Chapter 11: Noise and Vibration A. INTRODUCTIONweb.mta.info/capital/sas_docs/deis/chapter_11.pdf ·...

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Chapter 11: Noise and Vibration

A. INTRODUCTION

This chapter of the MIS/DEIS assesses the potential for noise and vibration impacts from opera-tion of the proposed alternatives. All three Build alternatives could result in changes to noise andvibration levels nearby, either from new transit service (whether buses, subway, or LRT) orfrom changes to traffic patterns in the area. This chapter assesses the potential noise andvibration impacts that may occur during operation of each project alternative. Noise andvibration during construction are assessed separately in Chapter 15, “Construction andConstruction Impacts.”

The TSM Alternative would create dedicated bus lanes on First and Second Avenues, usingarticulated buses in these lanes. The articulated buses are assumed to create noise similar to thatproduced by current buses. However, the dedication of bus lanes on First and Second Avenueswould cause some traffic diversions onto parallel adjacent avenues, in particular, Third andLexington Avenues. Because rubber-tired buses produce very little vibrations on normally pavedroads, and because the TSM Alternative would not add a significant number of buses to anystreet in the study area, there is no potential for vibration impacts anticipated from thisalternative.

The new subway to be provided in Build Alternative 1 would create new noise and vibration onits route from 125th Street to 63rd Street, primarily beneath Second Avenue. While this alter-native is not anticipated to generate significant amount of traffic diversions, traffic volumeswould change because of the new ridership on the subway. Noise from subway operation wouldprimarily be from noise emanating through openings to the street through ventilation shafts andsubway station entrances. Vibration would depend on such factors as volume, speed, railwayconstruction methods, and soil conditions, and could be conducted through building foundationsand be perceived as noise.

Build Alternative 2, like Build Alternative 1, would have the potential for new noise and vibrationfrom the new subway. Additional noise and vibration could also occur because of the new lightrail transit (LRT) on the Lower East Side and in Lower Manhattan, which would include bothabove- and below-ground sections. Changes in noise levels could occur both from operation ofthe new system itself and from changes to street traffic, since the LRT would cause somediversions and rerouting of traffic, and some changes in traffic volumes due to the capture ofsome ridership on the LRT. Vibration from the LRT would depend on such factors as volume,speed, railway construction methods, and soil conditions, and in some cases could be perceivedas noise.

This chapter examines the potential for impacts related to noise and vibration in two sections: B,“Noise,” and C, “Vibration.” Each of these sections includes a discussion of methodology and

Manhattan East Side Transit Alternatives MIS/DEIS

* Average ability to perceive changes in noise levels from Bolt Beranek and Neuman, Inc., Fundamen-tals and Abatement of Highway Traffic Noise, Report No. PB-222-703. Prepared for the FederalHighway Administration, June 1973.

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an evaluation of existing conditions and the future conditions predicted for each projectalternative.

B. NOISE

INTRODUCTION AND METHODOLOGY

NOISE FUNDAMENTALS

Quantitative information on the effects of airborne noise on people is well documented. If suffi-ciently loud, noise may adversely affect people in several ways. For example, noise may inter-fere with human activities, such as sleep, speech communication, and tasks requiring concen-tration or coordination. It may also cause annoyance, hearing damage, and other physiologicalproblems. Several noise scales and rating methods are used to quantify the effects of noise onpeople. These scales and methods consider such factors as loudness, duration, time of occur-rence, and changes in noise level with time. However, it must be remembered that all the statedeffects of noise on people vary greatly with the individual.

Sound is a fluctuation in air pressure. Sound pressure levels are measured in units called “deci-bels” (dB). The particular character of the noise that we hear (a whistle compared to a Frenchhorn, for example) is determined by the speed, or “frequency,” at which the air pressure fluctu-ates, or “oscillates.” Frequency defines the oscillation of sound pressure in terms of cycles persecond. One cycle per second is known as one Hertz (Hz). People can hear over a relativelylimited range of sound frequencies, generally between 20 Hz and 20,000 Hz, and the ear doesnot perceive all frequencies equally well. High frequencies (that whistle, for example) are moreeasily discerned and therefore more intrusive than many of the lower frequencies (the lowernotes on the French horn, for example).

"A"-Weighted Sound Level (dBA)

To bring a uniform noise measurement that simulates people’s perception of loudness and an-noyance, the decibel measurement is weighted to account for those frequencies most audible tothe human ear. This is known as the A-weighted sound level, or “dBA,” and it is the most oftenused descriptor of noise levels where community noise is the issue. As shown in Table 11-1, thethreshold of human hearing is defined as 0 dBA; very quiet conditions (as in a library, forexample) are approximately 40 dBA; levels between 50 dBA and 70 dBA define the range ofacceptable daily activity; levels above 70 dBA would be considered noisy, loud, intrusive, anddeafening as we move up the scale to 130 dBA. In considering these values, it is important tonote that the dBA scale is logarithmic, meaning that each increase of 10 dBA actually describesa doubling of sound pressure. Thus, the background noise in an office, at 50 dBA, is perceivedas twice as loud as a library at 40 dBA. In order for most people to perceive an increase innoise, it must be at least 3 dBA. At 5dBA, the change will be readily noticeable.*


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Effects of Distance on Noise

Noise will vary with distance. For example, highway traffic at 15 meters will typically producesound levels of approximately 70 dBA. The same highway noise will measure 65.5 dBA at adistance of 30 meters. This decrease is known as “drop-off.” The outdoor drop-off rate formoving noise sources, such as traffic, is a decrease of 4.5 dBA for every doubling of distance

Table 11-1Common Noise Levels

Sound Source (dBA)

Military jet, air raid siren 130

Amplified rock music 110

Jet takeoff at 500 meters 100

Train horn at 30 meters 95

Freight train at 30 meters 90

Heavy truck at 15 meters

Busy city street, loud shout 80

Busy traffic intersection

Highway traffic at 15 meters, train 70

Predominantly industrial area 60

Light car traffic at 15 meters, city or commercial areas orresidential areas close to industry

Background noise in an office 50

Suburban areas with medium density transportation

Public library 40

Soft whisper at 5 meters 30

Threshold of hearing 0

Note: A 10 dBA increase in level appears to double the loudness,and a 10 dBA decrease halves the apparent loudness.

Source: Allee King Rosen & Fleming, Inc.

between the noise source and receiver. For stationary noise sources, such as amplified rockmusic, the outdoor drop-off rate is a decrease of 6.0 dBA for every doubling of distancebetween the noise source and receiver.

Noise Descriptors Used in Impact Assessment

Because the sound pressure level unit of dBA describes a noise level at just one moment andvery few noises are constant, other ways of describing noise over more extended periods havebeen developed. One way of describing fluctuating sound is to describe the fluctuating noiseheard over a specific period as if it had been a steady, unchanging sound. For this condition, a


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descriptor called the "equivalent sound level," L , can be computed. L is the constant soundeq eq

level that, in a given situation and period (e.g., 1 hour, denoted by L , or 24 hours, denoted aseq(1)

L ), conveys the same sound energy as the actual time-varying sound. Statistical sound leveleq(24)

descriptors such as L , L , L , L , and L are sometimes used to indicate noise levels that are1 10 50 90 x

exceeded 1, 10, 50, 90, and x percent of the time, respectively. Discrete event peak levels aregiven as L levels.01

The relationship between L and levels of exceedance is worth noting. Because L is definedeq eq

in energy rather than straight numerical terms, it is not simply related to the levels ofexceedance. If the noise fluctuates very little, L will approximate L or the median level. If theeq 50

noise fluctuates broadly, the L will be approximately equal to the L value. If extreme fluctua-eq 10

tions are present, the L will exceed L or the background level by 10 or more decibels. Thus,eq 90

the relationship between L and the levels of exceedance will depend on the character of theeq

noise. In community noise measurements, it has been observed that the L is generally betweeneq

L and L . The relationship between L and exceedance levels is used to characterize the10 50 eq

noise sources and to determine the nature and extent of their impact at all receptor locations.

