GENERAL49817

• Permit No: C1984063
• IBM Index Class Name: General Documents
• Doc Date: 3/2/2000
• Doc Name: PROPOSED DECISION & FINDINGS OF COMPLIANCE FOR RN3
• Permit Index Doc Type: FINDINGS
• Media Type: D
• Archive: No

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resemblance to the quality of water found in the wells of the overlying coal seams. The
applicant concluded that the seep appeared to be emanating from the bum zone
overlying the uppermost entry. The source of the water was most probably recharge
from snowmelt and runoff The seep had an average yield of 2 gpm. Since pumping
ceased, the water in the mine has stabilized at approximately 20 feet below the portal
level at the surface. To date, there has been no discharge from the mine portal.
No springs or seeps were located within the life-of--mine permit boundary. A perennial
seep exists along the base of the Grass Valley Reservoir. The seep has an average flow
of ~ gpm. Seeps along the base of the reservoir create the perennial flow in the Harvey
Gap Drainage during period when no water is released from the reservoir for imgation.
This source of water is isolated from the mine by the impervious Mancos Shale.
The extraction of coal has ceased at the mine, and the mine portals sealed and covered.
The hydrostatic water level in the mine has apparently stabilized. The E-coal seam is
of low permeability, and is isolated by more impervious layers. The mine water quality
was representative of water of the coal seam. The only water apparently introduced to
the mine (near the portals) was of higher quality (perhaps surface water reaching the
mine through bum azeas). As the water level in the mine appears to have stabilized, the
Divisions finds that the mine has no impact on the quantity of ground water in the
potential aquifers of the area (no depletion, and apparent stabilized recharge). As the
water quality in the mine is representative of the water in the water of the coal seam,
perhaps improved slightly due to surface recharge, the Division finds that the
application poses no impact on the quality of ground water in the potential aquifers of
the area.
The potential for diminution or degradation of ground water in the bedrock aquifers
overlying the mined coal seam is small. This is due to: (1) the small size of the mine,
(2) the lack of communication of the coal seam with overlying beds due to interbedded
shale layers, and (3) the lack of potential of the rock strata within the affected'section
to supply a high quality ground water resource. However, although the water quality
in the overlying bedrock aquifers is poor, those aquifers are used for domestic supply
in the vicinity of the mine. Additionally, mining-related subsidence has the potential
to create fractures in the interbedded shale layers between the mined coal seam and the
aquifers. Although the existing domestic wells lie outside the angle of draw for the
mine, subsidence-related fractures could create communication between the aquifers
and the coal seam, thereby disrupting the recharge zones for these aquifers, which
could result in the diminution of water supply of current users. However, the operations
proposed by the application to not aggravate such potential impacts (none noted to
date) from operations approved for previous terms of the permit.
There has been no surface water discharges from disturbed areas of the mine. Soils of
disturbed areas are not toxic or acid forming. The seep from the Grassy Gap Reservoir
is isolated from surface waters of the mine workings by location (the seep is upstream
of the mine). The drainage thalweg is in an incised valley at an elevation
approximately sixty feet below disturbed surface areas of the mine. Ground waters of
the mine workings are isolated by impervious formations. There is potential for
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