GENERAL33488

• Permit No: C1981012
• IBM Index Class Name: General Documents
• Doc Date: 6/1/1984
• Doc Name: PROPOSED DECISION & FINDINGS OF COMPLIANCE for PR1
• Permit Index Doc Type: FINDINGS
• Media Type: D
• Archive: No

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For the Golden Eagle Mine, downward flow through the overburden in the absence
of open fractures or subsidence was calculated to be less than 3 gpm, an
insignificant portion of flow in the Purgatoire stream-alluvial aquifer
system. Inspection of underground workings in the New Elk Mine beneath the
Middle Fork by Division personnel did not identify significant inflows of
ground water that could be attributed to leakage through the roof from the
stream/alluvial aquifer System.
An inflow study for the New Elk Mine was conducted in November of 1983. This
study consisted of the mapping of all measurable mine inflows on a mine
workings map, measuring or estimating inflow rates, and determining inflow
sources. The information on New Elk Mine inflows is contained in the WFC
submittal 3, and on the New Elk Mine Map, both submitted December 1, 1983.
Mine inflows are not concentrated in areas of the New Elk Mine which are
overlain by streams, but are dispersed throughout the mine. Thus, the mine is
not inducing stream or alluvial ground water depletions directly through the
overburden strata.
The mapping of mine inflows indicate that faults and fractures are not a
source of mine inflows. No point source inflows were observed along faults
and fractures. This indicates that faults and fractures are healed with
impermeable clays and/or are not vertically extensive.
Major point source mine inflows are related to 2 air shafts and 1 power access
bore hole. These sources account for approximately 35 gpm of the total 123
gpm of inflow to the mine. These inflows represent dewatering of perched
overburden aquifers, which were intersected during boring operations.
The coal seam was observed to be weeping at 3 different mine faces. These
weeping faces are contributing 9 gpm. These inflows represent the dewatering
of the coal seam aquifer.
One channel sandstone was encountered in the 1 P.S. workings which contributes
3 gpm. This channel sand is probably draining ground water from the coal seam.
Only one minor inflow was observed issuing from the mine floor. The rate of
inflow was estimated to be 1 gpm. This indicates that the New Elk Mine is not
significantly impacting the quantity of ground water in underlying aquifers.
The major source of mine inflows measured in the New Elk Mine are from seals
which close off old mined-out areas. The total quantity of mine inflows from
mined-out areas was measured to be 88 gpm. The total area which contributes
to these inflows is about 2800 acres. The calculated inflow rate per unit
area for the mined-out workings is 0.03 gpm/acre. The total inflow rates
measured for the mined-out areas would be the sum of the inflows from weeping
coal faces, subsidence-induced fractures, any unsealed drill holes in these
areas, and vertical leakance through overburden strata. The major source of
mine inflows in these areas is probably the weeping coal faces, resulting from
dewatering of the coal aquifer. Coal faces on the western edge of the Allen
permit boundary are near the coal seam aquifer recharge area. These workings
could quickly capture any recharge waters and channelize flows of water down
the dip of the coal seam to the seals, where the inflows were measured.
Weeping coal faces were also observed as a major source of inflow in the
Golden Eagle Mine.