A descriptor for cumulative 24-hour exposure is the day-night sound level, abbreviated as L .dn

This is a 24-hour measure that accounts for the moment-to-moment fluctuations in A-weightednoise levels due to all sound sources during 24 hours, combined. Mathematically, the L noisedn

level is the average of all L noise levels over a 24-hour period, where nighttime noise levelseq(1)

(10 PM to 7 AM) are increased by 10 dBA before averaging.

For purposes of this analysis, the maximum 1-hour equivalent sound level (L ) or the day-nighteq(1)

sound level (L ) is used for impact assessment, depending on land use category as describeddn

below.

NOISE STANDARDS AND CRITERIA

Noise levels associated with the construction and operation of the alternatives under con-sideration as part of the MESA study are subject to the noise standards defined by the FederalTransit Administration (FTA), and provisions of the New York City Noise Control Code. Con-struction equipment is regulated by the Noise Control Act of 1972.

Federal Transit Administration (FTA) Noise Impact Criteria

FTA provides capital assistance for a wide range of mass transit projects, and the extent of therequired environmental analysis and review depends on the scope and complexity of the pro-posed project and the associated environmental impacts. Noise is one of the major elements ofthe environmental impact assessment process for mass transit projects, and experience hasshown that noise and vibration are among the major concerns with regard to the effects oftransit projects on the surrounding community. In April 1995, FTA issued its report, TransitNoise and Vibration Impact Assessment, as a guideline for the evaluation of noise and vibrationlevels resulting from mass transit projects, and the assessment of impacts that result. The noiseanalysis methodology in the FTA report determines operational noise impacts that result frommass transit projects based on peak-hour L and L noise levels, depending on the land useeq(1) dn

category of the affected areas near mass transit projects. Table 11-2 describes the land usecategories defined in the FTA report, and noise metrics used for determining operational noiseimpacts. Figure 11-1 shows FTA’s noise impact criteria for transit projects.


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New York City Noise Code

The New York City Noise Control Code promulgates sound-level standards for motor vehicles,air compressors, and paving breakers; requires that all exhausts be muffled; and prohibits all un-necessary noise adjacent to schools, hospitals, or courts. The code further limits constructionactivities to weekdays between 7 AM and 6 PM. In 1979, Section 1403.3-6.01 of the code wasreenacted as Local Law No. 64. This new law established ambient noise quality criteria andstandards based on existing land use zoning designations. Table 11-3 summarizes the ambientnoise quality criteria established under Local Law No. 64, which exempts all non-stationaryvehicles.

Table 11-2FTA’s Land Use Category and Metrics

for Transit Noise Impact Criteria

Land Use Noise MetricCategory (dBA) Description of Land Use Category

1 Outdoor L * Tracts of land where quiet is an essential element in the intendedeq(h)

purpose. This category includes lands set aside for serenity andquiet, and such land uses as outdoor amphitheaters and concertpavilions, as well as National Historic Landmarks with significantoutdoor use.

2 Outdoor L Residences and buildings where people normally sleep. This cate-dn

gory includes homes, hospitals, and hotels, where a nighttimesensitivity to noise is assumed to be of utmost importance.

3 Outdoor L * Institutional land uses with primarily daytime and evening use. Thiseq(h)

category includes schools, libraries, and churches, where it is im-portant to avoid interference with such activities as speech,meditation, and concentration on reading material. Buildings withinterior spaces where quiet is important—such as medical offices,conference rooms, recording studios, and concert halls—fall intothis category. Places for meditation or study associated with cem-eteries, monuments, museums. Certain historical sites, parks, andrecreational facilities are also included.

Note: * L for the noisiest hour of transit-related activity during hours of noise sensitivity.eq

Source: Transit Noise and Vibration Impact Assessment, FTA, April 1995.


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Table 11-3City of New York Ambient Noise Quality Zone Criteria (dBA)

Ambient Noise Quality Zone (ANQZ) (7 AM–10PM) (10 PM–7AM)

Daytime NighttimeStandards* Standards*

Low-Density Residential (R1 to R3) Land Uses (N1) 60 50

High-Density Residential (R4 to R10) Land Uses (N2) 65 55

Commercial (C1 to C8) and Manufacturing (M1 to M3) Land Uses 70 70(N3)

Note: * L .eq(1 hour)

Source: City of New York Local Law No. 64.

IMPACT DEFINITION

For purposes of impact assessment, this report defines a noise impact as an L or L noiseeq(1) dn

level (depending on land use category) generated from operations of the project alternatives thatfalls in the “Impact” or “Severe Impact” area of the curve represented in Figure 11-1. Thresh-olds for “Impact” or “Severe Impact” are determined based on existing noise levels.

NOISE PREDICTION METHODOLOGY

Future noise levels for this assessment were predicted using a combination of field measure-ments and empirical data and modeling techniques to determine project-generated noiseincrements. Noise measurements were performed at these receptor locations to establishexisting conditions. Traffic on adjacent roadways and streets was the dominant noise source ateach of the receptor locations. Future noise levels were then determined based on projectionsof future traffic volumes and noise emanating from transit operations. Noise due to traffic andfixed rail sources were modeled separately. Total noise levels were determined through logarith-mic summation of the noise from these two noise sources.

Selection of Noise Receptors

Noise is both site-specific and time-dependent. Therefore, specific analysis locations (referredto as "receptors") were chosen throughout the study area for the four alternatives. Twenty-threesuch receptor locations were chosen for the proposed project. Information on engineering, landuse, and traffic was used to identify those locations that would be particularly sensitive to noiseincreases (e.g., residences, hospitals, churches, parks) or that would be likely to experience thegreatest increases in noise from project alternatives. (Information regarding the location ofresidences, institutions, historic resources, and other sensitive receptors is provided in Chapters3, 4, and 7 of this document.) In many areas of Manhattan, institutional land uses that can beclassified as land use category 3 (see Table 11-2, above) are adjacent to residences, which areclassified as land use category 2. While it is beyond the scope of this project to identify allsensitive receptors in the corridors of the project’s alternatives, representative noise receptorlocations were selected to provide some geographic coverage throughout the study area. Thenoise receptor locations were chosen based on areas where maximum project-generated noiseincreases would be most likely to occur, as a result of both mass transit sources and the changes


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in vehicular traffic. Noise receptor locations were chosen to provide some geographic coveragethroughout the study area. The site and locations chosen as noise receptors are summarized inTable 11-4 (which also indicates each site’s study area zone and FTA land use category), andshown in Figures 11-2 through 11-6.

Noise Monitoring

Noise levels at receptor sites 1-6, 9-15, 18-21, and 23 were measured for 20-minute periodsduring the AM, midday, and PM weekday peak periods, as well as a nighttime period. Measure-ments were performed on Tuesdays, Wednesdays, and Thursdays throughout the time periodbetween November 4, 1997 and November 25, 1997. Twenty-four-hour noise measurementswere made at sites 7, 8, and 22 on November 17, 12, and 18, respectively. In addition, at tworeceptor locations—Sites 16 and 17—10-minute measurements were made throughout an hourduring the AM and PM peak periods. These 10-minute measurements were used to confirm thefact that for locations in Manhattan, 20-minute measured noise levels are representative of1-hour measured levels.

The instrumentation used for the 10- and 20-minute measurements at the sensitive receptor siteswas a Larson Davis Labs (LDL) Model MK224 microphone connected to an LDL preamplifierattached to an LDL Model 700 Type 1 (according to ANSI Standard S1.4-1983) sound levelmeter. The instrument was mounted at a height of 4 feet above the ground on a tripod. Themeter was calibrated before and after readings with a Brüel & Kjær Type 4230 sound levelcalibrator using the appropriate adaptor. Measurements at each location were made on theA-scale (dBA) for a sampling period of 1 hour. The data were digitally recorded by the noiseanalyzer and displayed at the end of the measurement period in units of dBA. Measuredquantities included Leq, L1, L5, L10, L50, and L90. A windscreen was used during all soundmeasurements except for calibration. All measurement procedures conformed with therequirements of ANSI Standard S1.13-1971 (R1976).


