MBTA Green Line Extension Noise and Vibration Technical Report

Transcription

1 MBTA Green Line Extension Noise and Vibration Technical Report Environmental Assessment HMMH Report No January, 2011 Prepared for: Vanasse Hangen & Brustlin, Inc. 99 High Street Boston, MA Massachusetts Department of Transportation 10 Park Plaza, Suite 3170 Boston, MA Massachusetts Bay Transportation Authority 10 Park Plaza, Suite 3910 Boston, MA Prepared by: Jason C. Ross, P.E. Tim M. Johnson Eric J. Cox Harris Miller Miller & Hanson Inc. 77 South Bedford Street Burlington, MA T F

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3 Contents Table of Contents 1 Introduction and Summary Summary of Results Noise Impact Assessment Vibration Impact Assessment Noise Mitigation Vibration Mitigation Environmental Noise and Vibration Basics Noise Fundamentals and Descriptors Ground-Borne Noise and Vibration Fundamentals and Descriptors Noise and Vibration Impact Criteria Noise and Vibration-Sensitive Land Use Categories Noise Impact Criteria Ground-Borne Noise and Vibration Impact Criteria Existing Conditions Noise and Vibration-Sensitive Land Use Noise and Vibration Measurements Noise and Vibration Measurement Equipment Noise Measurement Methodology Vibration Measurement Methodology Noise Measurement Results Existing Noise Conditions Reference Source Level Measurement Results Building Sound Insulation Measurement Results Vibration Measurement Results Vibration Propagation (Line Source Transfer Mobility) Results Vibration Levels of MBTA Commuter Trains Vibration Levels of MBTA Green Line Trains Noise and Vibration Impact Assessment Noise Projections Vibration Projections Future Build Conditions Noise Impact Assessment from Transit Operations Temporary Construction Noise Impacts Vibration Impact Assessment from Train Operations Temporary Construction Vibration Impacts Mitigation of Noise and Vibration Impacts Noise Mitigation for Transit Operations Construction Noise Mitigation Vibration Mitigation for Transit Operations Construction Vibration Mitigation Appendix A Appendix B Measurement Site Photographs Long-Term Noise Measurement Data iii

4 MBTA Green Line Extension Project Appendix C Appendix D Appendix E Appendix F Sound Insulation Measurement Results Noise and Vibration Measurement Location Figure Noise and Vibration Impact and Mitigation Location Figures Construction Equipment Noise Limits and Typical Usage Factors List of Figures Figure 1. Examples of outdoor noise exposure... 6 Figure 2. Typical ground-borne vibration levels... 7 Figure 3. FTA noise impact criteria (increase in future noise exposure) Figure 4. Criteria for detailed vibration analysis Figure 5. Vibration propagation test procedure Figure 6. Maximum sound levels of commuter train events at long-term noise sites Figure 7. Maximum sound level versus speed for Green Line trains at-grade (two-car trains) Figure 8. Sound exposure level versus speed for Green Line trains at-grade and on elevated guideway Figure 9. Commuter train and Green Line train spectra at 50 feet Figure 10. Line source transfer mobility of Site V-1: 200 Innerbelt Road Cambridge, MA Figure 11. Line source transfer mobility of Site V-2: 20 Vernon Street Somerville, MA Figure 12. Line source transfer mobility of Site V-3: Tufts Alumni Field Medford, MA Figure 13. Vibration levels versus distance from MBTA commuter and Amtrak trains at Tufts Alumni Field Figure 14. MBTA commuter train force density at 50 mph Figure 15. Vibration level versus distance for commuter trains Figure 16. Maximum vibration spectra for commuter trains Figure 17. Vibration level versus distance for MBTA Green Line trains and FTA generalized curve at 20 mph Figure 18. MBTA Green Line train force density at 50 mph Figure 19. Vibration projections for MBTA commuter trains at Site V Figure 20. Vibration projections for MBTA commuter trains at Site V Figure 21. Vibration projections for MBTA commuter trains at Site V Figure 22. Vibration projections for Green Line trains at Site V Figure 23. Vibration projections for Green Line trains at Site V Figure 24. Vibration projections for Green Line trains at Site V Figure 25. Long-term noise Site 1-39 Horace St. Somerville, MA... A-1 Figure 26. Long-term noise Site 2 5 Alston St. Somerville, MA... A-1 Figure 27. Long-term noise Site Medford St. Somerville, MA... A-2 Figure 28. Long-term noise Site 4 34 Richdale Ave. Somerville, MA... A-2 Figure 29. Long-term noise Site 5-86 Vernon St. Somerville, MA... A-3 Figure 30. Long-term noise Site 6-95 Boston Ave. Somerville, MA... A-3 Figure 31. Long-term noise Site 7-7/9 Winchester Pl. Somerville, MA... A-4 Figure 32. Long-term noise Site Burget Ave. Medford, MA... A-4 Figure 33. Long-term noise Site 9-76 Orchard St. Medford, MA... A-5 Figure 34. Long-term noise Site 11 - Brickbottom Artists Buildings Northeast Façade Somerville, MA... A-5 Figure 35. Long-term noise Site 12 - Brickbottom Artists Buildings South Façade Somerville, MA... A-6 Figure 36. Short-term noise Site 1 - Water Street (Hampton Inn Hotel) Cambridge, MA... A-6 Figure 37. Short-term noise Site 2 - Brickbottom Artists Buildings South Façade Somerville, MA... A-7 Figure 38. Short-term noise Site Somerville Ave. Somerville, MA... A-7 Figure 39. Short-term noise Site 4-2 Charlestown St. Somerville, MA... A-8 Figure 40. Short-term noise Site 5-45 Aldrich St. Somerville, MA... A-8 Figure 41. Short-term noise Site 6-81 Hinckley St. Somerville, MA... A-9 Figure 42. Short-term noise Site 7 - Colby St. (Tufts University) Medford, MA... A-9 Figure 43. Short-term noise Site 8 - End of Water St. Cambridge, MA... A-10 Figure 44. Short-term noise Site 9 - Archstone Phase II Cambridge, MA... A-10 Figure 45. Force density measurement site for Green Line trains (near Beaconsfeld Stop on D Branch)... A-11 iv January, 2011 HMMH Report No

5 Contents Figure 46. Vibration propagation measurement Site V-1 at 200 Innerbelt Road, Somerville MA... A-11 Figure 47. Vibration propagation measurement Site V-2 at 20 Vernon St. Somerville, MA... A-12 Figure 48. Vibration propagation measurement Site V-3a at Tufts University Alumni Field Somerville, MA... A-12 Figure 49. Vibration measurement Site V-3b at Tufts University (commuter trains)... A-13 Figure 50. Vibration measurement Site V-4 at Archstone Phase II Development parcel... A-13 Figure 51. Vibration measurement Site V-5 at Horace Street... A-14 Figure 52. Vibration measurement Site V-6 at Aldrich Street... A-14 Figure 53. Vibration measurement Site V-7 at Pearl Street Apartments... A-15 Figure 54. Vibration measurement Site V-8 at Richdale Avenue... A-15 Figure 55. Vibration measurement Site V-9 at Nashua Street... A-16 Figure 56. Vibration measurement Site V-10 at Cedar Street... A-16 Figure 57. Vibration measurement Site V-11 at Morton Avenue... A-17 Figure 58. Vibration measurement Site V-12 at Tufts Science and Technology Center... A-17 Figure 59. Sound insulation measurement site at Glass Factory Condominiums... A-18 Figure 60. Sound insulation measurement site at Hampton Inn Hotel... A-18 Figure 61. Sound insulation measurement site at Brickbottom Artists Buildings (Cannery East)... A-19 Figure 62. Sound insulation measurement site at Brickbottom Artists Buildings (Cannery East and West)... A-19 Figure 63. Sound insulation measurement site at Pearl Street Apartments... A-20 Figure 64. Sound insulation measurement site at Visiting Nurses Association... A-20 Figure 65. Sound insulation measurement site at Tufts Science and Technology Center... A-21 Figure 66. Sound insulation measurement site at Outside the Lines Studio... A-21 List of Tables Table 1. FTA ground-borne noise and vibration impact criteria Table 2. FTA ground-borne noise and vibration impact criteria for special buildings Table 3. Vibration criteria for detailed analysis Table 4. Construction vibration damage criteria Table 5. Noise and vibration measurement equipment list Table 6. Summary of existing noise measurements Table 7. Noise level reduction measurement results Table 8. Vibration measurement locations in study area Table 9. Potential noise impact at receptors prior to mitigation Table 10. Potential ground-borne noise impact at receptors prior to mitigation Table 11. Summary of potential airborne and ground-borne noise impact prior to mitigation Table 12. Construction lot-line noise limits Table 13. Day, evening and nighttime L10 noise levels Table 14. Construction noise projections Table 15. Potential vibration impact prior to mitigation Table 16. Summary of potential vibration impact prior to mitigation Table 17. Vibration source levels for and distances to potential impact for construction equipment Table 18. Summary of proposed noise barrier mitigation Table 19. Future exterior and interior noise levels at sound insulation candidate receptors Table 20. Summary of potential airborne and ground-borne noise impact prior to and with mitigation Table 21. Summary of proposed vibration mitigation Table 22. Potential vibration mitigation measures for crossovers and turnouts Table 23. Summary of potential vibration impact prior to and with mitigation v

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7 Environmental Assessment Noise and Vibration Technical Report 1 Introduction and Summary Harris Miller Miller & Hanson Inc. (HMMH) has conducted a noise and vibration impact assessment for the Massachusetts Department of Transportation (MassDOT) Green Line Extension Project. This assessment was carried out for MassDOT under subcontract to Vanasse Hangen & Brustlin, Inc. (VHB) in support of the Environmental Assessment (EA). The objective of the study was to assess the potential for noise and vibration impact at sensitive locations and identify mitigation along the Proposed Action corridor. Potential noise and vibration impact and mitigation were previously assessed for six operational alternatives in the Draft Environmental Impact Report/Environmental Assessment (DEIR/EA). 1 This technical report specifically addresses potential impact and mitigation for the locally-preferred alternative (LPA) which is the extension to Medford and Union Square (via commuter rail right-of-way) including the Option L maintenance facility. The Option L vehicle maintenance facility would be located within the Inner Belt area of Somerville, MA and immediately adjacent to the Massachusetts Bay Transportation Authority (MBTA) Boston Engine Terminal (BET) commuter rail maintenance facility. A summary of the study results are described below. Section 2 provides a discussion of environmental noise and vibration basics, and Section 3 describes the criteria used to assess noise and vibration impact. Section 4 includes existing noise and vibration conditions and Section 5 includes noise and vibration measurement results. Section 6 includes projections and impact assessment of future noise and vibration conditions and potential mitigation measures are outlined in Section 7. Appendix A includes measurement site photographs. Detailed long-term noise measurement and sound insulation measurement data are provided in Appendix B and Appendix C. A figure of noise and vibration measurement locations is provided in Appendix D and figures showing specific noise and vibration impact and mitigation locations are included in Appendix E. Appendix F includes a list of construction equipment noise level limits. 1.1 Summary of Results Noise Impact Assessment The Proposed Action involves relocating the MBTA Lowell commuter line to the east along the existing corridor and introducing the Green Line tracks on the west side of the corridor. Along the Union Square Branch, the MBTA Fitchburg commuter line would be relocated to the south along the existing corridor and the Green Line tracks introduced on the north side of the corridor. Prior to mitigation, 170 noise-sensitive receptors would be exposed to impact including 121 moderate impacts and 43 severe impacts at single-family and multi-family residential buildings, moderate impact at Tufts University Science and Technology Center and Outside the Line Artist s Studio (a teaching facility), moderate impact at Trum Playground, severe noise impact at the Walnut Street Center (a nonprofit support center for adults with developmental disabilities) near Union Square and ground-borne noise impact at Tufts Bacon Hall and Tufts Curtis Hall. 1 Green Line Extension Project Draft Environmental Impact Report/Environmental Assessment and Section 4(f) Statement, Executive Office of Transportation and Public Works, October,

8 MBTA Green Line Extension Project Potential noise impacts on the east side of the alignment along the existing MBTA Lowell commuter line are due primarily to the shifting of the commuter rail line closer to these sensitive properties. Future noise levels on the east side of the alignment would typically increase only one to three decibels. Since existing noise levels are relatively high at locations along the existing commuter rail line, even small increases in future noise levels are considered to have the potential for moderate or severe noise impact. Potential noise impacts on the west side of the alignment are due primarily to the close proximity of noise-sensitive receptors to the Green Line trains. Future noise levels at the impacted receptors on the west side would typically increase one to two decibels. At a few specific locations, such as Alston Street and the Walnut Street Center, the future increase in noise levels is higher (five to eight decibels) due to the close proximity to the proposed Green Line trains. At locations where there is no existing train activity between Lechmere Station and Fitchburg Street, the future increase in noise levels due to the Proposed Action would be higher because existing noise levels are lower. In particular, future noise levels for the Glass Factory Condominiums, Hampton Inn Hotel, future residential building at 22 Water Street and the northeast façade of the Brickbottom Artists Buildings are projected to be ten to 18 decibels higher than the relatively quiet existing conditions Vibration Impact Assessment Prior to mitigation, 96 vibration-sensitive buildings may potentially be exposed to impact due to the Proposed Action. This includes 92 single-family and multi-family residential buildings and four institutional buildings (Science and Technology Center, Bacon Hall and Bray Labs at Tufts University and Outside the Line Artist s Studio). Vibration impact prior to mitigation at the Tufts University buildings includes the potential effect to humans and vibration-sensitive equipment Noise Mitigation Noise mitigation by means of 20 noise barriers totaling approximately 13,600 feet in length and sound insulation improvements to the Pearl Street Apartment building, Visiting Nurses Association building, Outside the Lines Studio building and the Tufts University Science and Technology Center would be feasible, reasonable, and effective in mitigating potential noise impacts due to the Proposed Action. At locations along the existing MBTA Lowell and Fitchburg commuter lines, noise barriers would typically be effective in reducing noise levels from transit sources seven to 11 decibels and would result in substantial reduction in future noise levels in comparison to existing noise levels. At these locations, noise barriers would reduce future noise levels 6 to 7 db below existing levels on average. At the Glass Factory Condominiums and the Brickbottom Artists Buildings (northeast façade), double noise barriers (one barrier along the near edge of the Green Line guideway and one barrier between the near and far tracks) and track vibration isolation to reduce noise radiated by the guideway support structure would be effective in mitigating potential impact even at upper floor receptors. On the south façade of the Brickbottom Artists Buildings, three noise barriers would be effective in reducing noise from both Green Line and commuter trains. The three noise barriers include one barrier along the near Green Line track (outbound to Union Square), one noise barrier along the yard lead track and one noise barrier along the far Green Line track (inbound from Union Square). The noise barriers and track vibration isolation would reduce train noise between ten and 18 decibels at the Glass Factory Condominiums and future noise levels would increase only one to five decibels compared to existing levels. With mitigation, future noise levels at receptors up to the sixth floor would be below the moderate noise impact criterion and receptors on the seventh and eighth floor would be below the severe noise impact criterion. 2 January, 2011 HMMH Report No

9 Environmental Assessment Noise and Vibration Technical Report At the Brickbottom Artists Buildings (northeast façade), mitigation would reduce train noise up to 10 decibels and future noise levels would only increase up to two decibels compared to existing levels. Mitigation would keep future noise levels below the moderate noise criterion even at upper floor receptors. On the south façade, mitigation would reduce future noise levels at most receptors below existing noise levels. Future noise levels at all receptors, including those on upper floors, would be below the moderate impact criterion. The heights of the noise barriers along the Glass Factory Condominiums and Brickbottom Artists Buildings are dependent on the specific guideway designs and how close they can be constructed to the trains while not compromising safety requirements (i.e. emergency egress, train clearances, etc.) Assuming the tops of the barriers are effectively four feet from the near rail, barriers would be approximately ten feet in height. These noise barrier designs would also provide some visual privacy to the trains. At the Pearl Street Apartments, Visiting Nurses Association, Tufts Science and Technology Center and Outside the Lines Studio, sound insulation improvements would be effective in reducing noise from the Proposed Action. Sound insulation improvements would be provided for 36 units in the Pearl Street Apartments 45 units in the Visiting Nurses Association, three labs and three classrooms on 1st floor and five labs on 2nd floor of the Tufts Science and Technology Center and the main classroom of the Outside the Lines Artist Studio. These improvements would be effective in improving the OILR and keeping future noise levels below 45 Ldn and 65 Lmax at the Pearl Street Apartments and Visiting Nurses Association and below 65 Lmax at the Tufts Science and Technology Center and Outside the Lines Studio. See Section 7.3 for further details on the specific units and sound insulation improvements. The total estimated cost for noise mitigation is $7 million including $4.2 million for the noise barriers based on $30 per square foot (at-grade or on elevated structure) and $2.8 million for sound insulation improvements based on $25,000 per residential unit, $50,000 for the Outside the Lines Studio and $750,000 for the Tufts Science and Technology Center Vibration Mitigation Vibration mitigation, including up to 23,250 track-feet of track vibration isolation such as ballast mats, resiliently-supported ties or resilient fasteners on the proposed Green Line tracks and the relocated commuter rail tracks and the relocation or use of specially-engineered trackwork (flange-bearing, springrail frogs or moveable-point frogs) for 11 crossovers and turnouts, would be effective in keeping future vibration levels at or below existing levels for commuter trains and reducing future vibration from Green Line trains below impact criteria. The estimated cost for vibration mitigation is $4.2 million based on $180 per track-foot for ballast mats or resiliently-supported ties or $7.0 million based on $300 for resilient rail fasteners. 3

