2012-09-06_REPORT - C1981010

• Permit No: C1981010
• IBM Index Class Name: Report
• Doc Date: 9/6/2012
• Doc Name: DRMS Review of 2011 AHR
• From: DRMS
• To: Trapper Mining Inc
• Annual Report Year: 2011
• Permit Index Doc Type: Hydrology Report
• Email Name: JLE
• Email Name: SB1
• Media Type: D
• Archive: No

W. Prevention of
material damage
to the hydrologic
balance outside
the pen area
CDRMS
regulation
4.05.1(1)
yes
The only apparent significant impact to surface water outside
the permit area has been TDS loading of surface streams, and
this impact has not impaired water use. There are no data
indicating impacts to an aquifer outside the permit area.
Overall, PHC predictions appear to be accurate, as
illustrated by the following examples.
Per the PHC, TSS values in the surface water runoff are
expected to increase a few years after mining and then
decline. Data for NPDES sites 001 and 002 illustrate this
trend.
Per the PHC, elevated TDS levels will be detected in base
flows derived from backfill aquifers. During 2011,
relatively high TDS concentrations were reported for
NPDES sites in several gulches: Johnson, No Name, East
Pyeatt, and Flume. All four of these sites are downgradient
of potential spoil springs from the A Pit and East A Pit. In
general, the data reflect the inverse relationship between
TDS and flow.
Per the PHC, post -mine values of pH in surface water
runoff are not expected to be significantly lower or higher
than present or pre -mine levels. Field pH values for all
X. Agreement of
sites in 2011 were similar to previous data collected.
observed
CDRMS
hydrologic
regulation
Yes
Per the PHC, Trapper does not anticipate recharge to the
impacts with PHC
..
2056(3)
shallow aquifer systems to be adversely affected by
proj ected in
mining operations in the Third White Sandstone. Water
permit
levels in wells GC -2, GP -9, and P -8 (used to monitor the
Third White Sandstone) did not rise or fall considerably
between 2010 and 2011. Previous analysis has indicated
good recharge with above average precipitation over the
last few years.
Per the PHC, constituent concentrations in backfill
aquifers, namely TDS and sulfate, are expected to be
higher than pre- mining concentrations for an extended
period of time after mining. The data for TDS
concentrations in wells in backfill aquifers have shown
apparent impacts from mining. TDS concentrations in
GD -3 and GF -5 are somewhat higher to those of native
aquifers in these areas. TDS values for wells GF -7 and
GF -I1 were higher than the naturally observed
concentrations in the 1990s and 2000s, but have declined
in recent years. These trends have continued in 2011.
Sulfate concentrations exhibited similar trends as TDS for
wells GF -7 and GF -11. Sulfate concentrations increased
in GD -3 and GD -2 in 2010 and 2011, and should be
watched closely in future years.
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