2009-08-13_PERMIT FILE - C1981019A ‎(4)‎

• Permit No: C1981019A
• IBM Index Class Name: Permit File
• Doc Date: 8/13/2009
• Section_Exhibit Name: Rule 2 Permits -ST
• Media Type: D
• Archive: Yes

RULE 2 PERMITS
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Potential Surface Water Quantity Impacts
As described above, diminishment of flow into Good Spring Creek appears to be probable during and for
a period after mining and reclamation of the South Taylor pit is finished. The reduction can be estimated
by assuming no meteoric water infiltrating into the reclaimed pit will reach the creek from a pit aquifer
for approximately 45 yeazs after the end of operations (the time to saturate the pit -see above) or that
springs located downgradient from the mine will cease flowing during and for a time after mining.
The area of the proposed South Taylor pit is approximately 1,000 acres. Assuming that 1.8 inches of
precipitation infiltrates, the pit will receive approximately 150 ac-fr per yeaz, or 92 gpm or 0.21 cfs of
rechazge from infiltration as shown in the preceding paragraphs. Much of this infiltration may eventually
surface at springs, likely in West Fork Good Spring Creek.
The actual resultant spring discharge will likely vary from high flow to low flow periods by an order of
magnitude, as measured in the surface water features. Thus, the discharge of groundwater originating as
pit infiltration used in the following calculations is assumed to range from 0.06 to 0,6 cfs, which gives a
geometric mean of approximately 0.21 cfs (calculated infiltration rate from above).
Assuming that 0.06 cfs enters Good Spring Creek during low flow and 0.6 cfs enters Good Spring Creek
during peak flow, the pit contribution would be approximately 7% of the base flow and 5% of the peak
flow to Good Spring Creek at the NUGSC measuring point or about 3% of both base and peak flows at
the LGSC measuring point. This is a maximum value, since the calculated contribution from the pit spoil
aquifer is greater than the average measured flow from the potentially affected springs. Thus, the
probable reduction in flow will be up to 7% of base flow for 45 years after mining ceases.
Potential Surface Water Quality Impacts
Potential impacts to the surface water quality from the proposed South Taylor pit operations are
considered here. The water quality would be impacted by meteoric water that enters the hydrologic cycle
being impacted by contact with the overburden fill To estimate the impact to surface water quality,
existing geochemical and flow data for Good Spring Creek were modified by changing the flow entering
from the pit (described above) to have water quality similar to that found in the Streeter Well (completed
in backfill in the Streeter Fill) and Streeter Pond discharge. The Streeter Well is located in the Streeter
Fill of the existing East Pit, and would appear to represent water quality in direct contact with Colowyo
Mine spoils. The Streeter Pond accepts primarily groundwater from the Streeter Fill.
Assumptions used include:
1. All pit groundwater will have chemistry similar to Streeter Pond, Streeter Well, or published
pit spoil geochemistry
2. All pit groundwater will eventually enter the Good Spring Creek surface water regime
3. The quantity of water entering Good Spring Creek would match assumptions in the Potenttal
Surface Water Quantity Impacts section.
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South Taylor/Lower Wilson -Rule 2, Page 118 Revision Date: 3/30/07
Revision No.: PR-02