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11 Environmental Assessment Noise and Vibration Technical Report 2 Environmental Noise and Vibration Basics 2.1 Noise Fundamentals and Descriptors Noise is typically defined as unwanted or undesirable sound, where sound is characterized by small air pressure fluctuations above and below the atmospheric pressure. The basic parameters of environmental noise that affect human subjective response are (1) intensity or level, (2) frequency content and (3) variation with time. The first parameter is determined by how greatly the sound pressure fluctuates above and below the atmospheric pressure, and is expressed on a compressed scale in units of decibels. By using this scale, the range of normally encountered sound can be expressed by values between 0 and 120 decibels. On a relative basis, a 3-decibel change in sound level generally represents a barely noticeable change outside the laboratory, whereas a 10-decibel change in sound level would typically be perceived as a doubling (or halving) in the loudness of a sound. The frequency content of noise is related to the tone or pitch of the sound, and is expressed based on the rate of the air pressure fluctuation in terms of cycles per second (called Hertz and abbreviated as Hz). The human ear can detect a wide range of frequencies from about 20 Hz to 17,000 Hz. However, because the sensitivity of human hearing varies with frequency, the A-weighting system is commonly used when measuring environmental noise to provide a single number descriptor that correlates with human subjective response. Sound levels measured using this weighting system are called "A-weighted" sound levels, and are expressed in decibel notation as "dba." The A-weighted sound level is widely accepted by acousticians as a proper unit for describing environmental noise. Because environmental noise fluctuates from moment to moment, it is common practice to condense all of this information into a single number, called the equivalent sound level (Leq). Leq can be thought of as the steady sound level that represents the same sound energy as the varying sound levels over a specified time period (typically 1 hour or 24 hours). Often the Leq values over a 24-hour period are used to calculate cumulative noise exposure in terms of the Day-Night Sound Level (Ldn). Ldn is the A-weighted Leq for a 24-hour period with an added 10-decibel penalty imposed on noise that occurs during the nighttime hours (between 10 P.M. and 7 A.M.). Many surveys have shown that Ldn is well correlated with human annoyance, and therefore this descriptor is widely used for environmental noise impact assessment. Figure 1 provides examples of typical noise environments and criteria in terms of Ldn. While the extremes of Ldn are shown to range from 35 dba in a wilderness environment to 85 dba in noisy urban environments, Ldn is generally found to range between 55 dba and 75 dba in most communities. As shown in Figure 1, this spans the range between an ideal residential environment and the threshold for an unacceptable residential environment according to some U.S. Federal agencies criteria. 5

12 MBTA Green Line Extension Project Figure 1. Examples of outdoor noise exposure 2.2 Ground-Borne Noise and Vibration Fundamentals and Descriptors Ground-borne vibration is the oscillatory motion of the ground about some equilibrium position that can be described in terms of displacement, velocity or acceleration. Because sensitivity to vibration typically corresponds to the amplitude of vibration velocity within the low-frequency range of most concern for environmental vibration (roughly four to 80 Hz), velocity is the preferred measure for evaluating groundborne vibration from transit projects. The most common measure used to quantify vibration amplitude is the peak particle velocity (PPV), defined as the maximum instantaneous peak of the vibratory motion. PPV is typically used in monitoring blasting and other types of construction-generated vibration, since it is related to the stresses experienced by building components. Although PPV is appropriate for evaluating building damage, it is less suitable for evaluating human response, which is better related to the average vibration amplitude. Thus, groundborne vibration from trains is usually characterized in terms of the "smoothed" root mean square (rms) vibration velocity level, in decibels (VdB), with a reference quantity of one micro-inch per second. VdB is used in place of db to avoid confusing vibration decibels with sound decibels. Figure 2 illustrates typical ground-borne vibration levels for common sources as well as criteria for human and structural response to ground-borne vibration. As shown, the range of interest is from approximately 50 to 100 VdB, from imperceptible background vibration to the threshold of damage. Although the approximate threshold of human perception to vibration is 65 VdB, annoyance is usually not significant unless the vibration exceeds 70 VdB. 6 January, 2011 HMMH Report No

13 Environmental Assessment Noise and Vibration Technical Report Figure 2. Typical ground-borne vibration levels Ground-borne noise is produced when ground-borne vibration propagates into a room and radiates noise from the motion of the surfaces. The room surfaces essentially act like a giant loudspeaker from the vibration. Ground-borne noise is perceived as a low frequency rumble and is generally considered only when airborne paths are not present (e.g. train inside a tunnel or a large masonry building with no windows or other openings to the outdoors). Ground-borne noise is assessed according to the A-weighted sound level in dba. As presented in the following section, there are separate noise criteria for potential impact from airborne noise versus ground-borne noise. 7

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15 Environmental Assessment Noise and Vibration Technical Report 3 Noise and Vibration Impact Criteria 3.1 Noise and Vibration-Sensitive Land Use Categories The FTA classifies noise-sensitive land uses into the following three categories. Category 1: Tracts of land where quiet is an essential element in their intended purpose. This category includes lands set aside for serenity and quiet, and such land uses as outdoor amphitheaters and concert pavilions, as well as National Historic Landmarks with significant outdoor use. Also included are recording studios and concert halls. Category 2: Residences and buildings where people normally sleep. This category includes homes, hospitals, and hotels where a nighttime sensitivity is assumed to be of utmost importance. Category 3: Institutional land uses with primarily daytime and evening use. This category includes schools, libraries, theaters, and churches where it is important to avoid interference with such activities as speech, meditation and concentration on reading material. Places for meditation or study associated with cemeteries, monuments, museums, campgrounds, and recreational facilities can also be considered to be in this category. Certain historical sites and parks are also included. The FTA classifies vibration-sensitive land uses into the same three categories as noise. Although, since vibration is only assessed inside buildings, outdoor land uses are not considered to be sensitive. In addition to the potential for human annoyance from vibration, vibration impact is also assessed for certain equipment that is sensitive to vibration and the potential for damage to building structures. Vibration Category 1: High Sensitivity: Included in this category are buildings where vibration would interfere with operations. Vibration levels may be well below those associated with human annoyance. These buildings include vibration-sensitive research and manufacturing facilities, hospitals with sensitive equipment and university research operations. The sensitivity to vibration is dependent on the specific equipment present. Some examples of sensitive equipment include electronscanning microscopes, magnetic resonance imaging scanners and lithographic equipment. Vibration Category 2: Residential: Residences and buildings where people normally sleep. This category includes homes, hospitals, and hotels. Vibration Category 3: Institutional: This category includes buildings with primarily daytime and evening use. This category includes schools, libraries and churches. There are some buildings, such as concert halls, recording studios, and theaters that can be very sensitive to noise and/or vibration but do not fit into any of the three categories. Due to the sensitivity of these buildings, they usually warrant special attention during the environmental assessment of a transit project. Potential ground-borne vibration and ground-borne noise impact is assessed at special-use buildings such as concert halls, recording studios, auditoriums and theatres. 3.2 Noise Impact Criteria The FTA airborne noise impact criteria are founded on well-documented research on community reaction to noise and are based on the future change in noise exposure using a sliding scale. At locations with higher levels of existing noise, smaller increases in total noise exposure are allowed. The Day-Night Sound Level (Ldn) is used to characterize noise exposure for locations with nighttime sensitivity (Category 2). For institutional land uses with primarily daytime use, such as parks and school 9

16 MBTA Green Line Extension Project buildings (Categories 1 and 3), the one-hour equivalent sound level (Leq) during the facility s operating period is used. Ldn and Leq are explained in Section 2.1. There are two levels of impact included in the FTA criteria, as summarized below: Severe Impact: Project-generated noise in the severe impact range can be expected to cause a significant percentage of people to be highly annoyed by the new noise and represents the most compelling need for mitigation. Noise mitigation will normally be specified for severe impact areas unless there are truly extenuating circumstances that prevent it. Moderate Impact: In this range of noise impact, the change in the cumulative noise level is noticeable to most people but may not be sufficient to cause strong, adverse reactions from the community. In this transitional area, other project-specific factors must be considered to determine the magnitude of the impact and the need for mitigation. These factors include the existing noise level, the predicted level of increase over existing noise levels, the types and numbers of noise-sensitive land uses affected, the noise sensitivity of the properties, the effectiveness of the mitigation measures, community views and the cost of mitigating noise to more acceptable levels. The FTA noise impact criteria used in this assessment are shown in graphical form in Figure 3. Along the horizontal axis of the graph is the existing noise exposure and the vertical axis shows the noise exposure increase due to the project that would cause either moderate or severe impact. The noise exposure increase is the difference between the combination of the existing noise exposure and future noise sources introduced by the project and the existing noise level. Therefore, the future noise exposure increase will include modifications to the existing environment such as shifting the commuter rail tracks. Figure 3. FTA noise impact criteria (increase in future noise exposure) 10 January, 2011 HMMH Report No

17 Environmental Assessment Noise and Vibration Technical Report 3.3 Ground-Borne Noise and Vibration Impact Criteria The FTA vibration impact criteria are based on land use and train frequency, as shown in Table 1. There are some buildings, such as concert halls, recording studios and theaters that can be very sensitive to vibration but do not fit into any of the three categories listed in Table 1. Due to the sensitivity of these buildings, they usually warrant special attention during the environmental assessment of a transit project. Table 2 gives criteria for acceptable levels of ground-borne vibration for various types of special buildings. It should also be noted that there are separate FTA criteria for ground-borne noise, the rumble that can be radiated from the motion of room surfaces in buildings due to ground-borne vibration. Such criteria are particularly important for underground transit operations. However, because airborne noise tends to mask ground-borne noise from above ground (i.e. at-grade or elevated) rail systems, ground-borne noise levels are generally only assessed in buildings without significant airborne noise paths. Table 1. FTA ground-borne noise and vibration impact criteria Ground-Borne Vibration Impact Criteria (VdB re: 1 micro-inch per second) Frequent Occasional Infrequent Events Events Events Ground-Borne Noise Impact Criteria (dba re: 20 mico-pascal) Frequent Occasional Infrequent Events Events Events Land Use Category Category 1: Buildings where low ambient vibration is essential for 65 VdB 4 65 VdB 4 65 VdB 4 n/a 5 n/a 5 n/a 5 interior operations. Category 2: Residences and buildings where people normally 72 VdB 75 VdB 80 VdB 35 dba 38 dba 43 dba sleep. Category 3: Institutional land uses with primarily daytime use. 75 VdB 78 VdB 83 VdB 40 dba 43 dba 48 dba Source: FTA, Frequent Events is defined as more than 70 vibration events 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 kind per day. Most commuter rail 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 branch lines. 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. Table 2. FTA ground-borne noise and vibration impact criteria for special buildings Type of Building or Room Ground-Borne Vibration Impact Criteria (VdB re: 1 micro-inch per second) Occasional or Frequent Events Infrequent Events Ground-Borne Noise Impact Criteria (dba re: 20 mico-pascal) Occasional or Frequent Events Infrequent Events Concert Halls 65 VdB 65 VdB 25 dba 25 dba TV Studios 65 VdB 65 VdB 25 dba 25 dba Recording Studios 65 VdB 65 VdB 25 dba 25 dba Source: FTA, Auditoriums 72 VdB 80 VdB 30 dba 38 dba Theatres 72 VdB 80 VdB 35 dba 43 dba 11

18 MBTA Green Line Extension Project In addition to the criteria provided in Table 1 and Table 2 for general assessment purposes, FTA has established criteria in terms of one-third octave band frequency spectra for use in detailed analyses. Table 3 and Figure 4 show the more detailed vibration criteria and the description of their use. Table 3. Vibration criteria for detailed analysis Criterion Curve Maximum Vibration Level (VdB re: 1 micro-inch per second) Description of Use Workshop 90 Distinctly feelable vibration. Appropriate to workshops and non-sensitive areas Office 84 Feelable vibration. Appropriate to offices and non-sensitive areas Residential Day 78 Residential Night, Operating Rooms 72 VC-A 66 VC-B 60 Barely feelable vibration. Adequate for computer equipment and low-power optical microscopes (up to 20X) Vibration not feelable, but ground-borne noise may be audible inside quiet rooms. Suitable for medium-power optical microscopes (100X) and other equipment of low sensitivity Adequate for medium- to high-power optical microscopes (400X), microbalances, optical balances, and similar specialized equipment Adequate for high-power optical microscopes (1000X), inspection and lithography equipment to 3 micron line widths VC-C 54 Appropriate for most lithography and inspection equipment to 1 micron detail size VC-D 48 Suitable in most instances for the most demanding equipment, including electron microscopes operating to the limits of their capability VC-E 42 The most demanding criterion for extremely vibration-sensitive equipment Source: FTA, For residential buildings with nighttime occupancy, the applicable criterion for vibrations generated by commuter trains (occasional events) is a maximum velocity level of 75 VdB, measured in any one-third octave band over the frequency range from 4 Hz to 80 Hz. For residential buildings, the applicable criterion for vibrations generated from Green Line trains (frequent events) is 72 VdB. For institutional buildings such as schools, libraries and churches, the applicable criterion for vibration generated from commuter trains is 78 VdB and the criterion for Green Line trains is 75 VdB. For buildings with vibration-sensitive equipment, the applicable criterion for either Green Line or commuter trains is a maximum vibration level of 65 VdB. The applicable ground-borne noise criterion for the WMFO radio station in Curtis Hall at Tufts University is 25 dba (recording studio). For noisesensitive spaces inside Bacon Hall, which has no windows facing the tracks, the ground-borne noise criteria are 40 dba for Green Line trains and 43 dba for commuter trains. 12 January, 2011 HMMH Report No

19 Environmental Assessment Noise and Vibration Technical Report Figure 4. Criteria for detailed vibration analysis In addition to ground-borne vibration criteria for humans in residential, institutional and special buildings and vibration-sensitive equipment, there are ground-borne vibration criteria for potential damage to structures. The limits of vibration that structures can withstand are substantially higher than those for humans and for sensitive equipment. Table 4 presents criteria for assessing the potential for vibration damage to structures based on the type of building construction. This table includes rms vibration levels in VdB reference to 1 micro-inch per second and peak-particle velocity levels in inches per second. A crest factor of four, representing a difference of 12 decibels between peak and rms is used in this table. It should be noted that these criteria are more conservative than other standards such as the U.S. Bureau of Mines frequency-dependent vibration criteria which is equivalent to approximately 114 VdB at 40 Hz and above. Table 4. Construction vibration damage criteria Building Category Reinforced-concrete, steel or timber Ground-Borne Vibration Level (VdB) and Peak- Particle Velocity Equivalent (in/sec) 102 VdB (0.5 in/s) Engineered concrete and masonry Non-engineered timber and masonry buildings Buildings extremely susceptible to vibration damage 98 VdB (0.3 in/s) 94 VdB (0.2 in/s) 90 VdB (0.12 in/s) Source: FTA,

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21 Environmental Assessment Noise and Vibration Technical Report 4 Existing Conditions 4.1 Noise and Vibration-Sensitive Land Use Noise and vibration-sensitive land use near the Proposed Action includes residential properties, schools, libraries and other institutional sites. Parks that are considered to have passive recreation are sensitive to noise. The following describes the noise and vibration-sensitive land use in the study area. Lechmere Station to Fitchburg Street Noise and vibration-sensitive land use between Lechmere Station and Fitchburg Street includes the existing NorthPoint Tango and Sierra residential properties, the Glass Factory Condominiums, the Hampton Inn Hotel and the Brickbottom Artists Buildings. Future proposed buildings include NorthPoint residential buildings between Water Street and Charlestown Avenue south of the BET, Archstone Phase II development residential buildings east of East Street and west of Leighton Street and a development planned at 22 Water Street. Lechmere Canal Park south of Monsignor O Brien Highway and east of East Street is sensitive to noise. The existing noise environment for sensitive land use in this area is dominated by vehicular traffic. On Fitchburg Street, the south side of the Brickbottom Artists Buildings is adjacent to the proposed Green Line tracks for the Union Square Branch and the existing MBTA Fitchburg commuter line and the northeast side of the building is adjacent to the proposed Green Line tracks for the Medford Branch. The existing noise environment for the Brickbottom Artists Buildings is dominated by trains on the MBTA Fitchburg line including commuter trains and occasional freight train activity and vehicular traffic on Monsignor O Brien Highway. Short-term (1-hour) noise measurements were conducted on the north side of the Hampton Inn Hotel on Water Street (ST-1), the south side of the Brickbottom Artists Buildings (ST-2) and the end of Water Street near the BET (ST-8). Long-term noise measurements were conducted at the Glass Factory Condominiums (LT-10), the northeast façade of the Brickbottom Artists Buildings (LT-11) and the south façade of the Brickbottom Artists Buildings (LT-12). The Ldn s measured at sites LT-10, LT-11 and LT- 12 were 65, 64 and 67 dba, respectively. The estimated Ldn at ST-1 was 58 dba and at ST-2 was 64 dba. Vibration transfer mobility measurements were conducted in the field across from 200 Innerbelt Road (V-1) to characterize the efficiency of vibration propagation in the region of the Proposed Action between the eastern terminus and Walnut Street and the Union Square Branch. Vibration measurements of Green Line trains on elevated structure were conducted at the Archstone Phase II development parcel (V-4) east of East Street on Monsignor O Brien Highway in Cambridge, MA. Fitchburg Street to Union Square The branch line to Union Square includes single-family residences on Horace Street, apartments on Charlestown Street and the Walnut Street Center (a non-profit support center for adults with developmental disabilities). Existing noise levels for sensitive land use in this area is dominated by trains on the MBTA Fitchburg line. A long-term (24-hour) noise measurement was conducted on Horace Street (LT-1) and two short-term noise measurements were conducted on Somerville Avenue (ST-3) and Charlestown Street (ST-4). The Ldn measured at LT-1 was 64 dba and the estimated Ldn at sites ST-3 and ST-4 were 64 dba and 66 dba, respectively. Vibration measurements of existing commuter trains were conducted at the end of Horace Street (V-5). 15

