Noise and Vibration Impact Assessment Methodology for …greenlineextension.eot.state.ma.us/documents/advGroup0709/Mtg8... · Background Noise and vibration impact is assessed using

Noise and Vibration Noise and Vibration Impact Assessment Methodology for the

MBTA G Li E t i P j t MBTA Green Line Extension Project

Presentation to the Advisory Group Meeting Presentation to the Advisory Group Meeting

Somerville Public Library

August 4, 2008

Jason Ross, P.E.

Harris Miller Miller & Hanson Inc.

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Presentation Outline

� Backgground

� Noise and vibration basics

� T f i d ib ti iti lTypes of noise and vibration sensitive locatiions

� Impact criteria

� Noise and vibration projections

�� Potential mitigation options Potential mitigation options

� Questions

Backgground

� Noise and vibration impact is assessed using the Federal Transit Administration (FTA) Guidance Manual1

� ThThese guididelilines specifify hhow tto measure, evaluate and predict noise and vibration levels from transit sources.

� These guidelines were developed by Harris Miller Miller & Hanson Inc.

� Transit agencies are required to follow these assessment guidelines for all Federallyy-funded projects.p j

1 “Transit Noise and Vibration Impact Assessment”, Final Report FTA-VA-90-1003-06 prepared for the U.S. Federal Transit Administration byy Harris Miller Miller & p p

Hanson Inc., May 2006.

Noise and Vibration Basics

�� The basic measure of The basic measure of noise is the A-weighted noise level measured in decibels (dBA)decibels (dBA)

� Quiet urban areas may have ambient noise levels of 40 to 55 dBA

� Maximum noise levels from automobiles at 50 feet and 50 mph are typically about 70 to 75 dBA.


� Lmax – maximum noise level � Easy to understand � Does not take into account duration, number of events, or time

of dayof day

� Ldn “equivalent day-night sound level” � 24 h l ith htti lt24-hour levell with a niighttime penalty

� At residences or other places where people sleep

� LLeq “hourly equivalent sound level” � During 1-hour period of peak transit operations � At locations ith da time se (schools libraries m se ms At locations with daytime use (schools, libraries, museums,

etc.) � Both Ldn and Leq take into account the duration and number ofBoth Ldn and Leq take into account the duration and number of

events, Ldn accounts for nighttime noise



� Ground-borne vibration � Vibrations are the rapid fluctuation of building surfaces or

rattling of windows. � Measured in decibels, but not the same decibel as noise. � Vibration is measured in terms of the velocity of moving

surfaces and are labeled (VdB)surfaces and are labeled (VdB).


� The basic measure of vibration is the vibration velocity level in decibels (VdB)(VdB)

� The limit at which humans can feel vibrations in buildings is about 65 VdB

�� Vibration levels over 100 Vibration levels over 100 VdB are needed to cause physical damage to structuresstructures

� The number of events that occur determine the crititeriia

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� Ground borne noise Ground-borne noise � Produced when the vibrations of the floors, ceiling and walls of

a building act like a loudspeaker and radiate noise a building act like a loudspeaker and radiate noise. This noise This noise sounds like a low-frequency rumble.

�� Generally ground-borneGenerally, ground borne

noise is only a concern if

trains are in a tunnel (no

i b

h fairborne paths)) or for very sensitive facilities such as concert halls or recordingg

studios

t t t

Noise and Vibration Sensitive Locations

� Noise and vibration impact is assessed at: � Locations where people sleep (Category 2)

– Residences, hospitals, motels and hotels

�� Institutional land uses (Category 3) Institutional land uses (Category 3) – Schools, libraries, museums, theatres, places of worship

� Special buildings (Category 1)

– R di di h ll dit i TV di Recording studios, concert halls, auditoriums, TV studios

� Only noise impact is assessed at: � Outdoor land uses where quiet is important (Category 1)Outdoor land uses where quiet is important (Category 1)

– Outdoor amphitheatres, National Historic Landmarks, parks where quiet is essential to their use

�� Only vibration impact is assessed at: Only vibration impact is assessed at: � Vibration sensitive equipment (MRIs, Electron Microscopes)

� Noise and vibration impact are not assessed at:Noise and vibration impact are not assessed at: � Commercial or industrial land uses

t t

Noise and Vibration Sensitive Locations

� Sensitive locations along propposed MBTA Green Line g p Extension: � Residences

HHampton IInn Hotell � H

� Walnut Street Center (Union Square) � Somerville Community Access TV Studio (Union Square) Somerville Community Access TV Studio (Union Square) � Somerville High School � Somerville Public Library � Visiting Nurses Associations Assisted Living � Tufts University Classrooms

S i

d T h l C t– Science and Technology Center – Bray Laboratories – Nanotechnology Lab

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Noise and Vibration Imppact Criteria

� Noise and vibration impact criteria for transit projects is specifiedNoise and vibration impact criteria for transit projects is specified by the FTA. � Noise criteria were developed from well-documented research on

human response to community noisehuman response to community noise � Vibration criteria are based on International Standards Organization

(ISO) standards and experience with passenger transit operations

� Noise impact is assessed by comparing existing noise to future noise with the project. � AAs exiistiting noiise llevells iincrease, a smallller iincrease iin the ffutureth

noise levels is allowed. � Two levels of noise imppact: “moderate” or “severe”




Land Use Category Land Use Category GBV Impact Levels GBV Impact Levels (VdB re 1 micro-inch /sec)

GBN Impact Levels GBN Impact Levels (dB re 20 micro Pascals)

Frequent Events1 Occasional Events2

Infrequent Events3

Frequent Event1

Occasional Events2

Infrequent Events3

Category 1: Buildings where vibrations would interfere with interior operations.

