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

unit. The operator states that based on data from the
mining and reclamation plan and recent drilling, it is
reasonable to assume that the North Fork of the Gunnison
River recharges and receives discharge from the Rollins
Sandstone in a small area on the northern edge of the West
Elk property. It is evident from available data that the
Rollins behaves similarly to the Barren member and Coal
members in the permit area except the extreme northern edge
where it has an alluvial contact with the North Fork.
Ground water pore pressure is expected to be 100 feet above
the Rollins Sandstone in the permit area. Since there is a
unit downward gradient, mining in the B seam will not
impact -the Rollins Sandstone. .
The Rollins Sandstone is considered a marginal aquifer in
terms of yield and water quality and, to MCC's knowledge,
has no points of usage in the mine vicinity. Review of
data for the region indicates that none of the other mines
in the area have monitored the Rollins Sandstone. Since
the Somerset Mine has been active since 1906, any potential
for severe water quality impact would probably be evident
by this time. The water quality data for R-1, a well
completed in Rollins Sandstone and drilled by Mountain Coal
Company in 1976, indicates total dissolved solids generally
outside the range acceptable for drinking water. MCC has
completed a well to the Rollins Sandstone in the Jumbo
Mountain area, which should provide some additional
information to allow a more accurate description of this
formation.
The majority of Mountain Coal Company's hydrologic
monitoring concentrates on mine water discharges and wells
associated with B seam mining. Disturbances and changes to
water quality, if they occur, will be manifested in B seam
discharge water and B seam monitoring wells prior to any
potential impacts to the Rollins Sandstone. The B seam is
separated from the Rollins by siltstones, shales, and
another coal seam. It is unlikely that the Rollins
Sandstone would be used as a primary drinking water source
because of its great depth outside stream valleys and the
ready availability of better quality surface water near the
stream valleys.
MCC has mapped the B seam overburden thickness with
potential areas of ground water inflow highlighted. These
areas of potential inflows, similar to the F seam, are
associated with fracture zones beneath drainages and near
outcrops and areas of low overburden. Based on experience
in the F seam in these areas, the inflows are predicted to
be minor in nature. A map of the potentiometric surface of
the B seam has been produced and can be reviewed in Exhibit
17A.
MCC has made inflow estimates for the B seam mine plan for
the five-year permit area. The "probable maximum" estimate
of mine inflow shows a peak or initial inflow rate of about
15 gallons per minute (gpm) and a long term steady rate of
about 10 gpm. This estimate is based on a rate of mining
of 1 .4 million tons per year and no ventilation portals
extended to the northern outcrop.
An estimate of mine inflow for the projected life of mine
was also performed. This case showed an initial inflow
rate of about 45 gpm and a long term steady inflow rate of
about 30 gpm. Maximum inflow is estimated to be 100 gpm.
This case was based on a mining rate of 2 .8 million tons
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