Final Environmental Assessment: Selective Noncatalytic Reduction Project, Johnsonville Fossil Plant, Units 1-4, Humphreys County, Tennessee

摘要

In 2005, the Tennessee Valley Authority (TVA) installed a selective noncatalytic reduction (SNCR) system on Unit 1 at Johnsonville Fossil Plant to reduce NOx emissions. Results have been favorable, and TVA now proposes to install SNCR on Units 2, 3, and 4 and to operate the SNCR systems year-round. The two main issues addressed in the environmental review were air quality and water quality, including the potential effects of water-quality degradation on threatened and endangered mussels. Both air quality and water quality are potentially affected by ammonia slip (i.e., the passage of unreacted ammonia through the flue gas). Analysis indicated that overall air quality would benefit from implementing the proposed action. Operation of the proposed SNCR system on the four units would reduce NOx emissions, which would also reduce ozone formation. Similarly, water-quality degradation (primarily from the presence of unreacted ammonia, i.e., ammonia slip) would be minor and insignificant. Outfall discharges would be managed to comply with permit requirements. Also, because there is a large amount of mixing at the outfall, ammonia concentrations in the Tennessee River would be below toxic levels for mussels. Therefore, there would be no effects to endangered mussel species in the Tennessee River. Overall, potential environmental impacts would be minor and insignificant.