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Article 3: Zoning Districts
Section 3.8. Overlay Districts
3.8.1. General
Morrisville, NC
June 2013
Unified Development Ordinance – Public Hearing Draft
Page 3-69
SECTION 3.8. OVERLAY DISTRICTS
3.8.1.
General
A.
General Purpose of Overlay Districts
Overlay zoning districts are superimposed over portions of one or more underlying base, conditional, or
planned development zoning districts with the intent of supplementing generally applicable development
regulations with additional development regulations that address special area-specific conditions, features,
or plans while maintaining the character and purposes of the underlying districts. Some overlay districts
include standards that modify or supersede standards applied by the underlying district.
B.
Classification of Overlay Districts
Land shall be classified or reclassified into an overlay zoning district only in accordance with the
procedures and requirements set forth in Section 2.5.3, Rezoning, and this section.
3.8.2.
Airport Overlay (AO) Districts
A.
Purpose
The purpose of the Airport Overlay Districts is to promote the most appropriate use of land affected by
airport activities associated with the Raleigh-Durham International Airport. More specifically, the districts
are intended to ensure the safety and welfare of the community from danger from falling aircraft and the
annoyance and potential adverse health impacts of aircraft noise, and to ensure that development within
the districts are compatible with activities associated with air traffic and services associated with the
airport. To achieve these purposes, district regulations are intended, to the extent possible, to limit land
uses to specific industrial, commercial, agricultural, recreational, and other nonresidential uses that are not
subject to high population concentrations; restrict the aboveground storage of materials that pose major
safety hazards if subject to an airplane crash; limit land uses particularly sensitive to aircraft noise within
the area subject to average day/night sound levels (DNL or Ldn) of 65 decibels (dB)
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or greater; limit
land uses and development that pose potential obstructions to safe air traffic and effective air traffic
control; and ensure that development near the airport is located, designed, constructed, and maintained in
a manner that minimizes exposure to safety risks associated with the airport, mitigates noise impacts, and
avoids impediments to safe and efficient airport operations.
B.
Applicability
1.
The regulations in this section apply to the Airport Overlay-A (AO-A) and Airport Overlay-B
(AO-B) Districts.
2.
The Airport Overlay-A (AO-A) District consists of that part of the area subject to an average
day/night sound level (DNL) from aircraft noise of 65 dB or greater (as established by the
Raleigh-Durham Airport Authority and shown on the Town of Morrisville RDU Contours Map)
located east of Chapel Hill Road (NC54). The Airport Overlay-B (AO-B) District consists of that
part of such area located west of Chapel Hill Road (NC54).
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Airport noise regulations vary in the terms used to reference sound levels. The most common is “average day/night sound
levels” (alternatively abbreviated as DNL or Ldn), whose unit of measurement is the decibel. References to sound levels in this
Ordinance will refer to DNL.