Air quality modeling for the Brady Street Bus Garage

There are presently numerous types of Automobile and/or Bus Facilities that exist throughout the country. Each of these facilities have an environmental impact on the surrounding community. This impact may take various forms such as air, water, noise, or traffic pollution. These various impacts must be determined so as to protect the health and safety of the public and to meet all related federal regulations. This study in this report focused only on the air quality impact of a facility titled "Brady Street Bus Garage", located in Atlanta, GA. This air quality impact study was limited to Particulate Matter (PM10) and Nitrogen Oxides (NOx) emissions from the facility. The models PARTS and MOBILE5A were used to calculate the emission factors (grams/mile) for these pollutants; whereas, the model ISCST2 was used to calculate the pollutants' concentrations (μg/m³) around the facility. Evaluation of the calculated PM10 and NOx concentrations (μg/m³) at various receptors located around the bus facility for the time periods of 1-hour, 24-hour, and annual revealed the following:

1. The maximum PM10 and NOx receptor concentrations for all time periods were only a few per cent of the National Ambient Air Quality Standards (NAAQS).
2. The locations of the PM10 and NOx maximum receptor concentrations for all time periods were different. This was not expected; however, further investigations revealed that the variations in the NOx/PM10 Emission Factor Ratio throughout the facility had a direct effect upon the receptor(s) located near these sources; thus, the different receptor locations.
4. A receptor located near a queuing source does not always have a greater concentration value than a similar receptor located near a free flowing source in the same facility. The time period, the length of time queuing, the magnitude of the queuing source, the number of vehicles queuing, and meteorological conditions all affect the receptor concentration. Therefore, the estimation of the location of the maximum receptor concentration, before the model run, is imprecise, at best.
5. The concept of "All Night Idling", as expected, gave the greatest concentrations. However, these concentrations were at most only about 25 % of NAAOS.