1994-10-21_GENERAL DOCUMENTS - C1980007

• Permit No: C1980007
• IBM Index Class Name: General Documents
• Doc Date: 10/21/1994
• Doc Name: Proposed Decision & Findings of Compliance for PR5
• From: Jumbo Mountain Lease
• Permit Index Doc Type: FINDINGS
• Media Type: D
• Archive: No

The permit area lies on the southeast margin of the Piceance Basin and just
south of Grand Mesa. The general geology of this area consists of gently
(three to five degrees) north-northeast dipping beds of sandstone, shale, and
coal of upper Cretaceous and early Tertiary age.
The geologic formations exposed in the North Fork Drainage Basin consist of
Late Cretaceous to Early Tertiary Age sedimentary strata, Tertiary Age igneous
intrusives, and Quaternary Age alluvial and colluvial deposits. The units are
described below in ascending order.
The Mancos Shale is the oldest strata exposed in the region, and is of Late
Cretaceous Age. This unit is composed of over 4,000 feet of gray marine
shales and minor interbedded buff sandstones. This unit is highly erodible
and unstable. Erosion and oversteepening of slopes in this formation produce
the numerous rock falls and landslides observed in the lower North Fork
Drainage Basin (lunge, 1978) .
The Mesaverde Formation is of Late Cretaceous Age and conformably overlies the
Mancos Shale. This formation consists of approximately 2,300 feet of marine
and terrestrial sedimentary rocks. The Mesaverde Formation is the
coal-bearing formation in the region and is divided into four main members;
the Rollins Sandstone, the Lower Coal Bearing (Bowie) member, the Upper Coal
Bearing (Paonia) member, and the Barren (Undifferentiated) member (Johnson,
1948) .
The Rollins Sandstone is a white to buff-colored, well sorted, medium- to
fine-grained sandstone, ranging from 150 feet to 300 feet thick. This
sandstone is regionally extensive and resistant in outcrop and forms prominent
Cliffs.
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 and
is currently being mined 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. It
will not be mined on Jumbo Mountain because the E seam is split and comprised
of several thin (< 5 ft. ) coal benches which are separated by rock partings.
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. In the Jumbo Mountain
area, the F seam thins to less than five feet in thickness (Map 15A) and is of
limited aerial extent. Therefore, MCC does not plan to mine this seam in
Jumbo Mountain. Overlying the Upper Coal member is the Barren member of the
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