources are found in Alaska. Nearly 30 percent of U.S. mines are owned by public companies that produce approximately 75 percent of U.S. coal. Approximately two-thirds of coal production in 2009 within the U.S was from surface, rather than underground, mining.
UCM has identified a surface mineable reserve base of approximately 700 million tons, of which, 450 million can be classified as proven and 250 million as probable utiliz- ing surface mining techniques. Approximately 35,100 acres (14,200 hectares) are under coal lease primarily from the State of Alaska. Mining is primarily from seams 3, 4, and 6 of the Suntrana Formation. These seams average approximately 18’ (5.5m), 30’ (9.1m), and 24’ (7.3m) respectively. The 2015 annual UCM production level is approximately 1.5 million tons (1.35 million metric tons).
Subbituminous coal is generally considered a soft coal and relatively young, between 10 and 50 million years old. It can have a medium to high moisture content, but has lower mois- ture and higher heat content than lignite. This rank of coal is typically used for generating electricity. Subbituminous coals are mined primarily in the Powder River Basin of Wyoming and Montana.
Coal from the Usibelli mine is approximately 8 to 20 million years old and is ranked Subbituminous C. The age of the coal is one factor which determines its contained energy value. At 7,800 BTU, Usibelli coal is well suited for use in power plants for steam production which is utilized to spin the electrical tur- bines. The steam then can be utilized for heating commercial buildings and structures, resulting in its dual use of energy for both electricity and heat, or “cogeneration.”
The US Energy Information Administration website http://
www.eia.gov/coal/ contains an Annual Coal Distribution Report (ACDR). The ACDR (excerpted bullets below from 2013) provides detailed information on domestic coal distri-
bution by origin state, destination state, consumer category, and method of transportation. Also provided is a summary of foreign coal distribution by coal-producing state. Some high- lights in 2013 included:
tons (mmst), a decrease of 2.7% compared with 2012.
a decrease of 19.0 mmst (i.e. 2.2% decreases) compared with 2012. Distributions to foreign destinations were 117.7 mmst, a decrease of 8.1 mmst (i.e. 6.4% decreases) over 2012.
for about 385.5 mmst of domestic shipments, while Texas was the leading destination for coal, accounting for about 99.0 mmst of receipts.
river accounted for 12.6%, truck about 11.5% and tramway, conveyor, and slurry pipeline accounted for 8.0%. Great lakes and tidewater pier transport modes accounted for less than 0.1% of the total shipments.
the domestic distribution, while industrial plants excluding coke received 5.0%, coke plants about 2.3%, and commercial and institutional plants about 0.2%.
Coal seams #3 and #4 are exposed in this spectacu- lar natural outcrop of the coal-bearing rocks north of Hoseanna Creek, near Healy, Alaska. The two coal seams are typical of the ultra-low sulfur subbituminous coal found in the Nenana coal field and mined at UCM.
Usibelli reports that coal seams #3 and #4 continue deep below the surface until outcropping again near the mouth of Emma Creek, about 6 miles to the north. At the mine, the average thickness of seam #3 is approximately 25 feet and #4 averages 40 feet. UCM estimates that the near-surface coal from seams 3 and 4 contain enough reserves to power the Emma Creek Energy project for more than 50 years.
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56