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Cotter Response <br />• a. Referring to Section 6.0 in Appendix E-4, the waste dump does not <br />represent a source of contamination for Ralston Creek. The results <br />of Cotter's study of this MLRB concern were presented to MLRB repre- <br />sentatives during a June 23, 1983, meeting. Accordingly, the pre- <br />vention of infiltration using a clay cover is not necessary. <br />b. The placement of a permanent topsoil cover on the side slopes of the <br />waste dumps is not considered feasible. Operating the equipment <br />necessary to dump and spread the topsoil is not a major concern; <br />however, in order to have a finished, compacted topsoil depth cf six <br />inches, a significantly larger volume of soil (i.e., larger than that <br />required for six inches) must be delivered to the site to overcome <br />soil losses through the large pore spaces and the side slopes of the <br />waste material. In addition, relatively high soil losses due 1;o run- <br />off on the side slopes is another concern with regard to the long <br />term presence and benefits of topsoiled side slopes. Referring to <br />Section 6.0 in Appendix E-4, the waste dumps do not represent a <br />source of contamination for Ralston Creek. Also, it should be noted <br />that only about 9 acres of exposed rock material will remain fo]lowin9 <br />reclamation. This represents only 0.03" of the Ralson Creek w,ster- <br />shed, or about 1.4;~ of the land owned by Cotter's parent company. <br />In addition, the watershed is characterized by many soil types and <br />terrain configurations, including talus and outcrops of varying rock <br />types. <br />c. Please see Cotter's response to MLRB/hlcArdle comment E.6.a and <br />Pendleton Comment ;1. <br />McArdle Comment E.8 <br />"Please provide the staff with a detailed description of the energy <br />dissipation structures to be placed on top of the waste dumps where <br />naturally occurring drainage channels join the waste dump. Pleasf~ show <br />their placement on an appropriately detailed map." <br />Cotter Response <br />Please see Section 7.0 in Appendix E-4. <br />McArdle Comment E.10 <br />"Please describe in greater detail how the ventilation shafts will be <br />sealed with a concrete plug." <br />Cotter Response <br />Please see Figure E-l. <br />• <br />