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• i ~ • 7 Cotter Response • a. Referring to Section 6.0 in Appendix E-4, the waste dump does not represent a source of contamination for Ralston Creek. The results of Cotter's study of this MLRB concern were presented to MLRB repre- sentatives during a June 23, 1983, meeting. Accordingly, the pre- vention of infiltration using a clay cover is not necessary. b. The placement of a permanent topsoil cover on the side slopes of the waste dumps is not considered feasible. Operating the equipment necessary to dump and spread the topsoil is not a major concern; however, in order to have a finished, compacted topsoil depth of six inches, a significantly larger volume of soil (i.e., larger than that required for six inches) must be delivered to the site to overcome soil losses through the large pore spaces and the side slopes ~~f the waste material. In addition, relatively high soil losses due to run- off on the side slopes is another concern with regard to the l~>ng term presence and benefits of topsoiled side slopes. Referring to Section 6.0 in Appendix E-4, the waste dumps do not represent ~i source of contamination for Ralston Creek. Also, it should be noted that only about 9 acres of exposed rock material will remain following reclamation. This represents only 0.03`/ of the Ralson Creek w<<ter- shed, or about 1.4 of the land owned by Cotter's parent compar~y. In addition, the watershed is characterized by many soil types and terrain configurations, including talus and outcrops of varyine rock types. • c. Please see Cotter's response to MLRB/McArdle comment E.6.a and Pendleton Comment =1. McArdle Comment E.8 "Please provide the staff with a detailed description of the energy dissipation structures to be placed on top of the waste dumps where naturally occurring drainage channels join the waste dump. Please show their placement on an appropriately detailed map." Cotter Response Please see Section 7.0 in Appendix E-4. McArdle Comment E.10 "Please describe in greater detail how the ventilation shafts will tie sealed with a concrete plug." Cotter Response Please see Figure E-1.