2020-06-08_REVISION - C1982057 (20)

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TSS ranged from 214—14000 mg/L. TSS concentrations at the two outfalls in the Sage Creek Watershed (009 and 015)were similarly low with the average TSS ranging from 7.7—9.4 mg/L and the maximum concentrations ranging from 12—30 mg/L.These are comparable to the pre-mine average (7 mg/L) and maximum (24 mg/L)TSS concentrations measured at WSSF3.This indicates that the reclaimed parcels reporting to these ponds are adequately stable. As noted above the post mine TSS concentrations measured between 2015—2019 at stream point WSH7 (range: 6—475 mg/L; mean: 115 mg/L) are greater than the pre-mine concentrations (range: 6— 214 mg/L; mean: 73 mg/L). WSH7 is located downstream of Outfalls 016 and 017 but upstream of Outfall 006.The average (5.3 mg/L) and maximum (6 mg/L)TSS in the samples collected at Outfall 016 and 017 between 2015—2019 are two orders of magnitude less than the pre-mine average and maximum TSS concentrations at WSH7. Similarly the average and maximum TSS concentrations measured at Outfalls 016 (mean: 6.4 mg/L; max: 14 mg/L) and 017 (mean: 7.6 mg/L; max: 36 mg/L) during the five years prior to their status change to reclamation (June 2005—May 2010) were one to two orders of magnitude lower than the average and maximum TSS measured at WSH7 (mean: 130.4 mg/L; max: 340 mg/L) during the same time period.Table 15 summarizes TSS results from watershed monitoring events when Outfall 016, 017, and WSH7 were all monitored on the same date. Fourteen concurrent monitoring events occurred between September 2003 and July 2019. In 13 of the 14 events the TSS concentrations measured at the Outfalls were one to two orders of magnitude lower than the concentrations measured at WSH7. Furthermore, none of the effluent TSS concentrations exceeded the WSH7 pre-mine concentrations.This further demonstrate that the reclaimed mine parcels are stable and that the elevated post mine TSS concentrations at WSH7 are unrelated to runoff from the reclaimed mine site.