ARCHIVED REPORTS LEC APPLICATION FOR CERTIFICATION

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5.1 AIR QUALITY Annual Averages • CTG/HRSG at base load,hot temperature (maximum impact case from screening analysis),maximum annual emission rates • Auxiliary boiler in operation,maximum annual emission rates • Cooling tower in operation,maximum annual emission rate Emission rates and stack parameters used in the refined modeling analysis are shown in Appendix 5.113,Table 5.113-4. 5.1.5.7.2 Startup and Shutdown Impacts Analysis Short-term ambient impacts from the facility during turbine startup may be higher than impacts during normal operation because emission control systems are not fully operational during some part of the initial startup period when the turbine operates at low loads and the exhaust temperatures are low. Although the LEC gas turbine will use Rapid Response technology to minimize startup emissions,there are no in-use data available. Therefore, startup emissions and impacts were assessed using the very conservative assumption that there are no emissions or performance benefits from the Rapid Response technology.Turbine exhaust parameters for minimum load operation and under cold temperature conditions were used to characterize CTG exhaust during startup,because that operating case produced the highest modeled impacts in the screening analysis. CO and NO,,emission rates from Table 5.1-19 were used. Startup impacts were evaluated for the 1-hour averaging period; startup impacts are included in the modeling of 8-hour average CO impacts under normal operating conditions (above). The emission rates and stack parameters used are shown in Table 5.113-5,Appendix 5.113. The results of the analysis are summarized in Table 5.1-27. 5.1.5.7.3 Inversion Breakup Fumigation Modeling Inversion breakup fumigation occurs when a stable layer of air lies a short distance above the release point of a plume and unstable air lies below. Under these conditions,an exhaust plume may be drawn to the ground,causing high ground-level pollutant concentrations. Although fumigation conditions rarely last as long as 1 hour,relatively high ground-level concentrations may be reached during that time. For this analysis,fumigation was assumed to occur for up to 90 minutes,per EPA guidance. The SCREEN3 model was used to evaluate maximum ground-level concentrations for short-term averaging periods (24 hours or less). Guidance from EPA 15 was followed in evaluating fumigation impacts. The maximum fumigation impact from this analysis,which is shown in more detail in Appendix 5.1B,Table 5.1B-6, showed that impacts under fumigation conditions are expected to be lower than the maximum concentrations calculated by AERMOD under downwash conditions. Fumigation impacts for the turbine occurred between 10 km to 18 km from the facility, depending upon engine load (the AERMOD maximum 1-hour impact occurs about 1 km from the plant). Inversion breakup impacts are also shown in Table 5.1-27. 5.1.5.8 Total Facility Impacts The maximum facility impacts calculated from the modeling analyses described above are summarized in Table 5.1-27. The highest modeled short-term impacts are expected to occur 15EPA-454/R-92-019,"Screening Procedures for Estimating the Air Quality Impact of Stationary Sources,Revised." SAC/371322/082410013(LEC_5.1_AIR_QUALITY.DOC) 5.1-39