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<br />2 <br />Based on the small percentage of spoil with unsuitable characteristics, published studies of <br />spoil mixing, and results of regraded spoil sampling at the Seneca II Mine, it is reasonable <br />to expect that iterns 2,3, and 4 above will be ameliorated by mixing and dilution during <br />dragline handling, backfilling and grading. However, there is a reasonable likelihood that <br />acid or potentially acid forming spoil could end up at the surface of the reclaimed Wolf <br />Creek pit in isolated locations. <br />SCC proposes to sample some regraded spoil material on a 500 foot grid offset at 60 <br />degrees prior to topsoil replacement, for pH, particle size, acid-base potential, boron, and <br />saturation percent. Any areas with unsuitable characteristics will be ripped, treated <br />chemically, or covered with four feet of topsoil, depending on the problem. <br />Please forward the following adequacy questions to the applicant: <br />(They overlap between Tabs 6 and 21. I'll let you figure out where to insert them inyour <br />letter.) <br />1. in Tabs 6 and 21, SCC proposes to sample regraded spoil at the Wadge Pit where <br />the overburden is greater than sixty feet thick. How will this area be identified on the <br />ground following back£lling and grading? Due to the narrow and irregular shape of the pits <br />in the neck and north end of the mine, it would appear sampling all regarded spoil in those <br />areas may be necessary to detect potentially unsuitable spoil from the Lennox seam and <br />associated shales. Please explain how areas to be sampled will be identified or revise this <br />proposal. <br />2. Table 5 in Tab 21 contains suitability criteria for overburden, underburden, <br />and regraded spoils. There appear to be discrepancies between three of the criteria in this <br />table and guidelines currently available from other Rocky Mountain states and the USDI- <br />OSM. In the absence of published criteria for Colorado, the Division recommends general <br />adherence to criteria established in these publications. Three publications relevant to pH, <br />Se, and Mo criteria are, <br />a. Montana Department of State Lands Reclamation Division, 1994, Soil, <br />Overburden and Regraded Spoil Guidelines, 32p. <br />