Environmental Assessment - Tennessee Valley Authority

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Table 3. SFI Scores for Selected Sport Fish Species in Watts Bar Reservoir, 2008 Fish Species 2008 Score 2008 Valleywide Average Black Basses 30 37 Black Crappie 33 31 Channel Catfish 26 34 Crappie 28 31 Largemouth Bass 40 35 Smallmouth Bass 26 31 Spotted Bass 40 33 Striped Bass 24 35 White Bass 36 40 White Crappie 31 33 Benthic Monitoring - Benthic macroinvertebrates (primarily insects and mollusks) are included in aquatic monitoring programs because of their importance to the aquatic food chain and because these species have limited capability of movement compared to fish, thereby serving as more site-specific indicators of aquatic community health. Sampling and data analysis that are indicative of good (and poor) water quality include total abundance of species (except those indicative of poor water quality) and proportions of samples with no organisms present. Areas sampled on Watts Bar Reservoir near the project site include the Tennessee River inflow station (TRM 600) and the transition station (TRM 560.8). Benthic scores were variable among sites, ranging from very poor to good, with the best scores occurring in the transition zone (Table 4). Table 4. Recent (2006-2010) Benthic Community Scores 1 Collected as Part of the Vital Signs Monitoring Program in Watts Bar Reservoir Station River Mile 2006 2007 2008 2009 2010 Forebay TRM 533.3 Poor Poor Poor Very Poor - Inflow Tennessee River TRM 600 Very Poor - Poor Fair - Inflow Clinch River Clinch River Mile 19, 21 Good - Fair, Good Good - Transition TRM 560.8 Fair - Fair Good - 1 Benthic Community Score 7-12 13-18 19-23 24-29 30-35 Community Condition Very Poor Poor Fair Good Excellent Mussels - A 1997 mussel (Family: Unionidae) survey conducted by TWRA (November 21, 1997, letter from McKinney [TWRA] to Brisson [TDOT]) at five locations immediately upand downstream of the project site documented 12 species of unionid mussels, including three individuals of the pink mucket pearlymussel (federally listed as endangered). Based on five 100-foot-long transects sampled near the project site in 1997 (TWRA), estimated mussel density in the area was 0.07 mussel per square foot (ft 2 ) (or 0.75 mussel per square meter) (USFWS 2011). Additionally, the invasive zebra mussel (Dreissena polymorpha) 12
was documented to have colonized much of the substrate and attached to many of the native mussel shells. No Action Alternative - Under the No Action Alternative, no changes to environmental conditions would occur; thus, no effects to the aquatic environment or water quality would occur. Action Alternative With Modification - Under the Action Alternative, TVA would approve, under Section 26a of the TVA Act, LUB to construct and operate a 20-MGD water intake at TRM 592.3L and a water line across the Tennessee River at TRM 591.6. Aquatic life could be directly and indirectly affected due to modification of the riverbed, riparian zone, and storm water runoff resulting from construction and maintenance activities on the project site. Potential impacts due to removal of streamside vegetation within the riparian zone include increased erosion and siltation, loss of instream habitat, and increased stream temperatures adjacent the bank. Other potential construction and maintenance impacts include alteration of stream banks from construction equipment and runoff of herbicides from vegetation control into streams. Excavation of a trench for the water lines and anchoring water lines on the surface of the riverbed would likely result in the permanent or long-term loss of existing habitat and would likely cause modification of the surrounding riverbed (particularly downstream) due to elevated levels of suspended sediment during construction, as well as altered flow patterns that could change physical characteristics of the riverbed. The introduction of riprap to stabilize modified banks and protect exposed water lines would cause loss or degradation of habitat for some species, but would also provide refuge and improve habitat for other species such as snails or species (fish and macroinvertebrates) that prefer rock crevices. Siltation has a detrimental effect on many aquatic animals adapted to riverine environments. Elevated suspended fine sediments can negatively impact respiration, feeding, and spawning of many fish species (Sutherland et al. 2002). Likewise, macroinvertebrates and mussel species adapted to a heterogeneous mixture of sediment particles can be impaired by changes in sediment. For example, concentrations of silt can clog gills and hinder intake of food. Scouring of finer sediments can result in compacted substrate that prevents burrowing and colonization of macroinvertebrates and mussels. Changes to the habitat that affect fish community composition, particularly benthic (bottomdwelling) species, may also affect mussel reproduction that relies on specific fish hosts to complete their life cycle. In addition to the mitigative measures proposed by the applicant in the BA, the applicant would also comply with the reasonable and prudent measures (and supporting terms and conditions) outlined in the BO (USFWS 2011). Some loss or changes to the aquatic community are expected. The USFWS BO describes an area of 23,905 ft 2 (or 0.55 acre) that would be directly impacted by trenching/excavation and water lines. An estimated 6.36 million ft 2 (or 146 acres) could be affected indirectly by changes in substrate composition or water quality including the entire river width below the normal winter pool level from TRM 591.1 upstream to TRM 592.3 (USFWS 2011). However, in addition to any standard construction BMPs, the applicant would implement “special conditions” (mitigative measures) to minimize or reduce the environmental effects of the proposed project to federally listed aquatic species (CCR Environmental 2011), which would also benefit other nonlisted aquatic animals. Given the environmental protective 13
Page 1 and 2: Document Type: EA-Administrative Re
Page 3 and 4: FINAL ENVIRONMENTAL ASSESSMENT LOUD
Page 5 and 6: Figure 1. Map of Vicinity and Propo
Page 7 and 8: Resources that could be affected by
Page 9 and 10: No Action Alternative - Under the N
Page 11 and 12: No Action Alternative - Under the N
Page 13: indicators: (1) DO; (2) chlorophyll
Page 17 and 18: The proposed intake would be locate
Page 19 and 20: to an upland location, provided the
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Environmental Assessment - Tennessee Valley Authority

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