2015-10-06_PERMIT FILE - C1981019A ‎(3)‎

• Permit No: C1981019A
• IBM Index Class Name: Permit File
• Doc Date: 10/6/2015
• Doc Name: Performance Standards
• Section_Exhibit Name: Volume 15 Rule 4
• Media Type: D
• Archive: Yes

RULE 4 PERFORMANCE STANDARDS
When dealing with point of compliance monitoring of ground water in a mining area, the
monitoring is dependent on a continuous, non -perched ground water layer/zone that can be
monitored, the geologic and structural conditions, and the topography. Currently at the Colowyo
Mine (CM), Meeker, Colorado, where mining started over 30 years ago, the mining zone in both
the East and West Pits has not encountered any significant shallow or deep ground water, except
for an occasional perched ground water. As discussed in a previous paper, no point of
compliance monitoring can currently occur in the current CM mining area.
With current mining operations in the South Taylor area and, possibly, the Collom mining area,
the following is presented to clarify the geologic and shallow and deep ground water conditions,
to assist in determining whether point of compliance monitoring may be necessary for future
mining areas.
The following is a synopsis of the data submitted in previous permit applications for South Taylor
and, more recently, Collom to the Colorado Division of Reclamation, Mining and Safety. This
data are then used to determine if point of compliance monitoring at the CM and proposed mining
areas is possible.
Topographv
The active Colowyo mine area and associated properties owned by Colowyo are located on a
topographic high, known as the Danforth Hills. The elevation in the area of the CM and
associated property ranges from 8400 feet on the south to 6550 feet on the north in the incised
valleys. In addition, south of the topographic highs, the topography decreases in elevation before
another rise to the south. The valleys, themselves, have elevation ranges from approximately
7100 feet on the south to 6550 feet on the north.
The current mine area (East, West and South Taylor pits) is bordered on the east and west by
deeply incised valleys. These valleys are Good Spring Creek and Wilson Creek, on the east and
west respectively. The valleys slope from south to north, with similar topographic slope as found
at the higher elevations where the current mining occurs.
There are other valleys within the area of the Colowyo mining area and properties, west of Good
Spring Creek. However, the headwaters of these valleys (e.g., Taylor Creek, Jubb Creek, and
Collom Gulch) tend to originate in the higher elevations within the Colowyo properties. These
valleys do not create deep valleys like Wilson and Good Spring Creek, which cross the
topographic highs.
Geolo>;y
The current mine area and associated properties are located on the Williams Fork Formation of
the Cretaceous Mesaverde Group. The Williams Fork Formation is comprised of discordant
beds/units of sandstone, siltstone and mudstone and coal seams, with an approximate thickness of
1,200 to 1,300 feet in the both mine area.
The sediments in this area were deposited in a deltaic depositional environment. The geologic
beds vary in thickness and lateral extent both horizontally and vertically throughout the CM area.
The numerous coal seams in this formation also vary in thickness and lateral extent.
The sandstones tend to be very fine grained to fine grained and poorly sorted, with various
amounts of silt and clay. For the siltstones and mudstones, theses units contain various amount
Collom — Rule 4, Page 17 Revision Date: 9/28/11
Revision No.: PR -03