2011-10-31_REPORT - C1981010

• Permit No: C1981010
• IBM Index Class Name: REPORT
• Doc Date: 10/31/2011
• Doc Name: DRMS Review of 2010 AHR Report
• From: DRMS
• To: Trapper Mining, Inc
• Annual Report Year: 2010
• Permit Index Doc Type: Hydrology Report
• Email Name: RDZ
• Media Type: D
• Archive: No

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The post - mining uses of ground water in the permit area will be
irrigation and livestock uses. Only the three large sandstone
aquifers within the upper Williams Fork Formation at Trapper
(Twenty Mile Sandstone, Second White Sandstone, and Third
White Sandstone) could reasonably be expected to yield enough
high quality water to serve as a local supply source. Coal aquifers
in the area possess neither the deliverability nor water quality to be
considered for reliable water supplies.
The Twenty Mile Sandstone is the only regionally extensive
aquifer in the vicinity of the Trapper Mine. It is several hundred
feet deeper than the deepest mining at Trapper and has shown no
effect from Trapper's mining based on monitoring data from well
GF -1 and previously from well GD -1(2).
U. Prevention of
impacts to ground
The Second and Third White Sandstone aquifers overlie the
stratigraphic sequence being mined at Trapper. TDS
concentrations in both of these aquifers have increased over the
past several years based on monitoring of wells P -5 and P -8, which
water that
adversely impact
the postmining
land use within
the permit area
CDRMS
regulations
4.05.1(2) and
4.05.11
yes
are in the East Pyeatt Gulch basin. Water from both wells,
however, remains suitable for use by livestock and wildlife (see
discussion in item L. above).
Trapper believes the TDS and conductivity concentrations will
eventually subside, possibly hundreds of years after mining and
reclamation, as discussed in Section 4.8.3 of the permit. The
suitability of Trapper's ground water for livestock and wildlife is
expected to continue into the future based on long -term trends in
Trapper's water quality data.
In 2009, as well as in previous years, elevated levels of TDS
were detected in wells GF -7 and GF -11 (spoil backfill) and in
well P -8 (the Third White Sandstone). These have been
determined to be local impacts that do not impair potential use.
Elevated TDS levels in well P -8 may be the result of spoil
leachate discharging from A -pit, which is 1,100feet upgradient
from the well, or they may be due to surface impacts, given that
the well is only 35 feet deep and the well is completed in
sandstone beds that are likely highly permeable. Furthermore,
high nitrate content of samples in past years may indicate the
well receives infiltration of surface water.
V. Minimization of
disturbance to the
CDRMS
hydrologic
balance within
and adjacent to
the permit area
regulation
4.05.1(1)
yes
W. Prevention of
material damage
CDRMS
The only apparent significant impact to surface water outside the
to the hydrologic
regulation
yes
permit area has been TDS loading of surface streams, and this
balance outside
the permit area
4.05.1(1)
impact has not impaired water use. There are no data indicating
impacts to an aquifer outside the permit area.
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