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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The largest point source mine inflows were 3 to 10 gpm from 2 air shafts and 1
unsealed drill hole. These point source inflows are probably the result of
dewatering of overlying perched aquifers penetrated by the drill hole and air
shafts. The total mine inflow from point sources amounted to 16 gpm, or 53%
of the total mine inflow (30 gpm). The remaining mine inflows were from
weeping coal faces and weeping rock strata along the length of the rock slope
incline. These weeping areas contribute inflows approximating 14 gpm, or 41%
of the total inflow. These weeps represent dewatering of the coal aquifer.
The highest weep flows, totalling 11 gpm, are in the mine workings beneath the
Apache Canyon stream channel. Mine workings beneath the Ciruela Canyon
drainage only receive about 1 gpm from weeping coal faces. Development
mining, to date, is not significantly impacting the overlying stream/alluvial
systems.
The Golden Eagle Mine has undergone only development mining. Thus, there has
not been any pillaring or longwall mining which would result in subsidence.
There are no subsided areas in the Golden Eagle Mine from which the quantity
of inflows resulting from subsidence can be measured. Empirical data on
inflows to mined-out areas is, however, available from the New Elk Mine. The
calculated inflow rate per acre of mined-out workings at the New Elk Mine is
0.03 gpm/acre. This value indicates a very low inflow per unit area, and
represents inflows from sources other than subsided areas. Therefore,
subsidence is not presently a significant source of mine inflows at the New
Elk Mine.
Since the Golden Eagle and New Elk Mines have similar geology and mining
operations, subsidence inflows are not expected to be significant in the
Golden Eagle Mine. Also, mining in the immediate future will be restricted to
partial extraction and development mining at the Golden Eagle Mine.
Therefore, subsidence-related inflows will not occur at this mine. Future
mining plans 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 not adequately determined the probable hydrologic
consequences of the proposed underground mining operations upon springs and
seeps in or adjacent to the permit area, or the consequences upon the
stream/alluvial aquifer systems of Apache, Santistevan and Ciruela Canyons.
This is due to a deficient inventory of ground water resources. Until 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 south of the Purgatoire River and beneath the alluvium of
Santistevan Canyon cannot be approved by the Division (See Stipulation Nos. 7,
8 and 9 in Section VI, Hydrologic Balance; Ground Water of the original
findings document).
The applicant has provided a discussion of the water quality effects of mine
discharge from the Golden Eagle Mine upon the Purgatoire River stream-alluvial
aquifer system. The water discharged from the mine is a sodium-bicarbonate
type water with an average pH of 7.9, and an average total dissolved solids
level of 1,112 mg/1 (see Exhibit b, Table 6 of the Golden Eagle permit
application). Under low flow conditions, this discharge would increase the
total dissolved solids level in the river by 47 mg/1; under average flow
conditions the predicted increase is only 13 mg/1 (Exhibit 6, Table 8).