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Table 11-4Noise Receptor Sites And Locations

Site Location Zone Category

FTALand Use

1 Second Avenue between 107th and 109th Streets East Harlem 2

2 First Avenue between 104th and 105th Streets East Harlem 2

3 Second Avenue between 97th and 99th Streets East Harlem 2

4 Third Avenue between 95th and 96th Streets near P.S. 198 Upper East Side 3

5 Lexington Avenue between 87th and 88th Streets Upper East Side 2

6 First Avenue between 92nd and 93rd Streets Upper East Side 2

7* First Avenue between 81st and 82nd Streets Upper East Side 2

8* Second Avenue between 78th and 79th Streets Upper East Side 3

9 Third Avenue between 68th and 69th Streets Upper East Side 2

10 Second Avenue between 64th and 65th Streets Upper East Side 2

11 First Avenue between 63rd and 64th Streets Upper East Side 2

12 Second Avenue between 54th and 55th Streets East Midtown 2

13 First Avenue between 54th and 55th Streets East Midtown 2

14 Third Avenue between 47th and 48th Streets East Midtown 2

15 Lexington Avenue between 47th and 48th Streets East Midtown 2

16 Second Avenue between 28th and 29th Streets East Midtown 2

17 First Avenue between 23rd and 24th Streets East Midtown 2

18 14th Street between First and Second Avenues Lower East Side 2

19 Avenue C between 7th and 8th Streets Lower East Side 2

20 Avenue D between 7th and 8th Streets Lower East Side 2

21 East Broadway between Jefferson and Clinton Streets Lower East Side 3

22 Water Street between Fulton and Beekman Streets Lower Manhattan 2*

23 Water Street between Wall and Pine Streets Lower Manhattan 2

Note: *Indicates sites where 24-hour noise measurements were performed.For definition of land use categories, see Table 11-2.

The 24-hour noise monitoring at Sites 7, 8, and 22 was conducted using a Brüel & Kjær NoiseLevel Analyzer Type 4427, a Brüel & Kjær Sound Level Calibrator Type 4230, a Brüel & Kjær½-inch microphone Type 9133, and a Brüel & Kjær microphone preamplifier Type 2619. Mea-surements at these location were made on the A-scale (dBA) for a sampling period of 1 hour,throughout a 24-hour measurement period. The data were digitally recorded by the noise ana-lyzer and displayed at the end of the sampling period in units of dBA. Measured quantities in-cluded L , L , L , L , L , and L . A windscreen was used during all sound measurements ex-eq 1 5 10 50 90

cept for calibration. All measurement procedures conformed with the requirements of ANSIStandard S1.13-1971 (R1976).

Ldn . 10 log (3)@10

Leq(peakhour) & 2

10 % (12)@10

Leq(midday) & 2

10 % (9)@10

Leq(latenight) % 8

10 & 13.8

PG NL ' E NL & 10(log E PCE % 10(log F PCEB & F PCENB


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Calculation of L Noise Levelsdn

L noise levels can be easily calculated from 24-hour noise levels, but must be approximated ifdn

noise levels are not measured over a 24-hour period. The FTA report previously cited providesan equation to approximate the L noise level based on a peak, midday, and nighttime hourly Ldn eq

noise level. At receptor sites other than sites 7, 8, and 22 (measurements at these locations weremade over a 24-hour period), L noise levels were calculated based on the following equationdn

from the FTA report:

Modeling to Predict Project Impacts: Traffic Noise

To examine noise levels from vehicular sources, a proportional modeling technique was used todetermine approximate changes in noise levels due to traffic changes that would occur for eachof the four alternatives of the proposed project. Using this technique, project-generated trafficnoise levels are calculated using existing noise levels, existing traffic data, and future traffic datafor both No Build and Build conditions. The vehicular traffic volumes were converted into Pas-senger Car Equivalent (PCE) values, for which one medium-duty truck (having a gross weightbetween 9,400 and 25,000 pounds) is assumed to generate the noise equivalent of 16 cars, andone heavy-duty truck (having a gross weight of more than 25,000 pounds) or bus is assumed togenerate the noise equivalent of 85 cars. Project-generated noise levels from traffic sources arecalculated using the following equation (this formula is based on methodologies recommendedin New York City’s City Environmental Quality Review Technical Manual, December 1993):

where:

PG NL = Project-Generated Noise LevelE NL = Existing Noise LevelE PCE = Existing PCEsF PCEB = Future PCEs for Build conditionsF PCENB = Future PCEs for No Build conditions

Because sound levels use a logarithmic scale, this model proportions logarithmically with trafficchanges.

For example, if the existing volume on a street is 100 PCE with a noise level of 70 dBA, and ifthe future traffic volumes for No Build and Build conditions were 120 PCE and 150 PCE, re-spectively, then the No Build noise level would be 70.8 dBA, the Build noise level would be 71.8dBA, and the project-generated noise level would be 64.8 dBA. This example assumes that traf-fic is the dominant noise source at a particular location. This assumption is generally true at mostlocations in Manhattan.

eq(h)'SELref% 10 log Ncars % 20 log S50

% 10 log V & 35

Leq(day) ' Leq(h) *V'Vd

Leq(night) ' Leq(h) *V'Vn

dn ' 10 log (15)@10

Leq(day)

10 % (9)@10

Leq(night) % 10

10 & 13


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At locations where future traffic volumes for Build conditions were less than future trafficvolumes for No Build conditions, the project-generated noise level was assumed to be zero.

Modeling to Predict Project Impact: Rail Noise

Rail noise was analyzed using the methodologies contained in the FTA report, Transit Noiseand Vibration Impact Assessment, April 1995. Due to the short distances between fixed-railoperations and sensitive noise receptors in the project study area, the detailed noise analysis,rather than the screening analysis, methodology contained in the FTA report was used to deter-mine rail noise at all receptor locations in the study area.

Using the FTA methodology computation of L and L , noise levels for free-field acousticeq(1) dn

conditions (no reflections above ground) from fixed-rail sources are calculated at 50 feet, usingthe following equations:

Hourly L at 50 ft:eq

use the following adjustments as applicable:

+5 for Jointed Track

+3 for Embedded Track on Grade

+4 for Aerial Structure with Slab Track

Daytime L at 50 ft:eq

Nighttime L at 50 ft:eq

L at 50 ft:dn

where:

Ncars = average number of cars per trainS = train speed, in miles per hourV = average hourly volume of train traffic, in trains per hourVd = average hourly daytime volume of traffic, in trains per hour

= number of trains, 7AM to 10PM / 15Vn = average hourly nighttime volume of traffic, in trains per hour

= number of trains, 10PM to 7 AM / 9SELref = 82 dBA for subway and LRT cars

Ldn or Leq(1) ' (Ldn or Leq(1)) *at 50 feet

& 10(log D50

Lreflecteq(1) ' Leq(1) & 10(log10("S) % 42.4


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Noise levels calculated at 50 feet from the equations above were corrected for distance asfollows:

where

D = the distance from the source to the receptor in feet

The following assumptions were made regarding fixed rail noise: crossover tracks are roughlythe same as jointed tracks, and cause noise levels to increase by 5 dBA; all above-ground por-tions of the LRT are embedded track at grade, causing noise levels to be increased by 3 dBAas described above. Maximum speeds for each section of rail were used for all fixed-rail noiseprediction.

At locations adjacent to the subway and underground portions of the LRT, noise from rail vehi-cle operations would reverberate in the enclosed space of the underground rail tunnels and sta-tions. Noise levels calculated using the above equation predict noise that results from the source,but do not take into account reverberation effects from the tunnels and stations, and do not ac-count for attenuation effects of the ventilation shafts and station entrances. Reverberationeffects of the tunnel and stations would cause significantly higher noise levels that would be theresult of the source noise and the reflected noise. For portions of the rail system located in anunderground tunnels, noise levels were adjusted by calculating a noise level caused by thereflected portion of the fixed railway noise (which was assumed to bounce off acousticallyreflective surfaces in the tunnels and stations), and adding the noise level calculated for free-field conditions through logarithmic summation. For a conservative analysis, this report assumesthat all surfaces of an underground railway tunnel or station are hard reflective surfaces, withlittle or no sound absorption. Reflected noise levels were calculated using the following equation:

where:

" is the average absorption coefficient for the enclosed space; and

S is the total surface area of the enclosed space (in square feet)

For a conservative analysis, this report assumes that the tunnel space is 300 feet long, 70 feetwide, and 25 feet tall. The average absorption coefficient is assumed to be 0.02 (for concrete).The reflected noise levels calculated from this equation were added to the free-field predictednoise levels, and adjusted for noise receptor locations based on distance and acoustical attenua-tion through a ventilation shaft or station entrance. The analysis assumes that the ventilationshafts and station entrances would be designed to attenuate noise levels in the underground tun-nels by approximately 20 dBA at the surface ventilation openings and surface station entrances.