22 MBTA Green Line Extension Project Fitchburg Street to McGrath Highway Sensitive land use between Fitchburg Street and McGrath Highway along the MBTA Lowell Line includes single-family residences on Alston Street, Chester Avenue, Tufts Street and Auburn Place. A long-term noise measurement was conducted at a single-family residence on Alston Street (LT-2). The measured Ldn at site LT-2 was 74 dba. McGrath Highway to School Street Sensitive land use between McGrath Highway and School Street includes multi-family residences on Medford Street, multi-family and single-family residences on Gilman Street and Aldrich Street, Somerville High School and the Somerville Public Library. Residences on Medford Street, the Somerville High School and Public Library are located on an embankment south of the Lowell Line approximately 50 feet above the tracks, residences on Gilman Street and Aldrich Street are on a slight embankment approximately 10 feet above the tracks. A long-term noise measurement was conducted on Medford Street (LT-3) and a short-term noise measurement was conducted on Aldrich Street (ST-5). The measured Ldn at site LT-3 was 66 dba and the estimated Ldn at site ST-5 was 70 dba. Vibration measurements of existing commuter trains were conducted at the end of Aldrich Street (V-6) and at Pearl Street Apartments (V-7). School Street to Central Street Sensitive land use between School Street and Central Street includes residences on Montrose Street, Willoughby Street and Richdale Avenue. A long-term noise measurement was conducted on Richdale Avenue (LT-4). The measured Ldn at site LT-4 was 74 dba. Vibration measurements of existing commuter trains were conducted on Richdale Avenue (V-8). Central Street to Broadway Sensitive land use between Central Street and Broadway includes residences on Vernon Street, Hinckley Street, Henderson Street, Nashua Street, Murdock Street and Boston Avenue and the Visiting Nurses Association assisted living facility on Lowell Street. The Park of Somerville Junction near Woodbine Street and Centre Street and Trum Playground are noise-sensitive. Long-term noise measurements were conducted on Vernon Street (LT-5) and Boston Avenue (LT-6) and a short-term noise measurement was conducted on Hinckley Street (ST-6). The measured Ldn at sites LT- 5 and LT-6 were both 68 dba and the estimated Ldn at site ST-6 was 78 dba. Vibration transfer mobility measurements were conducted in the parking lot of 20 Vernon Street (V-2) to characterize the efficiency of vibration propagation in the region of the Proposed Action between Walnut Street and Cedar Street. Vibration measurements of existing commuter trains were conducted at the end of Nashua Street (V-9) and at Trum Playground on Cedar Street (V-10). Broadway to Harvard Street Sensitive land use between Broadway and Harvard Street includes single-family and multi-family residences on Winchester Court, Winchester Place, Granville Avenue, Morton Avenue, Newbern Avenue and a condominium complex on Boston Avenue. Grant Park south of Boston Avenue and East of Winthrop Street is sensitive to noise. A long-term noise measurement was conducted on Winchester Place (LT-7). The measured Ldn at site LT-7 was 77 dba. Vibration measurements of existing commuter trains were conducted at the end of Morton Avenue (V-11). 16 January, 2011 HMMH Report No

23 Environmental Assessment Noise and Vibration Technical Report Harvard Street to College Avenue Sensitive land use between Harvard Street and College Avenue include institutional buildings on Colby Street and Boston Avenue. These institutional buildings include the Science and Technology Center, Bacon Hall, Bray Laboratories, Psychology Building and Curtis Hall at Tufts University and the Outside the Lines Artist Studio (teaching facility). The Science and Technology Center includes classrooms and general vibration-sensitive equipment. Bacon Hall includes vibration-sensitive equipment within the Avian Visual Cognitive Lab and is sensitive to ground-borne noise since it has no windows facing the alignment. Bray Labs includes vibration-sensitive equipment within the Superconductivity and Fusion Research Lab. The Psychology Building includes vibration-sensitive equipment such as a functioning magnetic resonance imaging (MRI) device. Curtis Hall includes WMFO radio station which has been assessed as a recording studio and is sensitive to ground-borne noise and vibration. Future proposed properties include an Integrated Research Lab (550 to 574 Boston Avenue) at Tufts University. A short-term noise measurement near the Outside the Lines Studio and Tufts Memorial Field was conducted (ST-7). The estimated Ldn at site ST-7 was 80 dba. Vibration measurements were also taken at this location to determine the force density of commuter trains (V-3a and V-3b). Vibration levels from MBTA commuter trains at this location were found to be approximately 83 VdB at 50 feet from the track centerline and 76 VdB at 100 feet from the track centerline. Vibration transfer mobility measurements were conducted to characterize the efficiency of vibration propagation in the region of the Proposed Action between Cedar Street and the western terminus. Additional vibration measurements of existing commuter trains were also conducted near the Tufts Science and Technology Center building (V-12). College Avenue to Brookings Street Sensitive land use between College Avenue and Winthrop Street include single-family residences on Burget Avenue and Brookings Street. A long-term noise measurement was conducted on Burget Avenue (LT-8). The measured Ldn at site LT-8 was 71 dba. 17

24 MBTA Green Line Extension Project 18 January, 2011 HMMH Report No

25 Environmental Assessment Noise and Vibration Technical Report 5 Noise and Vibration Measurements 5.1 Noise and Vibration Measurement Equipment All noise measurement equipment used in the study conforms to American National Standards Institute (ANSI) Standard S1.4 for Type 1 (precision) sound level meters. Calibrations traceable to the U.S. National Institute of Standards and Technology (NIST) were carried out in the field before and after each set of measurements using acoustical calibrators. Table 5 presents a list of noise and vibration measurement equipment used including manufacturer, model and serial number. Table 5. Noise and vibration measurement equipment list Equipment Manufacturer Model Serial Number Sound Level Meter Bruel & Kjaer Microphone Bruel & Kjaer Calibrator Bruel & Kjaer Sound Level Meter Bruel & Kjaer Microphone Bruel & Kjaer Calibrator Bruel & Kjaer Sound Level Meter Bruel & Kjaer Microphone Bruel & Kjaer Calibrator Bruel & Kjaer Sound Level Meter Bruel & Kjaer Microphone Bruel & Kjaer Calibrator Bruel & Kjaer Sound Level Meter Bruel & Kjaer Microphone Bruel & Kjaer Calibrator Bruel & Kjaer Sound Level Meter Bruel & Kjaer Microphone Bruel & Kjaer Calibrator Bruel & Kjaer Digital Audio Tape Recorder TEAC RD Digital Recorder TEAC LX Accelerometer PCB 393A 5394 Accelerometer PCB 393A 5730 Accelerometer PCB 393A 5397 Accelerometer PCB 393A 4739 Accelerometer PCB 393C Accelerometer PCB 393C Load Cell Honeywell/Sensotec Type Loudspeaker Mackie SRM450 (21) CB Sound Level Meter Larson Davis 824 A3048 Microphone GRAS 40AQ Calibrator Larson Davis CAL Sound Level Meter Larson Davis Microphone PCB 377B

26 MBTA Green Line Extension Project 5.2 Noise Measurement Methodology Existing Noise Measurements Measurements to characterize the existing noise environment in the study area were conducted at representative noise-sensitive receptors. Both long-term (24-hour) and short-term (1-hour) noise measurements are conducted at representative locations. Long-term measurements provide a direct measurement of both Ldn and peak transit-hour Leq. Short-term measurements will provide a direct measurement of peak transit-hour Leq, and Ldn levels were estimated based on methods described in the FTA guidance manual. For long-term measurements along the existing MBTA Fitchburg and Lowell lines, one-second time histories of sound levels were measured along with audio recordings of events to identify noise from train activity. These measurements allowed us to separate noise generated from commuter trains from other ambient sources. Noise impact is assessed at outdoor land uses with frequent use such as patios or pools or at the nearest building façade. Noise measurement sites were selected based on the location of noise-sensitive land use along the proposed corridor, their proximity to the proposed alignment and the surrounding terrain. The distance from the measurement location to significant noise sources (i.e. commuter rail line or streets where there is no existing train activity) was chosen to be representative of typical noise-sensitive locations in each area. Furthermore, the microphone was positioned to characterize the exposure of the site to the dominant noise sources in the area. For example, microphones were located at the approximate setback lines of the receptors from adjacent roads or rail lines, and were positioned to avoid acoustic shielding by landscaping, fences or other obstructions. Reference Source Level Measurements Source level measurements were conducted of Green Line trains at-grade and on elevated structure at a setback of 50 feet from the near track. The speeds and consists of the trains were documented. These measurements allowed us to characterize the noise emissions of Green Line trains as a function of vehicle speed for modeling purposes. For measurements of the Green Line at-grade, the microphone was located at a height of five feet above ground with line of sight to the rails maintained. For measurements of the Green Line on elevated structure, the microphone was located at a height of approximately 30 feet along a section of the guideway without a parapet wall maintaining line of sight to the rails. Building Sound Insulation Measurements The objective of building sound insulation measurements was to determine the existing outdoor-to-indoor level reduction (OILR) characteristics of noise-sensitive rooms in specific buildings where sound insulation improvements may be required for mitigation. The test data are used along with the projected exterior noise levels to project interior noise levels and to determine if it would be necessary and effective to apply sound insulation treatments to reduce the interior noise from train operations. If so, specific recommendations for treatments, such as replacement or acoustical improvements to windows, doors and ventilation systems would be developed during final design. OILR measurements were carried out for representative rooms to document the current noise reduction properties of the buildings. To measure the OILR of specific rooms, the exterior facades of each room were exposed to an artificial noise source. The use of an artificial noise source allows the measurements to be made using a known, repeatable source over a controlled duration. The procedure uses pink noise, which is electronically generated sound with equal amounts of energy in each octave band, amplified through a loudspeaker as the artificial noise source. 20 January, 2011 HMMH Report No

27 Environmental Assessment Noise and Vibration Technical Report A loudspeaker, fed by a pink noise signal input, was positioned on a tripod to distribute the sound uniformly over the facades of the room under evaluation. During exposure to the noise source, the outdoor and indoor octave-band noise levels were measured with a sound level meter and ambient noise levels were recorded to ensure the accuracy of the results. The difference between outdoor and indoor octave-band noise levels yields the octave-band OILR. The overall A-weighted Noise Level Reduction (NLR) is calculated by applying the measured OILR to the noise generated by a representative noise source, either a commuter train, Green Line train on elevated structure or Green Line train at-grade. 5.3 Vibration Measurement Methodology Vibration Propagation and Vehicle Force Density Measurements Vibration propagation measurements were made to characterize the efficiency that vibration propagates from the train sources to nearby sensitive buildings. The measurements, in conjunction with vehicle force density measurements, are used to project future vibration levels. These measurements were conducted with high-sensitivity accelerometers mounted in the vertical direction on either paved surfaces, or on top of steel stakes driven into soil. The acceleration signals were recorded on a TEAC Model LX-110 multichannel digital recorder and subsequently analyzed using digital signal processing software. The vibration propagation test procedure is shown schematically in Figure 5. As shown in the cross section view at the top, the test basically consists of dropping a 60 lb weight from a height of three to four feet onto the ground. A load cell is used to measure the force of the impact and accelerometers are used to measure the resulting vibration responses at various distances from the ground. The relationship between the input force and the ground surface vibration, called the transfer mobility, characterizes vibration propagation at this location. It is then possible to estimate the ground vibration that would be caused by another source, such as a train, by substituting the train force for the impact force. The bottom sketch in Figure 5 shows how the dropped weight point source is used to simulate a line vibration source such as a train. Impact tests are made at regular intervals in a line along the rail alignment. For these tests, impacts were done at eleven points, spaced 15 feet apart along a line perpendicular to the line of accelerometers. The measurement sites were selected to be open and free of buildings so as not to affect the vibration propagation conditions. By measuring the line source transfer mobility at a given site and vibration levels of either the commuter rail trains or the Green Line trains at that same location, we are able to calculate the vehicle force density with the following relationship: L F = L v - TM line Where L F is the vehicle force density, L v is the measured train ground-borne vibration and TM line is the line source transfer mobility at the reference site. Once a vehicle force density is calculated, it is then used to project future vibration levels by combining it with line source transfer mobility measurements at sites along the project corridor. 21

28 MBTA Green Line Extension Project Figure 5. Vibration propagation test procedure Vibration Measurements of Existing Commuter and Green Line Trains Vibration measurements of existing commuter and Green Line trains were conducted to provide further detail on vibration generated by these sources. This information will be used to specify appropriate track vibration isolation during the final design of the Proposed Action. Similar to vibration propagation measurements, ground vibration measurements were conducted with high-sensitivity accelerometers mounted in the vertical direction on either paved surfaces, or on top of steel stakes driven into soil. The acceleration signals were recorded on a TEAC Model LX-110 multi-channel digital recorder and subsequently analyzed using digital signal processing software. Measurements were conducted at eight locations with existing commuter trains and one location with Green Line trains on elevated structure along the proposed corridor. These locations include the Archstone Phase II development parcel east of East Street (Green Line elevated), Horace Street, Aldrich Street, Pearl Street Apartments, Richdale Avenue, Cedar Street, Nashua Street, Morton Avenue and Tufts Science and Technology Center. 22 January, 2011 HMMH Report No

29 Environmental Assessment Noise and Vibration Technical Report 5.4 Noise Measurement Results Existing Noise Conditions To characterize the existing noise conditions throughout the Proposed Action, twelve long-term (24 hour) and nine short-term (1-hour) measurements were conducted. Locations adjacent to the MBTA Lowell and Fitchburg lines were dominated by train activity. Appendix D shows the noise measurement site locations. Table 6 shows the existing noise measurement results including Ldn, peak-transit hour Leq, the maximum noise levels from commuter trains and distance to the near track. The table shows that existing Ldn levels at locations with commuter train activity range from 64 to 80 dba. Figure 6 shows maximum noise levels of the commuter trains measured at long-term measurements sites range from 79 to 99 dba at distances between 50 and 120 feet. Based on these measurements, MBTA commuter trains were found to typically generate a maximum of 90 dba and an SEL of 96 dba at 50 mph and a distance of 50 feet. Measurements of Amtrak commuter trains show that noise levels are relatively quieter than those for MBTA commuter trains. At a distance of 50 feet from the track centerline at a speed of 50 mph, an Amtrak train generates an Lmax of 81 dba and an SEL of 86 dba. Table 6. Summary of existing noise measurements Existing Day-Night Average Existing Peak- Transit Hour Commuter Train Noise Sound Level Sound Level Level Location (Ldn) (Leq) (Lmax) e LT-1 39 Horace Street (Somerville) LT-2 5 Alston Street (Somerville) LT Medford Street (Somerville) LT-4 34 Richdale Avenue (Somerville) LT-5 86 Vernon Street (Somerville) LT-6 95 Boston Avenue (Somerville) LT-7 7/9 Winchester Place (Somerville) LT Burget Avenue (Medford) LT-9 76 Orchard Street (Medford) LT-10 Glass Factory Condominiums (Cambridge) 65 a 63 n/a n/a LT-11 Brickbottom Artists Buildings Northeast Façade (Somerville) n/a n/a Measurement Site Distance to Near Track (feet) LT-12 Brickbottom Artists Buildings South Façade (Somerville) d ST-1 Water Street Hampton Inn Hotel (Cambridge) 58 c 60 n/a n/a ST-2 Brickbottom Artists Buildings Southeast Façade (Somerville) 64 b d ST Somerville Avenue (Somerville) 64 c 66 n/a n/a ST-4 2 Charlestown Street (Somerville) 66 b ST-5 45 Aldrich Street (Somerville) 70 b ST-6 81 Hinckley Street (Somerville) 78 b ST-7 Colby Street Tufts University (Medford) 80 b ST-8 Water Street near Boston Engine Terminal (Cambridge) 62 c 65 n/a n/a ST-9 Archstone Phase II Site (Cambridge) 65 c 67 n/a n/a a Measurements conducted March, 2006 and reported in Environmental Assessment for the Lechmere Station Relocation Project (November, 2006). b Ldn estimated by comparing SEL levels of train events to long-term sites whose noise environment is dominated by train noise. c Ldn estimated according to FTA guidance for short-term measurements conducted between 7am and 7pm. d There is a siding track 37 feet and the Boston Engine Terminal drill track 51 feet from the measurement location. e Commuter train noise level is average of all events at site. 23

30 MBTA Green Line Extension Project Maximum Sound Level (dba) Average Measurement Site Figure 6. Maximum sound levels of commuter train events at long-term noise sites Reference Source Level Measurement Results Reference noise measurements of Green Line trains were conducted at two at-grade locations along the existing Green Line D Branch at Waldstein Playground (near Beaconsfeld station) in Brookline, MA and near Woodland station in Newton, MA. Measurements of Green Line trains on elevated guideway were conducted along the existing Green Line near Lechmere Station at the Archstone Phase II development parcel east of East Street on Monsignor O Brien Highway in Cambridge, MA. The noise emissions of light rail vehicles depend on many factors including the number of cars in the train, speed, track form, track support, type and condition of the rail and presence of special trackwork. Train speeds were measured with a radar gun and the number of cars in the trains were documented. The Green Line trains were typically 2-car trains operating on jointed track with ballast and tie track form at these locations. The maximum noise level of two-car Green Line trains at-grade at 50 feet from the near track centerline versus train speed is shown below in Figure 7. This figure shows that maximum sound levels increase as a function of speed with maximum noise levels of 70 dba at 10 mph up to approximately 84 dba at 50 mph. The sound exposure level (SEL) of two-car Green Line trains at-grade at 50 feet from the near track centerline versus train speed is shown in Figure 8. This figure shows that SEL increases as a function of speed with a 13 speed coefficient from a level of 79 dba at 10 mph to a level of 88 dba at 50 mph atgrade, for two-car trains. For trains on the existing elevated guideway near Lechmere Station, an increase of four decibels was measured compared to trains at-grade which agrees with the standard adjustment in the FTA Guidance Manual. Based on these measurements, a single Green Line light rail vehicle operating at 50 mph at-grade on ballast and tie track with jointed rail generates a maximum noise level of 81 dba and a sound exposure level of 85 dba at a distance of 50 feet from the track centerline. The proposed Green Line track is expected to be continuous-welded rail which typically generates lower noise levels than jointed rail. 24 January, 2011 HMMH Report No

31 Environmental Assessment Noise and Vibration Technical Report In addition to overall A-weighted noise levels, one-third octave band spectra were measured to characterize the frequency content of commuter line and Green Line trains on elevated structure and atgrade. Figure 9 show the relative spectra for these sources at a distance of 50 feet. These spectra show that the predominant frequencies generated by commuter trains and Green Line trains at-grade are between 400 and 800 Hz and those of Green Line trains on elevated structure are between 250 and 400 Hz. The lower frequency content of Green Line trains on elevated guideway is likely attributed to noise radiated by the structure. These spectra were used in conjunction with the sound insulation measurements to determine the existing NLR of specific buildings. 90 Maximum Sound Level at 50 feet (dba) Vehicle Speed (mph) Lmax Lmax regression Figure 7. Maximum sound level versus speed for Green Line trains at-grade (two-car trains) 25

32 MBTA Green Line Extension Project Sound Exposure Level for 2-car Green Line Trains at 50 feet (dba) db increase for elevated structure SEL = *Log (Speed/50) Vehicle Speed (mph) Events at Woodland Events at Beaconsfeld MBTA Greenline LRV (At-Grade) FTA SEL Reference Events at Archstone (Elevated) MBTA Greenline LRV (Elevated) Figure 8. Sound exposure level versus speed for Green Line trains at-grade and on elevated guideway 0-10 Relative Sound Level [db] Overall A-wtd /3-Octave Band Center Frequency [Hz] Commuter Green Line on Elevated Guideway Green Line At-Grade Figure 9. Commuter train and Green Line train spectra at 50 feet 26 January, 2011 HMMH Report No

