2004 Environmental Performance Update
On May 19, 2004, the TVA Board of Directors approved a new policy for operating the Tennessee River and reservoir system. This policy, which took effect on June 1, 2004, is the result of TVA’s Reservoir Operations Study (ROS), a comprehensive review of how TVA operates 35 of the 49 dams and reservoirs in the river system. The TVA Board approved the policy alternative that reduces environmental impacts and best matches the objectives identified by the public at the outset of the study.
To ensure compliance with the operating criteria established by the ROS, a new environmental indicator was developed to track how well TVA: (1) meets the schedule for capital improvements to aeration systems, designed to ensure that dissolved-oxygen targets for tailwaters continue to be met despite increased reservoir retention times resulting from the ROS; (2) achieves weekly flow requirements at Chickamauga Dam, which were established to restrict the drawdown at upstream reservoirs from June 1 through Labor Day while reducing the impacts to aquatic habitat, hydropower generation, and thermal compliance; (3) balances the drawdown of the tributary reservoirs when additional flow is required to meet downstream flow commitments from June 1 through Labor Day; (4) meets all new tailwater recreation commitments, established to sustain higher recreation potential on selected tailwaters; and (5) meets the different schedules for completing 27 monitoring and study tasks specified as part of the ROS.
Since its inception in April of 2000, both residential and business demand for Green Power Switch blocks has increased substantially, reaching 22,372 blocks by the end of TVA’s fiscal year 2004. A block represents 150 kilowatt-hours at a cost of $4. Strong demand for green power from both these sectors is encouraging, with demand from the business sector exceeding the national average. See chart on Green Power Switch participation.
To support the strong demand for green power, TVA expanded its wind generation capacity in November 2004 at Buffalo Mountain near Oak Ridge, Tennessee, through the installation of fifteen 1.8-megawatt Vestas V80 wind turbines. They provide an additional 27 megawatts of electricity, or 70 million kilowatt-hours, enough to supply another 39,000 blocks of green power Valley-wide. The additional 15 turbines began commercial generation in December 2004.
Satisfying this demand through green power sources instead of standard generation methods reduces TVA's impact on the environment. If the additional kilowatt-hours had come from standard generation sources, they would have resulted in 272,586 pounds of nitrogen oxides (NOx), 682,737 pounds of sulfur dioxide (SO2), and 103,736,853 pounds of carbon dioxide (CO2) emissions being put into the atmosphere each year. However, because these additional kilowatt-hours are generated from wind, none of these pollutants are released into the air. The 70 million kilowatt-hours generated from wind expansion equate to the addition of 14,140 acres of trees that remove CO2 from the atmosphere.
The wind resources necessary to produce low-cost power from wind turbines are generally not available in the Southeast. The strongest, most consistent wind is found at night in the higher elevations, which limits wind generation siting to mountaintops. However, mountaintops typically do not have power lines nearby for easy connection to the electric power grid, do not have a readily available road system for transporting heavy equipment, do not have the space available to arrange wind turbines in an economic manner, and due to topography variations, generally do not produce consistent power from turbine to turbine. In addition, due to the elevation, wind turbines on mountaintops can also be seen for much greater distances than in the Midwest or other regions. Their presence can disturb an otherwise unaffected ridgeline, especially at night, when safety lighting is required by the Federal Aviation Administration.
The Buffalo Mountain site is one of the few in the TVA region with wind speeds sufficient to support commercially viable wind generation. The site had previously been mined for coal and returned to brownfield conditions, with the result that environmental impacts from clearing and other construction-related activities were reduced. In addition, the majority of the surrounding land was owned or controlled by a single landowner and the site was not easily visible to any nearby valley development or population center. Construction of the 15 wind turbines, each standing approximately 260 feet tall with blades extending 135 feet long, was a major feat. Navigation of the steep, winding roads with specially designed tractor-trailer trucks to haul the turbines and blades was a daunting task, as was assemblage of the wind turbines on mountainous terrain.
As TVA’s nuclear program progresses, ensuring the availability of adequate, secure storage of spent nuclear fuel is critical. In 2004, three casks of used nuclear fuel were placed in aboveground spent-fuel storage facilities located at TVA’s Sequoyah Nuclear Plant in Tennessee. Spent nuclear fuel is stored underwater in the plant’s fuel-storage pool. Because the pool is getting full, an additional option needed to be found for storage until the U.S. Department of Energy (DOE) completes its underground repository at Yucca Mountain in Nevada.
Evaluations of available storage technologies to use until a DOE repository is operational revealed that the safest and most cost-effective option for Sequoyah was to store its spent fuel in aboveground dry storage (in concrete containers with steel inner canisters, called casks). Storing material onsite allows TVA to control and monitor the security of its spent fuel until the DOE repository is available.
A similar dry-cask storage facility is under construction at TVA’s Browns Ferry Nuclear Plant in Alabama. However, at TVA’s Watts Bar Nuclear Plant in Tennessee, there is sufficient storage capacity until 2018 in the fuel-storage pool. It is expected that the Yucca Mountain repository will be operational by then.
Increased demand for water could hinder TVA’s ability to maintain the critical balance of beneficial uses of the Tennessee River and the multiple public benefits derived from the integrated river management system. An extensive study published by the U.S. Geological Survey, Estimated Use of Water in the Tennessee River Watershed in 2000 and Projections of Water Use to 2030, projected a 15 percent increase in total water withdrawals from the Tennessee River watershed from 2000 to 2030. Interbasin transfers also are becoming a bigger issue in the Tennessee Valley as water-supply-constrained areas near the watershed look for additional sources of water.
Recognizing these issues, the Regional Resource Stewardship Council, which provides advice to TVA on resource management issues, recommended that TVA work to establish a basin-wide partnership to focus on water quantity issues. The goal of the partnership is to provide a framework for coordination and information exchange among the states. In addition, TVA continues to work with local communities within the Valley to help meet their local water supply needs.
The use of flue gas desulfurization (FGD) equipment, or scrubbers, to reduce SO2 emissions produces wastewater that contains trace elements of arsenic, selenium, and mercury, present in parts-per-billion levels. Power plants routinely use up to 10 million gallons of water per day to sluice, or wash, coal-combustion by-products such as ash and FGD scrubber gypsum to storage areas. While the sluice water returned to rivers and reservoirs meets past water quality standards, TVA continues to seek improved, cost-effective methods to treat this wastewater.
A project at Widows Creek Fossil Plant in northeast Alabama used a passive extraction trench containing small shavings of iron in a gravel-filled cell. As water passes through the iron-filled cell, iron oxides, or rust, are formed, creating a large surface area for binding metals and other compounds. This inexpensive, innovative system, developed by TVA, was effective in removing arsenic and other chemicals from the sluice water. TVA, EPRI, and DOE are cooperating to implement a large-scale demonstration of this technology in 2005 at TVA’s Paradise Fossil Plant in Kentucky.
See also previous.