UL Lafayette: CDW: I-49 Connector: Land Use

I-49 Connector: Sound Study


BACK \| NEXT TOPICS introduction public process case studies alignments garden urbanism alt. street links public realm neighborhoods lighting sound study public art conclusion recognition SUB-TOPICS introduction land use reducing noise noise barriers	Administrative Techniques for Land Use Control

	Existing sound level: Diagram illustrates 513 feet for the decibel level to drop from 95 dBA to 66 dBA, an appropriate exterior sound level.	Proposed sound level: Diagram illustrates that with the proposed elevated highway, 700 feet is needed for the decibel level to drop from 98 dBA to an appropriate exterior sound level of 66 dBA

	A sound shadow zone is created under the elevated highway. The mass of the concrete construction of the elevated highway buffers the area below and adjacent and reduces the dBA levels.

	Administrative techniques are available to local governments to encourage noise-compatible land use near highways. These techniques include zoning and other legal restrictions. Zoning is a common local administrative technique to direct land use in accordance with a plan for orderly community growth. Zoning has been used to control signage, lot size, parking, and maximum building height. These precedents make zoning a useful tool for noise control in many communities. One method of controlling noise within an existing neighborhood where impact of excessive noise may occur is through the use of a new noise impact zone on existing zoning maps. A noise Impact Overlay Zone is a special purpose zone which is superimposed over the regular zoning map. The overlay zone could be for those exterior sites which are exposed to noise over a certain level, such as 66 dBA, or it could be defined as all land within a certain distance from the highway, perhaps 200 to 500 feet. Land that falls in such a zone would be subject not only to regulations pertaining to the regular zone, but also to regulations for the overlay zone. If the existing Evangeline Thruway generates a 95 dBA sound level at St. Genevieve Church, then how far from the Thruway would one travel to reach an acceptable noise level? Since a 66 dBA exterior sound level is the goal, this diagram (figure, existing sound level) shows the distance from the Thruway required to reach that level is 513 feet. If noise from the proposed I-49 Connector raises the sound level to 98 dBA (figure, proposed sound level), then the distance to the 66 dBA sound level is more than 700 feet. These diagrams show that for a Noise Impact Overlay Zone to be effective at the St. Genevieve site, the zone required would be more than 700 feet on either side of the proposed I-49 Connector. Zoning of this sort would insure that future development be compatible with nearby noise sources; it may also exclude future construction of incompatible uses such as residences, churches, schools, and nursing homes. This zoning may have the effect of encouraging commercial development as new residential construction near the I-49 Connector is reduced. For a meaningful Noise Impact Overlay Zone to be used along the path of the I-49 Connector, existing and proposed noise levels during peak traffic conditions would be obtained. From those readings, the local administration could determine an appropriate method for determining the limits of such a zone.

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Document last revised Thursday, April 22, 2004 10:45 AM