GENERAL45390

• Permit No: C1981025
• IBM Index Class Name: General Documents
• Doc Date: 7/8/1983
• Doc Name: Proposed Decision and Findings of Compliance
• Permit Index Doc Type: Findings
• Media Type: D
• Archive: No

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The Maroon Formation conformably overlies the Eagle Valley Formation.
This formation consists of over 2,000 feet of red to tan arkosic
sandstones, siltstone, conglomerates and locally some limestones.
The lU0 to 2U0 foot thick Entrada Formation unconformably overlies the
Maroon Formation. This formation is a red to tan sandstone, which forms
slopes along the Grand Hogback.
The Morrison Formation is of Jurrasic Age and overlies the Entrada
Formation. This formation consists of a thick sequence of brightly
colored, variegated shales, siltstones and sandstone. The shale units
within this formation are highly erosive.
The Cretaceous Age, Dakota Sandstone overlies the Morrison Formation.
This unit consists of lU0 to 150 feet of hard gray to buff colored
sandstone, which is locally quartzitic. The Dakota sandstone is very
resistant to erosion and is a prominent ridge former.
Sedimentary rock strata exposed within the general area of the mines are
the Cretaceous Age Mancos Shale Formation and Mesaverde Group, and the
Tertiary Age Wasatch Formation. The Mancos shale consists of 3,000 to
4,000 feet of dark gray marine shales, and silty shales. The Mancos
shale consists of two shale members divided by a limestone member. This
formation is highly erosive, which results in the fonmation of broad
valleys alony the strike of this formation and an increase in total
suspended solids in areas east of the mines. The saline nature of this
marine shale formation results in an increase in total dissolved solids
downstream and east of the mines.
Conformably overlying the Mancos shale is the i+lesaverde Group. This
group is divided into two formations; the Iles Formation and the William
Fork Formation. The Iles consists of the basal i;ozzette sandstone
member; the middle member consisting of shales, siltstones and
fine-grained sandstones; and the upper Rollins sandstones consist of
medium to very fine-grained resistant sandstones. The two sandstones are
ridge and cliff formers.
The Williams Fork Formation consists of over 5,000 feet of sandstones,
siltstones, shales and coals. This formation conformably overlies the
Iles Formation and consists of marine and terrestrial deltaic deposits.
The Williams Fork Formation is divided into three members; the lower
coal-bearing Bowie member, the upper coal-bearing Paonia member, and the
non-coal-bearing Barren member.
The Bowie member is between 675 and 850 feet thick in the area of the
mines, and is composed of four general submembers. In ascending order,
these submembers are: 1) 420 to 480 foot thick coal-bearing lower Bowie
shale; 2) 30 to 130 foot thick Middle sandstone; 3) 150 to 200 foot thick
Upper Bowie shale submember; and 4) 50 to 100 foot thick Upper sandstone
submember. The lower Bowie coal-bearing shale submember contains several
coal seams. These coal seams vary in thickness and lateral extent along