2020-10-27_PERMIT FILE - C1981035 (20)

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Biological Assessment Federal Coal Lease Modification(COC-62920)and Federal Mine Permit(CO-0106A)Revision and Renewal Measured concentrations of mercury in MRG fish tissue ranged from 0.012 to 0.093 mg/kg wet weight(NMED 2008). When compared to concentrations detected from the 1997-98 BEST study, mercury showed decreases in concentrations in the MRG over time. In addition, these baseline Hg concentrations do not exceed adult fish body burden benchmarks of 0.20 mg/kg wet weight(Beckvar et al. 2005 as cited in USFWS 2014) and 0.8 mg/kg wet weight(AECOM 2013 as cited in USFWS 2014). These adult fish body burden benchmarks are intended to represent tissue burdens below which adverse effects in fish are unlikely (USFWS 2014). The average adult body burden for mercury for the Rio Grande silvery minnow is about 0.05 µg/g wet weight mercury (Lusk et al. 2012). The Tij eras plant mercury emissions would not likely increase those average concentrations above the 0.2 µg/g wet weight that is intended to be indicative of potential fish injury (Beckvar et al. 2005). Numerous studies have shown that within a species the older and larger fish have higher concentrations of mercury than younger and smaller fish(Huckabee et al 1979; Eisler 1987). In addition, studies suggest that predatory fish tend to have higher mercury levels than omnivorous or herbivorous species (ATSDR 1999; Eisler 1987). Hence, the likelihood of bioaccumulation of mercury in silvery minnow is further limited by their small size and short life span, and that they are non-piscivorous. Therefore, the determination of effect for the Proposed Action is may affect, not likely to adversely affect the Rio Grande silvery minnow. There would be no impacts to critical habitat constituent elements for the Rio Grande silvery minnow in the Rio Grande due to coal combustion from the Tij eras cement plant. Constituent elements of critical habitat for this species pertain to hydrologic flow, the seasonality of flow, water temperature, and substrate materials. Small releases of mercury via cement plant emissions 15 miles to the east would not change any these constituent elements; consequently, there would be no impacts to designated critical habitat of the Rio Grande silvery minnow. 6.2.2 Greenback Cutthroat Trout The Western Airborne Contaminants Assessment Project was completed by the National Park Service in 2008 (Landers et al. 2008). From 2002 to 2007, researchers analyzed the concentrations and biological effects of airborne contaminants in air, snow, water, sediments, lichens, pine needles, and fish in eight national parks, including Rocky Mountain National Park in Colorado. The study found that mercury levels in fish samples were low, although mercury levels increased with increasing age of fish. Poorly developed testes and or intersex trout were found in five of the nine lakes tested, indicating that endocrine and reproductive disruption was occurring (Landers et al. 2008). As part of this study, a sample from a male greenback cutthroat trout collected in Twin Lakes in the 1800s was also examined and found to be an intersex fish, showing that this is not a new phenomenon and likely does not pose a significant threat to greenback recovery. July 2017 32