Environmental Assessment - Tennessee Valley Authority

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No Action Alternative - The water intake and pipeline would not be installed; consequently, there would be no impacts to navigation. Action Alternative With Modification - The TVA navigation guideline for submarine pipeline crossings in commercial navigation channels on mainstream rivers is that the top elevation of the pipe or anchors should not be less than 3 feet below channel bottom grade. Channel bottom grade in the area is 724 feet. The original plans provided by LUB did not meet TVA navigation guidelines for installing water intakes. Minor design changes were required to lower the elevation of the main run of the pipeline (see Attachment E). The top of the buried pipeline and anchors would emerge from the bank below elevation 721 feet above msl and extend out along the river bottom perpendicular to the shoreline. At the end of the pipeline, the top of the intake screens are proposed to be at elevation 720.83 feet above msl, or 3.17 feet below channel bottom grade. The proposed action meets the minimum depth requirements. Additionally, shoreline warning signage indicating the presence of submerged pipelines should be clearly visible and legible from the water. Due to the amount of commercial and recreational activity in this area, timely communication of in-water work activities and schedules is imperative to reduce impacts to navigation. All in-water work activities and schedules should be coordinated with the USACE Nashville District for inclusion in a Notice to Navigation Interests as soon as the information is available. LUB should follow USACE’s guidance to minimize impacts from potential navigational situations during construction of the facilities, such as potential delays or rerouting during construction. Therefore, with the Section 26a Permit contingent upon the special conditions described in the Mitigation section, any impacts to navigation would be temporary and minor. Aquatic Ecology and Water Quality The Tennessee River has been impounded at numerous locations, including Fort Loudoun Dam that occurs upstream of the proposed project and Watts Bar Dam downstream. Sedimentation from agricultural practices, residential, commercial, and industrial development in the Watts Bar watershed has adversely impacted the aquatic habitat in the area. TDEC has the project area listed on the state’s Clean Water Act Section 303(d) list as impaired due to contaminated sediments from polychlorinated biphenyls (PCBs) and low dissolved oxygen (DO) from releases at Fort Loudoun Dam (TDEC 2008). Watts Bar Reservoir also has a fish consumption advisory for numerous species due to PCBs. The construction of a new raw water intake structure and piping would affect an area of riverbed approximately 500 feet long and 9.5 feet wide from installation of a 48-inch pipe and water from the water column withdrawn through five 27-inch intake screens at TRM 592.3L. The construction of a 1,300-foot-long 24-inch-diameter water line entrenched in the riverbed across the Tennessee River at TRM 591.6, within 100 feet upstream of the US 11 bridge, would affect approximately 1,000 feet of the riverbed within a path of up to 6 feet wide. An additional 50 feet downstream from each structure is expected to be influenced by indirect effects such as sedimentation and changes in hydrology. Substrate within the project area is predominately sand, gravel, and cobble occurring in the “transition zone” of Watts Bar Reservoir. Various habitats within Watts Bar Reservoir (and others throughout the TVA system) are routinely evaluated using TVA’s Ecological Health Monitoring Program to monitor reservoir health. The program provides data for comparing future water quality conditions, and serves as a screening program for targeting more detailed studies if the need arises. The ecological health scoring system is based on five 10
indicators: (1) DO; (2) chlorophyll, a measure of the amount of algae in the water; (3) sediment contaminants–PCBs, pesticides, and metals; (4) benthic macroinvertebrates; and (5) fish assemblage. Each indicator is evaluated separately, and then individual ratings are combined into a single, composite score for each reservoir. Reservoir Ecological Health Monitoring is one of five components of TVA’s overall river and reservoir monitoring effort, termed Vital Signs Monitoring. Other components of the monitoring program include: (1) examining ecological conditions in tributary streams to the Tennessee River; (2) monitoring toxic contaminants in fish flesh to determine their suitability for consumption; (3) evaluating the number and size of important game fish species to help ensure their populations remain abundant and robust; and (4) sampling bacteriological concentrations at recreational areas to evaluate their suitability for water contact with people. Fisheries Monitoring - Fish are included in Vital Signs Monitoring because they are important to the aquatic food chain and because they have a long life cycle that allows them to reflect water quality conditions over time. Fish are also important to the public for aesthetic, recreational, and commercial reasons. Ratings are based primarily on fish community structure and function using a metric known as the Reservoir Fish Assemblage Index (RFAI). Also considered in the rating is the percentage of the sample represented by omnivores and insectivores, overall number of fish collected, and the occurrence of fish with anomalies such as diseases, lesions, parasites, deformities, etc. (TVA 1999). Watts Bar Reservoir has been monitored on an annual basis from 2006 to 2010. Over the past five years, it has rated “good” or “fair” at all sites (Table 2). Table 2. Recent (2006-2010) RFAI Scores 1 on Watts Bar Reservoir Collected as Part of the Vital Signs Monitoring Program Station River Mile 2006 2007 2008 2009 2010 Forebay TRM 531 Good Fair Fair Good Good Inflow Tennessee River TRM 601 Good - Good Good Good Inflow Clinch River Clinch River Mile 22 Good - Good Good Good Transition TRM 560.8 Good - Fair Fair Good 1 RFAI Score 12-21 22-31 32-40 41-50 51-60 Community Condition Very Poor Poor Fair Good Excellent A Sport Fishing Index (SFI) has been developed to measure sport fishing quality for various species in Tennessee and Cumberland Valley reservoirs. The SFI is based on the results of fish population sampling by TVA and state resources agencies and, when available, results of angler success as measured by state resource agencies (i.e., bass tournament results and creel surveys). In 2008, Watts Bar Reservoir rated above the Valleywide average for black crappie, largemouth bass, and spotted bass and lower than the Valleywide average for the other sport fish species monitored (Table 3). 11
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Page 15 and 16: was documented to have colonized mu
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Environmental Assessment - Tennessee Valley Authority

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