2009-02-10_PERMIT FILE - C1981022 ‎(5)‎

• Permit No: C1981022
• IBM Index Class Name: Permit File
• Doc Date: 2/10/2009
• Section_Exhibit Name: 2.04 Environmental Resources
• Media Type: D
• Archive: No

Ste- 2. 04.5
Definition of Reeional Area
• For the Somerset, Sanborn Creek, and Elk Creek Mmes, the limits of regional geologic and hydrologic
information are defined by the watershed area for the North Fork of the Gunnison River, since the
North Fork watershed boundary nuns generally northeast-southwest along the crest of Grand Mesa
and the eastern and southern watershed boundaries follow the crest of the Elk Mountains and the
mine permit and adjacent areas fall within this watershed. Given that numerous other activities have
the potential to impact the North Fork of the Gunnison River downstream from the mine permit
area, regional information is provided for the North Fork to it's confluence with the Gunnison River
approximately 23 miles downstream from the Town of Somerset.
Regional Geology
The general topographic configuration of the region reflects both the relatively flat-lying sequence of
sedimentary and igneous rocks which underlie this area and the effects of structural uplift, faulting,
and subsequent igneous intrusion. The prominent mountain peaks, mesa landforms, steep cliffs, and
narrow drainage valleys which characterize the topography of this area result, in part, from massive
igneous intrusive bodies and the resistant sandstone units within the sedimentary sequence. In
addition, the Elk Mountains reflect thrusting and buckling of the sedimentary sequence during the
Paleozoic Era with subsequent laccolithic intrusion by quartz monzonite during the Tertiary and later
erosion and exposure of the igneous intrusives. Massive slumps and surface landslides are relatively
common in the area, resulting from a combination of steep terrain, low strength rock units and
surficial materials within the geologic sequence, and wetting along potential failure planes where
perched ground water migrates to the surface. Potential geologic hazards in the general area are
shown on the Regional Geology/Hydrology Map, (Map 2.04-M2)7
• The geologic sequence in this area consists of the following formations in descending sequence:
Wasatch Formation (Tertiary)
Ohio Creek Conglomerate
Mesa Verde Formation (Cretaceous)
Barren Member
Paonia Member
Bowie Member
Rollins Sandstone Member
Mancos Shale Formation (Cretaceous)
In this area, the mineable coal seams he within the Paonia Coal Field and are contained within the
Bowie and Paonia Members of the Mesa Vence Formation. The Paonia Coal Field extends south
from Grand Mesa and includes the area between Paonia on the west and the Elk Mountains on the
east. The B, C, D, and E Coal Seams which have been, are, or will be mined within the mine permit
area are contained within a sedimentary sequence of inter-bedded coal seams, sandstones, shales, and
siltstones. The B and C Coal Seams are part of the Bowie Member and the D and E Seams are part
of the Paonia Member.
Reeional Surface Water Hvdrolo
The North Fork of the Gunnison River is part of the larger Colorado River system and begins just
downstream of Paonia Reservoir where Anthracite Creek joins Muddy Creek The thine permit area
and Town of Somerset are on the north side of the river approximately 5 miles downstream from this
point. The North Fork flows to the southwest approximately 23 miles from the Town of Somerset,
• where it joins the Gunnison River west of the Town of Hotchkiss. From this confluence, the
Gunnison River flows approximately 70 miles to the nortltivest joining the Colorado River near
Grand Junction. The North Fork of the Gunnison River exhibits a perennial flow pattern, with flows
PR04 2.04-7 Revised August 2000