33 Environmental Assessment Noise and Vibration Technical Report Building Sound Insulation Measurement Results Existing OILR s were measured at the Glass Factory Condominiums, Hampton Inn Hotel, Brickbottom Artists Buildings, Pearl Street Apartment Building, Visiting Nurses Association, Tufts Science and Technology Center and Outside the Lines Artist Studio. The NLR were computed based on the measured OILR and the relative noise source spectra. Table 7 presents a summary of the NLR at each building and unit for commuter and Green Line trains (atgrade or on elevated structure as relevant sources). Detailed NLR spectra results are presented in Appendix C. Table 7. Noise level reduction measurement results A-weighted Noise Level Reduction (dba) Green Line Trains Green Line Trains Commuter Trains Building Unit/Room Elevated At-Grade 215/Bedroom /Living Room / Bedroom Glass Factory Condominiums 212/Bedroom /Living Room /Bedroom /Bedroom /Living Room 28.0 Range (Average) 27.2 to 34.9 (29.5) 212/Bedroom 31.3 Hampton Inn Hotel 214/Bedroom /Bedroom /Bedroom 27.6 Range (Average) 27.6 to 31.3 (29.9) C323/Studio a C321/Small Office C321/Large Office b F191/Studio c Brickbottom Artists Buildings B160/Loft Bedroom c C218/Living Room C216/Office a C214/Living Room C214/Bedroom Range (Average) 17.3 to 31.2 (23.4) 16.1 to 26.9 (21.5) 17.5 to 31.3 (23.8) 205/Living Room /Bedroom Pearl Street Apartments 210/Living Room /Bedroom /Living Room /Bedroom Range (Average) 23.7 to 30.2 (27.6) 24.4 to 30.9 (28.2) 203/Living Room /Bedroom Visiting Nurses Association 205/Living Room /Bedroom /Living Room /Bedroom Range (Average) 21.2 to 25.7 (23.9) 21.6 to 26.1 (24.3) Tufts Science and Technology 134/Classroom A/Lab Range (Average) 27.2 to 27.6 (27.4) 27.3 to 27.7 (27.5) Outside the Lines Studio Classroom Range (Average) a Room includes window air-conditioning unit b Room includes window ventilation fan. c Noise-exposed façade is roof. 27

34 MBTA Green Line Extension Project Glass Factory Condominiums is an eight-story residential building located at 169 Monsignor O'Brien Highway in Cambridge, MA. The northeast building facade facing the alignment is constructed of brick and concrete stucco on the exterior with painted gypsum board in the interior. There are two to four aluminum-framed, horizontal-sliding windows (some with a fixed center pane) in each unit along the northeast façade, with one window in each bedroom and one to two windows in the living room. The windows are all single-glazed pairs, with 4/32 interior and 6/32 exterior pane thicknesses, where operable, and 8/32 interior and exterior pane thicknesses where fixed. The air gap between the pair of windows is approximately 2 to Proper sealing was generally observed around all inspected windows, though minor degradation due to aging was occasionally noted. The measured NLR range from 27 to 35 dba with an average of 30 dba for elevated Green Line trains. The measured noise reduction of the Glass Factory Condominium building is relatively high compared to typical properties. The Hampton Inn Hotel is a seven-story hotel with guest rooms on the top six floors located at 191 Monsignor O'Brien Highway in Cambridge, MA. The northeast building facade facing the alignment is constructed of brick on the exterior and painted gypsum board in the interior. There is an aluminumframed, fixed window along this façade for each guest room. These windows are all double-glazed, with 4/32 pane thicknesses and 18/32 air spaces. Window gaskets were observed to be in generally good condition and provided proper sealing. There is also an in-wall air-conditioning unit installed below the window in each guest room, with exposed venting on the exterior façade. The rooms tested included both General Electric and LG models with two-speed fans were observed. The NLR range from 28 to 31 dba with an average of 30 dba for Green Line trains on retained fill. The existing noise reduction of the Hampton Inn Hotel is relatively high compared to other properties measured. The Brickbottom Artists Buildings include three separate buildings (Cannery, Bakery and Foundry) located at 1 Fitchburg Street in Somerville, MA. The Cannery and Bakery are large five-story buildings and the Foundry is a one-story building approximately 30 feet tall. The building facades facing the alignments are constructed of concrete stucco on the exterior with painted concrete in the interior. The residential units are large loft spaces with various configurations. While windows appear to be uniform in size from the exterior, these windows may actually be divided between units, or between rooms within a single unit, due to internal wall placement. Overall, there are windows of various widths and uniform heights within one or two rooms in each building unit. The windows are all aluminum-framed and double-glazed, with 3/32 to 4/32 pane thicknesses and 9/32 to 17/32 air spaces. Some window sections are double-hung while others are fixed. Sealing around the windows was generally observed to be degraded due to aging. In most units, one window section contains an in-window air-conditioning unit or a vent with an exhaust fan. For fixed windows the upper pane was typically removed, while for double hung windows the bottom pane was lifted. Sealing around these elements was generally observed to be poor. For units in the Foundry building, the northeast façade facing the proposed Medford Branch is a roof constructed of asphalt shingles on the exterior with painted sheet metal in the interior. The northeast wall of this building is primarily underground with no windows and therefore this wall is not a dominant path for airborne noise to enter the units. There are several aluminum-framed, fixed skylights along this section of roof for each unit. The skylights are all double-glazed, with 4/32 pane thicknesses and 12/32 air spaces. The units also have one to two small vents with exterior, roof-mounted, exhaust fans. On the first floor of the Bakery facing the courtyard, one façade that noise would enter the units through is the roof which is constructed of rubber/asphalt mat on the exterior with unpainted, corrugated sheet metal in the interior. There are one or more aluminum-framed, fixed skylights along this section of roof for each unit. The skylights are half-cylinder shaped. The curved sections are single-glazed with 6/32 pane thicknesses, and the flat ends are double-glazed with 6/32 exterior and 4/32 interior pane thicknesses and 2/32 air spaces. Proper sealing was generally observed around all inspected skylights. 28 January, 2011 HMMH Report No

35 Environmental Assessment Noise and Vibration Technical Report The NLR at the Brickbottom Artists Buildings ranged from 17 to 31 dba with an average of 23 dba for commuter trains, 16 to 27 dba with an average of 22 dba for Green Line trains on elevated structure and 18 to 31 dba with an average of 24 dba for Green Line trains at-grade. There was a greater range of NLR among the units measured than at other buildings with some providing relatively low noise reduction conditions. The rooms with the lowest noise reduction performance did not actually have airconditioning units or ventilation fans in the windows as might be expected. The rooms with the highest noise reduction performance were F191 and B160 which both have roofs as the primary noise-exposed surface. The Pearl Street Apartments is a six-story apartment building located at 240 Pearl St. in Somerville, MA. The noise-exposed building facade is constructed of brick on the exterior and painted gypsum board in the interior. There are two aluminum-framed, horizontal-sliding windows along this façade for each apartment, one within a living room and one in a bedroom. These windows are all double-glazed, with 3/32 to 4/32 pane thicknesses and 6/32 to 18/32 air spaces. Sealing around the windows was generally observed to be degraded due to aging. There is also an in-wall air-conditioning unit installed below the living room window in each apartment, with exposed venting on the exterior façade. Various models with two or three-speed fans were observed, with manufacturers including Frigidaire, General Electric, and Friedrich. The NLR of units within this building ranged from 24 to 30 dba with an average of 28 dba for commuter trains and 24 to 31 with an average of 28 dba for Green Line trains. The Visiting Nurses Association building is a three-story, assisted-living apartment building located at 259 Lowell St. in Somerville, MA. The noise-exposed building facade is constructed of vinyl-siding and cedar shakes on the exterior with painted gypsum board in the interior. There are two to three vinylframed, double-hung windows and one to two aluminum, solid-core doors along this façade for each apartment, with one window in the bedroom and all other elements within the living room. The windows are all double-glazed, with 4/32 pane thicknesses and 10/32 to 18/32 air spaces. The doors also contain fixed, double-glazed windows with 4/32 pane thicknesses and 24/32 air spaces. Proper sealing was generally observed around all inspected windows, while poor sealing was observed around most doors. There is also an in-wall heating and air-conditioning unit installed below one living room window in each apartment, with exposed venting on the exterior façade. A model manufactured by Amana with a two-speed fan was consistently observed. The NLR at the Visiting Nurses Association ranged from 21 to 26 dba with an average of 24 dba for both commuter trains and at-grade Green Line trains. The Tufts Science and Technology Center is a two-story building containing university classrooms, laboratories, and offices located at 4 Colby St. in Medford, MA. The noise-exposed building facade is constructed of painted brick on the exterior and painted gypsum board in the interior. There is typically one large set of aluminum-framed, fixed windows (with a few small, operable window sections to provide venting) along this façade for each classroom. The laboratories typically have two sets of similar windows along this façade, one at each side of the room. All windows are double-glazed, with 8/32 pane thicknesses and 16/32 to 20/32 air spaces. Gaskets were generally observed to be in good condition and provide proper sealing for the fixed window sections. However, all operable window sections required strong torque to be applied to the latching mechanism with a wrench to obtain good sealing. The ambient noise levels inside the building with the HVAC system operating were measured to be 55 to 60 dba. The measured NLR of the classrooms was 27 to 28 dba for commuter trains and Green Line trains at-grade. The Outside the Lines Artists Studio is a single-story teaching facility for developmentally-challenged artists located at 70 Colby St. in Medford, MA. The noise-exposed building facade is constructed of painted concrete block both on the exterior and in the interior. There are several small aluminum-framed, fixed windows along this façade, all contained within one large, open interior studio space. These windows are either single or double-glazed Plexiglas, with 3/32 pane thicknesses and 8/32 air spaces. 29

36 MBTA Green Line Extension Project Sealing around the windows was generally observed to be degraded due to aging. The NLR in the classroom was 28 dba to 29 dba for commuter trains and Green Line trains at-grade, respectively. While the overall NLR was relatively high at this location, this is due in part to the large volume of the classroom and the relatively small size of the windows. 5.5 Vibration Measurement Results Line source transfer mobility measurements, vibration levels of commuter trains and Green Line trains on elevated structure were conducted throughout the study area. Table 8 presents the vibration measurement locations in the study area. These measurement locations are also shown in Appendix D. Table 8. Vibration measurement locations in study area Measurement Site Location Type of Measurement V Innerbelt Road (Cambridge) LSTM V-2 20 Vernon Street (Somerville) LSTM V-3a Tufts Alumni Field (Medford) LSTM / Commuter Train Force Density V-3b Tufts Alumni Field (Medford) Commuter Train Levels V-4 Archstone Phase II Site (Cambridge) Elevated Green Line Levels V-5 39 Horace Street (Somerville) Commuter Train Levels V-6 45 Aldrich Street (Somerville) Commuter Train Levels V-7 Pearl Street Apartments (Somerville) Commuter Train Levels V-8 26 Richdale Avenue (Somerville) Commuter Train Levels V-9 39 Nashua Street (Somerville) Commuter Train Levels V-10 Trum Field/Cedar Street (Somerville) Commuter Train Levels V Morton Avenue (Medford) Commuter Train Levels V-12 Tufts Science and Technology Center (Medford) Commuter Train Levels Vibration Propagation (Line Source Transfer Mobility) Results Line source transfer mobility measurements were conducted at three sites along the corridor including a field across from 200 Innerbelt Road in Cambridge, MA, the parking lot of 20 Vernon Street in Somerville, MA and Tufts Alumni Field in Medford, MA. These measurement locations are shown in Appendix D. The results of these line source transfer mobility measurements are shown in Figure 10 through Figure 12. These figures show how vibration in the 31.5 to 80 Hz 1/3-octave bands generally propagates more efficiently than higher or lower frequency vibration. 30 January, 2011 HMMH Report No

37 Environmental Assessment Noise and Vibration Technical Report Site V Innerbelt Road Cambridge, Ma Line Source Transfer Mobility (db re 1 in/sec/lb) /3 Octave Band Center Frequency (Hz) 25 feet 50 feet 75 feet 100 feet 125 feet 150 feet Figure 10. Line source transfer mobility of Site V-1: 200 Innerbelt Road Cambridge, MA Site V-2 20 Vernon Street Somerville, Ma Line Source Transfer Mobility (db re 1 in/sec/lb) /3 Octave Band Center Frequency (Hz) 25 feet 50 feet 75 feet 100 feet 125 feet 150 feet Figure 11. Line source transfer mobility of Site V-2: 20 Vernon Street Somerville, MA 31

38 MBTA Green Line Extension Project Site V-3 Tufts Alumni Field Medford, Ma Line Source Transfer Mobility (db re 1 in/sec/lb) /3 Octave Band Center Frequency (Hz) 25 feet 50 feet 75 feet 100 feet 125 feet 150 feet Figure 12. Line source transfer mobility of Site V-3: Tufts Alumni Field Medford, MA Vibration Levels of MBTA Commuter Trains Reference vibration measurements of MBTA commuter trains and Amtrak trains were conducted at Tufts University Alumni Field to calculate the force density of commuter trains. Measurements were conducted of train pass bys at several distances away from the track centerline (50 to 250 feet). Figure 13 shows the maximum overall vibration levels for each train type as a function of distance and the typical FTA generalized curve for locomotive-powered passenger trains at 50 mph. This figure shows that the vibration levels from the MBTA commuter and Amtrak trains are about 5 to 10 VdB lower than the generalized curve. Amtrak commuter trains operating at 50 mph are shown to generate maximum vibration levels of approximately 72 VdB at a distance of 50 feet from the track centerline. Since the MBTA commuter trains were found to generate higher vibration levels than Amtrak trains (at distances within 150 feet of the near track centerline where impact may occur) and the vibration impact criteria are based on maximum levels of either type of commuter train, the assessment focuses on vibration generated by the MBTA commuter trains compared to Amtrak. The MBTA commuter train force density was calculated from the maximum pass by vibration levels and the line source transfer mobility as discussed in Section 5.3. Figure 14 shows the calculated vehicle force density. In addition to vibration measurements of commuter trains at Tufts Alumni Field for calculation of the vehicle force density, measurements were conducted at eight additional sites to provide further detail on vibration generated by these sources. These sites include Horace Street, Aldrich Street, Pearl Street Apartments, Richdale Avenue, Cedar Street, Nashua Street, Morton Avenue and Tufts Science and Technology Center. This information was used to identify the frequency content of vibration generated by the trains and will be used to specify appropriate track vibration isolation during the final design of the 32 January, 2011 HMMH Report No

39 Environmental Assessment Noise and Vibration Technical Report Proposed Action. Figure 15 shows a regression of the maximum overall vibration levels for commuter trains as a function of distance at all sites including Tufts Alumni Field. This figure shows that there is approximately a 10-decibel range of vibration levels across all measurement sites. In general, these measurements correlate closely to vibration projections using the vehicle force density and vibration propagation measurements. At some vibration measurement sites, the propagation conditions may have been affected by the close proximity of sensors to nearby buildings. At these locations, the exterior ground measurements may be more representative of levels inside the buildings. Figure 16 shows the maximum ground vibration spectra from commuter trains at each location at a distance of 50 feet. This figure shows that commuter trains generate the maximum vibration in the 50-Hz one-third octave band at Morton Avenue, Aldrich Street and Tufts Science and Technology Center. At the Cedar Street measurement site, maximum vibration was generated in the 80-Hz one-third octave band. At Horace Street, Nashua Street, Pearl Street Apartments and Richdale Avenue, maximum vibration from commuter trains was generated in the 25 and 31.5-Hz one-third octave bands. These measurements indicate that vibration mitigation should be effective down to the 50-Hz band at many locations and down to the 25 Hz-band at a few locations. 100 Overall Vibration Velocity (Vdb re.1 in/sec) Distance From Track Centerline, ft MBTA Commuter Trains Amtrak Trains FTA Generalized Curve for Locomotive-Powered Passenger at 50 mph Figure 13. Vibration levels versus distance from MBTA commuter and Amtrak trains at Tufts Alumni Field 33

40 MBTA Green Line Extension Project Force Density (db re 1 lb/ft 0.5 ) /3 Octave Band Center Frequency (Hz) MBTA Commuter Train at 50 mph 100 Figure 14. MBTA commuter train force density at 50 mph 95 Overall Vibration Velocity [VdB, re: 1 in/s] Distance [feet] Horace Street Nashua Street Morton Avenue Aldrich Street Richdale Avenue Pearl St Apartments Cedar Street Tufts Science and Technology Tufts Alumni Field FTA Reference at 50 mph Figure 15. Vibration level versus distance for commuter trains 34 January, 2011 HMMH Report No

41 Environmental Assessment Noise and Vibration Technical Report Vibration Velocity at 50 feet [VdB] Horace Nashua Morton Aldrich Richdale Pearl Cedar Tufts One-third Octave Band Center Frequency [Hz] Figure 16. Maximum vibration spectra for commuter trains Vibration Levels of MBTA Green Line Trains Reference vibration measurements of Green Line trains were conducted on the existing D branch near Beaconsfeld Station to calculate a vehicle force density. Measurements were conducted of train pass bys at several distances away from the track centerline (25 to 100 feet) at this site. Vibration measurements of Green Line trains on an elevated guideway were also conducted at the Archstone Phase II development parcel east of East Street on Monsignor O Brien Highway in Cambridge, MA. Measurements were conducted at distances of 10 to 50 feet from a guideway support column at this location. Figure 17 shows a regression of maximum overall vibration levels and the typical FTA generalized curve for light-rail vehicles operating at 20 mph. This figure shows that the vibration levels from the Green Line trains at-grade are up to 10 VdB higher than the generalized curve at close-in distances. This may be due to the jointed track causing localized increases in vibration levels close-in. Vibration levels from Green Line trains on elevated structure are shown to be lower than for trains at-grade, especially close-in to the guideway support column. This decrease in vibration is expected as the structure damps the vibration propagation from the train to the surrounding soil. The Green Line train force density (at-grade) was calculated from the maximum pass by vibration levels and the line source transfer mobility as discussed in Section 5.3. Figure 18 shows the calculated Green Line train force density. It should be noted that the high force density levels below 25 Hz is due primarily to the low vibration levels measured at the reference site in these frequency bands. 35