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Table 11-5Measured 20-Minute Existing Noise Levels

Site Number/ L Noise L Noise FTA CalculatedLocation Reference Time Period Level Level L Noise Level

Measured Measured

eq(1) 10(1)

dn

Site 1: Second Avenue between AM Peak 74.9 78.5107th and 109th Streets

77.5Midday 75.1 79.0

PM Peak 75.5 78.5

Late night 72.6 75.5

Site 2: First Avenue between 104th AM Peak 78.4 78.5and 105th Streets

76.4Midday 74.1 75.5

PM Peak 74.2 77.5


Site 3: Second Avenue between 97th AM Peak 75.6 78.0and 99th Streets

75.0Midday 73.9 77.0

PM Peak 73.3 76.0


Site 4: Third Avenue between 95th AM Peak 73.4 76.5and 96th Streets near P.S. 198

75.4Midday 70.6 74.0

PM Peak 72.6 75.5


Site 5: Lexington Avenue between AM Peak 71.4 74.587th and 88th Streets

75.8Midday 73.4 74.5

PM Peak 72.4 75.5


Site 6: First Avenue between 92nd AM Peak 75.1 78.5and 93rd Streets

77.4Midday 73.9 77.5

PM Peak 74.4 77.0


Site 9: Third Avenue between 68th AM Peak 77.7 80.5and 69th Streets

79.7Midday 73.4 76.5

PM Peak 76.5 78.0



78.4Midday 76.6 79.5

PM Peak 76.3 79.0


Site 11: First Avenue between 63rd AM Peak 76.0 79.0and 64th Streets

75.4Midday 73.1 76.5

PM Peak 73.9 77.0



77.7Midday 75.7 78.5

PM Peak 77.8 80.0


Site 13: First Avenue between 54th and AM Peak 75.6 79.055th Streets

76.8Midday 76.1 79.5

PM Peak 75.1 78.0



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Table 11-5 (Continued)Measured 20-Minute Existing Noise Levels

Site Number/ L Noise L Noise FTA CalculatedLocation Reference Time Period Level Level L Noise Level

Measured Measuredeq(1) 10(1)

dn

Site 14: Third Avenue between 47th AM Peak 79.3 83.0and 48th Streets

79.3Midday 77.4 80.5

PM Peak 76.8 80.0


Site 15: Lexington Avenue between AM Peak 77.6 80.547th and 48th Streets

78.8Midday 77.9 81.0

PM Peak 77.3 80.5


Site 16: Second Avenue between AM Peak 75.3 * 80.028th and 29th Streets

77.8Midday 76.8 80.0

PM Peak 73.6 * 76.6


Site 17: First Avenue between 23rd AM Peak 74.8 * 73.5and 24th Streets

77.9Midday 75.6 79.0

PM Peak 71.9 * 73.9


Site 18: 14th Street between First AM Peak 83.5 82.5and Second Avenues

78.4Midday 74.1 77.5

PM Peak 83.9 80.0


Site 19: Avenue C between 7th and AM Peak 69.8 73.58th Streets

72.0Midday 71.2 73.5

PM Peak 70.3 73.5


Site 20: Avenue D between 7th and AM Peak 74.4 79.08th Streets

73.5Midday 72.6 76.0

PM Peak 74.1 78.5


Site 21: East Broadway between AM Peak 68.9 71.5Jefferson and Clinton

69.7Midday 68.9 68.5

PM Peak 66.9 69.0


Site 23: Water Street between Wall AM Peak 74.7 77.5and Pine

76.0Midday 72.9 75.5

PM Peak 70.9 74.0


Note: * Indicates values are calculated (see Table 11-7).


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Table 11-6Measured 24-Hour Existing Noise Levels

Hour Ending Noise Level Noise Level Noise Level

Site 7 Site 8 Site 22Measured L Measured L Measured Leq(1) eq(1) eq(1)

01:00 AM 70.7 73.5 67.3

02:00 AM 69.4 73.5 64.5

03:00 AM 68.0 72.1 63.6

04:00 AM 67.0 73.4 63.9

05:00 AM 69.8 74.0 66.1

06:00 AM 70.4 75.8 68.3

07:00 AM 72.3 78.1 70.4

08:00 AM 73.8 79.4 72.6

09:00 AM 74.6 79.3 71.5

10:00 AM 74.4 79.8 70.3

11:00 AM 72.8 78.0 69.2

Noon 72.8 82.2 72.1

01:00 PM 73.7 77.8 71.7

02:00 PM 72.4 76.5 68.1

03:00 PM 72.2 84.1 68.0

04:00 PM 71.5 80.1 68.1

05:00 PM 72.1 82.6 68.8

06:00 PM 72.5 76.6 68.8

07:00 PM 73.7 74.8 68.1

08:00 PM 71.5 76.6 69.4

09:00 PM 71.6 73.7 68.0

10:00 PM 71.0 74.3 67.6

11:00 PM 75.9 74.4 68.1

Midnight 69.7 74.2 66.0

L 78.2 82.4 74.3dn


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EXISTING CONDITIONS

As described earlier, noise levels at receptor sites 1-6, 9-15, 18-21, and 23 were measured for20-minute periods during the AM, midday, and PM weekday peak periods, as well as a nighttimeperiods on Tuesdays, Wednesdays, and Thursdays between November 4 and November 25,1997. L and L noise levels, and the calculated L noise levels, for the above-mentionedeq(1) 10(1) dn

receptor sites are shown in Table 11-5. Twenty-four-hour noise measurements made at sites 7,8, and 22 on November 17, 12, and 18, respectively, are summarized in Table 11-6.

In addition, as also described earlier, 10-minute measurements were made throughout an hourduring the AM and PM peak periods at two receptor locations—Sites 16 and 17—to confirmthat the 20-minute measured noise levels are representative of 1-hour measured levels. The 10-minute measurements and the corresponding calculated 20-minute and 1-hour L noise levelseq

are shown in Table 11-7.

Table 11-7Comparison of 10-Minute, 20-Minute,

and Hourly L Noise Levelseq

Site Number/ 10-Minute 20-Minute HourlyTime Period L Noise Level L Noise Level L Noise Leveleq eq eq

SITE 16: AM Peak 74.974.9

75.375.3

74.9

74.4

76.1

76.275.6

74.9

SITE 16: PM Peak 73.373.3

73.672.9

73.3

72.4

73.4

75.074.6

74.1

SITE 17: AM Peak 73.674.0

74.875.0

74.3

74.4

75.6

74.875.4

75.9

SITE 17: PM Peak 72.172.2

71.971.6

72.3

72.5

70.6

71.771.8

71.8


11-16

As shown in the tables, in general, all of the measured noise levels are relatively high and reflectthe high level of vehicular activity that takes place in the study area.

PROBABLE IMPACTS OF THE PROJECT ALTERNATIVES

The following discussion analyzes possible noise impacts that could result from operation of thefour project alternatives. Noise impacts during construction are discussed in Chapter 15 of thisdocument.

NO BUILD ALTERNATIVE

In the future, traffic volumes throughout the study area are expected to grow, which will causesmall increases in ambient noise levels. Applying the previously described traffic noise modelingmethodology to the prediction of noise levels generated by changes associated with the No Buildalternative, and combining the results with existing noise levels, No Build noise levels werepredicted for the future. The maximum change in No Build L noise levels dBA when com-eq(1)

pared with existing noise levels would be 0.8. These changes are due to general growth in traffic(see Table 11-8).

