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CJ <br />1 <br /> <br />IJ <br /> <br />IJ <br />i <br /> <br /> <br /> <br /> <br />lJ <br /> <br /> <br /> <br /> <br />1 <br /> <br />stockpile locations for the entire site on the appropriate figures. <br />Response: Figure C-2 (formerly Figure C-I) has been revised to show all <br />topsoil stockpile locations. Note the change in the original <br />topsoil stockpile to waste rock disposal area with topsoil <br />stockpiled on the top bench. <br />Figure C-2 has been revised 2/15f89. <br />64. Consolidated rock areas, as those expected to be found in portions of <br />the east and the west pits, will require more than 8 to 12 inches of <br />plant growth medium replacement. Pant roots require greater depths of <br />moisture- and nutrient-holding material for successful vegetation <br />establishment and maintained growth, similar to the vegetative stands <br />currently inhabiting the project area. Soil Conservation Service (SCS) <br />Soil survey descriptions often describe plant roof depths which exceed <br />60 inches. Similarly, coarse rock fragments, expected to be encountered <br />in the east pit backfilTed areas and the waste rock dumps, will require <br />more than 8 to 12 inches of plant growth medium replacement. The coarse <br />rock fragments generally provide no moisture- or nutrient-holding <br />capacity, essential plant growth media requirements for plant <br />establishment and continued growth. Cook, Hyde, and Sims, 1974, specify <br />that in Sagebrush Foothil)) Vegetation Types receiving between 12 and <br />15 inches of annual precipitation, "it is advisable to save the top 10 <br />to 12 inches of (top)soil to be added back over the overburden materia] <br />to be revegetated. Suitable subsoil beneath the added topsoi] should, <br />in a71 cases, provide at least 18 inches or more of material for a <br />plant growth medium. This depth is desirable because root <br />concentrations of seeded grasses wil] extend to this depth and soil <br />moisture capacity wi)1 penetrate to this depth each spring following <br />the precipitation received as fall and winter snows." Therefore, 'we <br />recommend that an additional 2 to 3 feet of subsoil material be <br />replaced on the waste rock facilities prior to replacement of the <br />topsoi]. Please commit to this. <br />Response: Dr. Sam Bamberg, soils and vegetation consultant for the :San Luis <br />Project, has many years of experience in mine site reclamation. <br />In addition, Dr. Bamberg conducted his doctorate research on <br />plant soil substrates. Based on his experience, Dr. Bamberg <br />believes that the reclamation can be successfully accomplished <br />at the site without placement of an additional 2 to 3 feet of <br />subsoil material on the waste rock facilities. The clay fines <br />that will be generated in break down of the waste rock will <br />provide far better moisture and nutrient holding capacities than <br />the predominantly sandy subsoils found at the San Luis Project. <br />In addition, for the proposed reclamation of the waste rock <br />disposal areas to grassland the average rooting depth of the <br />proposed species is 12 to 15 inches. Sufficient rooting depth <br />will be available based on the current reclamation plan to allow <br />development of these species. <br />Dr. Bamberg has contacted Dr. Cook, whose writings are quoted in <br />the comment, to discuss Dr. Cook's experience with mine <br />reclamation in general and the site characteristics of the San <br /> <br />