Appendix I – Aircraft Noise Analysis Report Content Page AEDT Modeling Inputs and Outputs Technical Memorandum I-1 thru I-19 December 14, 2018 FAA AEDT Aircraft Substitution Approval Letter and Associated Request I-20 thru I-24 June 26, 2018 I-0 Technical Memorandum To: Metropolitan Airports Commission From: Mead & Hunt, Inc. Date: December 14, 2018 Subject: Crystal Airport EA/EAW AEDT Modeling Inputs and Outputs This technical memorandum presents the process and modeling inputs used to create the following noise contour scenarios for the Crystal Airport federal Environmental Assessment (EA)/state Environmental Assessment Worksheet (EAW) using the Federal Aviation Administration’s (FAA) Aviation Environmental Design Tool (AEDT) Version 2d: • 2017 Baseline Condition • 2025 No-Action Alternative • 2025 Preferred Alternative (with project) Per applicable FAA guidance, the environmental consequences section of an EA should include analysis of potential noise impacts of the proposed action and alternative(s) for each timeframe evaluated. Timeframes for this analysis were determined in consultation with the FAA Airports District Office in Minneapolis to represent appropriate baseline, no-action, and “with project” operational conditions. For aviation noise analyses, the FAA has determined that the cumulative noise energy exposure of individuals to noise resulting from aviation activities must be established in terms of Yearly Day-Night Average Sound Level (DNL), the FAA’s mandated noise metric for evaluating aircraft noise impacts and land use compatibility around US airports. This metric accounts for the noise levels of all individual aircraft events, the number of times those events occur, and the period of day/night in which they occur. The metric logarithmically averages aircraft sound levels at a location over a complete 24-hour period, with a 10-decibel (dB) adjustment added to those noise events occurring from 10:00 p.m. and up to 7:00 a.m. the following morning. This adjustment accounts for increased sensitivity to noise during normal nighttime hours and because ambient sound levels during nighttime are typically about 10 dB lower than during daytime hours. The AEDT model was initially released in 2015 to replace a series of legacy tools, including the Integrated Noise Model (INM), which was previously used for noise modeling in the recently completed Long Term Comprehensive Plan (LTCP) for Crystal Airport. According to FAA, there is an overlap in functionality and underlying methodologies between AEDT and the legacy tools, however updates were made in AEDT which result in differences when comparing outputs from AEDT and the legacy tools. The updates include smaller flight segments to more accurately model aircraft noise levels for a larger number of aircraft and positions and states along a flight path; a new standard (SAE-ARP-5534) for computing the effects of weather on noise; correcting misidentified aircraft engine mounted locations for three aircraft types; and moving from recursive grids to dynamic grids for noise contour generation. 1 I-1 Noise contours depict an annualized average day of aircraft noise impacts using model inputs, such as aircraft operations (i.e. takeoffs, landings, and touch-and-go’s), runway use, flight track use, aircraft fleet mix, aircraft performance and thrust settings, topography information, and atmospheric conditions. Quantifying aircraft-specific noise characteristics in AEDT is accomplished through the use of a comprehensive noise database that has been developed under Federal Aviation Regulation Part 36. As part of the airworthiness certification process, aircraft manufacturers are required to subject aircraft to a battery of noise tests. Through the use of federally adopted and endorsed algorithms, this aircraft-specific noise information is used in the generation of DNL contours. Justification for such an approach is rooted in national standardization of noise quantification at airports. Airport Operations In coordination with MAC staff, Mead & Hunt developed 2017 baseline aircraft operations counts, as well as 2025 forecast aircraft operations counts for the no-action and preferred alternative scenarios. The baseline operations counts were established based on data collected in 2017 by the MAC Noise and Operations Monitoring System (MACNOMS). This data was adjusted to reflect MACNOMS capture rates calculated based on the discrepancy between the MACNOMS counts and air traffic control tower counts. The forecast operations counts are based on the total operations forecasted by the recently-completed LTCP for Crystal Airport, with the fleet mix composition adjusted to align with the fleet mix composition observed in the 2017 MACNOMS data. Table A below summarizes the