2021-10-13_REVISION - C1980007 (19)

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cover of noxious weeds. Observations made during the SL-13 inspection(as well as regular monthly inspections) accord with the sampling data, although it is noted that control of noxious weeds should continue so as to ensure that dense patches(of particularly Cirsium arvense, Canada Thistle and Cynoglossum ofcinale, Houndstongue)do not become established. The contribution of suspended solids to streamflow outside the permit area was evaluated for pre-mining and post-mining conditions using the Revised Universal Soil Loss Equation(RUSLE): A = RxKxLSxCxP Where: A = predicted soil loss (tons/acre/year) R = erosivity index of local rainfall K = soil erodibility factor LS = length/slope factor C = vegetative cover factor P = management practice factor It was assumed that factors R, K, LS, and P were unchanged. No consideration of soil compaction was included in the estimation of K,however given the time since reclamation(6-11 years)took place natural settlement and compaction will have occurred, so the assumption is acceptable. No consideration was given to management practices in P, (although increased surface roughness was included in the estimation of C—see below). Based on the assumptions made,the difference in the calculated value of predicted soil loss,A,was solely due to differences in the vegetative cover factor, C. The value for C was determined from seven sub-factors: canopy cover,rock cover, litter cover, fall height, effective root mass,roughness, and land use. Of these,two were unchanged(fall height and land use) and a third(effective root mass)was calculated as a function of canopy cover. The roughness index was estimated to have increased from 0.8 to 1.1,based on site observations made by Cedar Creek Associates. The three cover sub-factors for post- mining conditions were taken from the vegetation sampling conducted for SL-13; for pre-mining conditions they were taken from baseline vegetation data included in section 2.4.10 of the PAP. The pre-mining cover data used in the sedimentology evaluation(40.50%total vegetative cover) is different from that used to assess revegetation success(53.04%total vegetative cover), however since the SL-13 sampling showed that post-mining total vegetative cover exceeded both of these values (55.68%), it is valid to conclude that the reclaimed parcels in Table I do not contribute more suspended solids to streamflow than they did before they were disturbed for mining. Summary and Conclusions Based upon a review of the mine permit,the applicant's bond release application, and site inspections, the Division finds that Mountain Coal Company, LLC has replaced topsoil in accordance with the approved reclamation plan. Mountain Coal Company,LLC has established vegetation which supports the approved post mine land use and meets the approved success standard for vegetative cover. The C-1980-007 Page 8 of 11