1992-12-16_GENERAL DOCUMENTS - C1980007

• Permit No: C1980007
• IBM Index Class Name: General Documents
• Doc Date: 12/16/1992
• Doc Name: Proposed Decision & Findings of Compliance for RN2
• Permit Index Doc Type: Findings
• Media Type: D
• Archive: No

The Lower Coal Bearing (Bowie) member consists of 260 to 350 feet of
interbedded gray shales, thin to thick lenticular beds of buff-colored, fine-
to medium-grained sandstones, and coals . Three coal horizons exist in this
member, the A (Old King) horizon, the B (Somerset) horizon, and the C (Bear)
horizon. The A horizon is immediately above the Rollins Sandstone and is not
currently mined at any operation in the vicinity. The B horizon contains two
coal seams and occurs about 20 to 120 feet above the Rollins Sandstone and
will be mined by MCC during this permit term. This horizon has been mined by
U.S. Steel at the Somerset Mine. The C horizon contains one coal seam that
occurs 50 to 100 feet above the B horizon. This horizon has been mined at
U.S. Steel ' s Elk Creek Mine and the Bear No. 1 and 2 Mines, and is currently
mined at the Bear No. 3 Mine. The top of the member is usually capped by a
massive buff-colored sandstone up to 90 feet in thickness . This sandstone,
however, appears not to be a single persistent bed, but is actually several
thick lenticular sandstones occurring at progressively lower stratigraphic
horizons from east to west.
The Upper Coal Bearing (Paonia) member consists of 200 to 500 feet of gray
shales, interbedded, buff-colored, lenticular sandstones , and coals . The top
of this member is generally considered to be capped by a massive,
cliff-forming sandstone. Three coal horizons have been identified in the
Upper Coal member, the D (Oliver) horizon, the E (Hawk' s Nest) horizon, and
the F horizon. The D horizon occurs directly above the massive sandstone of
the Lower Coal Bearing member and contains three seams . This horizon is
currently mined in the Orchard Valley Mine. The E horizon occurs about
130 feet above the D horizon and contains two coal seams . This horizon has
been mined at the Hawk' s Nest Mine and was historically mined at the Blue
Ribbon Mine. The West Elk Mine plans to mine the E seam in the future. The
F horizon contains two coal seams and has been mined at the West Elk Mine. At
the mine site, the coal is immediately overlain and underlain by shale. Coal
seams of the F horizon do not exist to the north of the North Fork of the
Gunnison River in thicknesses sufficient for mining. Overlying the Upper Coal
member is the Barren member of the Mesaverde Group. This unit consists of
interbedded sandstones , siltstones , shales, and coals . The unit is not
thought to be of marine origin and, as a result, the sandstones and the coals
are highly lenticular, discontinuous, and of limited lateral extent in
outcrop. This unit ranges up to 1 ,500 feet thick and outcrops throughout most
of the five-year permit area.
The Mesaverde Formation is unconformably overlain by the Tertiary Age Rudy or
Wasatch Formation. This formation consists of red to buff-colored shales , red
sandstones , and red to gray conglomerates. The sediments of this formation
are weathered volcanic rocks . The Ohio Creek conglomerate is the basal unit
within the formation and is 100 to 200 feet thick.
The alluvium of the North Fork of the Gunnison River consists of Quaternary
Age deposits of mixed coarse sand, cobbles and boulders . These coarse
sediments are composed primarily of igneous and metamorphic rock types, and
have their source area in the headwaters and upper reaches of the North Fork.
This coarse alluvium is capped by finer sands and silts . The North Fork
alluvium in the area of the Hawk' s Nest, Bear, West Elk and Somerset Mines is
fairly narrow in width and is between 50 and 70 feet thick. About a mile
below the town of Somerset, Colorado, the width of alluvium increases while
the thickness of alluvium decreases to about 35 feet.
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