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Between 2014 and 2018 total recoverable iron ranged from 0.49 — 9.09 mg/L (mean: 1.96 mg/L) <br /> at YSGF5 and 0.29 —2.53 mg/L (mean: 0.99 mg/L) at YSG5. Total recoverable iron exceeded <br /> the Yampa Segment 13j water quality standard six times (n: 15) at YSG5 during this time (Table <br /> 2). YSG5 receives drainage from both Outfalls 010 and 011. Total recoverable iron was <br /> monitored 60 times at outfall 010 and 12 times at outfall 011 between 2014 and 2018. During <br /> this time there was not a single exceedance of the 1 mg/L total recoverable iron water quality <br /> standard at either of these outfalls (Table 6 and Table 7). Although the total recoverable iron in <br /> the YSGF5 2014—2018 samples is more elevated than the iron observed at YSG5,the YSGF5 <br /> post mine concentrations fall within the range of total iron observed during the pre-mine <br /> monitoring period (range: 0.15 — 9.9 mg/L; mean 1.34 mg/L) (Table 14). Total recoverable iron <br /> at these stream points are strongly correlated(r2: 0.65 —0.91)with suspended solids which <br /> become naturally elevated during rain and snow melt runoff events (see Figure 1). Over the last <br /> five years there have been eight concurrent monitoring events: six events when samples were <br /> collected from Outfall 010, Outfall 011,YSG5 and YSGF5 on the same day and two events <br /> when samples were collected from at least three of these locations on the same day (Table 15). In <br /> all eight instances the total recoverable iron concentrations in the outfall discharges were lower <br /> than the concentrations observed at the stream points. During the five events when there were <br /> exceedances of the water quality standard at the stream points the total recoverable iron at the <br /> outfalls were at least an order of magnitude lower. This further demonstrates that the elevated <br /> iron in Grassy Creek is unrelated to the runoff from the reclaimed mine and is likely the result of <br /> natural erosional processes that are occurring within the unmined portions of the watershed. <br /> Ammonia, Nitrogen <br /> The Yampa Segment 13i ammonia, nitrogen water quality standard was exceeded once at YSG5 <br /> between 2013 and 2018. The aquatic life ammonia standard, as established by USEPA, is <br /> dependent on both the pH and temperature of the surface water body. The ammonia in the <br /> sample (0.07 mg/L) was compared to the temperature and pH dependent values of the chronic <br /> criterion found in Table 6 of USEPA's 2013 Aquatic Life Ambient Water Quality Criteria for <br /> Ammonia—Freshwater(USEPA 2013). The measured value was two orders of magnitude less <br /> than the chronic aquatic life criteria value (1.4 mg/L). <br /> Sulfide <br /> SL-7 - 36 <br />