PERMFILE49948

• Permit No: C1981022A
• IBM Index Class Name: Permit File
• Doc Date: 1/27/2003
• Section_Exhibit Name: 2.04 Miniumu Requirements for Information on Environmental Resources
• Media Type: D
• Archive: Yes

Scorer - 2.04.7
hydrologic investigation reports, hydrologic monitoring data, and other relevant hydrologic
• information are included in Exhibit 2.04-E4, Hydrologic Information.
Ground Water Information
Generally, in the mine permit and adjacent areas, beneficial use of ground water is minimal due to the
limited availability and quality, depth to ground water, the rugged terrain, and related limitations on
land development and intensive land uses. Given these considerations, the significance of ground
water resources relates to potential itnpacu on mining operations of ground water inflows; potential
mining-related itnpacu on seeps and springs which tray be utilized in conjunction with postrnining
land uses; and the quantity and quality of any ground water which may discharge to the surface water
system The following sections characterize ground water occurrence, environment, and conditions as
a basis for evaluation of these potential impacu.
Mine Area Hydrogeology, Ground Water Occurrence, and Relationship to Mining
Disturbance -The regional ground water basin, which includes the mine permit and adjacent areas,
generally corresponds to the surface watershed area for the North Fork of the Gunnison River. The
regional ground water basin is defined by the Grand Mesa monocline on the north, the West Elk
Mountains on the east and south, and the Colorado River Valley on the west. Within the
groundwater basin, the dominant sedimentary units generally have low potential yield due to
depositional characteristics. The depositional environment can be characterized as a deltaic complex,
which originally trended east to southeast, composed of a range of related deposiu including delta
front, distributary mouth, marsh, channel, and upper deltaic plain deposiu. Uniu are generally
mediurrr to fine-grained, very lenticular, and inter-tongued, with little continuity over large areas
except for the Rollins sandstone. There are no known oil or natural gas resources in the mine permit
and adjacent areas and consequently, no oil or natural gas production wells. In conjunction with
• ongoing mining operations, various mine operators have established degassification wells to drain
methane~rom none working areas. These wells are shown on the Mtne Area Geology Map, (Map
2.04-M3 and discussed in Section 2.05.3
The hydrogeologic environment in the immediate mine area is closely tied to site stratigraphy and
topography as illustrated by Figure 2.04.6F1, Typical Geologic Cross-Section. The existing and
proposed mine disturbance areas are on the north side of the North Fork of the Gunnison River. In
this area, the rock strata dip away from the river to the northeast at approximately 3.5 degrees. Since
all of the mineable coal units outcrop or sub-crop on the canyon walls of the North Fork Valley, their
outcrops are generally above the present level of the river and related alluvial/colluvial deposiu. The
B coal seam is an exception. The B-Seam sub-crops in or under the North Fork in the vicinity of the
Town of Somerset. Extensive historical mining in the B coal seam (Somerset and Sanborn Creek
Mines) generated very limited ground water inflows to the mine, so it appears that even though this
seam sub-crops in or under the North Fork River, it is relatively tight and receives and transmits very
little ground water. Dirett recharge to most of the mineable coal units is limited by both low
permeability and the steep valley sideslopes. The one exception may be the D Coal Seam, which due
to it's outcrop higher in the stratigraphic sequence and significantly higher secondary permeability (at
least in the outcrop zone) is recharged from both the overlying uncoruohdated surficial materials and
flowing surface drainages where the coal seam outcrop is exposed in the drainage valleys.
Ground water occurrence and movement is generally controlled by the semi-arid climate, rugged
topography, stratigraphy, and surface drainage patterns. Alluvia]/colluvialileposiu in the North Fork
Valley and major tributaries are recharged by and discharge to the associated flowing drainages with
seasonal fluctuations in surface water flow levels. The semi-arid climate limiu precipitation and
resulu in relatively high evaporation and transpiration rates, both of which limit infiltration and
• ground water recharge. The limited infiltration, which does occur, percolates readily through
unconsolidated surficial materiak until it reaches the underlying bedrock
PR04 2.04-19 _ Revised August 2000