Laserfiche WebLink
TR4 6, Pond 012 Slide Remediation Plan <br />Response to Comments <br />• Page 2 <br />c) The SCC summary page lists the slide scarp cut slope at 1.5H. I V, while the NIYWCC's text and Sheet 2 indicate <br />0.5H:1 V for competent bedrock (and 2H:1 V or flatter for weathered materials). Please explain the <br />discrepancy, clarify the planned slope of the scarp cut slope, and modify the text, plan view, <br />and cross sections accordingly. <br />Response: In the complete package, "competent bedrock" is the key-wording. In some locations a 0.5H:1 V <br />slope may not be achievable if competent bedrock cannot be excavated back to a slope that steep. Because of <br />the restricted room in which to work, drilling and blasting is not realistic, therefore a 0.5H:1V cut slope will <br />be constructed any where possible otherwise some lesser slope will be excavated into competent bedrock. In <br />all cases the cut slope will be in competent bedrock. The cut slope description on the summary sheet has <br />been revised to indicate a possible range of final slopes. <br />2. The proposal indicates that the slide scarp would be cutback into competent material, with a very steep cut slope (disparity <br />between NW ICC and SCC proposed slope will need to be clarified). Presumably, the intention is that the cut <br />slope in competent material would not be topsorled or seeded, but this needs clarified <br />Response: A statement has been added to the summary sheet indicating that topsoil won't be placed on the <br />cut slope in competent material. However, the approved Upland Seed Mix will be spread on the slope. <br />3. Postmaung Topography Map and Permanent Channel and Pond Watersheds Map exhibits will <br />need to be revised to incorporate the slide remediation topograpby and drainage modifications <br />• prior to revision approval. <br />Response: Exhibit 13-12.1A, Permanent Channel and Pond Watersheds Map and Exhibit 20-2, Postmining <br />Topography Map have been updated. <br />4. The design specifications intended for the short tributary channel that enters YPM-6-3 from the south at the approximate <br />location of cross-section J3 are not addrrssed Please provide design clarification and a YPM.... designation <br />for the Channel segment <br />Response: The referenced "short tributary channel" is simply a graveled area installed to capture and control <br />ground water flow that currently surfaces and saturates the area along the south side of the main drainage. <br />This graveled area does not change the configuration of the existing grass lined swale in this un-mined area. <br />SCC doesn't believe it needs a surface channel design or designation. <br />In addition SCC has included an updated backfill and grading schedule as shown on Exhibit 19-1A, Backfill <br />and Grading, per the 03/25/2010 Yoast Inspection report. <br />• <br />Seneca Coal Company • P.O. Box 670 * Hayden, Colorado 81639 <br />Telephone (970) 276-5217 a FAX (970) 276-5222