42 MBTA Green Line Extension Project 100 Overall Vibration Velocity (Vdb re.1 in/sec) Distance From Track Centerline, ft Green Line Train at 20 mph (At-grade on Jointed Track) FTA Generalized Curve for Light Rail Vehicles at 20 mph (At-Grade on CWR) Green Line Train at 20 mph on Elevated Guideway Figure 17. Vibration level versus distance for MBTA Green Line trains and FTA generalized curve at 20 mph Force Density (db re 1 lb/ft 0.5 ) /3 Octave Band Center Frequency (Hz) MBTA Green Line LRV at 50 mph Figure 18. MBTA Green Line train force density at 50 mph 36 January, 2011 HMMH Report No

43 Environmental Assessment Noise and Vibration Technical Report 6 Noise and Vibration Impact Assessment 6.1 Noise Projections Existing noise levels at all sensitive receptors have been estimated based on the nearest existing noise measurement location and relative distances to the dominant noise source (existing commuter rail line or roadway). Noise impact is assessed at the closer location of either an outdoor area with frequent human use or the nearest building façade. The effects of terrain and intervening objects such as buildings have been included in the estimation of existing noise levels. Future noise sources associated with the Proposed Action include mainline Green Line operations, commuter, Amtrak and freight train operations and maintenance facility noise sources. Future noise from the commuter, Amtrak and freight trains is projected based on the existing noise measurements which are dominated by commuter train noise and future changes to the alignment such as shifting the tracks. In general, when the commuter rail is shifted closer to sensitive receptors, the noise levels will increase; however, differences in sound propagation due to the terrain are also considered. For example, in some instances, moving the commuter rail closer to a retaining wall or berm will increase the acoustic shielding provided by those features. The relative contributions of noise from commuter trains on both tracks and from locomotives versus rail cars are included in the projections. The change in noise level due to the terrain features of the proposed commuter rail alignment is modeled based on methodology outlined in the FTA guidance manual. Since this modeling approach is based on the existing long-term measurements along the corridor, the projections include all operations from MBTA commuter trains, Amtrak trains, and freight rail activity and factors such as train speed, presence of special trackwork and other site-specific conditions. The contribution to future noise levels from the proposed Green Line trains is projected based on reference noise measurements of the Green Line trains, the distance between receptor locations and the Green Line tracks, site-specific conditions such as the terrain, intervening objects, presence of special trackwork and building rows and the operational plan to the extension including train consist (the number of cars), speed, and headways. Maintenance facility noise sources include train movements in and out of the yards, increases in noise from special trackwork (crossovers or turnouts), potential wheel squeal on tight radius curves, stationary cars in the yards operating with auxiliary equipment on, a traction power substation, and the employee parking lot. Train movements in and out of the yards are non-revenue operations between the proposed yards to and from the closest stations (Union Station, Lechmere Station and Brickbottom Station). These pull in and pull out movements are required to bring trains into service or to take trains out of service for maintenance or at the end of the service day. These movements are in addition to the standard revenue service train operations. Often these additional train movements represent the most significant noise source associated with the maintenance facilities. Maintenance lead tracks and yard tracks often include special trackwork (crossovers or turnouts) or tightradius curves which can increase noise levels associated with train movements into and out of the yards. Special trackwork introduces gaps into the rail running surface which will increase noise levels from the train as the wheels impact these gaps. Tight-radius curves, typically 400-foot radius or less, may cause wheel squeal which is a high-frequency tonal noise generated by the wheels. Another potentially significant noise source associated with the maintenance facilities are stationary cars in the storage yards operating with auxiliary equipment on. Cars are typically operated under this condition in the early morning to heat or cool the interior and prepare the trains for revenue service as well as at other times 37

44 MBTA Green Line Extension Project during the day when cars are in the yards but will be required to return to service. The contribution of noise from such operation of cars in the storage yards is generally not as significant as the train movements unless receptors are much closer to the storage yards than the mainline tracks. Maintenance operations within the building such as wheel truing, using pneumatic tools and the car wash are not expected to be significant noise sources in the community as the building will significantly shield these activities. The HVAC system for the maintenance building is also not expected to be a significant noise source. Unlike maintenance buildings for diesel-electric locomotives which require more substantial HVAC systems to handle the train exhaust, this building would only require normal levels of airflow for storing electric Green Line vehicles. The principal assumptions used in the analysis are summarized below: The track alignments used in the impact assessment were dated March, 2010 for segments except for tracks associated with the Option L Maintenance Facility (Additional Maintenance Facility Alternatives Analysis Report), Union Square Branch tracks between McGrath Highway/Route 28 and the Red Bridge Area (revision dated November 12, 2010) and the Medford Branch between Washington Street Station and the Red Bridge Area (revision dated November 12, 2010). The operating periods, schedule, consist and speed of the commuter trains are not expected to change as part of the Proposed Action. The locations of the commuter rail lines are expected to be modified along some portions of the Proposed Action to accommodate the proposed Green Line tracks. The operating periods and schedule of the proposed Green Line trains assumes: o Start of service is 5:00 am (inbound) and 5:30 am (outbound) o End of service is 12:00 am (inbound) and 12:30 am (outbound) o Peak periods are 6:30 am to 9:00 am and 3:30 pm to 6:30 pm o Off-peak period headways are ten minutes o Peak period headways are five minutes Green Line trains will consist of three light rail vehicles. The speeds of the proposed Green Line trains are expected to be up to 50 mph along the Medford Branch except approaching and leaving station locations. Speeds along the Union Square Branch are expected to be up to 50 mph along the MBTA Fitchburg Line. Transit warning horns will not be used on a routine basis for either the commuter trains or proposed Green Line trains. There are no proposed grade-crossings for the Medford or Union Square segments. Wheel impacts at turnouts are assumed to cause localized noise increases of 3 to 6 dba. Wheel squeal for Green Line trains operating on tight curves (radius less than 400 feet) is assumed to contribute an Lmax of 86 dba and an SEL of 92 dba at 50 feet from the nearest curved segment of the track. This noise emission is based on measurements of light rail transit cars on curved track on other systems. The Green Line track is expected to be continuous-welded rail which typically generates lower noise levels than jointed rail. Maintenance Facility It is assumed that cars will be stored in the east yard, south yard and in the building/surrounding tracks proportional to their storage capacity 27, 40 and 13 cars, respectively. While cars are in the 38 January, 2011 HMMH Report No

45 Environmental Assessment Noise and Vibration Technical Report yard, they may be powered with auxiliary equipment running (i.e. heating and air-conditioning units) in preparation of their use in revenue service operations. Stationary cars with auxiliary equipment running (i.e. heating and air-conditioning) are assumed to generate a constant noise level of 65 dba at 50 feet. The total contribution from these stationary cars in the yards depends on the number of cars and duration. A total of 260 movements of cars entering and leaving the yard (130 entering and 130 leaving) are expected to occur throughout a day. It is assumed that 100 of these movements will pull in/pull out of the yard to/from Lechmere Station, 100 will pull in/pull out of the yard to/from the Medford Branch and 60 will pull in/pull out of the yard to/from the Union Square Branch. o Movements to/from Lechmere Station will require trains to travel along the northbound mainline tracks past the Brickbottom Artists Buildings, cross over to the Medford Yard Lead Track, reverse direction and then travel past the Brickbottom Artists Buildings a second time. o Movements to/from Medford will only require trains to travel past the Brickbottom Artists Buildings once along the Medford Yard Lead Track. o Movements to/from the Union Square Branch will be made on the Union Square Yard Lead Track which is directly connected to the mainline tracks. o Yard movements are assumed to occur according to the following schedule: Prior to the start of service (between approximately 5:00 AM and 5:30 AM), 50 cars would leave the yard and deadhead to their respective terminal stations for early morning service. After 7:00 AM, another 30 cars would leave the yard for peak morning service and eight would return to the yard. Between the peak morning service and the peak evening service a total of 42 cars will enter and 42 cars will leave the yard. During peak evening service 4 cars will enter and 4 cars will leave the yard. After peak evening service four cars will leave the yard and 36 will enter the yard. Between 10:00 PM and 1:00 AM, the remaining 40 cars in service will return to the yard. An approximately 100-space parking lot would be located southwest of the maintenance building and a traction power substation would be located in this same area. o The reference SEL for noise from the 100-space employee parking lot is 82 dba. This equates to an Ldn of 53 dba at 50 feet. Maintenance operations within the building such as wheel truing, using pneumatic tools and the car wash are not expected to be significant noise sources in the community as the building will significantly shield these activities. The HVAC system for the maintenance building is also not expected to be a significant noise source. Unlike maintenance buildings for diesel-electric locomotives which require more substantial HVAC systems to handle the train exhaust, this building would only require normal levels of airflow for storing electric Green Line vehicles. Traction power substations (TPSS) are assumed to generate a constant noise level of 50 dba at 50 feet or less. Since TPSS operate constantly, this is equivalent to an Ldn of 56 dba. This assumption is consistent with American Public Transportation Association guidelines on the design of rapid transit facilities for substations. 39

46 MBTA Green Line Extension Project 6.2 Vibration Projections Vibration impact is assessed by conducting reference vibration measurements of commuter trains and Green Line trains to calculate train force densities, conducting measurements of the vibration propagation characteristics of the soil along the proposed corridor and projecting future vibration levels from the Proposed Action. Future vibration levels from the Proposed Action would be generated from the proposed Green Line trains and existing commuter trains including modifications to the commuter rail lines. The principal assumptions used in this analysis are similar to the noise projections with the following additional details: The future commuter train and Green Line tracks are expected to be on ballast and tie including a boat section trackform. A boat section is a concrete slab approximately two to three feet thick which supports all of the commuter train and Green Line train tracks. Green Line trains are expected to operate on continuous-welded rail which typically generates lower vibration levels than jointed rail. Commuter trains operate on continuous welded rail. Wheel impacts at special trackwork are assumed to cause localized vibration increases of 5 to 10 VdB. Vibration levels are projected at sensitive receptors based on the detailed vibration analysis methodology in the FTA guidance manual including adjustments for speed, building coupling and elevated structures. A two-decibel factor of safety has been added to vibration projections. Projections for both commuter trains and Green Line trains operating at 50 mph are shown for all three locations along the Proposed Action with the appropriate Category 2 vibration criterion in Figure 19 through Figure 24. These figures do not include any building coupling adjustments or factor of safety. 40 January, 2011 HMMH Report No

47 Environmental Assessment Noise and Vibration Technical Report MBTA Commuter Trains at 50 mph Site V-1: 200 Innerbelt Road Cambridge, Ma Vibration Velocity (db re 1 in/sec) /3 Octave Band Center Frequency (Hz) 50 feet 75 feet 100 feet 125 feet 150 feet Residential Impact Criterion for Commuter Trains Figure 19. Vibration projections for MBTA commuter trains at Site V-1 MBTA Commuter Trains at 50 mph Site V-2: 20 Vernon Street Somerville, Ma Vibration Velocity (db re 1 in/sec) /3 Octave Band Center Frequency (Hz) 50 feet 75 feet 100 feet 125 feet 150 feet Residential Impact Criterion for Commuter Trains Figure 20. Vibration projections for MBTA commuter trains at Site V-2 41

48 MBTA Green Line Extension Project MBTA Commuter Trains at 50 mph Site V-3: Tufts Alumni Field Medford, Ma Vibration Velocity (db re 1 in/sec) /3 Octave Band Center Frequency (Hz) 50 feet 75 feet 100 feet 125 feet 150 feet Residential Impact Criterion for Commuter Trains Figure 21. Vibration projections for MBTA commuter trains at Site V-3 MBTA Green Line Trains at 50 mph Site V-1: 200 Innerbelt Road Cambridge, Ma Vibration Velocity (db re 1 in/sec) \ /3 Octave Band Center Frequency (Hz) 50 feet 75 feet 100 feet 125 feet 150 feet Residential Impact Criterion for Green Line Trains Figure 22. Vibration projections for Green Line trains at Site V-1 42 January, 2011 HMMH Report No

49 Environmental Assessment Noise and Vibration Technical Report MBTA Green Line Trains at 50 mph Site V-2: 20 Vernon Street Somerville, Ma Vibration Velocity (db re 1 in/sec) /3 Octave Band Center Frequency (Hz) 50 feet 75 feet 100 feet 125 feet 150 feet Residential Impact Criterion for Green Line Trains Figure 23. Vibration projections for Green Line trains at Site V-2 MBTA Green Line Trains at 50 mph Site V-3: Tufts Alumni Field Medford, Ma Vibration Velocity (db re 1 in/sec) /3 Octave Band Center Frequency (Hz) 50 feet 75 feet 100 feet 125 feet 150 feet Residential Impact Criterion for Green Line Trains Figure 24. Vibration projections for Green Line trains at Site V-3 43

50 MBTA Green Line Extension Project 6.3 Future Build Conditions The Proposed Action is the extension of the Green Line to Medford and Union Square (via commuter rail rights-of-way) including the Option L maintenance facility. This section assesses the potential for longterm noise and vibration impact from transit operations and short-term impact from construction activities. 6.4 Noise Impact Assessment from Transit Operations Extending the Green Line would add a new noise source to the environment along the Proposed Action corridor. While there is existing noise exposure from sources such as commuter trains and vehicular traffic, introducing an additional noise source and relocating the commuter rail lines have the potential to increase future noise at noise-sensitive receptors. Noise level projections for sensitive receptors that may be exposed to noise impact prior to mitigation measures are shown in Table 9. This table shows the noise sensitive receptor location, side of tracks, distances to the future commuter line and Green Line near track centerlines, the existing noise levels at each location, moderate and severe noise impact criteria, the future projected noise level, increase in future noise level over the existing and the number of moderate and severe impacted buildings. Locations that may be exposed to noise impact are shown in Appendix E. Table 10 presents receptors that may be exposed to ground-borne noise impact prior to mitigation. All of the noise sensitive receptors listed in Table 9 are single-family and/or multi-family residential properties unless noted. Institutional land uses that may be exposed to airborne noise impact prior to mitigation include the Tufts Science and Technology Center, Outside the Line Artist Studio and the Walnut Street Center (a non profit support center for adults with developmental disabilities) in Union Square. Trum Playground would also potentially be exposed to noise impact, prior to mitigation. Curtis Hall at Tufts University (WMFO radio station) and Bacon Hall at Tufts University (building has no windows facing track) would potentially be exposed to ground-borne noise impact. Table 9. Potential noise impact at receptors prior to mitigation Distance to Near Track Centerline (feet) Existing Noise Impact Criteria Future Noise Total Number of Impacts (Buildings) Side of Comm. Green Level Level Noise Sensitive Receptor Location Tracks Line Line (Ldn) Mod. Sev. (Ldn) Increase Mod. Sev. Segment between Lechmere Station and Fitchburg Street Archstone Phase II Development Building East of East Street (proposed) East n/a 15 a NorthPoint (Tango and Sierra) East n/a Glass Factory Condominiums West n/a b Hampton Inn Hotel West n/a b Water Street (proposed) East n/a 60 a b Brickbottom Artists Buildings (Northeast façade) West n/a b Brickbottom Artists Buildings (South façade) North b c Totals between Lechmere Station and Fitchburg Street 2 5 Segment between Fitchburg Street and College Avenue Station Alston St near Cross St West Avon Place and Auburn Ave near McGrath Highway East Gilman St and Aldrich St East Pearl St near Medford St East January, 2011 HMMH Report No

51 Environmental Assessment Noise and Vibration Technical Report Distance to Near Track Centerline (feet) Existing Noise Impact Criteria Future Noise Total Number of Impacts (Buildings) Side of Comm. Green Level Level Noise Sensitive Receptor Location Tracks Line Line (Ldn) Mod. Sev. (Ldn) Increase Mod. Sev. Richdale Ave East Willoughby St near Sycamore St West Sycamore St near Richdale Ave East Visiting Nurses Assisted Living West Vernon St, Nashua St, Henderson St, Hinckley St East Vernon St and Berwick St East Murdock St West Cedar St East Wilson Ave and Cedar St East Trum Playground d East d 71.4 d 74.7 d 72.0 d e Boston Ave between Cedar St and Broadway West Newbern Ave, Morton, Granville Ave, Winchester Pl, Winchester Ct (1st row) East Newbern Ave, Morton, Granville Ave, Winchester Pl, Winchester Ct (2nd row) East Tufts - Science and Technology Center and Outside the Lines Art Studio d East d 77.7 d 81.5 d 80.3 d Burget Ave near College Ave East Burget Ave East Brookings St East 48 n/a Totals between Fitchburg Street and Medford Hillside Segment between McGrath Hwy and Prospect St. (Union Square) Horace St (1st and 2nd row) South Horace St (3rd row) South Walnut Street Center d North d 67.1 d 71.0 d 71.5 d Charlestown St North Totals between McGrath Hwy and Prospect St. (Union Square) 5 4 Total Noise Impacts for Category 2 Land Use (Residential) Total Noise Impacts for Category 3 Land Use (Institutional) 2 1 Total Noise Impacts for Category 3 Land Use (Park) 1 0 a b c d e Distance to alignment estimated for future proposed property Projected noise levels include following contributions from noise generated due to the maintenance facility (Option L). Glass Factory Condominiums, 57.3 Hampton Inn Hotel, Water Street, 59.3 Brickbottom Artists Buildings (northeast façade), 67.8 Brickbottom Artists Buildings (south façade), 63.4 Impact for Brickbottom Artists Buildings is counted under listing for Brickbottom Artists Buildings (northeast façade) Peak-transit hour Leq used for institutional land use. Noise impact at Trum Playground does not include a building structure. Table 10. Potential ground-borne noise impact at receptors prior to mitigation Distance to Near Track Centerline (feet) Comm. Green Line Line Ground-Borne Noise Impact Criteria (dba) Comm. Green Line Line Future Ground- Borne Noise Levels (dba) Comm. Green Line Line Total Rail Number of Line Impacts Causing (Buildings) Impact Noise Sensitive Receptor Location Side of Tracks Tufts Bacon Hall a West Both Tufts Curtis Hall (WMFO radio) b West Both Total Ground-Borne Noise Impact for Category 3 Land Use (Institutional) 2 a Potential ground-borne noise impact has been identified for Bacon Hall as it has no windows facing the tracks. b Sensitive use in Curtis Hall includes WMFO radio station which has been assessed as a recording studio. 45

