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District Relerem a No 70180953 E. Health Risk Assessment The following are comments on the DSElR's Health Risk Assessment(HRA) as recommended on prcviou�s documents for this Project: I. An analysis was performed to compare emissions increases with the District's significance thresholds for CEQA No analysis was provided to determine if the increased emissions from this project would cause or contribute to a O5 violation of the National and California Ambient Air Quality Standards (AAQS). An Increase in criteria pollutant emissions can cause or contribute to the violation of an AAQS in the vicinity of a project without exceeding the District's significance levels. ?. The following are deficiencies that were identified in the dispersion modeling with AERMOD conducted by the Project proponent.- a. roponent:a. I ruck traffic and truck idling emissions were modeled as single very large volume sources. Truck traffic should have been modeled as a series of volume sources following on-site truck routes. Truck idling should have been modeled as point sources at specific idling points such as scales and/or unloading locations. 3. Emissions from the landfill, flares and internal combustion engines were assumed to emit controlled landfill gas. Emissions were based on the concentrations of Hazardous Air Pollutants (HAPs) in landfill gas The emissions from a flare or engine burning landfill gas are different from the landfill itself. The District's emission factors for landfill gas fired flares and internal combustion engines should have been used for those types of sources. 4. The risk assessment does not conform to the District's methodology e.g , a 30-year exposure duration is used when the District requires a 70-year ® duration for determination of residential cancer risk and Inhalation only pathway. 5. District policy for MRAs requires that only those sensitive receptors that actually exist be modeled. Additionally, receptors should be located so that worker exposures can be determined. The report indicates that a grid of 0 receptors close to the boundary was modeled. Although modeling of such a grid is not necessary for the HRA, it would be required for the ambient air quality impact modeling to determine compliance with the NAAQS and CAAQS. 1