GENERAL32420

• Permit No: C1981013
• IBM Index Class Name: General Documents
• Doc Date: 6/28/1990
• Doc Name: Proposed Decision & Findings of Compliance for PR1
• Permit Index Doc Type: Findings
• Media Type: D
• Archive: No

Since the Golden Eagle and New Elk Mines have similar geology and mining
operations, subsidence inflows are also not expected to be significant in
the Golden Eagle Mine. Mining plans at Golden Eagle include the use of
longwall mining and pillaring in areas to the north and south of the
Picketwire Valley, and partial extraction mining under the Picketwire
Valley. Subsidence-induced mine inflows, therefore, would be limited to
areas outside of the Picketwire Valley.
The applicant has adequately determined the probable hydrologic
consequences of the proposed underground mining operations upon the
stream/alluvial aquifer systems of the Santistevan Canyon. The surface
and ground water resources are fully inventoried and the probable
hydrologic consequences of mining upon these resources is assessed,
secondary and retreat mining beneath the alluvium of Santistevan Canyon
has been approved by the Division. See Exhibit 30. The applicant
provided a discussion of the water quality effects of mine discharge from
the Golden Eagle Mine upon the Purgatoire River stream-alluvial aquifer
system. These anticipated effects were based on estimates of discharge
which are substantially less than those currently experienced.
The water discharged from the mine is a sodium-bicarbonate type water
with a pH in the range from 7.6 to 9.1. During the monitoring years 1984
through 1989, the water averaged a TDS level of 825. Maximum flow from
the mine in early 1988 was over 300 gpm, exceeding the earlier
anticipated maxirtum values of approximately 180 gpm. Lowering of the
piezometric surface associated with the fracture zone resulted in
steadily decreasing mine discharges, which averaged 232 gpm in 1988 and
184 gpm in 1989. Assuming that no additional large inflow sources are
encountered, flow from the mine may approach 500 gpm at maximum
development. Mass balance calculations of the effects of such flow on
the Q7-10 value for the Purgatoire River indicate this discharge would
increase TDS values in the river during such a low flow by 58 mg/1 to a
total of 261 mg/i. The resulting dissolved solids value for the river,
however, is below drinking water standards of 500 mg/1 so use of the
water for drinking purposes will probably not be affected. Using
representative values of Ca, Mg, and Na concentrations for
Purgatoire River water at PR-2, upstream from discharge of the mine water
and for the Golden Eagle Mine discharge water, a resulting SAR value of
7.68 was calculated for the Purgatoire River water below mine discharge
point. This does not exceed the normal irrigation water standard value
of 12; so use of the water for irrigation purposes is not precluded.
The applicant has received approval to construct a 6 acre coal refuse
pile at the mouth of Ciruela Canyon as a result of TR-04. In the process
of receiving this approval, the operator satisfied the requirements of
Stipulation No. 9.
After the cessation of mining operations, the Golden Eagle Mine water
would no longer be discharged and the workings would flood. The recovery
of the piezometric surface of the coal aquifer would occur in two
stages. The first stage would be a relatively slow increase that would
occur as the mine workings are filled by ground water inflows. Once the
underground workings have been filled, the piezometric surface would
rapidly rise toward its eventual steady state position.
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