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1111110 <br />Coal Company <br />June 20, 2011 <br />Seneca Coal Company <br />Ms. Susan Burgmaier <br />Division of Reclamation, Mining and Safety <br />1313 Sherman Street, Room 215 <br />Denver, CO 80202 <br />RE: Seneca II-W Mine (Permit C-82-057) 11 <br />TR-73 - Pond 016 Area Slide Remediation Plan ??N ?? 1?• <br />Round 2 Adequacy Responses ??visor? of ??S <br />06119 4n? <br />Ms. Burgmaier, <br />Seneca Coal Company (SCC) has reviewed your letter of May 31, 2011 and has developed the <br />following responses to the adequacy comments. <br />1. SCC's response provides additional details about the proposed construction sequence for the <br />backfilling of Pond 016A. This item has been satisfactorily addressed. The Division does <br />have one comment, however, regarding the final sentence which reads, "There will be no <br />anticipated source of water for continued infiltration into the. fill area. " While the <br />reconfiguration of channels, as proposed with this revision, is intended to capture and <br />redirect the surface and subsurface flow entering the area of Pond 016, a more prudent <br />approach to design and construction would be to assume that water will inevitably find its <br />way into the fill. <br />Response: No response necessary. <br />2. SCC responds that NWCC will sample fill materials as they are being excavated from the <br />slide and placed in Pond 016A. Compaction testing during placement of the fill is a key part <br />of the process, but separate from the development of Standard Proctor curves. <br />Moisture/Density ("Proctor' curves are developed in the laboratory prior to <br />commencement of placement and compaction. Curves are developed for each separate type <br />of fill material (or blend of materials) likely to be used; each curve will have a specific <br />maximum dry density and optimum moisture content. During placement, accurate <br />compaction results are dependent upon comparison to the proper Moisture/Density curve. In <br />the Division's cursory review of past compaction testing results reported for SCC, it is not <br />readily apparent that these procedures have been fully implemented. The purpose of this <br />comment was to ensure that compaction testing will be conducted in accordance with <br />standard materials engineering practice, from the laboratory to the field to the certified <br />report following completion of the project. <br />Seneca Coal Company • P.O. Box 670 • Hayden, Colorado 81639 <br />Telephone (970) 276-5219 9 FAX (970) 276-5222 <br />o <br />w