ARCHIVED REPORTS LEC APPLICATION FOR CERTIFICATION

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APPENDIX 5.1D Screening Health Risk Assessment The screening level health risk assessment has been prepared using CARB's Hotspots Analysis and Reporting Program (HARP) computer program(Version 1.4,May 2008) and associated guidance in the OEHHA's Air Toxics Hot Spots Program Guidance Manual for Preparation of Health Risk Assessments (August 2003). The HARP model was used to assess cancer risk as well as chronic and acute risk impacts. The following paragraphs describe the procedures used to prepare this risk assessment. Modeling Inputs The risk assessment module of the HARP model was run using unit ground level impacts to obtain derived cancer risks for each toxic chemical of interest.? Cancer risks for residential receptors were obtained for the derived (OEHHA) method,while the derived (adjusted) method was used to derive risks for workers. The HARP model output was cancer risk by pollutant and route for each type of analysis,based on an exposure of 1.0 pg/m3. HARP model output showing the unit values is included as Attachment 5.1D-1. Individual cancer risks are expressed in units of risk per Pg/m3 of exposure. To calculate the weighted risk for each source,the annual average emission rate in g/s for each pollutant was multiplied by the individual cancer risk for that pollutant in(µg/m3)-1. The resulting weighted cancer risks for each pollutant were then summed for the source. An identical approach was used to determine the acute and chronic health impacts associated with the proposed project. Details of the calculations of risk"rates" for modeling are shown in Tables 5.1D-2 through 5.1D-5 (provided at the end of this section). Risk Analysis Method The results of the turbine screening analysis (see Appendix 5.1B,Table 5.0-3) were used to determine the worst-case full load operating conditions for modeling for the annual and 1-hour averaging periods,used in determining cancer risk and chronic HHI,and acute HHI,respectively. The total weighted risk"rate" for each source was used in place of emission rates in the modeling analysis. The weighted risk"rates" used for the HRA modeling are summarized in Table 5.1D-6 (at the end of this section). The calculated value was then total cancer risk at each receptor. As discussed in Section 5.1.5.6,the screening analysis for the criteria pollutant modeling analysis was performed using the AERMOD model,the 2000 through 2004 Stockton meteorological data,and specific receptor grids. The exhaust characteristics for the highest full-load annual average unit impact from the screening analysis, Case 7,was used to model cancer risks from the CTG/HRSG for the proposed project. The contribution of each toxic compound to total cancer risk and total HHI for each analysis method was then determined using the individual contribution of each compound to the total weighted risk"rate." Procedure is described in Part B of Topic 8 of the HARP How-To Guides: How to Perform Health Analyses Using a Ground Level Concentration.