2011-03-21_PERMIT FILE - C2009087A ‎(2)‎

• Permit No: C2009087A
• IBM Index Class Name: Permit File
• Doc Date: 3/21/2011
• Doc Name: Mitigation of the Impacts of Mining Operations
• Section_Exhibit Name: 2.05.6 Mitigation of the Impacts of Mining Operations
• Media Type: D
• Archive: Yes

RULE 2 - PERMITS
. 2.05.6 (6) Subsidence Survey, Monitoring, and Control Plan
During the initial permit term, PSCM will construct the mine portals and related surface
facilities and begin development of the underground mine. Mining will consist of extending
the main entries underground and developing up to three continuous miner panels. No pillar
extraction or longwall mining is projected. Therefore no subsidence is anticipated. An
evaluation of the worst case subsidence potential was conducted by SubTerra, Inc and is
shown in Exhibit 2.05.6 -E1. This evaluation considers the potential for 1) mine roof failure;
2) pillar failure; 3) pillar punching; 4) unexpected faults; and 5) encounters of gas and water
inflows. The evaluation of the worst case conditions predicts that subsidence will not occur.
This prediction is supported by the mining history at Twentymile's Foidel Creek Mine with a
25 year record of mining. Main entries and continuous miner sections have been developed
under similar resources, as identified below, with no measurable subsidence occurring. The
mine development has been through faults, under creek areas and in depths that exceed those
that will be encountered at PSCM. Water inflows encountered at the Foidel Creek Mine have
shown to have no effect on pillar stability. No gas inflows have occurred that would cause
any pillar or roof instability. Pillar punching around a longwall extraction can cause floor
heave and degradation of the immediate roof but does not in itself lead to subsidence.
The publications, What is Mine Subsidence (Exhibit 2.05.6 -E2) and Illustrated Effects of
Mine Subsidence (Exhibit 2.05.6 -E3), both from the Pennsylvania Department of
Environmental Protection, are used as references for this subsidence evaluation.
• The structures and the renewable resource lands identified in the area above the mine works
are as follows:
1. Grassy Creek, a perennial drainage.
2. Little Grassy Creek, an intermittent drainage.
3. County Road 27
4. 135 and 340 KV power lines
5. 69 KV power line.
In reviewing the location of the identified structures, it is recognized that the greatest
potential for damage can occur at shallow depths and when coal extractions are high,
exceeding 60 %. Grassy Creek, County Road 27 and the 135 and 340 KV power lines are
located in areas of the mine that exceed 600 feet of depth and in areas where extraction ratios
will be less than 45 %. Any failures in the underground works will not cause any measurable
subsidence at the surface. Subsidence of up to 60 inches, at these depths, has been recorded
in longwall areas at the Foidel Creek Mine at areas of county roads, creeks and power lines
with no material damage to these structures. County Road 27 and 33 have experienced
subsidence with out damage to the road surface. Fish Creek and Foidel Creek have been
subsided and the flows have been maintained and with no connection to the mine workings.
Power line towers have been subsided and show a small amount of tilt but no damage to the
structure or the lines. Therefore, subsidence is highly unlikely to these structures and if it did
• occur, in a worst case, would not cause material damage or diminution of reasonably
foreseeable use of these structures.
PSCM Permit App. 2.05 -103 Revision 04/19/10