2020-12-12_REVISION - C1981010 - Laserfiche WebLink

Home Browse Search

Table 6 cont. SEDCAD Variables and Basis for Selection Postmining Parameter Trapper's Trapper's basis for selection Division's Comment Selection Produces the minimum 0.5 inch Design 2.75 inches of runoff necessary to Event in 24 hours maintaining program accuracy Same event as used in preming model (SL22 application Sec 1.4.2). 61 AMC Trappers selected cover, soil CN II, 78.8 group, hydrologic conditions Reasonable as per selections of cover, soil group, hydrologic conditions and C factor. AMC III and CP factor(see below). Pasture, Grassland & Rangeland Postmining land use Reasonable as per postmining land use. "Good" hydrologic None Reasonable as per"Good" in SCS TR55 for condition other lands corresponding to Hydrologic soil group Permit application,Appendix Q classification "B" Section XII SEDCAD 4 table for permanent Cover values and treatment practices CP Factor: 0.014 pasture & rangeland indicate reasonable selection of this variable Based on Trapper's SEDCAD 4 modeling using baseline data, the Division finds that the lands proposed for Phase II bond release are not contributing suspended solids to streamflow or runoff outside the permit area in excess of premining levels. DRMS approves the SEDCAD evaluation of sediment production and yield as demonstrated by TMI with Phase H bond release of the SL22 parcels. Summary and Conclusions Based upon a review of the mine permit,the applicant's bond release application, the 13 October 2020 bond release inspection and other prior site inspections, the Division finds that Trapper Mining, Inc. has replaced topsoil in accordance with the approved reclamation plan. Trapper Mining, Inc. has established vegetation which supports the approved post-mine land use and meets the approved success standards. The Division finds that the reclaimed area subject to this bond release is not contributing suspended solids to streamflow or runoff outside the permit area in excess of pre- mining levels. V. PROPOSED DECISION Based on the above observations, the Division proposes to approve Trapper Mining, Inc.'s request for a partial Phase II bond release block. This proposed decision will release the applicant from Phase II reclamation liability for those SL22 bond release parcels totaling 175.0 acres as shown above, in Table 2. Permit Number C1981010 SL22 Page 16 of 18