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As a result of the high outdoor noise levels, the current project will require a mechanical <br />supply of outdoor air ventilation to allow for a habitable interior environment with closed <br />windows and doors. Such a ventilation system would allow windows and doors to be kept <br />closed at the occupant's discretion to control exterior noise within building interiors. <br />PM2.5 Outdoor Concentrations Impact. An additional impact of the nearby motor vehicle <br />traffic associated with this project, are the outdoor concentrations of PM2.5. According to <br />the 4a' and Mortimer Project — Environmental Impact Report Addendum, SCH <br />#2006071100, (City of Santa Ana, 2020), the Project is located in South Coast Air Basin, <br />which is a State and Federal non -attainment area for PM2.5. <br />An air quality analyses should to be conducted to determine the concentrations of PM2.5 in <br />the outdoor and indoor air that people inhale each day. This air quality analyses needs to <br />consider the cumulative impacts of the project related emissions, existing and projected <br />future emissions from local PM2.5 sources (e.g. stationary sources, motor vehicles, and <br />airport traffic) upon the outdoor air concentrations at the Project site. If the outdoor <br />concentrations are determined to exceed the California and National annual average PM2.5 <br />exceedence concentration of 12 µg/m3, or the National 24-hour average exceedence <br />concentration of 35 µg/m3, then the buildings need to have a mechanical supply of outdoor <br />air that has air filtration with sufficient removal efficiency, such that the indoor <br />concentrations of outdoor PM2.5 particles is less than the California and National PM2.5 <br />annual and 24-hour standards. <br />It is my experience that based on the projected high traffic noise levels, the annual average <br />concentration of PM2.5 will exceed the California and National PM2.5 annual and 24-hour <br />standards and warrant installation of high efficiency air filters (i.e. MERV 13 or higher) in <br />all mechanically supplied outdoor air ventilation systems. <br />Indoor Air Quality Impact Mitigation Measures <br />The following are recommended mitigation measures to minimize the impacts upon indoor <br />quality: <br />796 16 <br />