Guidebook for Assessing Airport Lead Impacts (2016)

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8C H A P T E R 5 In December 2010, the EPA established requirements for ambient lead monitoring around facilities known to have substantial lead emissions. These facilities included airports with suf- ficient piston-powered aircraft activity leading to estimated annual lead emissions of 1.0 ton or more, and industrial facilities with estimated annual lead emissions of 0.5 ton or more. More- over, the EPA also completed a 1-year monitoring study of 14 additional airports with estimated annual lead emissions between 0.5 and 1.0 ton to investigate whether general aviation aircraft may have the potential to cause violations of the lead NAAQS. Table 3 summarizes the results of the EPA airport monitoring, which was conducted at 17 airport facilities through December 2013 (U.S. EPA 2015a). The results shown are “design values” for maximum 3-month average concentrations which can be compared directly to the lead NAAQS of 0.15 microgram per cubic meter of air. There are considerable variations in the monitored ambient lead concentrations from airport to airport. However, maximum 3-month average concentrations for two California sites—McClellan-Palomar Airport south of Carlsbad and the San Carlos Airport south of San Francisco—exceed the current NAAQS level. The maximum 3-month average at a third site—Palo Alto Airport, also south of San Francisco—approached the level of the NAAQS. These results suggest that lead emissions at general aviation airports could lead to violations of the lead NAAQS, and strategies for reducing aircraft lead emissions may need to be considered. However, to assess the need for control strategies at any particular airport, as well as to effectively develop and implement them if needed, it is vital to have a detailed understanding of the sources of lead emissions from airport activities and their impacts on ambient lead concentrations. Based on previous research, including ACRP Project 02-34, “Quantifying Aircraft Lead Emis- sions at Airports,” the primary sources of lead emissions associated with piston-engine aircraft operating at general aviation airports are as follows: • Idling and taxiing before and after takeoff and landing; • Run-up; and • Takeoff and climb-out. The amount of lead emitted by a given aircraft during each of these activities is determined by the fuel it consumed during each activity and the lead content of that fuel. The amount of lead emitted at an airport over any period of time depends on the number of aircraft in operation and their individual lead emissions. Ambient concentrations of lead at and around the airport depend on the temporal and spatial distributions of the lead emissions from aircraft operation as well as meteorological conditions. A methodology to quantify lead emissions associated with aircraft operations and to assess airborne lead concentrations at and around airports through air quality modeling was developed Assessing Lead Impacts in the Vicinity of Airports

Assessing Lead Impacts in the Vicinity of Airports 9 as part of ACRP Project 02-34, “Quantifying Aircraft Lead Emissions at Airports.” That project led to the release of an emissions inventory development tool for airports as well as a related guid- ance document. Furthermore, the technical report for that project, ACRP Web-Only Document 21: Quantifying Aircraft Lead Emissions at Airports, documented how the inventory tool could be used in combination with aircraft operations data and air quality models to develop detailed estimates of airborne lead concentrations at and around an airport, as well as the contribution of specific operating modes to those estimated concentrations. As part of ACRP Project 02-57 that produced this guidebook, the prior study’s methodology was applied to three general aviation airports. Application of the methodology required use of detailed data at each airport, including spatial and temporal aircraft activity patterns, number and types of operating aircraft, and AVGAS lead content. These data were used to create a detailed spatially and temporally resolved emissions inventory for each airport that was used as input data into an air quality model to estimate ambient lead concentrations. Results for a general aviation airport, denoted here as airport “A,” are shown in Figure 3a; Figures 3b, 3c, and 3d show the relative contributions associated with taxiway; engine test run-up (i.e., run-up); and takeoff/landing operations, respectively. Although quantitative data are generated through application of the ACRP Project 02-34, “Quantifying Aircraft Lead Emissions at Airports” methodology, the results shown in Figure 3 are qualitative and presented only for purposes of illustrating their value towards assessing airport lead impacts. Figure 3 illustrates a number of important points related to the assessment of airport lead impacts. First, Figure 3a shows the estimated lead concentration levels both at the airport as well as in adjacent areas outside the airport footprint. This information is critical in evaluating the magnitude of impacts from piston-engine aircraft using leaded fuel, and peak estimated levels can be compared to the lead NAAQS. Second, because of the way the emissions inventory is constructed, it is possible to evaluate the contributions from different types of aircraft operations Table 3. Concentration of lead at airports in 2013 (microgram per cubic meter). Source: U.S. EPA 2015a /www.epa.gov/otaq/documents/aviation/ 420f15003.pdf Note: Maximum 3-month average concentration in the monitoring dataset through December 2013. Airport, State Maximum 3-Month Average San Carlos, CA 0.33 McClellan Pallomar, CA 0.17 Palo Alto, CA 0.12 Reid-Hillview, CA 0.10 Gillespie Field, CA 0.07 Merrill Field, AK 0.07 Auburn Municipal, WA 0.06 Van Nuys, CA 0.06 Deervalley, AZ 0.04 Brookhaven, NY 0.03 Stinson Municipal, TX 0.03 Centennial, CO 0.02 Harvey Field, WA 0.02 Oakland County International, MI 0.02 Nantucket Memorial, MA 0.01 Pryor Field Regional, AL 0.01 Republic, NY 0.01

