1994-10-21_GENERAL DOCUMENTS - C1980007

• Permit No: C1980007
• IBM Index Class Name: General Documents
• Doc Date: 10/21/1994
• Doc Name: Proposed Decision & Findings of Compliance for PR5
• From: Jumbo Mountain Lease
• Permit Index Doc Type: FINDINGS
• Media Type: D
• Archive: No

Occurrences of ground water have been noted in the
Mesaverde Formation based upon information obtained from
drilling, experience in the mines, and from the presence of
springs and seeps in the region. This information also
indicates that the only potential regional bedrock aquifer
in the general area is the laterally continuous Rollins
Sandstone. The laterally discontinuous lenticular
sandstones within the Upper Mesaverde. Formation support
only localized ground water flows.
Recharge to the Rollins Sandstone occurs along outcrops,
along subcrops beneath stream alluvium and in the channels
of the .north Fork and its tributaries. However, due to the
steepness of the topography in the outcrop areas (i.e. ,
sandstones are ledge formers) and the narrowness of the
stream valleys, these local aquifers receive little
recharge. Some recharge to the continuous units and much
of the recharge to the more discontinuous, lenticular units
will cane directly from the percolation of snvnnelt and
precipitation downward through sandstone lens and along
fractures. The same is true in the Jumbo Mountain area.
Of 112 exploration drill holes at the West Elk Mine that
were drilled prior to the mine opening, only three of the
holes produced water from the F seam at a production rate
of 3 gpm or less. Three other holes in the Barren member
had rates of about 0.75 gpm.
Some fractures and faults transect the Mesaverde Formation
and extend vertically to the surface. These faults and
fractures produce narrow bands of secondary permeability
within the rock strata. Due to the low permeability of the
rock strata within the Mesaverde Formation, these faults
and fractures provide the primary path through which water
flows both vertically between rock strata and horizontally
within rock strata.
When faults and fractures are encountered within the mines
in the North Fork region, they generally produce mine
inflows. The flow characteristics of each mine inflow
associated with faults and fractures depend upon the
lateral extent and the proximity of the fault or fracture
to a stream valley. All inflows from these sources are
characterized by an initial surge of water which then
either decreases or ceases completely with time.
Locally, water flow through fractures probably occurs more
rapidly, as suggested by the seasonal fluctuation in
discharge rates of some springs in the mine plan area.
Mine inflow studies conducted as recently as 1985 have
shown that the primary source of inflows are from fractures
in areas of low overburden.
Since the geologic strata dips to the northeast, one would
expect the ground water to flow in the same direction. The
monitor'.ng wells generally support this, but there are
exceptions. Some wells are dry, indicating no ground water
flow and other wells that are closely spaced but completed
. at different portions of the Barren member have water
levels that vary greatly. This may indicate the
discontinuity of the water bearing strata. Generally,
springs in the permit area seem to act independently of the
bedrock water leasing zones and appear to be surface
features related to weathered and fractured bedrock. Flow
from these springs tend to be highly ephemeral and only
discharge during spring snow melt. These springs recharge
and discharge in relatively small areas.
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