TSM ALTERNATIVE

The TSM Alternative could result in changes to ambient noise levels because of its new bus ser-vice, which would be run with articulated buses, or because of changes to other traffic patternsas a result of the new bus lanes. Operational noise from the TSM Alternative was modeled as-suming that noise levels from articulated buses, which are proposed to replace existing busesalong the TSM route, produce noise levels similar to existing buses. The TSM Alternative wouldnot increase the number of buses on the route; rather, it would permit buses to operate indedicated bus lanes along First and Second Avenues. The new bus lanes are predicted to causetraffic diversions to adjacent avenues. This would primarily affect noise levels along Third andLexington Avenues. These traffic diversions are expected to occur primarily during daytimehours when traffic volumes are high and not during nighttime hours when traffic flows easily ortraffic is not congested. In addition, the TSM Alternative also includes the rerouting and reallo-cation of existing M15, M21, and M22 bus service on the Lower East Side. These changes toexisting bus service would cause an increase in the number of buses on some streets on theLower East Side.

Noise levels due to traffic changes resulting from this alternative (which includes buses), existingnoise levels, land use categories, impact thresholds, and resulting Build noise levels with thisalternative are summarized in Table 11-9. Under FTA criteria, the TSM Alternative would resultin noise impacts at noise receptor locations 18 and 20, which are located in the Lower East Sidezone. The primary cause of these impacts would be due to the relocation and reallocation ofexisting M15 and M22 bus service, particularly during late night hours. The maximum change inL or L noise levels for the TSM Alternative, when compared with existing noise levels,dn eq(1)

would be 2.3 dBA.

BUILD ALTERNATIVE 1

The new subway proposed in Build Alternative 1 could result in noise due to the new below-ground rail activity. Operational noise from the Build Alternative 1 was modeled assuming that


11-17

10-car subway trains would operate on the new subway line, which would run between 63rd and125th Streets. South of 63rd Street, the new subway would run along an existing route. Thenoise from the train depends on the speed of the subway and the frequency of service. The sub-way would operate with an average speed of 20 miles per hour (mph), and could possibly reachspeeds of 40 miles per hour. However, for analysis purposes, subway speeds were assumed tobe 40 miles per hour to conservatively estimate noise levels from rail sources. During themorning and evening peaks, both the northbound and southbound subway would operate with2.5-minute headways (intervals between trains). During the midday (nonpeak) period, the sub-way would operate with 7.5-minute headways in each direction. During the evening (7-11 PM),

Table 11-8Impact Evaluation of Noise from the

No Build Alternative

Noise Existing No BuildReceptor Land Use Noise Noise Noise

Site Category Descriptor Level Level

1 2 L 77.5 77.9dn

2 2 L 76.4 77.0dn

3 2 L 75.0 75.4dn

4 3 Max L 73.4 73.8eq(1)

5 2 L 75.8 76.2dn

6 2 L 77.4 77.8dn

7 2 L 78.2 80.5dn

8 3 Max L 84.1 84.5eq(1)

9 2 L 79.7 80.1dn

10 2 L 78.4 78.8dn

11 2 L 75.4 75.8dn

12 2 L 77.7 78.1dn

13 2 L 76.8 77.2dn

14 2 L 81.6 82.0dn

15 2 L 81.7 82.1dn

16 2 L 77.8 78.2dn

17 2 L 77.9 78.3dn

18 2 L 78.4 78.9dn

19 2 L 72.0 72.4dn

20 2 L 73.5 74.0dn

21 3 Max L 68.9 69.4eq(1)

22 2 L 74.3 75.7dn

23 2 L 76.0 76.6dn

Note: For definition of land use categories, seeTable 11-2.


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Table 11-9Impact Evaluation of Noise from TSM Alternative

Noise Existing d Noise Level for Generated BUILDReceptor Land Use Noise Noise Level for “SEVERE Noise Noise

Site Category Descriptor Level “IMPACT” IMPACT” Level Result Level

Allowable Project-Project- Generate

Generate d Noise Project-

Allowable

1 2 L 77.5 65.0 75.0 0.0 No impact 77.9dn

2 2 L 76.4 65.0 74.3 0.0 No impact 77.0dn

3 2 L 75.0 65.0 73.2 0.0 No impact 75.4dn

4 3 MAX L 73.4 70.0 77.0 59.5 No impact 74.0eq(1)

5 2 L 75.8 65.0 73.8 55.1 No impact 76.2dn

6 2 L 77.4 65.0 75.0 0.0 No impact 77.8dn

7 2 L 78.2 65.0 75.0 0.0 No impact 80.5dn

8 3 MAX L 84.1 70.0 80.0 0.0 No impact 84.5eq(1)

9 2 L 79.7 65.0 75.0 60.3 No impact 80.1dn

10 2 L 78.4 65.0 75.0 0.0 No impact 78.8dn

11 2 L 75.4 65.0 73.5 0.0 No impact 75.8dn

12 2 L 77.7 65.0 75.0 0.0 No impact 78.1dn

13 2 L 76.8 65.0 74.6 0.0 No impact 77.2dn

14 2 L 81.6 65.0 75.0 58.3 No impact 82.0dn

15 2 L 81.7 65.0 75.0 60.8 No impact 82.1dn

16 2 L 77.8 65.0 75.0 60.2 No impact 78.3dn

17 2 L 77.9 65.0 75.0 59.0 No impact 78.4dn

18 2 L 78.4 65.0 75.0 74.4 IMPACT 80.2dn

19 2 L 72.0 65.0 70.9 64.4 No impact 73.0dn

20 2 L 73.5 65.0 72.1 70.0 IMPACT 75.5dn

21 3 MAX L 68.9 68.5 73.7 0.0 No impact 69.4eq(1)

22 2 L 74.3 65.0 72.7 10.4 No impact 75.7dn

23 2 L 76.0 65.0 74.0 0.0 No impact 76.6dn

Note: For definition of land use categories, see Table 11-2.

trains would operate with 10-minute headways in each direction. During the nighttime, trainswould operate with 15-minute headways in each direction

Noise levels due to subway operations were predicted (where applicable) at receptor locationsusing these data, and combined with project-generated noise levels from traffic changes resultingfrom this alternative (discussed in Chapter 9). Project-generated noise levels for this alternative,existing noise levels, land use categories, impact thresholds, and resulting Build noise levels withthis alternative are summarized in Table 11-10.

As shown in the table, no significant adverse noise impacts are predicted to occur at any recep-tor locations under Build Alternative 1. The maximum change in L or L noise levels fordn eq(1)

Build Alternative 1, when compared with existing noise levels, would be 2.3 dBA. Maximum


11-19

noise levels (L ) along the Second Avenue corridor are expected to reach as high as 75.3 dBAmax

during peak pass-by of subway trains. L levels are included for information purposes.max

Table 11-10Impact Evaluation of Noise: Build Alternative 1

Noise Use Noise Existing BuildReceptor Categor Descripto Noise NoiseSevere Traffi Combine

Site y r Level Result LevelImpact Impact c Railway d

Land

AllowableProject-

Generated Project-GeneratedNoise Level Noise Level

1 2 L 77.5 65.0 75.0 0.0 60.7 60.7 No impact 78.0dn

2 2 L 76.4 65.0 74.3 0.0 42.0 42.0 No impact 77.0dn

3 2 L 75.0 65.0 73.2 0.0 60.7 60.7 No impact 75.5dn

4 3 MAX L 73.4 70.0 77.0 0.0 44.8 44.8 No impact 73.8eq(1)

5 2 L 75.8 65.0 73.8 0.0 37.5 37.5 No impact 76.2dn

6 2 L 77.4 65.0 75.0 0.0 42.0 42.0 No impact 77.8dn

7 2 L 78.2 65.0 75.0 0.0 47.1 47.1 No impact 80.5dn

8 3 MAX L 84.1 70.0 80.0 0.0 68.5 68.5 No impact 84.6eq(1)

