11.0 NOISE
11.1 Applicability
All new power plants subject to Article X in New York State are required to examine noise impacts and to control such impacts, if necessary. Generally, the emphasis of environmental noise regulation is toward noise-sensitive receptors, such as residences, near a facility that produces noise. The Public Service Law requires that TGE's Application include a noise study and document noise abatement measures. PSL164.1(c)(i-ii). Furthermore, New York City has a Noise Control Ordinance which sets absolute noise limits.
This section presents information regarding a proposed measurement program to document existing noise levels in the vicinity of the Project, as well as the methodology to conduct a noise impact assessment under the Article X process. Baseline field measurements to establish existing noise conditions are proposed to be conducted in September 2001, and another set of measurements will be conducted in winter 2001-2002. An operational noise impact assessment will be performed using both the Modified Composite Noise Rating (CNR) Method and through a comparison to the City's applicable regulatory noise limits and acoustic design goals for operational noise. Construction noise impacts will be estimated and evaluated as well.
11.2 Ambient Survey
11.2.1 Measurement Types
Because the sounds in our environment usually vary with time, they cannot simply be described with a single number. Two methods are used for quantifying sounds: exceedance levels and equivalent level. The exceedance levels are the sound levels exceeded a given percent of the time. For example, the residual octave band sound pressure levels (L90) is the sound level exceeded 90 percent of the time during a measurement period (almost the lowest sound level observed). The L10 level is exceeded 10 percent of the time. The equivalent level, designated Leq, is an average of sounds measured over time. It is strongly influenced by occasional loud, intrusive noises. Because it is able to account for such noises, the Leq is the best descriptor for the intermittent sound levels from construction activities.
The human ear is more sensitive to sounds of middle frequencies, and less so to sounds of high or low frequencies. A weighting scale, known as the "A" scale, has been developed to approximate the response of the human ear, and decibels are often listed as A-weighted decibels (dBA).
11.2.2 Measurement Locations and Periods
Pursuant to proposed Stipulation 6, an ambient noise level survey is proposed to be conducted during two different time periods to characterize the existing noise environment in the vicinity of the Project site. The dual survey is designed to characterize the ambient noise environment under various conditions. The measurement program will consist of a consecutive weekday and weeknight period at several measurement locations (to be determined through consultation with City and State agencies). The locations used for measurement will generally be at the boundary between the industrial waterfront uses and residential inland uses. Zoning district lines will be used during this assessment as well, in order to evaluate compliance with the New York City Noise Code.
11.3 Impact Assessment
11.3.1 Input Data and Propagation Model
Noise source input data used in noise propagation computer models will be a combination of data acquired from the vendors of major noise-producing equipment, data based on actual measurements of similar equipment at other facilities, and computations from published empirical equipment noise equations.
A noise propagation model will be used. For construction, the model will use average noise levels during major construction phases at the Project. For operation, the model can be used with greater accuracy, since there is a limited number of noise sources which are expected to operate simultaneously. This type of model predicts the noise contributed by each activity at each receptor point being examined. It accounts for distance, atmospheric conditions, structural barriers that could block sound, etc. Such models account for the noise emissions from each source in each octave band, and can also produce a corresponding single "A"-weighted level. The model will estimate noise levels from each source at the Project for each of the nearest noise-sensitive receptors (including residential district property lines) during operation of the Project.
11.3.2 Noise Standards
Various noise standards are proposed to be used to establish the acoustic design goals of the Project. Each is described below.
The Modified CNR method is a sociologically based noise evaluation procedure that considers the measured existing community sound levels along with the proposed Project's predicted operational sound levels to rank the acceptability of the proposed noise source within the current environment. The ranking is then adjusted to account for other potential factors such as the time of day the noise will be present, seasonal variations, frequency distribution, and the tonal and impulsive character of the emitted sound.
The New York City Noise Code is found in Title 24 of the Administrative Code (Chapters 243 and 244, "Ambient Noise Quality Zones, Criteria and Standards"). New York City is divided into three types of noise zones, on the basis of the zoning district. The Project site (industrial Zone M-3) is in the least restrictive zone (N-3). The absolute daytime and nighttime noise limit is an Leq (an average sound level) of 70 decibels (dBA) for any one hour, measured at the property line (or 25 feet away from the edge of the noise source for buildings with less than 25 feet setback).
The performance standards under the Zoning Resolution (Sections 42-213 and 42?214) are based on octave band sound pressure levels, as measured at the property line. In the second column of Table 11-1 below, the maximum sound pressure levels at the "zoning lot" line (Kent Avenue) are shown. In the third column, the maximum levels for the nearest residential district boundary are shown, consistent with the requirement that at residential district boundaries maximum levels must be reduced by 6 decibels for each octave band. The Application will include evaluations of compliance under both existing and proposed zoning at nearby parcels.
Table 11-1: Maximum Sound Levels Permitted under New York City Zoning Resolution Octave band (Hz) Maximum at Lot Line (dB) Max. at Residential Zone (dB) 20 to 75 80 74 75 to 150 75 69 150 to 300 70 64 300 to 600 64 58 600 to 1,200 58 52 1,200 to 2,400 53 47 2,400 to 4,800 49 43 Above 4,800 46 40
11.4 Initial Impact Assessment and Mitigation Measures
11.4.1 Construction Noise
Noise due to construction will occur. However, it is temporary in nature. In order to mitigate the possible effect of noise caused during the temporary construction period, the Project will use sound muffling devices on construction equipment to the extent practical, and outdoor work will be scheduled for daytime hours to the extent practical. In addition, the Project will comply with federal regulations limiting truck noise. Because of the temporary nature of the construction noise, no adverse or long-term effects are anticipated.
Among the mitigation measures to be studied, the Project will likely coordinate and, in some cases, notify the nearest businesses and residences of any periodic activity producing atypically loud noises.
11.4.2 Operation Noise
The Project will be designed to operate up to 24 hours per day, and measurement of impacts at nighttime periods is therefore proposed. Detailed sound level reference data will either be obtained from the equipment vendors, measurements made from comparable equipment on another project, or calculated using techniques prescribed by the Edison Electric Institute Guide. It is expected that the Project will comply with all the above-described noise standards.
11.5 Post-Construction Noise Evaluation
As part of Project testing (that is, after Project construction), ambient background and operational noise measurements are proposed to be taken at points used in the pre-construction baseline measurement program. The results of this measurement program will be used to ascertain conformance with the Project's noise design goals.