PERMFILE46063 - Laserfiche WebLink

Home Browse Search

SubTerra, Inc. Twentymile Coal Company 6/19/2003 PR6 Rail Line Evaluation • H:V) on either side of the track which may, or may not, require extension of the culvert(s) beneath the track and placement of fill in Fish Creek or its AVF. The third and fourth areas of potential concern are where Fish Creek passes beneath the Energy Spur (approximately at Station 388+50) and where the track is located immediately above Fish Creek and its AVF (approximately at Station 385). Figure 18 shows the plan and cross-section for the track at these locations. The predicted magnitudes of required re-elevation at both Station 388+50 and Station 385 are shown in Table 5, Column 9 as just less than 2-ft. This will require extending the base of the ballast prism by less than 4-ft (at 2:1, H:V) on either side of the track at each location. At the crossing area, this may, or may not, require culvert extension and possibly fill placement in Fish Creek as the existing fill slope is at or greater than the 2:1 gradient preferred by the railroad. However, it appears that the additional fill or ballast width can be accommodated at Station 385 where the Energy Spur is located on the embankment above the AVF. 3.3 Detailed Remedial Planning and Field Implementation Field implementation of the re-elevation (or re-leveling) program will require either (1) pre- ballasting of the Energy Spur in advance of undermining followed by periodic survey of the alignment during undermining, or (2) re-leveling the Energy Spur during undermining. Additional detailed remedial planning work will be carried out prior to each panel undermining the track. Tasks will include: 1. Quantifying ballast requirements. The amount of material required for re-leveling will be estimated from the existing ballast cross-sections and predicted subsidence. • 2. Making drainage provisions. Surface water drains alongside each side of the track to culverts placed at strategic locations. These culverts must be lengthened during track re- ballasting, the additional length being determined based on the required increase in ballast height. 3. In the case of Option (1), evaluating pre-placement of the Ballast. This involves assessing whether pre-ballasting will result in unacceptable track gradients prior to and during undermining. 4. Additional Work and Data requirements 4.1 Evaluation of Fill Slope Stability at Fish Creek Crossinos Track elevation may be accomplished in the creek crossing areas by locally steepening the fill slopes above the creek if the existing fill geometry permits. Detailed survey will therefore be required at each of the crossings to determine: culvert diameter and length, track position, ballast prism shape, and fill prism shape. Sufficient survey data will be required to permit construction of the sections shown on Figures 12, 15, and 18. Concern was also raised regarding the effects of subsidence on the elevation of Fish Creek's flow-line and the potential effects of an increase in surface water elevation on the stability of the fill/ballast prism at the creek crossings. This concern is unwarranted at the crossing located near the start room for 18-Right as subsidence will be limited by proximity to the start room. • Resolution of this concern for the crossing over 17-Right awaits receipt and evaluation of the detailed survey data noted above, and inspection of actual conditions at this location. We