52 MBTA Green Line Extension Project Since existing noise levels are relatively high at locations along the existing commuter rail line, even small increases in future noise levels are considered to have the potential for moderate or severe noise impact. Potential noise impacts on the east side of the alignment along the existing Lowell commuter line are due primarily to the shifting of the commuter rail line closer to these sensitive properties. Future noise levels on the east side of the alignment would typically increase only one to three decibels. Potential noise impacts on the west side of the alignment are due primarily to the close proximity of noise-sensitive receptors to the Green Line trains. Future noise levels at the impacted receptors on the west side would typically increase one to two decibels. At a few specific locations, such as Alston Street and the Walnut Street Center, the future increase in noise levels is higher (five to eight decibels) due to the close proximity to the proposed Green Line trains. At locations where there is no existing train activity between Lechmere Station and Fitchburg Street, the future increase in noise levels due to the Proposed Action would be higher because existing noise levels are lower. In particular, future noise levels for the Glass Factory Condominiums, Hampton Inn Hotel, future building at 22 Water Street and the northeast façade of the Brickbottom Artists Buildings are projected to be ten to 18 decibels higher due to the relatively quiet existing conditions. Noise projections include contributions from the proposed Option L maintenance facility. While the maintenance facility contributes to the noise levels, the majority of the increase in noise levels from the Proposed Action would be due to mainline Green Line operations. In fact, at the Brickbottom Artists Building (northeast façade), where influence from the Option L yard is greatest, noise from the mainline operations (including potential wheel squeal from mainline operations) is projected to be 72.6 Ldn and noise from all of the maintenance yard operations is projected to be 67.8 Ldn. The total future noise level which combines both of these project sources and existing noise sources would be 74.3 Ldn. The future noise level would be Ldn 73.2 dba without any contribution from the maintenance facility. Therefore, the maintenance facility would only increase future noise levels by 1.1 decibels compared to the mainline operations alone. At other locations, the contribution of noise from the maintenance facility is even lower than at the northeast façade of the Brickbottom Artists Buildings. Table 11 shows the summary of noise sensitive receptors that would be exposed to moderate and severe airborne noise impact and ground-borne noise impact prior to mitigation. Prior to mitigation, 170 noisesensitive receptors would be exposed to impact including 121 moderate impacts and 43 severe impacts at single-family and multi-family residential buildings, moderate impact at Tufts University Science and Technology Center and Outside the Line Artist s Studio (a teaching facility), moderate impact at Trum Playground, severe noise impact at the Walnut Street Center (a non-profit support center for adults with developmental disabilities) near Union Square and ground-borne noise impact at Tufts Bacon Hall and Tufts Curtis Hall. Table 11. Summary of potential airborne and ground-borne noise impact prior to mitigation Residential Buildings Impacted Institutional Buildings and Parks Impacted Moderate Severe Moderate Severe Ground-Borne Noise a 1 2 b a Institutional airborne noise impacts include the Tufts University Science and Technology Center, Outside the Line Studio and Trum Playground. b Ground-borne noise impact includes Tufts Bacon Hall (no windows facing tracks) and Tufts Curtis Hall (WMFO radio station). 46 January, 2011 HMMH Report No

53 Environmental Assessment Noise and Vibration Technical Report 6.5 Temporary Construction Noise Impacts The construction noise criteria applicable to the Proposed Action are based on the Central Artery/Tunnel (CA/T) Noise Control Specification This detailed construction noise specification is consistent with the City of Cambridge Noise Ordinance (Ord. 1326, Chapter , adopted May 18, 2009), the City of Somerville Noise Ordinance (No , I VII, IX, adopted Nov. 22, 2000) and the City of Medford Noise Ordinance (Revised Ordinances Chapter 38, Article II, Sec ). This specification establishes noise criteria limits according to time of day and type of sensitive land use, defining allowable limits for the maximum noise emissions of specific equipment, requirements for a noise monitoring plan to be prepared prior to construction, noise monitoring equipment, noise reduction measures and reporting requirements. Unlike the assessment of long-term noise impact from the train operations, potential shortterm noise impact from construction activities is assessed at commercial and industrial land uses. Table 12 presents the construction lot-line noise limits as defined in the Noise Control Specification. Construction lot-line noise limits are based on the L10 noise descriptor and depend on the existing noise levels, time of day (daytime, evening or nighttime) and the type of sensitive land use (FTA-defined sensitive land use, commercial areas and industrial areas). The L10 noise level describes the level that is exceeded only 10 percent of the time. Therefore, it is representative of the higher noise levels in the community. For daytime construction (7:00 AM to 6:00 PM), the limits are defined as the greater of 75 dba or the background ambient level plus 5 dba for FTA-defined noise sensitive sites, 80 dba or the background plus 5 dba for commercial areas and 85 dba or the background plus 5 dba for industrial areas. For evening construction (6:00 PM to 10:00 PM), the L10 limit for FTA-defined noise sensitive sites is the background plus 5 dba. For nighttime construction (10:00 PM to 7:00 AM), the L10 limit for FTA-defined noise sensitive sites is the background plus 5 dba (if background is less than 70 dba) and plus 3 dba (if the background is greater than 70 dba). Commercial and industrial areas are not considered to be sensitive to construction noise during the evening or nighttime since they are generally closed during these periods. Table 12. Construction lot-line noise limits Land Use (c) Time of Day L10 Level (dba) Lmax Level (dba) FTA Land Use Categories (1,2,3) Daytime 75 or Background + 5 (a) 85 (b) / 90 (impact equip.) Commercial Daytime 80 or Background + 5 (a) None Industrial Daytime 85 or Background + 5 (a) None FTA Land Use Categories (1,2,3) Evening Background Commercial Evening None None Industrial Evening None None FTA Land Use Categories (1,2,3) FTA Land Use Categories (1,2,3) Nighttime Nighttime Background + 5 (existing < 70) Background + 3 (existing > 70) Commercial Nighttime None None Industrial Nighttime None None Source: CA/T Noise Specification a Noise from impact equipment is exempt from this requirement. b All measurements shall be taken at the affected lot-line. In situations where the work site is within 50 feet of a lot-line, the measurement shall be taken from a point along the lot-line such that a 50 foot distance is maintained between the sound level meter and the construction activity being monitored. c Lot-line noise limits shall apply to all points along the receptor s lot-line

54 MBTA Green Line Extension Project Although the Noise Control Specification requires that site-specific background L10 measurements are conducted more immediately prior to construction in order to define the allowable limits, Table 13 provides a preliminary indication of the relevant noise criteria. This table presents the day, evening and nighttime L10 noise levels measured at long-term monitoring sites throughout the Proposed Action area. Since existing measured daytime L10 noise levels ranged from 50 to 64 dba, it is expected that the daytime L10 noise limits of 75 dba, 80 dba and 85 dba for FTA-defined land use, commercial and industrial land uses, respectively, will be applicable. The measured evening L10 noise levels ranged from 47 to 60 dba and consequently the applicable L10 criteria for the evening hours is expected to range from 52 to 65 dba. During the nighttime hours, the measured L10 noise levels ranges from 44 to 58 dba and consequently the applicable L10 criteria for the evening hours is expected to range from 49 to 63 dba. In addition to construction lot-line noise limits, noise limits at 50 feet for specific equipment have been identified. A list of these construction noise limits is provided in Appendix F. Table 13. Day, evening and nighttime L10 noise levels Daytime (7am to 6pm) Evening (6pm to 10pm) L10 Noise Level L10 Noise Level Location (dba) (dba) LT-1 39 Horace Street (Somerville) Measurement Site Nighttime (10pm to 7am) L10 Noise Level (dba) LT-2 5 Alston Street (Somerville) LT Medford Street (Somerville) LT-4 34 Richdale Avenue (Somerville) LT-5 86 Vernon Street (Somerville) n/a LT-6 95 Boston Avenue (Somerville) LT-7 7/9 Winchester Place (Somerville) LT Burget Avenue (Medford) LT-9 76 Orchard Street (Medford) LT-10 Glass Factory Condominiums (Cambridge) n/a n/a n/a LT-11 Brickbottom Artists Buildings Northeast Façade (Somerville) LT-12 Brickbottom Artists Buildings South Façade (Somerville) Significant construction activities associated with the Proposed Action would include at-grade track construction, elevated guideway construction, utility relocation and bridge replacement. Table 14 presents projections of L10 noise levels for these four construction activities. Since actual noise levels depend significantly on the contractor s equipment, scheduling and construction methods, these results should only be used as a preliminary indication of the worst-case potential limits to impact. 48 January, 2011 HMMH Report No

55 Environmental Assessment Noise and Vibration Technical Report Table 14. Construction noise projections Hourly-equivalent sound level (Leq) (dba) Construction Equipment Maximum Noise Level at 50 ft (dba) Usage Factor At-Grade Track Construction Elevated Guideway Construction Utility Relocation Bridge Replacement Air Compressor 80 40% Backhoe 80 40% Crane 85 20% Bulldozer 85 40% Generator (25 kva or less) 70 50% Front End Loader 80 40% Dump Truck 84 40% Impact Pile Driving 95 20% Concrete Mixer 85 40% Concrete Pump 82 20% Jackhammer 85 20% 78 Total Leq (dba) at 50 feet Total L10 (dba) at 50 feet Total L10 (dba) at 250 feet Table 14 indicates that temporary noise impacts could result from these construction activities. Such impacts may occur in residential areas and at other noise-sensitive land use located within several hundred feet of the alignment. The potential for noise impact would be greatest at locations near pile driving operations for bridges and other structures, and at locations close to any nighttime construction activities. Construction noise mitigation is discussed in Section Vibration Impact Assessment from Train Operations The Proposed Action would add a new vibration source to the environment along the proposed corridor. While there is existing vibration exposure from sources such as commuter trains and vehicular traffic, introducing the Green Line trains and relocating the commuter rail lines have the potential to increase future vibration at some sensitive receptors. Sensitive receptors that may be exposed to vibration impact prior to any mitigation measures are shown in Table 15. This table shows the vibration-sensitive receptor location, side of tracks, the distances to the near track centerline and vibration projections for the existing commuter line, future commuter line and Green Line, the number of impacted buildings, and the rail line causing impact. Locations that may be exposed to vibration impact are shown in Appendix E. All of the receptors listed in this table are single-family or multi-family residential properties unless noted. Institutional land uses that are projected to be exposed to vibration impact include the Science and Technology Center, Bacon Hall and Bray Labs at Tufts University and Outside the Line Artist Studio. Vibration impact at Tufts Science and Technology Center and Bacon Hall includes potential affect to humans and vibration-sensitive equipment. Vibration impact at Bray Labs is due only to potential affect to vibration-sensitive equipment. The potential for vibration impact at the future proposed Tufts Integrated Research Laboratory at 550 to 574 Boston Ave depends on the construction of the building and its setback from the rail corridor. There would be no potential for impact to humans (annoyance) but there would be a potential for impact to vibration-sensitive equipment. Since this building would be on the west side of the alignment and the commuter lines would be shifted further away, vibration impact would not be expected unless the building was constructed very close to the near track of the proposed Green Line. 49

56 MBTA Green Line Extension Project Table 15. Potential vibration impact prior to mitigation Existing Vibration Sensitive Receptor Location Side of Tracks Comm. Line Segment between Lechmere Station and Medford Distance to Near Track Centerline (feet) Future Com. Line Green Line Maximum Vibration Velocity in any 1/3-octave band from 4 to 80 Hz (VdB re: 1 -in/sec) Existing Comm. Line Future Com. Line Green Line Total Number of Impacted Buildings Rail Line Causing Impact Brickbottom Artists Buildings (South) North Green. Alston St near Cross St West a 4 Both Avon Place East Comm. Auburn Ave near McGrath Hwy East Comm. Aldrich St East a Comm. Gilman St near Aldrich St East Comm. Gilman St near Walnut St East Comm. Medford St west of Walnut St West Green. Pearl St near Medford St East Comm. Montrose Ct and Jerome Ct West Green. Richdale Ave East Comm. Willoughby St near Sycamore St West a 1 Green. Vernon St near Lowell St East Comm. Lowell St near Vernon St East Comm. Nashua, Henderson, Hinckley St East a 95 a 58 4 Comm. Hinckley St East a 95 a 59 2 Comm. Berwick St East a 82 a 58 2 Comm. Murdock St West a 1 Green. Murdock St near Cedar St West a 1 Green. Cedar St East Comm. Newbern Ave East Comm. Morton Ave, Granville Ave East Comm. Winchester Place East Comm. Winchester Place East Comm. Winchester Place East Comm. Winchester Court East Comm. Tufts - Science and Technology c Center East Comm. Outside the Lines Art Studio East Comm. Tufts Bacon Hall c West a 1 Both Tufts Bray Labs c West Green. Brookings St East Comm. Totals between Lechmere Station and Medford Hillside 93 Segment on Fitchburg Mainline between McGrath Hwy and Prospect St. (Union Square) Horace St (1st row) South a 2 Both Horace St (2nd row) South a 1 Green. Totals on Fitchburg Mainline between McGrath Hwy and Prospect St. 3 Total Vibration Impacts for Category 2 Land Use (Residential) 92 Total Vibration Impacts for Category 3 Land Use (Institutional) 4 a Projected vibration levels include contributions from special trackwork. b Green Line is on elevated structure at this location. c Building includes vibration-sensitive equipment assessed with a vibration criterion of 65 VdB. 50 January, 2011 HMMH Report No

57 Environmental Assessment Noise and Vibration Technical Report Table 16 shows the summary of vibration-sensitive receptors that would be exposed to impact prior to vibration mitigation. Vibration impact is projected at 92 single-family and multi-family residential buildings and at four institutional buildings (Tufts Science and Technology Center, Tufts Bacon Hall, Tufts Bray Labs and Outside the Line Artist s Studio). Vibration impact from the commuter trains generally occurs within 60 feet of the future commuter rail near track and within 40 feet of the proposed Green Line near track. Most receptors that would be exposed to vibration impact from commuter train activity are located on the east side of the Lowell line or the south side of the Fitchburg line where the commuter tracks would be shifted closer than their current location. Most receptors that would be exposed to vibration impact from Green Line train activity are located on the west side of the alignment along the Medford Branch. Table 16. Summary of potential vibration impact prior to mitigation Residential Buildings Impacted Institutional Buildings Impacted 92 4 a a Institutional buildings include the Tufts Science and Technology Center, Tufts Bacon Hall, Tufts Bray Labs and Outside the Lines Studio. 6.7 Temporary Construction Vibration Impacts Only in very rare instances do vibrations generated by transit operations pose any risk of damage to nearby structures. Typically, the only potential risk of vibration causing damage to nearby structures is from certain construction activities at very close distances. The most significant construction activities for which potential damage is assessed include clam shovel drops, impact pile driving, caisson drilling, loaded trucks, hoe rams, and jackhammers. Although construction vibrations are only temporary, it is still reasonable to assess the potential for human annoyance and damage. Since buildings in the study area are typically engineered concrete and masonry or reinforced-concrete, steel or timber construction, a vibration damage criterion of 98 VdB has been used to asses potential impact. Source vibration levels at 25 feet and the distances to potential residential annoyance (72 VdB criterion) and potential damage (98 VdB criterion) are presented in Table 17. This table shows that potential damage to nearby structures will not occur beyond 18 feet for most equipment. Distance to potential human annoyance is less than 80 feet for a hoe ram, caisson drilling and loaded trucks, 43 feet from a jackhammer, 135 feet from a clam shovel drop and 291 feet from impact pile driving. Temporary vibration impacts along the proposed corridor could result from construction activities. The potential for vibration impact would be greatest at locations near pile driving and vibratory compactor operations. Since the exact location of construction equipment is critical to projecting vibration levels, a more detailed assessment of potential vibration damage will be performed during final design including more accurate equipment locations. Please note that these criteria do not address potential damage to structures due to soil settlement or displacement caused by construction activities. Table 17. Vibration source levels for and distances to potential impact for construction equipment Distance to Potential Annoyance (72 VdB Criterion) (feet) Distance to Potential Damage (98 VdB Criterion) (feet) Ground-Borne Vibration Equipment Level (VdB) at 25 feet Clam Shovel (drop) Hoe Ram Impact Pile Driving Caisson Drilling Loaded Trucks Jackhammer

58

59 Environmental Assessment Noise and Vibration Technical Report 7 Mitigation of Noise and Vibration Impacts 7.1 Noise Mitigation for Transit Operations Noise mitigation is considered depending on the need, feasibility, reasonableness and effectiveness of potential options. The FTA states that in considering potential noise impact, severe impacts should be mitigated if at all practical and effective. At the moderate impact level, more discretion should be used, and other project-specific factors should be included in considering mitigation. These factors include the predicted increase over existing noise levels, the types and number of noise-sensitive land uses affected, existing outdoor-to-indoor sound reduction, and the effectiveness of mitigation options and the costeffectiveness of mitigating the noise. However, the FTA also states that there is a stronger need for mitigation if a project is proposed in an area currently experiencing high noise levels (Ldn above 65 dba) from surface transportation sources. This is clearly the case at sensitive receptors along the existing MBTA Fitchburg and Lowell Lines where existing Ldn levels range between 65 to 80 dba. In view of this guidance by the FTA, the Proposed Action would mitigate both moderate and severe noise impacts wherever practical and wherever existing noise levels are above 65 dba. For receptors with no significant outdoor land use where only interior spaces are sensitive to noise, mitigation would be provided if interior Ldn levels would be above 45 dba from project sources or single-event maximum noise levels would be above 65 dba. To mitigate noise impact from train operations, noise control can be considered at the source, along the sound path, or at the receiver. Source noise control options, for example, may include special hardware at turnout locations (i.e. spring-rail or moveable-point frogs in place of standard rigid frogs), relocating special trackwork away from sensitive areas and using continuous welded rail. Noise barrier construction is the most common sound path noise control treatment and can be very effective at reducing noise levels in the community. Noise control at the receiver can also be achieved by using sound insulation treatments at residences and institutional buildings. The mitigation recommendations in this section would be refined further during the final design process of the Proposed Action. Noise barriers have been used to mitigate potential noise impact for numerous transit lines across the United States and internationally. Noise barriers are generally effective means of reducing noise from most transit sources when they break the line-of-sight between the source and the receiver. The height necessary for providing sufficient noise reduction depends on the source height and the distance from the source to the barrier. Effective noise barriers can easily reduce noise levels 10 decibels or more depending on the specific implementation. During final design, illustrations of proposed barriers may be available to the community and the public will have an opportunity to provide input into the specific noise barrier design. For many locations along the Proposed Action, noise barriers are a feasible and effective means of noise mitigation. Noise barriers would be constructed with an absorptive surface to minimize the potential of sound reflecting off barriers to sensitive locations on the opposite side of the tracks. Typically, the noise barriers would be tall enough to block the line of sight to the top of the commuter trains from groundlevel receptors. Table 18 presents a summary of all the noise barriers including the receptor locations, length, side of tracks, barrier height, noise reduction at representative receptors and the barrier locations along the alignment. At the Glass Factory Condominiums, a double-noise barrier system (noise barriers with absorptive surfaces on both the near edge of the elevated guideway and between the inbound and outbound tracks) would be effective in reducing noise from Green Line trains even at upper floor receptors. The barrier between the inbound and outbound tracks would be needed for reducing noise from trains on the far track. Vibration isolation of the track by means of ballast mats (if ballast and tie track is installed on the 53

