2012-09-10_REVISION - C1980005 - Laserfiche WebLink

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The observations during the on- the - ground inspection and the quantitative data indicate a relatively diverse vegetative cover of perennial species and life forms supportive of the rangeland /wildlife habitat postmining land use. Sedimentolo2y The Seneca II Mine is located within the Fish Creek drainage basin. The permit area is principally drained by minor tributaries of Fish Creek. Surface water runoff and sediment control consists of the construction and maintenance of sedimentation pond 008 and permanent established postmine drainage channels SIIPM -8, SIIPM -13, and SIIPM-13A. The sedimentation pond associated with the SL -05 bond release request is Pond 008, which has been approved as a permanent impoundment. Pond 008 was approved as permanent in 2006 under Technical Revision No. 37. Pond 008 is within BRB -4, for which the Division is proposing to approve Phase II Bond Release. The outlet of Pond 008 is designated as an NPDES discharge point. Runoff from all disturbed areas for which the Division proposes to approve Phase II bond release passes through this NPDES discharge point prior to exiting the permit area. In Attachment F of the bond release document, SCC submitted pond discharge sample data for Pond 008 as well as receiving stream sample data from monitoring points upstream and downstream of the pond outfalls. The pond outfall data indicate that total suspended solids (TSS) contributions do not exceed the limits set forth by the Colorado Department of Public Health and Environment. Monitoring data of the upstream and downstream receiving stream sites indicate that TSS is reduced from the upstream site at the downstream site. In addition to the pond effluent sample data submitted by SCC, the Division requested annual sediment level data from Seneca Coal Company for Pond 008 (Table 1). The data show that sediment levels in the pond have stabilized since revegetation activities began in 2003. The pond has never required cleaning and has never been dredged. Table 3 — Sediment Data Provided by Seneca Coal Company Sediment Trends (ac -ft gained /lost by year) Pond ID 2005 2006 2008 2010 008 0.0 -0.1 -0.1 + -0.2 The Division also independently completed a Revised Universal Soil Loss Equation (RUSLE) calculation comparing the reclaimed areas to the adjacent undisturbed areas. The Division's calculation was based on data in the permit application package for climate, soil types and Seneca II Mine Page 10 September 10, 2012 Phase 11 Bond Release