2010-02-09_PERMIT FILE - C1982056A ‎(6)‎

• Permit No: C1982056A
• IBM Index Class Name: Permit File
• Doc Date: 2/9/2010
• Section_Exhibit Name: 2.04 Environmental Resources
• Media Type: D
• Archive: Yes

TCC reviewed historic records and interviewed personnel who worked at the mine to determine the extent of mine
inflow into the short-lived Middle Creek Mine. The available information indicates that the inflow into the mine
• was approximately 60 gallons per minute. This information was obtained from a 1981 memorandum from Mike
Ludlow to J. Weston. In addition to the mine flow rates, there was additional information addressing dewatering
wells that had been installed at the site. The memorandum indicates that the wells produced anywhere from 0.5
to 120 gallons per minute. Therefore, it appears that the maximum inflow into the mine in this area was 60
gallons per minute, while the maximum pumping rate for a dewatering well was 120 gallons per minute. The
outline of the mine is shown on Map 5. As noted, the mine only advanced approximately 900 feet before the
decision was made to abandon the project.
Based on the historic record, it appears the inflow came into the mine from the roof strata. The Middle Creek
mine was under low overburden ranging in height from 300 to 650 feet, and the overburden was highly fractured
due to its location near the previous surface mine highwall, and localized faulting. It was always the intent of the
Middle Creek mine plan to cross the fault located in Section 12, T5N, R86W where mining conditions on the west
side of that fault were anticipated to be much improved for both groundwater inflow and dip of coal seam. It is
known that water flowed into the mine from the Wadge overburden through roof -bolt drillholes, and that the mine
portals were aligned close to parallel with the local and regional faults, cleats, joints, and fractures.
Twentymile drilled two exploration holes in Section 14, T5N, R86W, with no evidence of significant
groundwater flows. Twentymile has also mined entries in the Wadge coal seam and currently maintains
ventilation through the East Mine District bleeder shafts in Section 14, T5N, R86W. Again there is no
groundwater water inflow in these mined -out areas. Based on these observations, and the experiences in the
Wadge coal seam for both the Western and Eastern mining districts, no major groundwater inflow is anticipated
for the development mining proposed for the Wadge Coal Seam in Sections 11 and 14, T5N, R86W. The
proposed development will occur in areas with a minimum of 700 feet of overburden, which has not led to
groundwater inflow in comparable areas of the Western and Eastern mining districts. The 6 -Right out -by section
• of the Eastern Mining District, where groundwater inflows were experienced, was developed in an area of less than
500 feet of overburden. If groundwater inflow were to be encountered in the development mining of Sections 11
and 14, T5N, R86W, TCC would use local sumps driven into the floor of the gateroad section to collect the water
and pump it downdip to the Northeast Mains section where it would then be collected in the existing sump, and
pumped through the present mine dewatering system.
NMD (Panels 17 -Right through 25- Right, PR03 -06 and PR06 -07)
The general geology and hydrology of the remaining NMD segment has been described in the previous No. 4 and
No. 5 permit revisions. Exploration drilling in 2002 was used to establish mining limits related to steep grades
near the eastern flank of the Tow Creek Anticline. Combined results of the 1999 and 2002 surface 2D seismic
exploration further helped to define the eastern and northern regional fault trends, which control the mining
boundary for the remaining NMD district longwall panels. Revised steep grade and fault limits are displayed on
the Surface Geology and Wadge Seam Structure maps (Maps 5 and 6).
WMD (Panels 12 -Left through 17 -Left, PR06 -07)
The general geology and hydrology of the WMD is described under 2.04.5. The majority of the exploration
drilling for this area was completed in the 1980's (1981 through 1989), as indicated by the drillhole locations and
numbers shown on Map 6. Drilling information, along with more recent seismic work in the area, have helped to
delineate structural controls, and coal seam occurrence and characteristics for the WMD, as shown on Maps 5 and
6, and reflected in the geologic cross - sections (Maps 7 -9).
The WMD is bounded on the north by the Twentymile Park synclinal axis and the Tow Creek anticline, on the
west by a minor fault and the Fish Creek anticline, on the south by the mined -out Southwestern Mining District
workings, and on the east by a major regional fault and TCC's Eastern and Northern MiningDistricts. Exploration
drilling and seismic work do not indicate any significant additional faulting within the WMD beyond that
previously identified and discussed for the general mining area.
PR09 -08 2.04 - 16.913 04/10/09