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5.9 PUBLIC HEALTH • The analysis includes representative weather data over a period of five years to assure that the least favorable conditions producing the highest ground-level concentration of power plant emissions are included. • LEC is assumed to operate at hourly, daily, and annual emission conditions that produce the highest ground-level concentrations. • The location of the highest ground-level concentration of LEC emissions is identified and the analysis then assumes that a sensitive individual resides at this location constantly over the entire 70-year period. Taken together,these methods and assumptions create a scenario that cannot exist in the real world. For example,if the worst-case weather conditions occur on a winter evening,but the worst-case emission rates occur on a summer afternoon,the analysis nonetheless assumes that these events occur at the same time. The point of using these unrealistic assumptions is to consciously overstate the potential impacts. No one individual will experience exposures as great as those assumed for this analysis. By determining that even this highly overstated exposure will not be significant, the analysis enables a high degree of confidence that the much lower exposures that actual persons will experience will not result in any significant increase in cancer risk. In short,the analysis assures that there will not be any significant public health impacts at any location,under any weather condition,under any operating condition. A separately transmitted compact disc contains the HRA modeling input and output files. 5.9.4.6 Hazardous Materials Hazardous materials will be used and stored at the LEC site.The hazardous materials stored in significant quantities on-site and descriptions of their uses are presented in Section 5.5. Use of chemicals at the project site will be in accordance with standard practices for storage and management of hazardous materials. Normal use of hazardous materials, therefore,will not pose significant impacts to public health.While mitigation measures will be in place to prevent releases,if an accidental release migrated offsite,potential impacts to the public could result. The California Accidental Release Program (CalARP) regulations and Code of Federal Regulations (CFR) Title 40 Part 68 under the Clean Air Act establish emergency response planning requirements for acutely hazardous materials. These regulations require preparation of an RMP,which is a comprehensive program to identify hazards and predict the areas that may be affected by a release of a program-listed hazardous material. Anhydrous ammonia is currently stored and used at the existing STIG plant and no new ammonia storage facilities will be constructed as part of the project. The existing RMP will be revised to include LEC. 5.9.4.7 Operation Odors A small amount of ammonia used to control NOX emissions can"slip" past the SCR catalyst and be emitted from the exhaust stack,but this amount is less than that required to produce an odor off site. The expected exhaust gas ammonia concentration,known as ammonia "slip," will be less than 10 ppmv. After mixing with the atmosphere, the concentration at ground level will be far below the detectable odor threshold of 5 ppmv that the Compressed SACI371322I082340007(LEC_5.9_PUBLIC_HEALTH.DOC) 5.9-19