9.2 Noise Quality
Identify any applicable state or local noise regulation.
9.2.1 Existing Noise Levels
Ensure that the plot plans (scale 1:3,600 or greater) as shown on Figure 1.1-4, submitted in response
to Resource Report 1, show the sites of existing and proposed compressor units, station fencing,
property lines, and any nearby NSAs.
The plot plan should also identify the location of noise measurements and NSAs, NSAs (which include residences, schools, hospitals, churches, playgrounds, farms, and camping facilities) should be identified in Resource
Report 1 and quantitatively described
in this report.
In this section, identify all NSAs near
the proposed compressor unit building on 1:24,000/1:25,000 scale USGS topographic maps provided
in Resource Report
1 or describe by distance
and direction from the location
of the proposed compressor modification or addition.
Provide the existing
Ldn for
each NSA, and as appropriate, denote NSAs and noise measurement locations
on the plot plans.
If the compressors are to be installed at a new site, calculate
the existing Ldn from sound level measurements, or estimate
using typical noise
levels for a land use type, such as in the EPA publication Community Noise (EPA, 1971).
If the compressor units are being added to an existing facility, conduct a noise survey
of the site property line and nearby NSAs when the station is operating
at full load.
Provide the results of the noise survey of the existing
compressor units as: Leq (day), Leq (night), and Ldn, where Leq is the steady sound with the same total (equivalent) energy as the time-varying sound averaged over a specified period.
Ldn is calculated using the formula:
Describe conditions during the noise survey, including:
·
time of day;
·
duration of measurements;
·
weather conditions;
·
wind speed and direction;
·
engine load; and
·
other sources of noise present
at each measurement location.
During any sound level measurement, try to avoid times when unusual or extraneous noise which is not typical of station operation,
such as noise from pets, lawnmowers, air compressors used in spray painting, or nearby construction activity, is occurring.
If the noise generated by the existing compressor station impacts any nearby residences with an Ldn greater than 55 dBA, indicate if an acoustical analysis of the existing
units(s) at the compressor station
would be performed
to quantify the magnitude and frequency spectrum of principal noise sources associated with the operation
of the existing unit(s).
Specify possible mitigation measures, including
specific noise control
equipment, necessary to reduce the noise level(s) from the unit(s)
to 55 dBA Ldn at the nearby NSAs.
Specify which noise reduction
measures would be implemented and the schedule
for implementing the mitigation measures.
9.2.2 Noise Impacts
Describe noise impacts from construction activities, including drilling if storage wells are proposed to be constructed. Calculate
the noise impact of the compressor unit additions or modifications on all nearby
NSAs and summarize as shown in table 9.2-1. The noise impact from the compressor units should be based on far-field
sound data provided by the manufacturer, or on sound level measurements of a similar unit in service
elsewhere.
If measured noise levels from a similar unit are used, that unit should be as similar to the proposed unit as possible, including
engine/turbine model, silencing
equipment, and compressor building attenuation capabilities. In addition,
no extraneous noise should be occurring during the sound level measurements of the comparative unit. As part of the impact
assessment, provide the far-field sound
data on the compressor or the results
of the sound level measurements of the comparative unit.
Include step-by-step supporting calculations or identify the computer
program used to model the noise levels, the input and raw output data and all assumptions made when running the model, far-field sound level data for maximum facility operation, and the source of the data.
Include:
·
Sound pressure
levels for unmuffled
engine inlets and exhausts, engine casings, and cooling equipment;
·
Dynamic insertion loss for all mufflers;
·
Sound transmission loss for all compressor building components, including walls, roof, doors, windows
and ventilation openings;
·
Sound attenuation from the station to nearby noise-sensitive areas;
·
The manufacturer’s name, the model number, the performance rating; and
·
A description of each noise source and noise control
component to be employed at the proposed compressor station.
Identify all proposed noise control equipment (e.g., inlet and exhaust
silencers, building
insulation, etc.) and provide the noise absorption capabilities of this equipment. Provide the sources of this information. Also explain how the noise level (Ldn) attributable to the proposed compressor units was calculated, including
barrier, distance, air and other
attenuation factors that
were used, and include any model results or calculation spreadsheets or procedures.
For proposed compressors the initial
filing must include at least the proposed horsepower, type of compression, and energy source for the compressor.
Far-field sound level data measured
from similar units in service
elsewhere, when available,
may be substituted for manufacturer’s far-field sound level
data.
If specific noise control equipment has not been chosen, include
a schedule for submitting the data prior
to certification.
9.2.3 Mitigation
The noise estimate must demonstrate that the project will comply with applicable noise regulations and show how the facility will meet the following requirements:
The noise attributable to any new compressor station,
compression added to an existing
station, or any modification, upgrade
or update of an existing
station, must not exceed a day-night sound level
(Ldn) of 55 dBA at any pre- existing noise-sensitive area (such as schools, hospitals, or residences).
New compressor stations or modifications of existing stations
shall not result in a perceptible increase in vibration at any noise-sensitive area.