T.F. Green Airport Improvement Program - FEIS Chapters - PVD

T.F. Green Airport Improvement ProgramEnvironmental Impact Statement and Final Section 4(f) Evaluation4.2.1.1 Common Noise MetricsCommon metrics used to describe and evaluate aircraft and airport-related noise include:• The Decibel (dB) – The standard unit of measure for sound. It is a logarithmic quantity reflecting the ratio ofthe pressure of the sound source of interest and a reference pressure.• A-Weighted Decibel (dBA) – An important characteristic of sound is its frequency, or "pitch". TheA-weighted level has been adopted as the basic measure of environmental noise by the United StatesEnvironmental Protection Agency (EPA) and by nearly every other federal and state agency concerned withcommunity noise, including the FAA.• Day-Night Average Sound Level (DNL) – A measure of the cumulative noise exposure over a 24-hour day.It is the 24-hour, logarithmic (or energy) average, A-weighted sound pressure level with a 10-dB penaltyapplied to the nighttime event levels that occur between 10:00 PM and 7:00 AM. The DNL is theFAA-defined metric for evaluating noise and land use compatibility.4.2.1.2 Noise Study AreaTo adequately capture the effects of aircraft noise, the Noise Study Area must include not only the immediateAirport environs where aircraft flight paths are aligned with the runways, but other potentially affected areasbeyond that, over which aircraft will fly as they follow new or changed flight corridors that join thesurrounding airspace. A circular area with a radius of approximately 27 miles was used to determine the extentof flight track modeling. Figure 4-1 shows the Noise Study Area (the baseline flight tracks in combination withmodeled tracks).4.2.1.3 Noise Analyses ConductedAs required by NEPA and the FAA Order 1050.1E, the noise analysis for the Baseline Condition identifies:• The DNL aircraft noise exposure contours and estimates of associated population within each contourinterval; and• Noise-sensitive receptors.For the purposes of this EIS, the appropriate model is the Integrated Noise Model (INM) which, as required bythe FAA (FAA Order 1050.1E, Appendix A, paragraph 14.2b), was used to produce DNL contours at 75 dB,DNL 70 dB, and DNL 65 dB, and others as needed. 147 Refer to DEIS Appendix F.2, Noise Assessment Methodology,for further details on the INM model used in the noise evaluation.Noise measurements were conducted to provide an understanding of the baseline noise environment at selectedsites and to provide a check that the assumptions used in the noise modeling effort are reasonable. 148 The noisemeasurements provide information on single-event and cumulative noise exposure, and information onbaseline roadway and aircraft operations, all of which are useful in understanding the noise environment at and147 Consistent with FAA policy, the most current release of the model at the time the EIS was initiated, INM Version 6.1, was used for all noise exposure computationsand specific point analyses for the Baseline Condition assessment. The noise analysis conducted to identify noise impacts of the Build Alternatives compared to theNo-Action Alternative included a sensitivity analysis that assesses the results for selected conditions using the most recent version of the INM, Version 7.0a.148 Noise measurement data were obtained from an aircraft short-term noise monitoring program which was performed during August 2005 and from trafficnoise measurements taken on July 22, 2006.Chapter 4 – Affected Environment 4-3 July 2011\\mawatr\ev\09228.00\reports\FEIS_Final_July_2011\PVD_CH04_Affected_Env_JUL_2011.doc