The affordable, reliable electric power generated by TVA, which helps create economic opportunity and a high quality of life in the Tennessee Valley region, is generated by a variety of methods, including fossil, nuclear, and hydropower plants, wind turbines, and solar panels. Coal-burning power plants provide approximately 60 percent of the electricity generated by TVA. These plants emit sulfur dioxide (SO2) and nitrogen oxides (NOx), which can affect the region’s air quality. In taking a balanced, integrated approach to power generation, TVA is continually looking for ways to reduce emissions more cost-effectively from its fossil plants while still meeting the increasing power demands of consumers.
TVA has spent $4 billion on emissions reductions since 1976 and is currently in the midst of spending on the order of $2 billion more to further reduce emissions. In addition to a $1.3 billion NOx reduction program, TVA plans to spend $1.5 billion on the installation of five additional flue-gas desulfurization systems, or scrubbers, which help reduce SO2 emissions from coal-fired plants. The sites where TVA chooses to install scrubbers are those that provide the greatest air quality and regulatory benefit for the investment, including the mountains of east Tennessee and western North Carolina.
When the current program is complete, 11 scrubbers will be operational on units that account for 55 percent of TVA’s coal-generation capacity. Six of these scrubbers have already been operating for some time: those on two units at Widows Creek Fossil Plant in Alabama since 1981, two units at Paradise Fossil Plant in Kentucky since 1983, and both units at Cumberland Fossil Plant in middle Tennessee since 1994. This substantial investment in scrubbers underscores TVA’s determination to achieve an 85 percent reduction in SO2 emissions from 1977 levels.
TVA also continues its commitment to reducing its NOx emissions as it proceeds with one of the most aggressive pollution-control programs in the nation. During 2002–2003, TVA completed four more selective catalytic reduction system installations—one each at Cumberland, Widows Creek, Allen, and Paradise fossil plants—as part of a $1.3 billion NOx reduction investment. This brings TVA’s installed SCR total to eight, and 17 additional SCRs or equivalent systems are scheduled for installation by 2005.
When all the SCR installations are completed, NOx emissions during the summer ozone season, which lasts from May to September, are projected to be reduced by 75 percent from 1995 levels. During 2002, TVA recorded its lowest SO2 emissions on record and in 2003 its lowest NOx emissions, although it missed its ozone season target by 5 percent. These reductions were achieved through the operation of new and existing SCRs and the six scrubbers, and by the burning of low-sulfur coal.
The SCR installations have not been without setbacks. Ash carryover and buildup initially plugged the catalyst on the Paradise Unit 3 SCR, so TVA switched back to a higher-sulfur coal as a short-term fix until components of the SCR could be changed to provide a better, long-term solution. Because of this switch and increases in fossil generation, SO2 emissions in 2003 exceeded TVA’s target by 7 percent. In addition to dealing with the challenges at Paradise, TVA had to delay the installation of the Bull Run SCR from 2003 until 2004 due to the complexity of the installation, which required additional design modifications. Despite these challenges, TVA plans to achieve further SO2 reductions in 2004 by switching to low-sulfur coal at Colbert Fossil Plant Unit 5 and by making scrubber improvements at Widows Creek Unit 8. These steps are expected to help reduce emissions to near or below the record-low 2002 levels, even with increased generation demands.
During 2003, TVA continued testing and development of the NOxStar technology, which reduces emissions by creating a plasma within a boiler. This plasma mixes the NOx-containing flue gas with ammonia to reduce NOx emissions without the need for the expensive catalysts required by SCRs. Although NOxStar does not lower NOx emissions as much as an SCR, lower capital costs and ease of installation will enable TVA to add the technology to more units.
An earlier version of NOxStar was installed at Kingston Fossil Plant Unit 9 in 2002 with mixed results. NOx reductions were achieved, but the boiler was damaged. Despite the setback, TVA continues to assess the viability of the NOxStar emissions reduction technology.
Another area of focus is the chemical emissions produced by TVA’s coal-burning plants. The EPA’s Toxics Release Inventory (TRI) requires about 31,000 U.S. facilities to report the release of approximately 650 chemicals defined by EPA as potentially hazardous to human health. TVA uses or manufactures (i.e., produces during the combustion of coal) 25 of the chemicals on EPA’s list in quantities sufficient to require TRI reporting.
Because TVA operates a large number of fossil-fuel plants, it ranks high among the top TRI-reporting industries in Alabama, Kentucky, and Tennessee. TVA voluntarily performs inhalation health-risk assessments for each of its 11 coal-fired plants. They provide estimates of exposure conditions within a radius of 50 kilometers (31 miles) around each facility, the area of greatest potential impact based on meteorology, terrain, and emission levels. These assessments consistently demonstrate that exposures to TVA-emitted TRI chemicals are very low and pose no significant health risk to employees or Valley residents.
