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Ongoing stream monitoring points include YSGF5 and YSG5 within the Grassy Creek watershed <br />and YSSF3 and YSS2 within the Sage Creek watershed. YSGF5 is located downstream of <br />Outfall 011 but upstream of Scotchmans Gulch. Monitoring point YSG5 is located downstream <br />of Scotchmans Gulch and receives drainage from both Outfall 010 and 011. Monitoring at YSG5 <br />did not begin until after mining began in the watershed and therefore no background data is <br />available for this location. This portion of Grassy Creek also receives drainage from the adjacent <br />Sage Creek Mine. Sage Creek monitoring point YSSF3 is located upstream of Outfalls 012, 013, <br />and 014 and YSS2 is located downstream of Outfalls 012, 013, and 014. <br />Analytical results for the Grassy Creek (YSGF5, YSG5) and Sage Creek (YSSF3, YSS2) stream <br />points between 2014 — 2018 are included in Tables 1 — 4 of Attachment G. Table 5 (Attachment <br />G) provides a comparison of the pre -mine and post -mine total suspended solids (TSS) for these <br />locations. The range of TSS concentrations observed between 2014 — 2018 are lower than the <br />ranges observed prior to mining at Sage Creek YSSF3 and YSS2. Although Grassy Creek stream <br />point YSG5 does not have location specific baseline data the post mining TSS range does fall <br />within the pre -mine range observed upstream at Grassy Creek YSGF5. The post mining TSS <br />range at YSGF5 exceeds the pre -mine range. The post mine TSS range at YSGF5 is skewed by <br />the sample collected September 11, 2018. The 495 mg/L TSS in this sample was more than four <br />times greater than the TSS in any of other samples collected from 2014 — 2018 (n:18; range: 10 - <br />118 mg/L). The TSS measured at downstream point YSG5 during the same event was 36 mg/L. <br />Minimal flow was present at YSGF5 during this event (0.7 gpm) and the elevated TSS is likely <br />from the disturbance of sediment at the base of the channel during sample collection. If this <br />sample is excluded all remaining post mining TSS results fall within the pre -mine range. <br />Analytical results for the mines five NPDES outfalls for 2014 — 2018 are provided in Tables 6 — <br />10 of Attachment G. TSS was removed as a monitoring requirement from the outfalls when their <br />drainage status was changed to reclamation. Outfalls 010 and 011 were reclassified as <br />reclamation in November 2006 and Outfalls 012, 013, and 014 were reclassified to reclamation <br />in July 2010. Between 2014 and 2018 only 13 TSS samples were collected from the outfalls <br />(010: 4; 011: 1; 013: 8) and the TSS ranged from <0.5 - 12 mg/L. None of these samples <br />exhibited TSS above the pre -mine maximums measured in Grassy Creek and Sage Creek (Table <br />5). Table 11 (Attachment G) includes a summary of the five outfalls TSS analytical data during <br />the five years prior to the reclamation drainage status change. <br />The TSS at Outfall 010 during this time period ranged from <5 — 46 mg/L (mean: 8.9 mg/L) and <br />is less than the pre -mine concentrations observed at Grassy Creek point YSGF5 (range: 33.8 — <br />296 mg/L; mean: 33.8 mg/L). The TSS at Outfall 011 during this time period ranged from <5 — <br />38 mg/L (mean: 13.8 mg/L) and is less than the pre -mine concentrations observed at Grassy <br />Creek point YSGF5 (range: 33.8 — 296 mg/L; mean: 33.8 mg/L). The TSS measured at the three <br />outfalls that discharge to Sage Creek during the five years prior to being classified as reclamation <br />drainage ranged from <5 — 25 (mean: 8.6) at Outfall 012, <5 — 26 mg/L (mean: 8.5 mg/L) at <br />Outfall 013, and <5 — 170 mg/L (mean: 26.8 mg/L) at Outfall 014. The average TSS <br />SL-8 - 10 <br />