WTC site damage assessment map, Sept 21, 2001

NYC 9/11 Public Portal Document

Implementation of any of the action alternatives is not expected to increase the pre­ disaster number of vehicles or traffic demand along area streets, roadways, and highways in Lower Manhattan. The implementation of any of the proposed action alternatives is not expected to result in significant impacts to area roadways. Temporary detours would occur with the construction of underground utilities, repair or renovation of existing buildings, construction of replacement buildings, repair and/or replacement of subway systems, and repair, replacement or construction of pedeu rian walkways, parks, open public spaces or restoration of landscaping. It is likely that the traffic management plans implemented during the disaster recovery period will form the basis of future traffic management planning. Some measure of vehicular access would be provided by standard traffic control practices that will likely be implemented in stages or phases depending on the planned construction activities. Construction and water quality BMPs would be implemented as appropriate to mitigate impacts. Altemat’ve routes would likely be available during the rebuilding period, although there may be delays and an impact to emergency response services.

Potential impacts to local traffic may occur during construction, although the majority of traffic constraints are related to the on-going debris removal actions at the WTC since September 11, 2001. Potential mitigation for construction-related traffic and transportation issues are as follows:

• Adequate on-site parking or transport areas for construction employees • Use of rail and waterways for delivery of heavy and oversize equipment • Avoidance of peak commuting hours for deliveries of heavy and oversize materials by roadways and streets. • Avoidance of residential and school areas for delivery routes • Phasing of the construction over an extended period. »

3.4 NOISE

Noise, defined is unwanted or unwelcome sound, is Federally regulated by the Noise Control Act of 1972 (NCA). Sound is a fluctuation in air pressure. Sound pressure levels are measured in units called decibels (dB). The Federal Interagency Committee on Urban Noise developed land use compatibility guidelines for noise in terms of day-night average soimd level (DNL) measured in decibels (dB). The A-weighted sound level or “dBA” is used to simulate people’s perception of loudness and annoyance and accounts for those fi-equencies most audible to the human ear. These values of noise are logarithmic; meaning an increase in. 10 dBA describes a doubling of sound pressure. The background noise of an office, at 50 dBA, is perceived as being twice as noisy as a library, at 40 dBA. Noise varies with distance from the source. The outdoor drop off rate for moving noise sources, such as trucks or cars, is a decrease of 4.5 dBA for every doubling of distance. For stationary noise sources, such as compressors or jackhammers, the outdoor drop off rate is 6.0 dBA for every doubling of distance between the noise source and receiver. Since the dBA sound pressure level describes instantaneous noise levels and few noises are constant, other ways of describing noise that occurs over extended periods have been developed. Fluctuating sound can be described by assuming that this fluctuating noise

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