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20 relies on a continuous average emission rate to simulate maximum downward concentrations from point, area, and volume emission sources. To account for the variability in equipment usage and truck trips over Project operation, we calculated an average DPM emission rate by the following equation: 𝐸𝑚𝑖𝑠𝑠𝑖𝑜𝑛 𝑅𝑎𝑡𝑒 ቀ 𝑔𝑟𝑎𝑚𝑠 𝑠𝑒𝑐𝑜𝑛𝑑ቁ ൌ 129.4 𝑙𝑏𝑠 365 𝑑𝑎𝑦𝑠 ൈ 453.6 𝑔𝑟𝑎𝑚𝑠 𝑙𝑏𝑠 ൈ 1 𝑑𝑎𝑦 24 ℎ𝑜𝑢𝑟𝑠 ൈ 1 ℎ𝑜𝑢𝑟 3,600 𝑠𝑒𝑐𝑜𝑛𝑑𝑠 ൌ𝟎.𝟎𝟎𝟏𝟖𝟔 𝒈/𝒔 Using this equation, we estimated an operational emission rate of 0.00186 g/s. Construction and operational activity was simulated as a 1.6‐acre rectangular area source in AERSCREEN with dimensions of 100 by 65 meters. A release height of three meters was selected to represent the height of exhaust stacks on operational equipment and other heavy‐duty vehicles, and an initial vertical dimension of one and a half meters was used to simulate instantaneous plume dispersion upon release. An urban meteorological setting was selected with model‐default inputs for wind speed and direction distribution. The AERSCREEN model generates maximum reasonable estimates of single‐hour DPM concentrations from the Project site. EPA guidance suggests that in screening procedures, the annualized average concentration of an air pollutant be estimated by multiplying the single‐hour concentration by 10%.35 According to the Checklist, the closest sensitive receptors are located 100 meters from the Project site (p. 4‐17). Thus, the single‐hour concentration estimated by AERSCREEN for Project operation is approximately 3.138 µg/m3 DPM at approximately 100 meters downwind. Multiplying this single‐hour concentration by 10%, we get an annualized average concentration of 0.3138 µg/m3 for Project operation at the MEIR. We calculated the excess cancer risk to the MEIR using applicable HRA methodologies prescribed by OEHHA, as referenced by the Checklist (p. 4‐17). Consistent with the construction schedule utilized in the Checklist’s CalEEMod model, the annualized averaged concentration for operation was used for the latter 0.58 years of the infantile stage of life (0 – 2 years), as well as the entire child stage of life (2 – 16 years) and adult stage of life (16 – 30 years). Consistent with the methodology utilized by the Community Health Risk Assessment (“HRA Report”), provided as Appendix B to the Checklist, we used Age Sensitivity Factors (“ASFs”) to account for the heightened susceptibility of young children to the carcinogenic toxicity of air pollution (Appendix B, p. 4‐ 5). When applying ASFs, the quantified cancer risk should be multiplied by a factor of ten during the third trimester of pregnancy and during the first two years of life (infant), as well as multiplied by a factor of three during the child stage of life (2 – 16 years) (Appendix B, p. 5). Furthermore, in accordance with the guidance set forth by OEHHA, we used the 95th percentile breathing rates for infants.36 Finally, 35 “Screening Procedures for Estimating the Air Quality Impact of Stationary Sources Revised.” EPA, 1992, available at: http://www.epa.gov/ttn/scram/guidance/guide/EPA‐454R‐92‐019_OCR.pdf; see also “Risk Assessment Guidelines Guidance Manual for Preparation of Health Risk Assessments.” OEHHA, February 2015, available at: https://oehha.ca.gov/media/downloads/crnr/2015guidancemanual.pdf p. 4‐36. 36 “Supplemental Guidelines for Preparing Risk Assessments for the Air Toxics ‘Hot Spots’ Information and Assessment Act,” June 5, 2015, available at: http://www.aqmd.gov/docs/default‐source/planning/risk‐ assessment/ab2588‐risk‐assessment‐guidelines.pdf?sfvrsn=6, p. 19. 135