Travis AFB Sustainability Study Report Final Background Report | Page 78
maintain mission noise protection and civilian development. The 2015
maximum mission noise contours are depicted on Figure 3‐9.
Aircraft Noise Contours
Aircraft noise is produced from flight operations (overflight, take‐offs,
landings, touch‐and‐go operations) and engine maintenance run‐ups. An
engine run‐up is a maintenance procedure performed on the airfield to test
for proper engine performance. The Air Force considers how its operations
impact the local community by calculating an average‐weighted noise level
measured as a day‐night average sound level (DNL). The Travis AFB AICUZ
uses the DOD NOISEMAP program to produce noise contours indicating
noise exposure levels from aircraft operations; this is an average of all types
of aircraft at Travis AFB.
To the northeast, east, and south of Travis AFB are agricultural and open
space uses. Currently, there are no existing incompatible land uses resulting
from aircraft noise. However, there is concern for future incompatibility as
the surrounding jurisdictions grow and develop. Noise exposure can also be
a concern for certain sensitive biological resources that may be near the
airfield. In reviewing noise contours, it should be noted that these are
annual averages, and noise exposure at any given time will vary based on a
number of factors, including weather.
The contour lines developed in the model range from 60 decibel (dB) DNL to
80 dB DNL and increase in increments of five dB. The 80 dB DNL is the
loudest contour line computed and the 60 dB DNL is the quietest. The DNL
has been determined to be a reliable measure of community sensitivity to
aircraft noise and has become a standard metric used to map aircraft noise
impacts.
About eight percent of the total daily operations occur during the evening
(7:00 p.m.‐10:00 p.m.) while 41 percent occur at night
(10:00 p.m.‐7:00 a.m.). Approximately 22 percent of the aircraft
maintenance run‐ups at Travis AFB occur during the evening, while
35 percent occur at night. In efforts to minimize noise for citizens in
surrounding communities, engine run‐up locations have been placed in
areas that are less likely to impact day‐to‐day life. Also, to reduce noise
impacts, Travis AFB does not utilize the western flight pattern after
9:00 p.m.
Instead of DNL, the State of California uses Community Noise Equivalent
Level (CNEL) as the standard for aircraft noise contours, in which a five‐dB
penalty is added to each aircraft operation in the 7:00 p.m. to 10:00 p.m.
period, and a 10‐dB penalty to each operation in the 10:00 p.m. to 7:00 a.m.
period. Air Force uses the DNL metric, which is identical to the CNEL, except
that the evening noise penalty is not added on this metric. The DNL metric
includes the same 10‐dB penalty for operations after 10:00 p.m.
Source: Air Insta llation Compatible Use Zone Report, Travis Air Force Base,
November 2009
The Travis AFB Land Use Compatibility Plan (LUCP) established CNEL noise
contours based on a maximum mission estimate. The LUCP utilized
Federal Aviation Administration (FAA) methodology to determine the
Annual Service Volume of the Travis AFB runway and taxiway system. By
defining the maximum mission annual operations, a realistic level for future
noise contours can be established. The LUCP noise contours cover a larger
area than the AICUZ noise contours and will be utilized in this TSS to
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Travis AFB Profile