65 VdB4 65 VdB4 65 VdB4 N/A4 N/A4 N/A4

Category 2: Residences and buildings where people normally sleep.

72 VdB 75 VdB 80 VdB 35 dBA 38 dBA 43 dBA

Category 3: Institutional land uses with primarily daytime use.

75 VdB 78 VdB 83 VdB 40 dBA 43 dBA 48 dBA

Notes: 1. "Frequent Events" is defined as more than 70 vibration events of the same source per day. Most rapid transit projects fall into this category. 2. “Occasional Events” is defined as between 30 and 70 vibration events of the same source per day. Most commuter trunk lines have this many operations. 3. "Infrequent Events" is defined as fewer than 30 vibration events of the same kind per day. This category includes most commuter rail systems 4 This criterion limit is based on levels that are acceptable for most moderately sensitive equipment such as optical microscopes Vibration sensitive 4. This criterion limit is based on levels that are acceptable for most moderately sensitive equipment such as optical microscopes. Vibration sensitive

manufacturing or research will require detailed evaluation to define the acceptable vibration levels. Ensuring lower vibration levels in a building often requires special design of the HVAC systems and stiffened floors.

5. Vibration-sensitive equipment is generally not sensitive to ground-borne noise.


Noise and Vibration Projjections

� Document existing levels Document existing levels

� Measure vehicle source levels

� Model noise and vibration levels

� Assess impactAssess impact

� Determine locations for mitigation, if required


� Existing noise measurements at 16 sites alongExisting noise measurements at 16 sites along proposed corridor

�� Existing vibration measurements at Tufts University Existing vibration measurements at Tufts University (MBTA Commuter , Amtrak)

�� Vibration propagation characteristics at 3 sites along Vibration propagation characteristics at 3 sites along corridor

� Reference noise and ibration meas rements of Green Reference noise and vibration measurements of Green Line vehicle �� D Branch near Beaconsfeld Station D Branch near Beaconsfeld Station

� D Branch near Woodland Station

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� Existing noise levels Existing noise levels Site Location Ldn Leq

LT-1 39 Horace Street (Somerville) 64 63 LT-2 5 Alston Street (Somerville) 74 71 LT-3 283 Medford Street (Somerville) 66 63 LT-4 34 Richdale Street (Somerville) 74 71 LT-5 86 Vernon Street (Somerville) 68 65 LT-6 95 Boston Avenue (Somerville) 68 65 LT-7 7/9 Winchester Place (Somerville)( ) 77 74 LT-8 131 Burget Avenue (Medford) 71 68 LT-9 76 Orchard Street (Medford) 71 68 ST-1 Water St (Cambridge) – Hampton Inn Hotel 58 60 ST-2 Fitchburg St (Somerville) – Brickbottom Lofts 64 61 ST-3 ST 3 248 Somerville Avenue (Somerville) 248 Somerville Avenue (Somerville) 6464 6666 ST-4 2 Charlestown Street (Somerville) 66 64 ST-5 45 Aldrich Street (Somerville) 70 62 ST-6 81 Hinckley Street (Somerville) 78 72 ST-7 Colby Street (Medford) – Tufts Universityy ( ) y 80 76

Source: HMMH, 2008.

ST-1, ST-3 - no existing train activity

– ~

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�� MBTA green line train reference levels MBTA green line train reference levels � 2-car trains, 50 feet, 50 mph

� Noise – (Lmax) ~ 84 dBA (Lmax) 84 dBA� Noise

� Vibration – (Lmax) ~ 71 VdB

� MBTA commuter train reference levels

�� 1 locomotive and 4-6 cars 50 feet 50 mph 1 locomotive and 4 6 cars, 50 feet, 50 mph � Noise – (Lmax) ~ 95 to 100 dBA � Vibration – (Lmax)(Lmax) ~ 86 VdB Vibration 86 VdB


� Modeling of future transit operations includes:Modeling of future transit operations includes: � Specific vehicle type � Vehicle sppeeds � Track design (continuous welded rail, turnouts, crossovers)


� Modeling of future transit operations includes: � OOver-groundd soundd propagati tion � Effects of intervening objects (barriers, berms, buildings) �� Effects of elevated structures Effects of elevated structures

– Along several areas the alignment is in a cut – Near Lechmere station the alignment is on elevated structureNear Lechmere station the alignment is on elevated structure

� Vibration propagation characteristics of soil and buildings

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Noise and Vibration Mitiggation

� Noise mitiggation opptions � Source noise mitigation

– Rolling noise - maintenance (wheel truing, rail grinding) R lli i k– Rolling noise - skikirts over trucks

– Wheel squeal - resilient wheels – Wheel sqqueal - vibration damppers for wheels – Wheel squeal - rail lubrication / friction modifiers – Horn and crossing bells - quiet zones (horns and grade crossing

bells are not expected under normal operation)bells are not expected under normal operation) – Impact noise - specific location of special trackwork (crossovers,

turnouts) � Path noise mitigation Path noise mitigation

– Noise barriers (could be extensions to retaining walls)

� Receiver noise mitiggation ((rare))

– Sound Insulation

Noise and Vibration Mitiggation

� Vibration mitigation options Vibration mitigation options � Maintenance

– Wheel truing Wheel truing – Rail grinding

� Sppecific location of sppecial trackwork ((crossovers, turnouts)) � Use of continuous welded rail vs. jointed rail � Trackform design

– Resilient rail fasteners – Ballast mats – RResili iliently supportted tiestl d ti – Floating slabs

www hmmh com www.hmmh.com

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Noise and Vibration Impact Assessment Methodology for …greenlineextension.eot.state.ma.us/documents/advGroup0709/Mtg8... · Background Noise and vibration impact is assessed using