TVA continues to work on reducing the production of hazardous waste but its success has been offset by a few large-scale remediation and cleanup projects that increased the total amount generated. Waste production in 2002 increased as a result of the continued cleanup of Watts Bar Fossil Plant, permanently shut down in 1997, which was constructed with materials that have since been identified as posing environmental and health hazards if not handled properly. TVA has undertaken a variety of remediation measures, including removing smokestacks, electrostatic precipitators, and the coal conveyor housing (containing asbestos and lead paint); installing a spill containment pond and new powerhouse roof; and removing and recycling 79,494 liters (21,000 gallons) of turbine oil.
In 2003, remediation work at the Environmental Research Center Firing Range to remove lead-contaminated soil resulting from the accumulation of bullets required the removal and proper disposal of 243,460 kilograms (268 tons) of material. The site’s remediation was the primary reason that TVA failed to meet its hazardous waste target for 2003.
An additional area of focus is the low-level radioactive waste generated by TVA’s nuclear power plants. TVA missed its 2002 target by approximately 10 percent (98 cubic meters) and its 2003 target by 4 percent (40 cubic meters). These increases were directly related to several unplanned outages, which created additional generation of low-level radioactive waste.
Operations at TVA’s nuclear and coal-fired plants have the potential to adversely affect water temperatures. The Clean Water Act requires that, at a minimum, power plant thermal discharges not interfere with the ability to “sustain balanced indigenous aquatic populations.” The water must be kept cool enough to protect the health of aquatic life downstream, which is important to anglers, to state regulators, and to TVA.
TVA’s Hydrothermal Team is responsible for ensuring that water discharges from nuclear and fossil plants do not cause temperatures downstream to exceed environmental limits. When temperatures begin to approach these limits—typically during hot, dry weather when power demands are greatest—the team conducts around-the-clock monitoring of water temperature data collected by automatic sensors at each plant. Team members also run computer models to see how changes to water release schedules from upstream dams would affect compliance and other river system objectives. The Hydrothermal Team is in constant contact with the coal-fired and nuclear plant managers, sharing information and making operational recommendations. During 2002 and 2003, TVA met water-temperature regulatory limits while providing adequate, reliable power, a particular challenge in 2002, when drought conditions were coupled with critical peak power demands.
While the expectation is that TVA will comply with state and federal environmental regulations, certain events occur that are serious enough to trigger notification to or enforcement action by a regulatory agency. These reportable environmental events (REEs) may include spills or small releases of oil in quantities that can produce a sheen on water.
In 2002, TVA experienced 29 REEs, down from the previous year’s 39. However in 2003, the number of REEs increased to 44, exceeding TVA’s target of 35. Notices of Violation for paperwork reporting errors and monitoring oversights contributed to the higher-than-expected REE figure for 2003. The three REEs that had the greatest potential effect on the environment are described in detail here:
1. About 568 liters (150 gallons) of insulating oil was spilled from the Unit 2 main transformer at Paradise Fossil Plant. The spill occurred when a fan blade support cracked due to fatigue and heat stress and separated from a fan on the transformer cooler. The blade punctured an oil-containing section of the transformer. Although the majority of the spill was absorbed by the surrounding gravel and soil or contained within a concrete trench, rain washed 133 liters (35 gallons) into the storm-drain system that discharges into the Green River.
TVA personnel immediately placed absorbent materials within the transformer yard and concrete pipe trench and placed a containment boom around a section of the oil sheen that had moved into the discharge channel. Containment and absorbent booms were also placed on the river to contain and control the oil and oily debris along the bank for recovery and disposal. The gravel, which had absorbed most of this oil, was removed and disposed of properly.
To prevent similar spills, TVA has implemented additional preventive maintenance procedures, including the inspection of fan blades and construction of a new containment system beneath the transformer.
2. Approximately 5,000 catfish were trapped and subsequently died in the Unit 3 discharge tubes at Watts Bar Hydro Plant in Tennessee. A powerhouse fire (see sidebar) caused a power outage, making it impossible to operate the tube gates. Since the gates couldn’t be adjusted, the fish became trapped inside the tube. TVA notified the Tennessee Wildlife Resources Agency (TWRA) and the fish were removed and disposed of. In conjunction with TWRA, TVA is preparing a habitat enhancement plan, scheduled for implementation in spring 2004, to offset the loss of the fish.
3. Sewage discharges at Browns Ferry Nuclear Plant in northern Alabama, a repeat REE, slightly exceeded state limits for suspended solids and fecal coliform bacteria, indicating that the discharged water was contaminated with the fecal material of humans or other animals. The problem was associated with the plant’s sewage lagoon. TVA personnel determined that an increased employee population, as well as the presence of waterfowl and other wildlife close to the sampling point, contributed to the elevated reading. TVA temporarily isolated the sewage lagoon, performed a retention study, installed 12 additional aeration systems, and raised the operating water level of the lagoon for more efficient operation.
Employees at TVA plants and other facilities conduct assessments of all REEs. Audits are done by a central staff of environmental specialists to monitor the effectiveness of the Environmental Management System (EMS) at TVA facilities and check for compliance with local, state, and federal regulations. Since 1995, the audit findings have shown a significant downward trend.