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Prop 7.A. - Pag@ �97 edwood City GDF Expansion Air G�uau�yi�.w i ia�c��a��y�h��alysis Appendix C: Modeling Assessment Updates Table C-2. Update to Project-Level Health Risk Screening Analysis for Costco Wholesale Redwood City GDF. U date to 2008 Health Risk Screenin Anal sis for Benzene to Reflect Current BAAQMD Guidance and Maximum Throu h ut. Max.Annual Inhalation Chronic 2008 Current BAAQMD Maximum Average Cancer Reference Estimated Recommended Adjusted Non-cancer Maximum Concentration Potency Exposure Maximum Cancer Risk Maximum Hazard Throughput (�ag/m3 per Factor Level(REL) Cancer Risk Age Sensitivity Cancer Risk Index Rece tor million allons million allons 1/m /k -da /m3 er million Factors er million HI Resident 18 0.00234 1.00E-01 60 1.22 1.7 2.08 0.0007 Worker 18 0.01581 1.00E-01 60 1.62 1 1.62 0.0047 Student(Hoover 18 0.00129 60 0.036 3 0.11 0.0004 Elementary School) 1.00E-01 Bay Area AQMD Project-Level Significance Thresholds 10.0 1.0 Significant? No No Notes: 1. The maximum throughput for the proposed 20 fueling position GDF will not exceed 18 million gallons per year(double the throughput assumed in the 2007 Certified EIR). Note that the Bay Area Air Quality Management District(BAAQMD)2008 health risk screening analysis(see reference below)was based on a maximum permitted gasoline throughput of 29.8 million gallons/year. 2. Maximum annual average concentrations,in micrograms per cubic meter(�ag/m3)per million gallons,are maximum annual average concentrations for each receptor type from the dispersion model outputs documenting the Bay Area Air Quality Management District (BAAQMD)health risk screening analysis prepared for the Costco Wholesale Redwood City GDF in 2008. Source: Bay Area Air Quality Management District,Results of Health Risk Screening Analysis for Costco Gasoline#409(Redwood City, CA),Maximum Allowable Throughput, GDF#11922,Application#17157,memorandum from Lorna Santiago, February 13,2008. 3. Inhalation cancer potency factor and chronic reference exposure level for benzene are also from the above source,and have been confirmed to have not changed since 2008. Sources: Technical Support Document for Cancer Potency Factors: Methodologies for Derivation,Listing of Available Values,and Adjustments to Allow for Early Life Stage Exposures,California Office of Environmental Health Hazard Assessment,May 2009,Appendix A(Hot Spots Unit Risk and Cancer Potency Values);andAll OEHHA Acute, 8-hour and Chronic Reference Exposure Levels(chRELs),California Office of Environmental Health Hazard Assessment, December 18,2008. The preceding two documents are available at oehha.ca.gov/air/hot_spots/index.html(accessed July 23,2012). 4. Maximum cancer risk is estimated from the maximum annual average benzene concentration for each receptor type using the following: Cancer Risk=[Gasoline Throughput(million gals.)x Annual Ave.Conc.(per million gals)x(BR x ET x EF x ED x UCF)=AT]x CPF 5. Maximum non-cancer chronic hazard index is estimated from the maximum annual average benzene concentration using the following: Non-cancer Hazard Index=[Gasoline Throughput(million gals.)x Annual Ave.Conc.(per million gals)]=Chronic REL 6. The Bay Area AQMD's current guidelines for conducting health risk screening analyses recommend that cancer risk estimates should incorporate Age Sensitivity Factors to account for the increased susceptibility of infants and children to carcinogens. The District recommends the following Age Sensitivity Factors: student receptors: 3;residential receptors: 1.7;and worker receptors: 1. Source: Bay Area Air Quality Management District,BAAQMD Air Toxics NSR Program Health Risk Screening Analysis(HRSA)Guidelines, January 2010,Section 2.3(Cancer Risk Calculations),available at:www.baaqmd.gov/Divisions/Engineering/Air-Toxics/Review-of-Air- Toxics.aspx(accessed January 20,2012). The Adjusted Maximum Cancer Risk values reflect use of the above Age Sensitivity Factors. 7. Source for Bay Area AQMD significance thresholds: Bay Area Air Quality Management District,California Environmental Quality ActAirQualityGuidelines,May 2011,Section 5.2(Local Community Risk and Hazard Impacts: Single Source Impacts). Ex osure Parameters Used in Health Risk Screenin Anal sis. Breathing Exposure Exposure Exposure Units Averaging Rate BR Time Frequency Duration Conversion Time(AT- Receptor Daily Hourly (ET) (EF) (ED) Factor(UCF) 70 years) T e L/k -da L/k -hr hours/da da s/ ear ears (mg-m3)/(�ag-L) da s Resident 302 12.6 24 350 70 1.00E-06 25,550 Worker 149 18.6 8 245 40 1.00E-06 25,550 Student 581 24.2 10 180 9 1.00E-06 25,550 Notes: 1. The above table reflects the exposure parameters used in the Bay Area AQMD's 2008 health risk screening analysis. Source: see Note 1,above. 2. The hourly breathing rates for residential and student receptors assume 24 hours/day. The hourly breathing rates for worker receptors assume 8 hours/day. 3. Values in the above table have been verified against the current District guidelines for conducting health risk screening analyses(see above Note 5 for reference.) Page 3 Date: 7/30/2012