9 2 L 79.7 65.0 75.0 0.0 42.0 42.0 No impact 80.1dn

10 2 L 78.4 65.0 75.0 0.0 60.7 60.7 No impact 78.9dn

11 2 L 75.4 65.0 73.5 0.0 42.0 42.0 No impact 75.8dn

12 2 L 77.7 65.0 75.0 0.0 0.0 0.0 No impact 78.1dn

13 2 L 76.8 65.0 74.6 0.0 0.0 0.0 No impact 77.2dn

14 2 L 81.6 65.0 75.0 0.0 0.0 0.0 No impact 82.0dn

15 2 L 81.7 65.0 75.0 0.0 0.0 0.0 No impact 82.1dn

16 2 L 77.8 65.0 75.0 0.0 0.0 0.0 No impact 78.2dn

17 2 L 77.9 65.0 75.0 0.0 0.0 0.0 No impact 78.3dn

18 2 L 78.4 65.0 75.0 0.0 0.0 0.0 No impact 78.9dn

19 2 L 72.0 65.0 70.9 0.0 0.0 0.0 No impact 72.4dn

20 2 L 73.5 65.0 72.1 0.0 0.0 0.0 No impact 74.0dn

21 3 MAX L 68.9 68.5 73.7 0.0 0.0 0.0 No impact 69.4eq(1)

22 2 L 74.3 65.0 72.7 0.0 0.0 0.0 No impact 75.7dn

23 2 L 76.0 65.0 74.0 0.0 0.0 0.0 No impact 76.6dn


In addition to the noise from the new subway service in Manhattan, Build Alternative 1's newEast Side subway extension could also result in changes in noise levels at the 36th-38th StreetYard in Brooklyn where the trains would be stored. Use of the 36th-38th Street Yard for middayand overnight storage for approximately half of the new B Division trainsets could potentiallyresult in significant impacts to ambient noise levels at nearby residential uses.

The 36th-38th Street Yard is currently used for storage of four 10-car passenger subway trainsand 8 to 12 work trains. Preliminary calculations indicate that with the new East Side subwayextension, 17 of the 32 new B Division 10-car trains would be stored at the yard. (For moreinformation on storage at the yard, see Appendix D, the Final Engineering Report.) In terms of


11-20

train operations, it is expected that 17 trainsets would depart the yard between 5 and 6:30 AMeach day, with 10 returning between 10 AM and 11:30 AM (after the morning peak period) formidday storage. The 10 trains would again depart from the yard between 2:30 PM and 4 PM forthe evening peak period service, and return to the yard between 9 PM and 11 PM. Theremaining seven trains would return to the yard after midnight for overnight storage until 5 AM,when the operating cycle would begin again.

The potential for noise impacts due to these operations at the yard were assessed using theFTA’s General Noise Assessment procedures, outlined in FTA’s Transit Noise and VibrationImpact Assessment (April 1995). Due to the number of late night (10 PM-7 AM) trainoperations expected at the yard, the results of the general noise assessment indicate that BuildAlternative 1 could result in significant adverse noise impacts at nearby residential structures. (Aland use map illustrating the location of nearby uses is provided in Appendix G, Figure G-21.)However, it should be noted that the general noise assessment is a simplified analysis used todetermine the need for further, more detailed analysis. There are several factors that requirefurther engineering and operational analysis before a more detailed examination of potentialnoise impacts can proceed. First, the yard is very large and complex, and a more detailedoperating plan must be developed to determine which portions of the yard would generate noiseand the exact distance between those areas and the nearest residential uses. It should be notedthat the general noise assessment is based on a simple assumption of L noise levels at 50 feet.dn

Second, portions of the yard are shielded from various noise receptors by grade changes and byintervening structures. Further, work on the yard under Build Alternative 1 could involvechanges to retaining walls at the yard boundaries, and these changes could incorporate newnoise barriers. Once additional engineering and operational analysis is performed for BuildAlternative 1, a more detailed analysis of potential noise impacts on residential structures and thefeasibility and efficacy of any potential mitigation measures will be conducted.

BUILD ALTERNATIVE 2

Operations from Build Alternative 2 would contain all the subway elements of Build Alternative1, but would add an LRT to serve the Lower East Side and Lower Manhattan. Noise levels forthe subway component of this alternative are assumed to be the same as for Build Alternative1, above. Noise from the LRT would be related to operation of that new transit service and tochanges in traffic on surrounding streets. Noise from the LRT operation would depend on thespeed of the trains and frequency of service. The noise analysis assumes that two-car LRTtrains would operate at 15 mph on Water and Pearl Streets, 35-50 mph in the tunnel portion, 9mph on East Broadway, 30 mph on Avenue D, and 9 mph on 14th Street. During the morningand evening peaks, the LRT would operate with 3-minute headways in each direction. Duringthe midday (nonpeak) period, the subway would operate with 6-minute headways in eachdirection. During the evening (7-11 PM), trains would operate with 7.5-minute headways in eachdirection. During the nighttime, trains would operate with 20-minute headways in each direction.

In addition to the noise associated with the new LRT, this alternative would also result in noiseassociated with changes in traffic patterns. As a result of the introduction of the new right-of-way, some traffic would be diverted to other streets. Traffic diversions would primarily affectnoise levels along Avenue C, due to the proposed change of Avenue D to a one-way street(southbound only), and the diversion of northbound traffic to Avenue C.


11-21

Noise levels due to railway operations were predicted (where applicable) at receptor locationsusing these data, and combined with noise levels from traffic changes resulting from this alterna-tive. Maximum speeds were assumed in the noise model to conservatively estimate noise levelsfrom rail sources. Project-generated noise levels for this alternative, existing noise levels, landuse categories, impact thresholds, and resulting Build noise levels under this alternative aresummarized in Table 11-11.

Table 11-11Impact Evaluation of Noise: Build Alternative 2

Noise Existing BuildReceptor Land Use Noise Noise NoiseSevere

Site Category Descriptor Level Result LevelImpact Impact Traffic Railway Combined

AllowableProject-

Generated NoiseLevel Project-Generated Noise Level

1 2 L 77.5 65.0 75.0 0.0 60.7 60.7 No impact 78.0dn

2 2 L 76.4 65.0 74.3 0.0 42.0 42.0 No impact 77.0dn

3 2 L 75.0 65.0 73.2 0.0 60.7 60.7 No impact 75.5dn

4 3 MAX L 73.4 70.0 77.0 0.0 44.8 44.8 No impact 73.8eq(1)

5 2 L 75.8 65.0 73.8 0.0 37.5 37.5 No impact 76.2dn

6 2 L 77.4 65.0 75.0 0.0 42.0 42.0 No impact 77.8dn

7 2 L 78.2 65.0 75.0 0.0 47.1 47.1 No impact 80.5dn

8 3 MAX L 84.1 70.0 80.0 0.0 68.5 68.5 No impact 84.6eq(1)

9 2 L 79.7 65.0 75.0 0.0 42.0 42.0 No impact 80.1dn

10 2 L 78.4 65.0 75.0 0.0 60.7 60.7 No impact 78.9dn

11 2 L 75.4 65.0 73.5 0.0 42.0 42.0 No impact 75.8dn

12 2 L 77.7 65.0 75.0 0.0 0.0 0.0 No impact 78.1dn

13 2 L 76.8 65.0 74.6 0.0 0.0 0.0 No impact 77.2dn

14 2 L 81.6 65.0 75.0 0.0 0.0 0.0 No impact 82.0dn

15 2 L 81.7 65.0 75.0 0.0 0.0 0.0 No impact 82.1dn

16 2 L 77.8 65.0 75.0 0.0 0.0 0.0 No impact 78.2dn

17 2 L 77.9 65.0 75.0 0.0 0.0 0.0 No impact 78.3dn

18 2 L 78.4 65.0 75.0 0.0 53.9 53.9 No impact 78.9dn

19 2 L 72.0 65.0 70.9 63.9 45.8 64.0 No impact 73.0dn

20 2 L 73.5 65.0 72.1 0.0 64.4 64.4 No impact 74.5dn

21 3 MAX L 68.9 68.5 73.7 0.0 56.5 56.5 No impact 69.6eq(1)

22 2 L 74.3 65.0 72.7 0.0 58.4 58.4 No impact 75.8dn

23 2 L 76.0 65.0 74.0 0.0 58.4 58.4 No impact 76.7dn


No significant adverse noise impacts are predicted to occur at any receptor locations under BuildAlternative 2. The maximum change in L or L noise levels for Build Alternative 2, whendn eq(1)

compared with existing noise levels would be 2.3 dBA. As described earlier for Build Alter-native 1, maximum noise levels (L ) along the Second Avenue corridor are expected to reachmax

as high as 75.3 dBA during peak pass-by of subway trains. Similarly, L noise levels aremax

expected to reach as high as 80.1 dBA on Water Street, 73.0 dBA on East Broadway, 77.5 dBAon Avenue D, and 83.0 dBA on 14th Street, during peak pass-by of LRT trains. L levels aremax

included for information purposes.


