|
The 97 -013 TM/TC monitoring wells, which were installed on the northern side of the property, as shown on Map
<br />13A, located the fault which was previously projected for this area. The fault has an estimated displacement of
<br />200 -250 feet, and will define the mining boundary for the panels in the second North Mining District. No major
<br />inflows of water were encountered during the drilling of this well.
<br />The expansion of the mine into the NMD resulted in continued development of the Wadge Seam reserves located in
<br />the Twentymile Park Basin. As presented in PR -04 and described in the previous section, this is an enclosed
<br />ground water basin, which is rimmed by the outcrops of the major lithologic units. The NMD is located near the
<br />center of the closed ground water basin. TC continues to monitor the existing ground water wells in the
<br />Twentymile Sandstone, Wadge Overburden, Trout Creek Sandstone and Alluvial wells in the alluvium of Foidel,
<br />Fish, Middle and Trout Creeks. In the NMD, mining progressed towards the center of the basin and then up -dip.
<br />As in PR -04, the focus of the hydrologic monitoring program for the bedrock units continues to focus on the
<br />Twentymile and Trout Creek Sandstones.
<br />During development of the Northeast Mains, TC crossed the same fault that was first intercepted in the 10 -Right
<br />gate -road. No significant problems were encountered while driving through this fault, and TC did not encounter
<br />significant ground water inflows. As with the 7 -Right through 2 -Right panels, all of the longwall panels are to the
<br />east of the fault. Only the sub -mains were driven through the fault. Roof, floor and coal samples were obtained from
<br />Drillholes 97006 and 97007, with the core and analysis data presented in Tables 20D, 20E, and 20F.
<br />TC reviewed historic records and contacted personnel who were involved, to determine the extent of mine inflows
<br />into the short-lived Middle Creek Mine. Available information indicates that the inflow into the mine was
<br />approximately 60 gallons per minute. This information was obtained from a 1981 memorandum from Mike
<br />Ludlow to J. Weston. In addition to the mine flow rates, there was additional information addressing dewatering
<br />wells that had been installed at the site. The memorandum indicates that the wells produced anywhere from 0.5 to
<br />120 gpm. Therefore, it appears that the maximum inflow into the mine in this area was 60 gallons per minute,
<br />while the maximum pumping rate for a dewatering well was 120 gallons per minute. The outline of the mine is
<br />shown on Map 5. As noted, the mine only advanced approximately 900 feet before the decision was made to
<br />abandon the project.
<br />Based on the historic record, it appears the inflow came into the mine from the roof strata. The Middle Creek Mine
<br />was under a low overburden height of 300 -650 feet and the overburden was highly fractured from previous surface
<br />mining operations in the highwall area, and its location in a fault zone. The intent of the Middle Creek Mine plan was
<br />to cross the fault located in Section 12, TSN, R86W, where mining conditions on the west side of that fault were
<br />anticipated to be much improved relative to both ground water inflow and the dip of coal seam. It is known that water
<br />inflows to the mine were from the Wadge overburden by means of roof bolting drillholes, and that the mine portals
<br />were aligned close to parallel with the local and regional faults, cleats, joints, and fractures.
<br />TC drilled two exploration holes in Section 14, TSN, R86W, with no evidence of significant groundwater flows.
<br />TC has also mined entries in the Wadge coal seam, and currently maintained ventilation through the EMD bleeder
<br />shafts in Section 14, TSN, R86W during active mining of the EMD. Again there is no groundwater water inflow in
<br />these mined -out areas. Based on these observations and the experiences in the Wadge coal seam for both the SWMD
<br />and EMD, no major groundwater inflow was anticipated or encountered for the development mining of the Wadge
<br />Coal Seam in Sections 11 and 14, TSN, R86W. Mining in this area occurred under a minimum of 700 feet of
<br />overburden, and did not result in groundwater inflows comparable to areas of the SWMD and EMD. The 6 -Right out -
<br />by section of the EMD was developed in an area of less than 500 feet of overburden where groundwater inflow was
<br />experienced. Minor groundwater inflows encountered in the development mining of Sections I 1 and 14, TSN, R86W,
<br />were addressed using small sumps in the floor of the gate -road sections to collect the water and pump it down -dip to
<br />the Northeast Mains section, where it was collected in the existing main sump and pumped through the mine
<br />dewatering system.
<br />Similar to the previous discussion for the WCR, geologic and hydrologic conditions for the Wolf Creek Coal Seam
<br />and Wadge /Wolf Creek interburden in the portion of the WCR underlying the NMD are expected to be similar to
<br />those characterized through previous baseline work and actually encountered for the Wadge Coal Seam and
<br />TR13 -83 2.04 -16.3 11/03/14
<br />
|