60 MBTA Green Line Extension Project elevated structure) or resilient rail fasteners (if direct fixation track is used) will minimize the contribution of noise radiated from the structure. While track vibration isolation is often intended to mitigate potential vibration impact, they would also be effective in this circumstance in reducing radiated noise from the structure. Since the Glass Factory Condominium building has relatively good existing noise reduction performance (NLR 27 to 35 dba), mitigation by means of noise barriers and vibration track isolation (ballast mats or resilient rail fasteners) would be expected to be more effective than sound insulation improvements and would also provide benefit to other exterior areas near the relocated Lechmere Station. The noise barriers and track vibration isolation would reduce train noise between ten and 18 decibels at the Glass Factory Condominiums and future noise levels would increase only one to five decibels compared to existing levels. With mitigation, future noise levels at receptors up to the sixth floor would be below the moderate noise impact criterion and receptors on the seventh and eighth floor would be below the severe noise impact criterion. On the northeast façade of the Brickbottom Artists Buildings, the Medford Branch would have two Green Line tracks on retained fill. Exterior land use with frequent human use was identified at the Brickbottom Artists Buildings (both northeast and south facades) and, therefore, noise mitigation should be provided to protect these land uses. A double-noise barrier system and track vibration isolation on the proposed Green Line tracks would be effective in reducing noise levels substantially at sensitive receptors on the northeast façade including upper floor receptors. This includes a barrier on the near edge of the guideway which would be effective for trains on the near track (inbound) and a barrier between the two tracks which would be effective for trains on the far track (outbound). Mitigation would reduce train noise up to nine decibels and future noise levels would increase up to two decibels compared to existing levels. Mitigation would keep future noise levels below the moderate noise criterion even at upper floor receptors. On the south façade of the Brickbottom Artists Buildings, tracks include the at-grade Green Line track outbound from Lechmere Station to Union Square, the maintenance yard lead track which would transition from at-grade to elevated on retained fill, the BET drill track which would be at-grade and underneath the elevated Green Line track inbound to Lechmere Station from Union Square and the inbound and outbound commuter train tracks which would be at-grade and shifted south of the new Green Line track. Three noise barriers along the Green Line tracks would be effective in reducing noise from both Green Line trains and commuter trains. One noise barrier would extend along the near Green Line track, one noise barrier would extend along the maintenance yard lead track and one noise barrier would extend along the far Green Line track. The noise barriers and retained fill structure would provide some acoustic shielding to the commuter trains. These noise barriers would be effective in reducing noise levels four to 10 decibels at sensitive receptors. Mitigation would reduce future noise levels at most receptors below existing noise levels. Future noise levels at all receptors, including those on upper floors, would be below the moderate impact criterion. The heights of the noise barriers along the Glass Factory Condominiums and Brickbottom Artists Buildings are dependent on the specific guideway designs and how close they can be constructed to the trains while not compromising safety requirements (i.e. emergency egress, train clearances, etc.) Assuming the tops of the barriers are effectively four feet from the near rail, barriers would be approximately ten feet in height. These noise barrier designs would also provide some visual privacy to the trains. To mitigate potential noise impact at residential properties on Alston Street south of Cross Street, a 300- foot noise barrier west of the alignment approximately seven feet tall would reduce future noise levels from train operations by nine decibels. This noise barrier would be located on top of an existing retaining wall on the right-of-way line. Future noise levels would be up to four decibels lower than existing levels. 54 January, 2011 HMMH Report No

61 Environmental Assessment Noise and Vibration Technical Report A noise barrier east of the alignment between Cross Street and McGrath Highway approximately seven feet tall and 500 feet long would be effective in mitigating potential noise impact at receptors on Avon Place and Auburn Avenue. This noise barrier would reduce noise levels from the Green Line and commuter trains up to nine decibels and future noise levels would be up to eight decibels lower than existing levels. This noise barrier would be located along the right-of-way line on top of an existing ten to 12-foot high retaining wall/embankment. A noise barrier between McGrath Highway and Walnut Street east of the alignment approximately 750 feet long and ten feet high would be effective in mitigating potential noise impact on Gilman Street. This noise barrier would reduce noise levels up to seven decibels and future noise levels would be six decibels lower than existing levels. This noise barrier would be constructed along the right-of-way line on top of an embankment that ranges from three to 12 feet high above the top of rail. A noise barrier between School Street and Sycamore Street east of the alignment approximately 850 feet long and nine feet high would be effective in mitigating potential noise impact on Richdale Avenue. This noise barrier would reduce noise levels up to eight decibels and future noise levels would be six decibels lower than existing levels. This noise barrier would be constructed along the right-of-way line on an embankment that ranges from six to 20 feet high above the top of rail. A 300-foot noise barrier west of the alignment north of Sycamore Street would be effective in mitigating potential noise impact along Willoughby Street and a 200-foot noise barrier east of the alignment would be effective in mitigating potential impact at 58 Sycamore Street. The Susan Russell House at 58 Sycamore Street is a historic property and mitigation would be provided in accordance with applicable criteria. These noise barriers would be constructed along the right-of-way line on top of exiting embankment/retaining walls that are approximately 20 feet above the top of rail. The barriers would be approximately seven feet in height and would reduce train noise up to ten decibels. Future noise levels would be six decibels lower than existing levels with the mitigation along Willoughby Street and nine decibels lower than existing levels at 58 Sycamore Street. A 250-foot noise barrier west of the alignment near Woodbine Street and Centre Street would be effective in mitigating potential noise impact. This noise barrier would be approximately eight feet tall on top of a future retaining wall. The noise barrier would reduce train noise up to eight decibels and future noise levels would be six decibels lower than existing levels. To mitigate potential noise impact at Vernon Street, a 1,050-foot noise barrier that ranges in height from ten to 18 feet would be effective. This noise barrier would be located east of the alignment along the right-of-way line. The terrain in this area is a slope that gradually increases in height to the backyards of the homes on Vernon Street. Although this terrain is a more difficult condition for noise barriers to be effective than other locations along the corridor, train noise would be reduced seven to eight decibels from the barriers and future noise levels would be five decibels lower than existing levels. To mitigate potential noise impact at locations on Lowell Street, Nashua Street, Henderson Street, Hinckley Street and Berwick Street, a 1,000-foot noise barrier approximately 12 feet tall would be effective. This noise barrier would be located east of the alignment along an embankment that is approximately ten to 12 feet above the top of rail. The noise barrier would reduce train noise up to 13 decibels and future noise levels would be up to ten decibels lower than existing levels. A 400-foot noise barrier west of the alignment would be effective in mitigating potential noise impact on Murdock Street. This noise barrier would be approximately 12 feet high located on top of an existing retaining wall/embankment that is four to six feet above the top of rail. The noise barrier would reduce train noise up to 11 decibels and future noise levels would be ten decibels lower than existing levels. 55

62 MBTA Green Line Extension Project To mitigate potential noise impact at Trum Playground, a 100-foot noise barrier east of the alignment south of Cedar Street would be effective. This noise barrier would be approximately eight feet tall located on top of an existing retaining wall that is approximately ten feet above the top of rail. The noise barrier would reduce train noise up to 12 decibels and future noise levels would be up to eight decibels lower than existing levels. A 400-foot noise barrier east of the alignment north of Cedar Street would be effective in mitigating potential impact at Wilson Avenue. This noise barrier would be approximately 12 feet tall built on top of an embankment that is eight feet above the top of rail. The barrier would reduce train noise levels up to 12 decibels and future noise levels would be eight to nine decibels lower than existing levels. To mitigate potential impact on Boston Avenue between Cedar Street and Broadway, an 800-foot noise barrier approximately 12 feet tall would be effective. This noise barrier would be on the west side of the alignment built on top an embankment which is typically ten feet above the top of rail. The barrier would reduce train noise up to 11 decibels and future noise levels would be ten decibels lower than existing levels. A 1,200-foot noise barrier east of the alignment north of Broadway would be effective in mitigating potential impact at receptors on Newbern Avenue, Morton Avenue, Granville Avenue, Winchester Place and Wareham Street. This noise barrier would be approximately 14 feet tall and would reduce train noise up to 13 decibels. This noise barrier would be located on the right-of-way line which is generally at the same elevation or slightly below the top of rail. Future noise levels would be five to seven decibels lower than existing levels. A 1,000-foot noise barrier east of the alignment between College Avenue and Brooking Street would mitigate potential noise impact at receptors on Burget Avenue and Brookings Street. This noise barrier would be approximately six feet tall located on the right-of-way line on top of an embankment which is typically 12 feet above the top of rail. The noise barrier would be effective in reducing train noise up to six decibels and future noise levels would be three to four decibels lower than existing levels. To mitigate potential noise impact at residences on Horace Street along the Union Square Branch, an eight-foot tall noise barrier approximately 250 feet long south of the alignment would be effective. This noise barrier would be located on the right-of-way line which is at the same height as the top of rail and typically six feet above the sensitive receptors. The noise barrier would reduce train noise up to ten decibels and future noise levels would be two decibels lower than existing levels. The Walnut Street Center (a non-profit support center for adults with developmental disabilities) had previously been identified as a potential candidate for sound insulation mitigation; however, exterior land use with frequent human use has been identified south of the building facing the alignment. The main classroom inside the building does not have any windows or door on the south façade facing the alignment, but has windows and doors facing the west façade which is setback further from the alignment. Therefore, a noise barrier would be more effective in reducing train noise at exterior and interior locations at the Walnut Street Center and receptors on Charlestown Street. A 600-foot noise barrier approximately ten feet tall north of the alignment would be effective in mitigating potential noise impact at the Walnut Street Center and residential receptors on Charlestown Street. The noise barrier would be located on the right-of-way which is generally at the same height as the top of rail and the sensitive receptors nearby. The noise barrier would reduce train noise up to ten decibels and future noise levels would be up to two decibels lower than existing levels. 56 January, 2011 HMMH Report No

63 Environmental Assessment Noise and Vibration Technical Report Table 18. Summary of proposed noise barrier mitigation Barrier Number Receptor Locations Length (feet) Side of Tracks N-1 N-2 N-3 Glass Factory Condominiums Brickbottom (Northeast Façade) Brickbottom (South Façade) Barrier Height (feet) Noise Reduction (dba) Barrier Location 900 a West a to 18 c track and between Two barriers; near tracks 1000 a West a 10 8 to 9 c track and between Two barriers; near tracks 1750 b East b 10 4 to 10 c track, yard track, far Three barriers; near track Existing retaining wall on right-of-way N-4 Alston Street 300 West 7 9 N-5 N-6 N-7 Between Cross Street and McGrath Highway (Avon Place) Between McGrath Highway and Walnut Street (Gilman Street) Between School Street and Sycamore Street (Richdale Avenue) 500 East East East 9 8 Existing retaining wall on right-of-way Embankment on right-of-way Embankment on right-of-way N-8 Willoughby Street 300 West 7 9 Embankment on right-of-way N-9 Sycamore Street near Embankment 200 East 7 10 Richdale Avenue on right-of-way N-10 Woodbine Street near Future retaining wall 250 West 8 8 Centre Street on right-of-way N-11 Vernon Street 1050 East 10 to 18 7 to 8 Right-of-way N-12 Nashua Street/Henderson Street/Hinckley Street 1000 East 12 9 to 13 N-13 Murdock Street 400 West N-14 Trum Playground 100 East 8 12 N-15 N-16 N-17 Cedar Street and Wilson Avenue Between Cedar Street and Broadway (Boston Avenue) Newbern Ave/Morton Ave/Granville Ave 400 East to West 12 7 to 11 Embankment on right-of-way Embankment/retaining wall on right-of-way Existing retaining wall on right-of-way Embankment on right-of-way Embankment on right-of-way 1200 East 14 7 to 13 Right-of-way N-18 Burget Avenue 1000 East 6 6 Embankment on right-of-way N-19 Horace Street 250 South 8 7 to 10 Right-of-way N-20 Walnut Street Center 600 North Right-of-way Total Length (feet) 13,600 Total Area (ft 2 ) 141,650 Total Cost $4.2 million a Noise barrier length includes two segments; one noise barrier for near track and one noise barrier for far track. b Noise barrier length includes three segments; one noise barrier for near Green Line track (700 feet), one noise barrier for the maintenance yard lead track (350 feet) and one noise barrier for far Green Line track (700 feet). c Noise reduction includes track vibration isolation for reduction of radiated noise from structure. At the Pearl Street Apartments, Visiting Nurses Association, Tufts Science and Technology Center and Outside the Lines Studio, noise barriers would not be feasible or effective in mitigating potential impact. Sound insulation improvements for these buildings to improve the outdoor-to-indoor noise reduction have been considered. While this mitigation approach has no effect on noise in exterior areas, it is the best 57

64 MBTA Green Line Extension Project choice for these sites where noise barriers are not feasible or effective. Substantial improvements in building sound insulation (on the order of 5 to 10 dba) can often be achieved by adding an extra layer of glazing to windows, by sealing any holes in exterior surfaces that act as sound leaks. In order for sound insulation improvements to be effective, windows and doors must remain closed; therefore, these building improvements would require adequate heating, cooling and ventilation be provided if it does not already exist to allow windows and doors to remain closed. If the existing noise reduction of these buildings would already be sufficient to keep future interior noise levels from project sources below 45 Ldn and 65 Lmax (single event train pass-bys), then sound insulation improvements would not be necessary. The OILR of representative rooms in these buildings was measured to project future interior noise levels and assess the need for sound insulation mitigation. Interior future noise levels were calculated by subtracting the minimum NLR from the exterior noise levels including a three decibel factor of safety. The results of this assessment, presented in Table 19, show that future interior noise levels at these receptors would be above 45 Ldn and 65 Lmax and therefore sound insulation mitigation would be necessary at these locations. At some locations where noise barriers would be effective there is no exterior land use with frequent human use and, therefore, the only noise-sensitive locations are interior spaces. These locations include the Glass Factory Condominiums and Hampton Inn Hotel. The need for mitigation at these locations is also determined by whether future interior noise levels from project sources would be above 45 Ldn or 65 Lmax from single train pass-bys. The results of this assessment are presented in Table 19. Future interior noise levels prior to mitigation would be above 45 Ldn in the Glass Factory Condominiums and therefore noise barrier mitigation is required. At the Hampton Inn Hotel, future interior noise levels would be below 45 Ldn and 65 Lmax and mitigation is therefore not required. Table 19. Future exterior and interior noise levels at sound insulation candidate receptors Noise Sensitive Receptor Glass Factory Condominiums Exterior Future Noise Levels from Project Sources Day-Night Single-Event Sound Maximum Level Level (Ldn) (Lmax) Noise Level Reduction (db) Interior Future Noise Levels from Project Sources Prior to Mitigation Day-Night Sound Level (Ldn) Single-Event Maximum Level (Lmax) Mitigation Required for Future Interior Noise Levels above 45 dba Ldn or above 65 dba Lmax (Green Line) 27.2 (Green Line) (Green Line) Yes Hampton Inn Hotel (Green Line) 27.6 (Green Line) (Green Line) No Pearl Street Apartments Visiting Nurses Association Tufts Science and 84 Technology Center a (80 Leq) a Outside the Lines Studio a 84 (80 Leq) 87 (Green Line) 95 (Commuter) 91 (Green Line) 86 (Commuter) 89 (Green Line) 95 (Commuter) 89 (Green Line) 95 (Commuter) 24.4 (Green Line) 23.7 (Commuter) 21.6 (Green Line) 21.2 (Commuter) 27.5 (Green Line) 27.2 (Commuter) 28.6 (Green Line 28.3 (Commuter) (56 Leq) 59 (55 Leq) 66 (Green Line) 74 (Commuter) 73 (Green Line) 68 (Commuter) 64 (Green Line) 71 (Commuter) 63 (Green Line) 70 (Commuter) Need for mitigation of interior spaces at institutional land use is assessed based on Ldn. Yes Yes Yes Yes At the Pearl Street Apartments, noise barriers would not be an effective mitigation measure due to its close proximity to the alignment and upper floor receptors. The existing NLR of the building was 24 dba for both commuter and Green Line trains and future interior noise levels would be 52 Ldn and 74 Lmax (for commuter trains). Sound insulation improvements to 36 units within the building closest to the alignment would be effective in improving the OILR and keeping future interior noise levels below 45 Ldn and 65 Lmax. These units include 207, 208, 209, 210, 211, 212, 307, 308, 309, 310, 311, 312, 407, 408, 409, 410, 411, 412, 507, 508, 509, 510, 511, 512, 607, 608, 609, 610, 611 and 612. Units in this 58 January, 2011 HMMH Report No

