Travis AFB Sustainability Study Report Final Background Report | Page 98
and engine maintenance run‐ups. The Air Force considers how its
operations impact the local community by calculating the CNEL. The CNEL
is depicted as a contour around a noise source connecting points of equal
value, usually in 5 decibel increments.
The primary elements of the AICUZ are:
Health, Safety, and Welfare. These elements seek to reduce the
nuisance of excessive noise generated by aircraft operations and
public danger by discouraging the development of incompatible land
uses such as businesses and housing in Accident Potential Zones.
Public Investment. Promoting compatibility between a military
installation and local communities safeguards military operations and
protects the public’s investment in the installation.
Public Awareness and Communication. By working with the
community and informing local citizens of operations and safety
measures, the military can promote safety for community residents.
As local leaders work with military officials to adopt compatible
development practices, their relationship is strengthened through the
resolution of mutual concerns.
Accident Potential Zones
As part of the AICUZ program, and to aid in land use planning surrounding
military bases, the DOD established Accident Potential Zones (APZs). These
are made up of Clear Zones (CZ), Accident Potential Zone I (APZ I), and
Accident Potential Zone II (APZ II). These zones are determined using a
historical and statistical analysis of all DOD aircraft accidents.
APZs typically follow departure, arrival, and pattern flight tracks. The CZ is a
square area that extends directly beyond the end of the runway and
outward along the extended runway center line.
Height Obstructions
To prevent man‐made structures from creating an obstruction that could
prevent aircraft from accessing airports or otherwise impact the safety of air
navigation, the AICUZ Study provides an overview of height restrictions
surrounding Travis AFB. Runway airspace imaginary surfaces are the result
of the application of obstruction height criteria to Travis AFB airfield.
Noise Zone Profile
Noise is the cornerstone of the AICUZ Study. The noise generated by
military aircraft operations and the effects of that noise on local
communities are presented in a variety of ways in the study (e.g., written
text, graphically, etc.). To fully appreciate the findings and
recommendations presented in the AICUZ Study, it is beneficial to provide
an understanding of how military aircraft noise is measured, evaluated, and
graphically illustrated. Day night average sound level (DNL) is a measure of
noise commonly used at military installations. The DNL averages the noise
levels of all aircraft operations that occur within a 24‐hour period. In
California, the term Community Noise Equivalent Level (CNEL) is used. CNEL
is a weighted average of noise level over time. CNEL is the average sound
level over a 24‐hour period, with a penalty of 5 dB added between 7:00 p.m.
and 10:00 p.m. and a penalty of 10 dB added for the nighttime hours of
10:00 p.m. to 7:00 a.m. The main sources of noise at airfields are flight
operations, which include take‐offs, landings, and touch‐and‐go operations,
Page 4‐12
The 2009 Travis AFB AICUZ Study is an update to the previous
Travis AFB AICUZ Study completed in 1995. It presents a description of the
current noise environment around Travis AFB. It reaffirms the Air Force
policy of promoting public health, safety, and general welfare in areas near
Air Force installations. This study identifies changes in flight operations that
have occurred since the 1995 study and provides current noise zones and
compatible use guidelines for land areas adjacent to the installation. It is
provided as a tool to assist local communities in future planning and zoning
activities. Changes that required an update of the AICUZ Study included:
Existing Compatibility Tools