11-22

NOISE MITIGATION

No mitigation measures are available for the significant adverse noise impacts predicted for theTSM Alternative as a result of bus reroutings on the Lower East Side, other than not reroutingthis bus service.

As described above, the operation of new subway trains at the 36th-38th Street Yard inBrooklyn could result in significant noise impacts at nearby residences. Additional analysis ofthese potential noise impacts will be conducted for the FEIS. Possible mitigation measures wouldinclude construction of noise barriers at the edge of the yard.

C. VIBRATION

INTRODUCTION AND METHODOLOGY

The proposed project’s alternatives would introduce two potential sources that may affect vibra-tion levels in the study area—vehicular sources (i.e., buses and diverted traffic) and fixed rail-way operations (i.e., subways and LRT cars).

Vehicular sources contact the ground through soft rubber tires, and it is unusual for vibrationfrom sources such as buses and trucks to be perceptible, even in locations close to major roads.Vehicular sources produce vibration levels which are typically below the threshold of humanperceptibility, and are not of concern for this project.

Fixed railway operations have the potential to produce very high vibration levels, since railwayvehicles contact a rigid steel rail with steel wheels. The effects of ground-borne vibration includediscernable movement of building floors, rattling of windows, shaking of items on shelves orhanging on walls, and rumbling sounds. In extreme cases, the vibration can cause damage tobuildings. Train wheels rolling on the steel rails create vibration energy that is transmitted into thetrack support system. The amount of vibrational energy is strongly dependant on factors such ashow smooth the wheels and rails are, and the vehicle suspension system. The vibration of thetrack structure “excites” the adjacent ground, creating vibration waves that propagate throughthe various soil and rock strata to the foundations of nearby buildings. As the vibration pro-pagates from the foundation through the remaining building structure, certain resonant, or natural,frequencies of various components of the building are excited.

The vibration of floors and walls may cause perceptible vibration, rattling of items such as win-dows or dishes on shelves, or a rumble noise. The rumble is the noise radiated from the motionof the room surfaces. This is called ground-borne noise.

Each alternative’s potential effects on vibration are analyzed in this section, after a brief intro-duction to vibration fundamentals and impact criteria.

VIBRATION FUNDAMENTALS

Vibrations consist of rapidly fluctuating motions in which there is no “net” movement. When anobject vibrates, any point on the object is displaced from its initial “static” position equally in bothdirections so that the average of all its motion is zero. Any object can vibrate differently in threemutually independent directions; vertical, horizontal, and lateral. It is common to describe vi-bration levels in terms of velocity, which represents the instantaneous speed at a point on the


11-23

object that is displaced. In a sense, the human body responds to an average vibration amplitude.Because the net average of a vibration signal is zero, the root mean square (rms) amplitude isused to describe vibration amplitude.

Measurement of Vibration Levels

The root mean square of a vibration signal is the average of the squared amplitude of the signalover a given time period (usually 1 second). The rms velocity is normally described in inches persecond in the USA and meters per second in the rest of the world. Decibel notation is in com-mon use for vibration level, defined as:

Lv = 20 X log10 ( V / Vref ),

where L is the velocity level in decibels, V is the rms velocity amplitude, and V is the ref-v ref

erence velocity amplitude. All vibration levels in this document are referenced to 1 x 10 in./-6

sec.“Vdb” is used in this document for vibration decibels to reduce the potential for confusionwith noise decibels.

Effect of Propagation Path

Vibrations are transmitted from the source to the ground, and propagate through the ground tothe receiver. Soil conditions have a strong influence on the levels of ground-borne vibration. Stiffsoils, such as some clay and rock, transmit vibrations over substantial distances. Sandy soils,wetlands, and groundwater tend to absorb movement and thus reduce vibration transmission.Because subsurface conditions vary widely, there is no way to accurately model the propagationpath through soil. Therefore, vibration levels are most accurately determined as close to thesource as possible. However, soil conditions give an important clue to the eventual propagationof vibrations to neighboring sites. Bedrock layers illustrated in engineering drawings were usedto model the effect of the vibration propagation paths for the fixed railways of Build Alternatives1 and 2.

Vibration Levels

Although the perceptibility threshold for ground-borne vibration is about 65 VdB, human res-ponse to vibration is not usually significant unless the vibration exceeds 70 VdB. As a compari-son, buses and trucks rarely create vibration that exceeds 70 VdB unless there are significantbumps in the road, and these vehicles are operating at moderate speeds. Vibration levels for ty-pical human and structural responses and sources are shown in Table 11-12. Background vibra-tion is usually well below the threshold of human perception, and is of concern only when thevibration affects very sensitive manufacturing or research equipment. Electron microscopes,high resolution lithography equipment, and laser and optical benches are typical of equipment thatis highly sensitive to vibration.

VIBRATION STANDARDS AND CRITERIA

With the construction of new rail rapid transit systems in the past 20 years, considerable ex-perience has been gained as to how communities would react to various levels of building vibra-tion. This experience, combined with the available national and international standards, repre-sents a good foundation for predicting annoyance from ground-borne noise and vibration in resi-dential areas.


11-24

The FTA-developed criteria for environmental impact from ground-borne vibration and noise arebased on the maximum levels for a single events. The impact criteria are defined in the FTAreport, Transit Noise and Vibration Impact Assessment. The criteria for acceptable ground-borne vibration are expressed in terms of rms velocity levels in decibels and the criteria for ac-ceptable ground-borne noise are expressed in terms of A-weighted sound level. The limits arespecified for the three land use categories defined below:

Table 11-12Typical Levels of Ground-Borne Vibration

Human/Structural Response (VdB) Typical Sources (@ 50 feet)Velocity Level

Threshold, minor cosmetic damage fragile 100 Blasting from construction projectsbuildings

Bulldozers and other heavy trackedconstruction equipment

Difficulty with vibration-sensitive tasks, 90such as reading a video screen

Commuter rail, upper range

Residential annoyance, infrequent events 80 Rapid Transit Rail, upper range

Commuter Rail, typical range

Residential annoyance, frequent events Bus or Truck over bump

70 Rapid Transit Rail, typical range

Limit for vibration sensitive equipment. Bus or truck, typicalApprox. Threshold for human perception ofvibration

60

Typical background vibration

50

Source: U.S. Dept of Transportation, FTA, Transit Noise and Vibration Impact Assessment, April1995.

! Vibration Category 1: High Sensitivity—Buildings where low ambient vibration is essen-tial for the operations within the building, which may be well below levels associated withhuman annoyance. Typical land uses are vibration-sensitive research and manufacturing,hospitals, and university research operations. Although the FTA methodology does notclassify historic structures in this category, this report will apply Category 1 to historicbuildings. Historic buildings are potentially sensitive to architectural damage from frequentvibration levels higher than 65 VdB. Architectural damage includes cosmetic damage, suchas cracked plaster, etc. Architectural damage is not considered potentially dangerous.

!! Vibration Category 2: Residential—This category covers all residential land uses andany buildings where people sleep, such as hotels and hospitals. No differentiation is madebetween different types of residential areas. This is primarily because ground-bornevibration and noise are experienced indoors and building occupants have practically no


11-25

means to reduce their exposure. Even in a noisy urban area, the bedrooms often will bequiet in buildings that have effective noise insulation and tightly closed windows. Hence, anoccupant of a bedroom in a noisy urban area is likely to be just as sensitive to ground-bornenoise and vibration as someone in a quiet suburban area.

! Vibration Category 3: Institutional—This category includes schools, churches, other in-stitutions, and quiet offices that do not have vibration-sensitive equipment, but still have thepotential for activity interference.

