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

T.F. Green Airport Improvement ProgramEnvironmental Impact Statement and Final Section 4(f) Evaluation5.3.7 Supplemental Noise MetricsAt the request of the public and agencies, during the EIS Scoping process, other noise metrics, in addition to DNL,were calculated to further describe the noise environment for Alternatives B2 and B4, and were compared to theNo-Action Alternative. Time Above (TA) and Number of Events above (N) a threshold and L maxnoise metrics werecomputed for each of the noise measurement sites (Figure 4-2) and non-residential noise-sensitive sites exposed tonoise levels at or above DNL 60 dB (Figure 5-9). While not required by the FAA, these metrics provide informationthat the DNL metric does not, such as the time that a particular location experiences noise above a specified level,the number of aircraft events causing noise above a specified level, and the maximum level at each of the sites. TheTA metric is given in terms of the total number of minutes. For example, if 65 dB is the specified threshold, themetric would be referred to as “TA-65.” There is no FAA standard for significant impact for these additionalmetrics and no threshold for incompatible land use for noise exposure measured in TA.The L maxhelps to characterize the magnitude of the noise, but does not provide information regarding the duration ofor cumulative exposure to the noise. These noise metrics were modeled using the same geographic and census inputdata used to develop the noise contours. Appendix F.4, Supplemental Noise Metrics, provides additional informationon the other noise metrics methodology and presents the full results. In general, the highest computed DNL and L maxvalues and longest TA values would occur at those sites closest to the Airport and most exposed to aircraft operationsunder all FEIS Alternatives.Each of the noise measurement site locations is described in DEIS Noise Supporting Attachment A.5, NoiseMonitoring, and shown on Figure 4-2. Tables 5-29 and 5-30 present the computed TA-75 at each of themeasurement sites and non-residential noise-sensitive sites with DNL above 60 dB, for the No-ActionAlternative and Alternatives B2 and B4 in 2015, 2020, and 2025. In general, the highest computed TA-75 wouldoccur at those sites closest to the Airport and most exposed to aircraft operations.Table 5-29 Comparison of Computed Time Above-75 at Noise Measurement Sites 1Computed TA-75 (minutes)2015 2020 2025Site 2 Address No-Action B2 B4 No-Action B2 B4 No-Action B2 B4P1 Gertrude Ave. 15.0 15.0 -- 3 -- 3 --- 3 -- 3 -- 3 -- 3 -- 3P2 Glen Drive 3.2 3.0 3.4 3.4 3.6 3.7 3.6 3.7 3.8P3 Commodore Ave. 12.9 12.9 -- 3 -- 3 -- 3 -- 3 -- 3 -- 3 -- 3P4 Louisiana Ave. 3.2 3.2 3.3 3.4 3.5 3.4 3.7 3.7 3.7S1 Winman Court 2.9 2.9 3.4 2.9 3.1 3.4 3.2 3.4 3.7S2 Alice Ave. 0.9 0.9 1.2 0.9 1.1 1.2 1.0 1.2 1.3S3 Rosegarden St. 4.6 4.6 5.5 5.1 6.2 5.8 5.6 6.7 6.3S4 Manolla Ave. 1.1 1.1 0.9 1.1 1.0 0.9 1.2 1.1 1.0S5 Wilbur Ave. 17.9 17.9 21.6 18.8 18.3 22.5 20.9 20.2 24.6S6 Grace St. 4 0.4 0.4 0.3 0.4 0.3 0.3 0.4 0.4 0.4S7 Spring Green Dr. 1.0 1.0 1.0 1.0 1.1 1.0 1.1 1.2 1.1S8 Collingwood Dr. 7.1 7.1 6.9 7.6 8.9 7.4 8.8 10.1 8.5Source: HMMH, 2011.TA Time above a threshold.1 “Time Above” means the time that a particular location experiences noise above a specified level. The TA metric is given in terms of the total number of minutes.For example, if 65 dB is the specified threshold, the metric would be referred to as “TA-65.”2 See Figure 4-2 for locations. (P - Long-term measurement sites, S - Short-term measurement sites).3 Included in acquisition due to airport construction or for noise mitigation.4 This site is located in Cranston; all other sites are in Warwick.Chapter 5 - Environmental Consequences 5-41 July 2011\\mawatr\ev\09228.00\reports\FEIS_Final_July_2011\PVD_CH05_Environmental_Cons_JUL_2011.doc