GENERAL47431

• Permit No: C1984062
• IBM Index Class Name: General Documents
• Doc Date: 8/2/1984
• Doc Name: PROPOSED DECISION AND FINDINGS OF COMPLIANCE
• Permit Index Doc Type: FINDINGS
• Media Type: D
• Archive: No

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Description of the Environment
The proposed permit area is approximately 7,000 feet above sea level. The
topography consists of rolling hills grading to relatively flat, narrow
valleys along the two streams draining the area. In the general vicinity of
the permit area, the Twentymile Sandstone has formed prominent cliffs making
it an easily recognizable unit.
The permit area is located in the upper reaches of the Yampa River Basin and
it is drained by Foidel Creek and Middle Creek. Both are intermittent streams
flowing in response to snowmelt or precipitation events. The confluence of
Foidel Creek with Middle Creek is immediately northwest of the proposed mine
area within the permit boundary. Middle Creek drains into Trout Creek east of
the northern most section of the permit boundary.
The proposed permit area lies on the southeastern flank of the Twentymile Park
Structural Basin. The basin is a synclinal extension of a much larger basin,
the Washakie-Sand Wash Structural Basin. The syncline forming the basin is a
doubly plunging, north-south trending syncline known as the Twentymile Park
Syncline.
The only major structural feature existing on site is a 200 foot wide fault
zone. The zone lies to the west of the proposed mining area and trends
northwest - southeast. It has a normal type displacement of 60 to 100 feet.
Four geologic formations exist in the vicinity of the proposed Energy Mine No.
3. They are, in ascending order, the Mancos Shale, the Iles and Williams Fork
Formation of the Mesaverde Group, and the Lewis Shale Formation (see Figures 2
and 3 of this document). These strata were all deposited during the late
Cretaceous Period. Generally, the strata dip to the west at 8 to 14o into
the Twentymile Park Basin.
Three mineable coal seams, the Lennox, Wadge, and Wolf Creek coals, are
located within the Williams Fork Formation. The Wadge coal seam will be mined
in the Energy Mine No. 3 surface mine.
There are three regional bedrock aquifers within the permit and adjacent areas
of the Energy Mine No. 3. These aquifers are the Trout Creek Sandstone, the
Twentymile Sandstone, and the Wadge coal-overburden zone.
The alluvia of Trout Creek and its tributaries are also important sources of
ground water. The alluvial bodies are used as water supplies, provide
subirrigation to vegetation and supply base flow to the streams. The alluvial
bodies are recharged by both the streams and the bedrock aquifers. The two
alluvial aquifers within the permit boundary are the Foidel Creek alluvium and
the Middle Creek alluvium. These aquifers do not receive significant water
from the bedrock ground water system. Most of the water in these aquifers is
from surface runoff.