aircraft operations for each scenario. Table A: Airport Operations Summary by Scenario Aircraft Type Baseline (2017) No-Action (2025) Preferred Alternative (2025) Single-Engine Piston 33,272 92.1% 35,562 91.1% 35,470 90.4% Multi-Engine Piston 1,099 3.0% 1,559 4.0% 1,668 4.2% Turboprop 105 0.3% 114 0.3% 236 0.6% Jets 7 0.0% 7 0.0% 79 0.2% Rotor 1,650 4.6% 1,782 4.6% 1,806 4.6% Total 36,134 39,025 39,258 The operations shown in Table A were then assigned to specific aircraft types based on the prevalence of specific aircraft types observed in the MACNOMS data. Tables 1, 2, and 3 attached to this memorandum present the daily baseline and forecast operations counts by aircraft type used to generate the AEDT inputs. Approval of Non-Standard Aircraft Substitutions In a letter dated June 26, 2018, the FAA Office of Environment and Energy (AAE) approved use of specific aircraft noise profiles for this study, to represent aircraft types for which AEDT does not identify a standard substitution. These aircraft types and substitution aircraft noise profiles are summarized in a table attached to the June 26 letter, which is attached to this report. 2 I-2 Runway Use Baseline 2017 runway use and flight track distributions were estimated for aircraft type category based on MACNOMS flight track data for which the aircraft type was known. Runway use distribution was unique for aircraft type and whether the operations were arrivals or departures. The 2017 baseline and 2025 no action alternatives used the same assumptions for runway and track utilization. However, in the 2025 preferred alternative scenario, aircraft will utilize Runway 14L/32R more frequently after Runway 14R/32L is closed. All new jet and turboprop aircraft operations in the 2025 preferred alternative scenario were assigned to Runway 14L/32R. Operations on Runway 14R/32L were redistributed to the remaining open runways under the preferred alternative scenario. Tables 4 and 5 attached to this memorandum summarize runway use assumptions by aircraft type. Day/Night Split MACNOMS data was used to extract time-of-day by aircraft type. The following day/night splits were used for the baseline scenario, no action alternative, and preferred alternative: Helicopters: 91.1% day – 8.9% night Business Jet: 100% day – 0.0% night Single-Engine Piston: 97.4% day – 2.6% night Twin-Engine Piston: 93.9% day – 6.1% night Turboprop: 93.9% day – 6.1% night Those operations which occur at night incur the 10-dB nighttime noise sensitivity penalty within the AEDT model. Flight Tracks Flight tracks were developed based on MACNOMS flight tracks and are modeled to reflect those used in the recently-completed LTCP. The AEDT study used multiple arrival and departure tracks for each runway end. Some runways had two arrival tracks and three departure tracks, while other runway ends had one arrival track and one departure track. Departure track dispersal was utilized where appropriate to reflect MACNOMS flight track data and the LTCP flight tracks. The image on the next page depicts arrival, departure and touch-and-go tracks as drawn in the AEDT model; red flight tracks represent aircraft arrivals, blue flight tracks represent aircraft departures, and magenta flight tracks represent aircraft touch-and-go’s. Track utilization percentages used in the AEDT study are shown in Table 6 attached to this memorandum. It is worth noting that the primary drivers of the location and distribution of aircraft noise at this airport are the runway end utilization percentages and aircraft types modeled. 3 I-3 Figure: AEDT Flight Tracks Weather The weather data used in the noise study were acquired from the National Oceanic and Atmospheric Administration (NOAA) National Climatic Data Center, which are auto-populated in the AEDT model based on the Airport’s location. The following weather inputs were auto-populated within the AEDT model to represent average operating conditions at Crystal Airport: • Ambient temperature = 45° Fahrenheit • Sea level pressure = 1015.869995 millibars • Relative humidity = 68.88% • Dew point = 36.08° Fahrenheit • Headwind speed = 7.22 knots 4 I-4 Results The baseline (2017) noise contours are shown in Figure 4-9 attached to this report. The contours represent the Federal Aviation Regulations (FAR) Part 150 (14 C.F.R. Part 150) yearly day-night average sound level (DNL) metric, which is measured in decibels (dB). As noted previously, DNL is a cumulative noise metric that represents the average daily noise level, accounting for the added intrusiveness of noise at night compared to during the day. The FAA currently considers the 65 dB DNL contour line as the threshold of significance for noise impact. The 65 DNL contour is mostly contained on Airport property in the baseline (2017) scenario,