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Response to CDRMS Comments Mr. Robert Noren, P.E. <br /> Disposal of Alluvial Fill Cotter Corporation(N.S.L.) <br /> Seeding: The USDA (2005) states that "...drill seeding is generally limited to slopes less <br /> than 3:1. " Thus, we do not recommend drill seeding due this recommendation along with <br /> safety concerns related to placing seeding equipment on a 2H:1 V slope. In addition, direct <br /> seeding requires a vertical alignment of the seeder for placement due to the steep nature of <br /> the slope and vertically aligning the vegetation can lead to increased surface water flow. We <br /> instead recommend broadcast seeding followed by hydromulching. Hydroseeding is not <br /> recommended as it is not typically successful in our and climate. <br /> Mulching: For 2H:1 V and steeper slopes, mulch is necessary to keep the seed and topsoil in <br /> place. Mulch can also provide shade to the seedlings and help the soil to retain moisture. We <br /> recommend Hydromulching with addition of a tackifier. Tackifier is a botanical glue that <br /> can also be applied to the slope to prevent erosion. The hydromulch and tackifier should <br /> effectively stabilize the surface of the slope. For example, a publication by Munshower titled <br /> "Practical Handbook of Disturbed Land Revegetation", states that "...the slopes were capped <br /> with oxidized rock, topsoiled, pitted with large depressions, broadcast seeded, and <br /> hydromulched with a tackifier. In the second growing season the slopes had remained stable <br /> and erosion was controlled. " <br /> Soil Amendments: Soil amendments may be required to improve the performance of the <br /> vegetation. This could include composted biosolids or manufactured amendments such as <br /> Biosol. <br /> 2. Adequacy Review #1, Comment # 18: "Appendix D addresses terracing of the WRPs. <br /> Cotter's response to Comment No. 4 is contained within Section 7.2 of Appendix E-4. The <br /> recommendations within Section 7.2 state a 10 foot wide terrace would be included in the <br /> WRP construction. Please clarify how many terraces will be constructed on the expanded <br /> WRPs. Also, provide the Division with cross sections showing the terraces on the WRPs or <br /> speck where these documents may be found in the permit file. " <br /> Response: Section 7.2 of Appendix E-4 (McDermid and Geo-Hydro, 1983) recommends a <br /> 10-foot wide terrace to provide an additional factor of safety against slope failure. However, <br /> the results of the slope stability analyses presented in the 1983 Cotter Corporation Mine <br /> Permit Revision (Cotter, 1983)showed that terraces were not required for stability purposes. <br /> EA collected soil samples from the north and south waste rock piles, additional alluvial waste <br /> rock source (new waste rock), topsoil source, and colluvium for strength testing to be used in <br /> stability analyses. The complete results of the field investigation and laboratory testing are <br /> provided in Attachment A. The locations of the test pits are presented on Figure A-1 and a <br /> summary of the laboratory testing is provided in Table A-1. Slope stability analyses were <br /> performed for the waste rock piles using the laboratory obtained strength values and <br /> published strength values for the underlying bedrock. <br /> EA recommends using benches in reclamation of the waste rock piles. The benching is <br /> needed to provide access to the reclaimed waste rock piles and will also be utilized for <br /> surface water conveyance structures and erosion control. The benching follows the roads that <br /> are currently at the site as shown on Figure B-2 of Attachment B. <br /> October 26, 2016 2 Engineering Analytics, Inc. <br />