2012-07-02_REVISION - C2009087 - Laserfiche WebLink

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C. Suspended Solids Demonstration In accordance with Section III.A.7.a. of the Division's 1995 "Guideline Regarding Selected Coal Mine Bond Release Issues ", SCC submitted pond discharge sample data for the Pecoco, Wadge, and 004 ponds, which receive discharge from the proposed release area. The pond outfall data for the period of January 1, 2006 to December 31, 2010 indicate that total suspended solids (TSS) contributions do not exceed the limits set forth by the Colorado Department of Public Health and Environment. The sediment ponds receiving runoff from the proposed release area have been approved as permanent ponds; the operator demonstrated that the quantity and quality of impounded water is appropriate for its intended use, water rights will not be adversely affected, safe access to the impounded water has been provided, and the pond is appropriate for the post - mining land use. In addition to the pond effluent sample data submitted by SCC, the Division requested annual sediment level data from Seneca Coal Company (Table 2) for the ponds. The data for Pond 004 show that sediment levels in the pond have stabilized since revegetation activities began in 2003. Detailed data for the Pecoco and Wadge impoundments was not available due to surveying errors. None of the three sediment ponds treating runoff from the reclaimed area have required cleaning or been cleaned since reclamation activities were completed. Table 2 — Sediment Data Provided by Seneca Coal Company Sediment Trends (ac -ft gained /lost by year) Pond ID 2005 2006 2008 2010 004 0.0 O.l -0.1 0.0 The Division also independently completed a Revised Universal Soil Loss Equation ( RUSLE) calculation comparing the reclaimed areas to the adjacent unmined areas. The Division's calculation was based on data in the permit application package for climate, soil types and control/practice factors; slope measurements from the existing topography maps submitted annually by SCC; and vegetation monitoring data from the SL -1 application for the Phase H bond release and Extended Reference areas. Several slopes in the reclamation area were individually modeled and then averaged and compared to the arithmetic and weighted average of the extended reference areas. The calculations, presented in Table 3, indicate that sediment delivery from the mined areas is within the range of the arithmetic and weighted averages for the unmined areas. Table 3 — Division's RUSLE Calculations Area* I A R I K LS C P