Note: Modeled using (a) the current run-up areas; (b) the Z1 run-up areas; and (c) the Z2 run-up areas.
When the run-up emissions were moved 80 meters to the southwest of the original run-up area, the three-month average maximum concentration decreased to 68 ng/m3—a 24% reduction from the base case and 69% of the maximum possible reduction by removing run-up emissions.
Moving the run-up emissions to Z2 further reduced the maximum three-month average
concentration to 65 ng/m3, which is a 27% reduction from the base case and 78% of the maximum possible reduction. The effect of moving the run-up areas incrementally farther away from their original positions diminished quickly because the relative impact of run-up emissions is reduced, compared to other airport sources, with increasing distance. In addition to reducing the maximum modeled concentration, moving the run-up area away from the airport fence line reduced the size of the area outside the airport footprint exposed to higher airport impacts.
Palo Alto Airport
The primary run-up area location at PAO (SE Orig), as well as alternative run-up area locations approximately 50 meters (SE Z1) and 100 meters (SE Z2) to the southwest, is shown in Figure 14. In contrast to RVS and SMO, the modeled run-up areas were moved away from the runway ends and into the aircraft tie-down areas instead of parallel to the runway. This prevents additional congestion and two-way traffic on the taxiways and taxi-lanes that would occur if the run-up area were moved to the northwest along the runway. The new run-up areas were kept the same size and shape as the original areas.
Figure 14
Map of PAO with Current and Hypothetical Run-up Locations
Hourly concentrations were modeled using AERMOD; the highest three-month, rolling-average hot spot was observed for November–January with a Pb concentration value of 121 ng/m3, which is 80% of the Pb NAAQS. Figure 15 shows the concentration field for this three-month average for (a) the base-case scenario of using the original run-up area; (b) the Z1 run-up area; and (c) the Z2 run-up area. Compared to taxiways and takeoffs (55%, 26%), run-up areas (8%) had a relatively low contribution to the maximum
Figure 15
Modeled Three-Month Average Concentrations from November-January at PAO
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