10 Guidebook for Assessing Airport Lead Impacts to ambient lead concentrations at and around the airport. At this particular airport, taxi operations (Figure 3b) have the largest impact, followed by takeoffs (Figure 3d) and run-up (Figure 3c). Furthermore, these figures show that impacts from these three types of activities tend to be co-located and therefore contribute to the magnitude of the peak lead concentration; although at this airport the contributions from run-ups are relatively low. The results for a different general aviation airport, denoted as airport “B,” are shown qualita- tively in Figure 4. Again, total lead concentrations from all airport activities are shown in Figure 4a, with the contributions from taxiways, run-up areas, and takeoffs shown in Figures 4b, 4c, and 4d, respectively. In this case, the contribution of run-up area activity to peak lead concentrations is much greater than at airport A, and the contributions from the other activities are relatively less important. Overall, the key observation from the comparison of Figure 3 to Figure 4 is that results tend to be airport specific—conclusions or observations drawn from one airport may not apply to another airport. In addition to its utility in assessing airport lead impacts, the ACRP Project 02-34, “Quantify- ing Aircraft Lead Emissions at Airports” methodology allows the impact of potential lead miti- gation strategies to be evaluated. During the course of the project, a literature review identified two potential approaches for lowering peak lead concentrations at and around general aviation Note: Airport property boundaries are designated by a thick black line; the dark interior line indicates the runway. Figure 3. Average lead concentrations at a general aviation airport A.

Assessing Lead Impacts in the Vicinity of Airports 11 airports, in addition to the availability of the unleaded AVGAS sought through the FAA research program described previously: • Relocation of run-up areas to reduce the magnitude of lead concentration hot spots; and • Use of unleaded MOGAS in aircraft for which it is a suitable substitute for 100LL AVGAS. Each of these was evaluated, along with the combination of both strategies. The MOGAS strategy was evaluated based on the assumption that it would be used in all aircraft for which it would be suitable, meaning that maximum impacts were assessed. The two strategies and their combined implementation were evaluated for airports A, B, and a third airport denoted as airport “C.” In addition, a detailed assessment of other factors that should be considered in the design and potential implementation of these strategies at a particular airport is presented in the following section of this guidebook. The observed impact of implementing either strategy or both strategies at each of the three airports is summarized in Figure 5 as the percentage reduction in peak lead concentration com- pared to the base case value (i.e., no mitigation). The impacts of implementing either strategy or both varied considerably from airport to airport, with run-up area relocation reducing the Note: Airport property boundaries are designated by a thick black line; the dark interior line indicates the runway. Figure 4. Average lead concentrations at a general aviation airport B.

12 Guidebook for Assessing Airport Lead Impacts peak lead concentration by 7% to 31%, use of MOGAS by 19% to 35%, and the combination of the two by 36% to 56%. These findings again underscore the fact that results from one airport should not be generalized to other airports and highlight the need for conducting an airport- specific analysis using the ACRP Project 02-34, “Quantifying Aircraft Lead Emissions at Airports” methodology, or a similar approach, when considering implementation of general aviation aircraft lead control strategies. In addition, the impacts on peak concentrations at and around the airports were evaluated. Figures 6, 7, and 8 show qualitative modeled base case lead concentrations (a) and concentra- tions reflecting the implementation of both control strategies (b) at airports A, B, and C, respec- tively. As expected, these figures show not only reductions in peak lead concentrations but also Figure 5. Impacts of control strategies on peak lead concentrations at three general aviation airports. Note: Airport property boundaries are designated by a thick black line; the dark interior line indicates the runway. (a) (b) Figure 6. Modeled lead concentrations at airport A for the base case (a) and combination of run-up area relocation and MOGAS use (b).

Assessing Lead Impacts in the Vicinity of Airports 13 Note: Airport property boundaries are designated by a thick black line; the dark interior line indicates the runway. (a) (b) Figure 7. Modeled lead concentrations at airport B for the base case (a) and combination of run-up area relocation and MOGAS use (b). Note: Airport property boundaries are designated by a thick black line; the dark interior line indicates the runway. (a) (b) Figure 8. Modeled lead concentrations at airport C for the base case (a) and combination of run-up area relocation and MOGAS use (b). reductions in the size of impacted areas. Again, the different impacts from implementing both strategies at the different airports underscore the need for airport-specific analyses. Also, it must be stressed that the benefits modeled for the unleaded MOGAS strategy reflect the maximum impact of that strategy because MOGAS was assumed to be used in all aircraft for which it would be suitable; this might not occur in practice and would reduce the effectiveness of the strategy.