F-22 Plus-Up Environmental Assessment - Joint Base Elmendorf ...

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3.2.1.2 Sound Exposure Level F-22 Plus-Up Environmental Assessment 3.0 Affected Environment L max alone may not represent how intrusive an aircraft noise event is because it does not consider the length of time that the noise persists. The SEL metric combines both of these characteristics into a single measure. It is important to note, however, that SEL does not directly represent the sound level heard at any given time, but rather provides a measure of the total exposure of the entire event. Its value represents all of the acoustic energy associated with the event, as though it were present for one second. Therefore, for sound events that last longer than one second, the SEL value will be higher than the L max value. The SEL value is important because it is the value used to calculate other time-averaged noise metrics. In this EA, all stated SEL values are A-weighted, stated re 20 µPa, and used to describe sound levels in air. 3.2.1.3 Sound Pressure Level The SPL metric, which is used to assess impacts to aquatic animals, simply states the unweighted sound intensity at a particular time. In this EA, SPL levels are used to describe peak noise level in water (re 1 µPa) associated with aircraft overflights and ambient noise levels underwater. 3.2.1.4 Time-Averaged Cumulative Day-Night Average Noise Metrics The number of times aircraft noise events occur during given periods is also an important consideration in assessing noise impacts. The “cumulative” noise metrics that support the analysis of multiple time-varying aircraft events are L dn and the Onset-Rate Adjusted Monthly Day-Night Average Sound Level (L dnmr). These metrics sum the individual noise events and average the resulting level over a specified length of time. Thus, L dn and L dnmr are composite metrics representing the maximum noise levels, the duration of the events, the number of events that occur, and the time of day during which they occur. These metrics add a ten decibel (dB) penalty to those events that occur between 10:00 p.m. and 7:00 a.m. to account for the increased intrusiveness of noise events that occur at night when ambient noise levels are normally lower than during the daytime. L dnmr adds to the L dn metric the startle effects of an aircraft flying low and fast where the sound can rise to its maximum very quickly. Because the tempo of operations is so variable in airspace units, L dnmr is calculated based on the average number of operations per day in the busiest month of the year. L dn and L dnmr may be thought of as the continuous or cumulative A-weighted sound level which would be present if all of the variations in sound level which occur over the given period were smoothed out so as to contain the same total sound energy. These cumulative metrics do not represent the variations in the sound level heard. For example, an L dn of 65 dB could result from a very few noisy events, or a large number of less noisy events. Nevertheless, they do provide an excellent measure for comparing environmental noise exposures when there are multiple noise events to be considered. Studies of community annoyance caused by numerous types of environmental noise show that L dn/L dnmr correlates well with effects, and Schultz (1978) showed a consistent relationship between noise levels and annoyance (Table 3.2-1). A more recent study reaffirmed and updated Page 3-8
F-22 Plus-Up Environmental Assessment 3.0 Affected Environment this relationship (Fidell et al. 1991). The updated relationship, which does not differ substantially from the original, is the current preferred form (see Appendix D). The correlation between L dn/L dnmr is weaker for the annoyance of individuals. This is not surprising considering the varying personal factors that influence the manner in which individuals react to noise. The inherent variability between individuals makes it impossible to predict accurately how any individual will react to a given noise event. Nevertheless, findings substantiate that community annoyance to aircraft noise is represented quite reliably using L dn. Use of the L dn metric to predict human annoyance to noise has been endorsed by the scientific community and governmental agencies (American National Standards Institute 1980, 1988; USEPA 1974; Federal Interagency Commission on Urban Noise 1980; Federal Interagency Commission on Noise 1992). Table 3.2–1. Relation Between Annoyance and L dn L dn (dB) CDNL(dB) Average Percentage of Highly Annoyed Population 55 52 3.3 60 57 6.5 65 61 12.3 70 65 22.1 75 69 36.5 Source: Fidell et al. 1991, Committee on Hearing Bioacoustics and Biomechanics 1981; Schultz 1978, Stusnick et al. 1992. Community effects from sonic booms, in the form of annoyance, correlates well with the C- weighted Day-Night Average Noise Level (CDNL) (see Table 3.2-1). CDNL is similar to L dn, but uses C-weighting to account for the low frequency impulsive nature of sonic booms. Interpretation of CDNL uses a slightly different relation than interpretation of L dn, with a given numeric value of CDNL generally representing more annoyance than the same numeric value of L dn. In this EA, L dn noise levels can be assumed to be A-weighted unless specifically designated as being C-weighted. 3.2.2 Base Existing Conditions This section describes existing noise conditions in land areas near JBER as well as in the Knik Arm, which is located to the west and north of the installation. The CIBW has recently been listed as endangered under Section 7 of the Endangered Species Act. This section will provide description of the baseline noise environment in the Knik Arm to facilitate assessment of noise impacts to the CIBW and other wildlife in the Knik Arm associated with the Proposed Action. Additional discussion of baseline and proposed noise levels on biological resources in the Knik Arm can be found in section 3.6 and 4.6 (Biological Resources). 3.2.2.1 Land Areas JBER-Elmendorf has supported a variety of aircraft and operations since its inception in the early 1940s. Aircraft and associated missions have ranged from World War II bombers and cargo aircraft to the current suite of F-22, C-17, E-3, C-12, and C-130 aircraft. The variety of missions and aircraft over the years has formed the shape and extent of areas affected by aircraft operations and associated noise. Page 3-9
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F-22 Plus-Up Environmental Assessme
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Cover Sheet ENVIRONMENTAL ASSESSMEN
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Table 5.1-1. Past, Present, and Rea
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Table 5.1-2. Past, Present, and Rea
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Appendix A Characteristics of Chaff
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APPENDIX A CHARACTERISTICS OF CHAFF
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Table 2. Characteristics of RR-188
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they demonstrate ejection of 98 per
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Appendix B Characteristics and Anal
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APPENDIX B CHARACTERISTICS AND ANAL
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Figure 1. MJU-10/B Flare F-22 Plus-
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Flare failure would occur if the fl
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4.2 Flare Strike Risk Residual flar
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and velocity. A slug is defined as
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The S&I device maximum momentum wou
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Appendix C Public and Agency Outrea
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Senator Lisa Murkowski ATTN: Karen
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New Koliganek Village Council ATTN:
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Alaska Department of Natural Resour
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Eklutna Native Village ATTN: Doroth
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Village of Stony River ATTN: Mary W
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Village of Stony River ATTN: Mary W
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Appendix D Aircraft Noise Analysis
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Appendix E Sec 7 (ESA) Compliance W
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SECTION 7 (ENDANGERED SPECIES ACT)
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not require additional construction
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Other diet items include cod, pollo
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1.5.6 Northern Sea Otter—Southwes
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Most sound is actually transmitted
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The visual experience of an F-22 ov
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Figure 2. Water Surface Area Below
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approached by projected sound level
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whale are considered to be possible
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_____. 2010c. Proposed Critical Hab
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APPENDIX 1. NOISE IMPACTS ASSESSMEN
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important in determining whether an
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SPL (dB) Frequency (Hz) Figure 2. U
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e 1 µPa, 125-130 dB re 1 µPa, and
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1.18 Appendix 1 References Blackwel
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APPENDIX 2. INFORMATION ON BELUGA W
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Delphinapterus leucas, after exposu
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F2.1 Ungulates Wild ungulates appea
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F2.2 Waterfowl and Other Waterbirds
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leaving an aircraft during training
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Cavedo, A. M., K. S. Latimer, H. L.
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Perry, E. A., D. J. Boness, and S.
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