There are some buildings, such as concert halls, TV and recording studios, and theaters, that canbe very sensitive to vibration and ground-borne noise, but do not fit into any of these three cate-gories. The FTA report has defined special vibration levels for these land uses. None of the landuses within the MESA study area along the proposed alternatives’ routes fall into this special usecategory. Therefore, for simplicity, this assessment considers only the three vibration categorieslisted above. Table 11-13 includes ground-borne vibration and noise impact criteria for the threeland use categories defined above.

Table 11-13Ground-Borne Vibration and

Noise Impact Criteria

Vibration Frequent Infrequent Frequent InfrequentCategory Events Events Events Events

Ground-Borne Vibration Impact Levels

(VdB re 1 micro inch/sec) (dBA re 20 micro Pascals)

1 2 1 2

1 65 VdB 65 VdB 35 dBA 43 dBA3 3 4 4

2 72 VdB 80 VdB 35 dBA 43 dBA

3 75 VdB 83 VdB 40 dBA 48 dBA

Notes: “Frequent Events” are defined as those with more than 701

vibration events per day. Most rapid transit projects fall intothis category.“Infrequent Events” are defined as those with fewer than 702

vibration events per day. This category includes most com-muter rail systems.This criterion limit is based on levels that are acceptable for3

most moderately sensitive equipment such as optical micro-scopes. Vibration sensitive manufacturing or research willrequire detailed evaluation to define the acceptable vibrationlevels. Ensuring lower vibration levels in a building often re-quires special design of the HVAC systems and stiffenedfloors.Vibration-sensitive equipment is not sensitive to ground-4

borne noise. However, historic structures may include resi-dences. Therefore ground-borne noise levels for category 1land use will match those for category 2.

Source: Transit Noise and Vibration Impact Assessment, FTA, April1995, pages 8-2 through 8-3.


11-26

VIBRATION PREDICTION METHODOLOGY

To assess vibrations from project alternatives, the procedures set forth in the general vibrationassessment section of the FTA report were used to predict vibration levels from Build Alter-natives 1 and 2's fixed railway operations. Information on vehicle speeds, headway, and trackalignment/profiles were used to predict vibration levels resulting from operation of Build Alterna-tive 1 and Build Alternative 2, in the corresponding areas of these alternatives. Geological infor-mation from engineering railway profile diagrams was used in the analysis of soil conditions andfoundation types, in the project areas.

Maximum speeds for each section of railway were used to predict vibration levels from the fixedrailway operations. Crossovers and other special trackwork were assumed to increase predictedvibration levels by 10 VdB. All rails are assumed to be steel welded construction, except atcrossover points.

PROBABLE IMPACTS OF THE PROJECT ALTERNATIVES

NO BUILD ALTERNATIVE

As mentioned previously, vehicular sources contact the ground through soft rubber tires, and itis unusual for vibration from sources such as automobiles, buses, and trucks to be perceptible,even in locations close to major roads. Vehicular sources produce vibration levels which aretypically below the threshold of human perceptibility, and only need to be considered under spe-cial circumstances such as rough or unpaved road surfaces, major road discontinuities (bumps,expansion joints, etc.), and significant increases in traffic. The No Build Alternative would notadd a significant number of vehicles to any street in the study area, and any changes in vehiculartraffic under No Build conditions represent general growth in traffic volumes in New York City.There are no vibrational impacts anticipated with the No Build Alternative.

TSM ALTERNATIVE

As described above, it is unusual for vibration from sources such as buses and trucks to be per-ceptible, even in locations close to major roads. Vehicular sources produce vibration levels thatare typically below the threshold of human perceptibility, and only need to be considered underspecial circumstances such as rough or unpaved road surfaces, major road discontinuities(bumps, expansion joints, etc.), and significant increases in traffic. The TSM Alternative wouldnot add a significant number of buses to any street in the study area; therefore, no vibrational im-pacts are anticipated with the TSM Alternative.

BUILD ALTERNATIVE 1

The vibrations from the new subway proposed under Build Alternative 1 would depend on thelength of the subway trains and the speed and frequency of service. A screening analysis ofoperational vibrations and ground-borne noise from Build Alternative 1 was performed assuming10-car subway trains; subway operation at maximum speeds of 40 miles per hour; morning andevening peak operation with 2.5-minute headways in each direction; midday (nonpeak) periodoperations with 7.5-minute headways in each direction; evening (7-11 PM) train operations with10-minute headways in each direction; and nighttime train operations with 15-minute headways


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in each direction. The screening analysis assumed no vibration mitigation measures, maximumsubway speeds, and welded steel rail construction.

The screening analysis showed the potential for vibration impacts or ground-borne vibrationnoise impacts at each of the proposed subway stations as follows: 69th to 72nd Street (LenoxHill station), 83rd to 86th Street (Yorkville station), 96th to 97th Street (East 96th Street station),106th to 109th Street (Franklin station), and 124th to 125th Street (125th Street station). Inaddition, the following areas were also identified as possible areas for vibration impacts orground-borne vibration noise impacts: Second Avenue between 81st and 82nd Streets, SecondAvenue between 113th and 115th Streets, and an area just east of Lexington Avenue between122nd and 124th Streets. High vibration and ground-borne vibration noise levels in these areasare due to the proposed locations for crossover tracks. The discontinuities in crossover trackscause vibration levels to be roughly 10 dB higher than those on welded rail. Potential mitigationmeasures for these significant vibration impacts are discussed below under “VibrationMitigation.”

BUILD ALTERNATIVE 2

Operations from Build Alternative 2 would contain the same subway elements and result in thesame vibration impacts related to the subway as Build Alternative 1. In addition, the LRT couldresult in increased vibration. The vibrations from the LRT would depend on both the speed andfrequency of the new LRT service. A screening analysis of operational vibrations and ground-borne noise on the LRT portion of this alternative was performed assuming two-car LRT trainoperations at 15 mph on Water Street, 35-50 mph in the tunnel portion, 9 mph on East Broad-way, 30 mph on Avenue D, and 9 mph on 14th Street. The analysis also assumed morning andevening peak operations with 3-minute headways in each direction; midday (nonpeak) periodsubway operations with 6-minute headways in each direction; evening (7-11 PM), train opera-tions with 7.5-minute headways in each direction; and nighttime train operations with 20-minuteheadways in each direction. The screening analysis assumed no vibration mitigation measures,maximum speeds, and welded steel rail construction.

The screening analysis showed the potential for vibration impacts or ground-borne vibrationnoise impacts at Water Street between Coenties Slip and Old Slip, and on Centre Street betweenPearl Street and Leonard Street. High vibration and ground-borne vibration noise levels in theseareas are due to the proposed locations for crossover tracks. The discontinuities in crossovertracks cause vibration levels to be roughly 10 dB higher than those on welded rail. Potentialmitigation measures for these significant vibration impacts are discussed below under “VibrationMitigation.”

VIBRATION MITIGATION

No significant adverse vibration impacts would occur under the No Build or TSM Alternative,and therefore no mitigation would be required. The mitigation requirements for Build Alterna-tives 1 and 2 are described below.

BUILD ALTERNATIVE 1

As described above, the new subway would result in vibration impacts at each station locationand at three locations where tracks would have crossovers. Vibration levels or ground-borne


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vibration noise levels in those areas would require 10 dB reduction of vibration levels. A reduc-tion in vibration levels of 10 dB would require mitigation options such as ballast mats or resilientlysupported ties, which the FTA manual has identified to provide 10 dB reduction in vibrationlevels. With these types of vibration mitigation options employed in the areas mentioned above,there would be no anticipated vibration or ground-borne vibration noise impacts from thisproposed alternative.

BUILD ALTERNATIVE 2

With the same subway as Build Alternative 1, this alternative would require the same mitigationmeasures for vibration impacts from the subway. In addition, significant vibration impactsare also predicted at two locations where crossover tracks are proposed. Vibration levels orground-borne vibration noise levels in those areas would require 5 dB reduction of vibrationlevels. A reduction in vibration levels of 5 dB would require the use of high resilience fastenersin these areas. With these types of vibration mitigation options employed for the LRT (togetherwith the vibration mitigation proposed for the subway), there would be no anticipated vibrationor ground-borne vibration noise impacts from this proposed alternative. v

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