65 Environmental Assessment Noise and Vibration Technical Report building have in-wall air-conditioning units installed below the living room window in each apartment, with exposed venting on the exterior façade. Sound insulation improvements to this building would include replacing or retrofitting the existing windows and adding a removable panel for the airconditioners that can be mounted over the units when they are not in use. These panels would increase the noise reduction of the building when the air-conditioning is not in use and also provide greater thermal insulation. At the Visiting Nurses Association building, noise barriers would not be an effective mitigation measure due to its close proximity to the alignment, relative elevation to the alignment and upper floor receptors. The existing NLR of the building was 21 dba for commuter trains and 22 dba for Green Line trains and future interior noise levels would be 54 Ldn and 73 Lmax (for Green Line trains) prior to mitigation. Sound insulation improvements to 45 units on the northeast façade of the building would be effective in improving the OILR up to ten decibels and keeping future noise levels below 45 Ldn and 65 Lmax. Units in this building have in-wall air-conditioning with exposed venting on the exterior façade. Sound insulation improvement to this building would include replacing or retrofitting the existing windows and potential modifications to the air-conditioning ventilation to reduce noise transmission through this path. The Tufts University Science and Technology Center is located close to the existing right-of-way line and a potential noise barrier would not be feasible or effective for reducing interior noise levels. The existing NLR of the building was 27 dba for commuter trains and 28 dba for Green Line trains and future interior noise levels would be 60 Ldn (56 Leq) and 71 Lmax (from commuter trains). Sound insulation improvements by means of installing a third sash in classrooms and laboratories (not administrative spaces or offices) would reduce interior noise levels. This includes three labs and three classrooms on 1st floor and five labs on 2nd floor; (rooms) 165B, 163, 156, 137, 135, 134, 290, 289, 287, 285 and 283. Since the building already has central HVAC, no modifications to the system are required. The mitigation goal for this building is to improve outdoor-to-indoor noise reduction by 10 decibels or more. Detailed architectural designs will be completed during final design. Future interior noise levels with sound insulation improvements would be expected to be below 65 dba Lmax. The Outside the Lines Studio is located close to the existing right-of-way line and a potential noise barrier would not be feasible or effective for reducing interior noise levels. The existing NLR of the building was 28 dba for commuter trains and 29 dba for Green Line trains and future interior noise levels would be 59 Ldn (55 Leq) and 70 Lmax(from commuter trains). Sound insulation improvements by means of retrofitting or replacing six small windows in the main classroom will reduce interior noise levels. Since the building already has central HVAC, no modifications to the system are required. Future interior noise levels with mitigation would be expected to be below 65 dba Lmax. In total, noise mitigation by means of 20 noise barriers totaling approximately 13,600 feet in length and sound insulation improvements to the Pearl Street Apartment building, Visiting Nurses Association building, Outside the Lines Studio building and the Tufts University Science and Technology Center would be feasible, reasonable, and effective in mitigating all potential noise impact due to the Proposed Action. The noise barriers would be effective in reducing noise levels from transit sources typically seven to 11 decibels and would result in substantial reduction in future noise levels in comparison to existing noise levels at many locations. At locations along the existing Fitchburg and Lowell commuter lines, noise barriers will reduce future noise levels 6 to 7 db below existing levels on average. The total estimated cost for noise mitigation would be $7.0 million including $4.2 million for noise barriers based on $30 per square foot (not including design or inspection costs) and $2.8 million for sound insulation improvements based on $25,000 per residential unit in multi-family buildings (36 units in Pearl Street Apartments and 45 units in Visiting Nurses Association), $750,000 for the Tufts Science and Technology Center building and $50,000 for the Outside the Lines Studio. 59

66 MBTA Green Line Extension Project Table 20 shows the summary of noise sensitive receptors that would be exposed to moderate and severe airborne noise impact and ground-borne noise impact with and without noise mitigation. Prior to mitigation, 170 noise-sensitive receptors would be exposed to impact due to the relocation of the existing commuter lines and the introduction of the Green Line trains. These include 121 moderate impacts and 43 severe impacts at single-family and multi-family residential buildings, moderate impact at Tufts University Science and Technology Center and Outside the Line Artist s Studio (a teaching facility), moderate impact at Trum Playground, severe noise impact at the Walnut Street Center (a non-profit support center for adults with developmental disabilities) near Union Square and ground-borne noise impact at Tufts Bacon Hall and Tufts Curtis Hall. With mitigation, there would be no residual impacts due to the Proposed Action. Table 20. Summary of potential airborne and ground-borne noise impact prior to and with mitigation Residential Buildings Impacted Institutional Buildings and Parks Impacted Prior to Mitigation With Mitigation Prior to Mitigation With Mitigation Ground- Borne Ground- Borne Moderate Severe Moderate Severe Moderate Severe Noise Moderate Severe Noise c 3 a 1 2 b a Institutional airborne noise impacts include the Tufts University Science and Technology Center, Outside the Line Studio and Trum Playground. b Ground-borne noise impact includes Tufts Bacon Hall (no windows facing tracks) and Tufts Curtis Hall (WMFO radio station). c Mitigation at the Brickbottom Artists Buildings would be effective in keeping future noise levels below the severe impact criterion at all receptors including upper floor receptors and keeping future noise levels below existing levels at most receptors along the south façade. Mitigation at Glass Factory Condominiums would reduce train noise between ten and 18 decibels and future noise levels would increase one to five decibels compared to existing levels. With mitigation, future noise levels at receptors up to the sixth floor would be below the moderate noise impact criterion and receptors on the seventh and eighth floor would be below the severe noise impact criterion. 7.2 Construction Noise Mitigation Construction noise mitigation includes the preparation of a Noise Control Plan in conjunction with the contractor s specific equipment, schedule and methods of construction, maximum noise limits for each piece of equipment, prohibition on certain types of equipment during the nighttime hours and engineering noise control measures. An Acoustical Engineer will prepare a Noise Control Plan in conjunction with the contractor s specific equipment and methods of construction. This Plan will be consistent with that specified in the CA/T Noise Specification. Key elements to the Plan include: Identification of specific sensitive sites where noise monitoring will occur Background noise monitoring prior to and during construction Construction equipment noise certification testing Prohibition of impact pile-drivers during evening and nighttime hours (i.e. 6:00 PM to 10:00 PM and 10:00 PM to 7:00 AM) Prohibition of vibratory sheet pile driving and all impact devices including hoe rams, jackhammers and pavement breakers during nighttime hours Requirement for ambient-adjusting or manually adjusted backup alarms set to 5 dba over background levels Truck idling limited to five minutes Acoustic shield requirement for jackhammers, chainsaws and pavement breakers Methods for projecting construction noise levels Detailed engineering noise control measures 60 January, 2011 HMMH Report No

67 Environmental Assessment Noise and Vibration Technical Report Methods for responding to community complaints Reporting of noise monitoring results, noise reduction measures used and responses to the community Noise control measures will be used to reduce noise emissions and potential impact to sensitive receptors where feasible. Many types of construction equipment include diesel engines which can be the most significant noise source. Therefore, reducing engine noise is often a key element to mitigating potential impact. Examples of such noise control measures include: Shields, shrouds or intake and exhaust mufflers Noise deadening materials adhered to chutes or storage bins Temporary noise barriers Acoustic enclosures Specialized back-up alarms Limiting the size of generators and the duration of their use Truck routes that minimize exposure to sensitive receptors 7.3 Vibration Mitigation for Transit Operations The purpose of vibration mitigation is to minimize adverse effects from a project at sensitive locations. While the consideration of noise mitigation is well-defined, there is more variability in the approach to vibration mitigation and the specific measures that may be considered. The goal for mitigating potential vibration impact from the Proposed Action is to reduce future vibration below the impact criteria which is 72 VdB for Green Line trains and 75 VdB for commuter trains for potential human annoyance in residential buildings. For vibration-sensitive equipment, the goal for mitigating potential impact is to reduce future vibration below 65 VdB for either Green Line or commuter trains. At some locations close to the existing commuter trains where the commuter line would be shifted closer to the receptors, future vibration levels cannot be reduced below the impact criteria with reasonable mitigation measures. At these locations, mitigation measures that would reduce vibration levels five decibels or more will be considered reasonable and effective with the intention of keeping future vibration levels at or below existing vibration levels. The effectiveness of specific vibration mitigation measures is dependent on several factors such as the component design, installation techniques, axle loads of the trains and frequencies of concern. The following are common vibration mitigation options: Resilient rail fasteners are specially-designed fasteners between the rails and the ties. Resilient rail fasteners typically reduce vibration by five to 10 VdB at frequencies above 30 to 40 Hz. Ballast mats are rubber or other elastomer pads placed in the trackform between the ballast and the sub-grade or ground. These are typically effective in reducing vibration levels 10 to 15 VdB at frequencies above 25 Hz. Resiliently supported ties have a rubber or other resilient material placed between the ties and the ballast. These ties are typically effective in reducing vibration 10 VdB at frequencies above 15 Hz. Floating slab trackforms consist of a concrete slab supported on resilient elements such as rubber or elastomer pads. Floating slabs can be very effective at controlling vibrations down to frequencies near 10 Hz. Drawbacks towards floating slab trackforms include difficulties in designing for heavy axle loads, difficulties in designing for outdoor exposure to the elements and the relatively high cost. 61

68 MBTA Green Line Extension Project Similar to noise, special trackwork such as turnouts and crossovers increase vibration levels of the trains. Mitigation includes using special hardware (i.e. flange-bearing or moveable-point frogs in place of standard rigid frogs), relocating special trackwork away from sensitive areas and using continuous welded rail rather than jointed rail. Maintenance programs can also be essential for controlling vibration. Maintaining a proper wheel/rail profile, minimizing the number and extent of wheel flats and minimizing potential rail corrugation are important factors. Rail grinding, truing wheels and monitoring wheel/rail profiles can be effective means of reducing potential vibration impact. The Proposed Action introduces a boat section for all of the commuter train and Green Line train tracks. A boat section is a concrete slab approximately two to three feet thick that may damp vibrations from the trains due to the increased mass of the trackform. The boat section would be used throughout the extended Green Line corridor. Generally, well-designed and properly-installed ballast mats or resilient rail fasteners would be effective in reducing vibration levels up to 15 VdB for the Green Line trains and up to 10 VdB for commuter trains, keeping future vibration levels generated from commuter trains at or below existing levels and reducing vibration levels generated from Green Line trains below the impact criterion. Vibration mitigation generally performs better for light rail vehicles because they do not weigh as much as commuter trains. Although these mitigation measures would provide a substantial reduction in vibration levels and future levels would be the same or lower than existing levels, future vibration levels would be above the impact criteria at some locations. These locations are considered to be residual vibration impacts from the Proposed Action. Table 21 summarizes the locations, length and rail line of proposed vibration mitigation for the Proposed Action. Track vibration isolation would be ballast mats, resiliently-supported ties or resilient fasteners. A total of 23,250 track-feet of track vibration isolation is proposed to mitigate potential impacts. An estimated cost for installed ballast mats or resiliently-supported ties is $4.2 million based on a cost of $180 per track-foot and an estimated cost for resilient fasteners is $7.0 million based on a cost of $300 per track-foot. Vibration mitigation locations are shown in Appendix E. Although vibration impact would not occur at the Glass Factory Condominiums or the northeast façade of the Brickbottom Artists Buildings prior to mitigation, track vibration isolation would be included to reduce the potential for noise radiating from the guideway support structures. Potential vibration impact is projected on the south façade of the Brickbottom Artists Buildings due to the close proximity to the near Green Line track. Track vibration isolation would be included on both tracks along the northeast façade (500 feet). On the south facade, track vibration isolation would be included on the near Green Line track (outbound to Union Square, 600 feet), on the Green Line track (inbound to Lechmere Station, 500 feet) where on retained fill and on the Green Line maintenance yard lead track (350 feet) where on retained fill. For receptors on Alston Street, 300 feet of track vibration isolation on both the commuter and Green Line tracks and the relocation or use of specially-engineered trackwork for a double crossover on the proposed Green Line tracks would be effective in keeping future vibration levels at or below existing levels for commuter trains and slightly above the vibration criterion for Green Line trains. Receptors at four buildings on Alston Street are considered to be residual impacts of the Proposed Action. Track vibration isolation (950 feet) south of Cross Street to McGrath Highway would be effective in reducing future vibration levels from the commuter trains at receptors on Tufts Street, Avon Place and Auburn Avenue. There is the potential that future levels may still be above the impact criterion (75 VdB) with mitigation and these four buildings are considered to be residual impacts of the Proposed Action. 62 January, 2011 HMMH Report No

69 Environmental Assessment Noise and Vibration Technical Report Track vibration isolation on the commuter line (800 feet) between McGrath Highway and Walnut Street would be effective in reducing future vibration levels from the commuter trains at receptors on Gilman Street. At some receptors vibration levels would be below the impact criterion; however, there is the potential that future levels may still be above the impact criterion (75 VdB) with mitigation at some locations near Walnut Street. These nine buildings are considered to be residual impacts of the Proposed Action. Future vibration levels from Green Line trains are projected to be 74 VdB at receptors on Medford Street west of Walnut Street potentially causing impact prior to mitigation. Approximately 400 feet of vibration mitigation on the Green Line tracks north of Walnut Street would mitigate potential impact. At the Pearl Street Apartments, 200 feet of track vibration isolation on the commuter line would reduce future vibration levels and mitigate potential impact. Future vibration levels from commuter trains at receptors on Richdale Avenue are projected to be 78 VdB prior to mitigation. Approximately 900 feet of track vibration isolation on the commuter lines would reduce future levels below the impact criterion and mitigate potential impact. Vibration impact is projected at receptors on Jerome Court and Willoughby Street due to their close proximity to the proposed Green Line trains and a double crossover. Approximately 600 feet of track vibration isolation and the relocation or use of specially-engineered trackwork would reduce future vibration levels below the impact criterion and mitigate potential impact. Approximately 1,200 feet of track vibration isolation on the commuter line and the relocation or use of specially-engineered trackwork would reduce future vibration levels at sensitive receptors on Lowell Street, Nashua Street, Hinckley Street and Berwick Street. Although future vibration levels are projected to be below existing levels, they may still be above the impact criterion at nine buildings. These locations are considered to be residual impacts of the Proposed Action. Approximately 400 feet of vibration mitigation on the Green Line tracks and relocation or use of specially-engineered trackwork for a crossover on the Green Line would be effective in mitigating potential impact at receptors on Murdock Street. Future vibration levels at these receptors would be below the impact criterion. There is the potential for vibration impact at one building on Cedar Street due to its close proximity to the commuter trains. Approximately 150 feet of track vibration isolation on the commuter line would be effective in reducing vibration levels from the trains; however, future levels would not be below the impact criterion. This building is considered to be a residual impact of the Proposed Action. Approximately 1,100 feet of vibration mitigation on the commuter line between Broadway and Wareham Street would be effective in reducing vibration levels from trains. At many locations in this area, future vibration levels would be reduced below the impact criterion. Future levels may still be above the impact criterion at five buildings with mitigation and these are considered to be residual impacts of the Proposed Action. Vibration levels at the Tufts Science and Technology Center would be 78 VdB from commuter trains prior to mitigation which could potentially impact humans (annoyance) and vibration-sensitive equipment. Approximately 700 feet of track vibration isolation on the commuter line would reduce future vibration levels slightly below existing levels. Future vibration levels with mitigation would be 68 VdB which is below the criterion for human annoyance (75 VdB) but above the criterion for vibration-sensitive equipment (65 VdB). Therefore, while future vibration levels would be reduced, this building is considered to be a residual vibration impact of the Proposed Action. 63

70 MBTA Green Line Extension Project The potential for impact to vibration-sensitive equipment at the future proposed Tufts Integrated Research Laboratory at 550 to 574 Boston Avenue depends on the construction of the building, the setback from the alignment and the location of equipment within the building. Impact has not been identified at this future building and no track vibration isolation mitigation is proposed. An effective method of mitigating potential impact to future equipment would be to take consideration of the vibration levels in locating equipment within the building and to provide equipment-based vibration isolation pads. There is the potential for vibration impact to humans and vibration-sensitive equipment and ground-borne noise impact at Tufts University Bacon Hall. Future vibration levels from the commuter trains would be below the impact criterion for human annoyance but above the criterion for sensitive equipment prior to mitigation. Future vibration levels from the Green Line trains would be above both criteria prior to mitigation due to the proximity of the Green Line tracks and a double crossover. Approximately 200 feet of vibration mitigation on both the commuter line and the Green Line tracks and the relocation or use of specially-engineered trackwork for the double crossover would reduce future vibration levels below the vibration impact criteria and ground-borne noise impact criteria. Approximately 250 feet of track vibration isolation on the commuter line at the Outside the Lines Studio would be effective in mitigating potential impact. Future vibration levels would be below the impact criterion. There is the potential for vibration impact to sensitive equipment at Bray Labs in Tufts University from the proposed Green Line. Approximately 350 feet of track vibration isolation on the Green Line tracks would be effective in mitigating potential impact. Tufts University Curtis Hall houses the WMFO radio station (recording studio) which may be exposed to ground-borne noise impact due to vibration generated from both the commuter line and Green Line trains. Although this building would not be exposed to vibration impact, approximately 250 feet of track vibration isolation on both the commuter line and Green Line tracks would reduce the potential for ground-borne noise impact. Future ground-borne noise levels would be below the impact criteria. Approximately 250 feet of track vibration isolation on the commuter line would be effective in mitigating potential impact at Brookings Street. There is the potential for vibration impact at receptors on Horace Street south of the proposed Union Square Branch due to their close proximity to the shifted commuter line and the Green Line tracks which includes a double-crossover. Mitigation by means of approximately 250 feet of track vibration isolation on both the commuter line and Green Line tracks and relocation or use of specially-engineered trackwork for the Green Line crossover would reduce future vibration levels. Although future vibration levels would be similar to existing levels from commuter trains, levels would still be above the impact criterion and two of these buildings are considered to be residual impacts of the Proposed Action. 64 January, 2011 HMMH Report No

71 Environmental Assessment Noise and Vibration Technical Report Table 21. Summary of proposed vibration mitigation Vibration Mitigation Location Location Length (feet) Rail Line V-1 Glass Factory Condominiums a 450 Green Line V-2 V-3 V-4 V-5 V-6 V-7 Brickbottom Artists Building a (northeast façade) Brickbottom Artists Building a (south façade) Alston Street (south of Cross Street) Tufts Street/Avon Place/Auburn Ave (south of Cross Street to McGrath Highway) Gilman Street (McGrath Highway to Walnut Street) Medford Street (north of Walnut Street) 500 Green Line 600 b Green Line 300 Green Line 950 Commuter 800 Commuter 400 Green Line V-8 Pearl Street Apartments 200 Commuter V-9 V-10 V-11 V-12 V-13 V-14 Richdale Avenue (School Street to Sycamore Street) Jerome Court (near Sycamore Street) Lowell Street/Nashua Street/Hinckley Street/Berwick Street (south of Lowell Street to Charles E Ryan Road) Murdock Street (south of Cedar Street) Cedar Street (north of Cedar Street) Newbern Avenue/Morton Avenue/Granville Avenue/Winchester Place/Wareham Street (Broadway to Warren Street) 900 Commuter 600 Green Line 1,200 Commuter 400 Green Line 150 Commuter 1,100 Commuter V-15 Tufts Science and Technology Center 700 Commuter V-16 Tufts Bacon Hall c Green Line Commuter V-17 Outside the Lines Artist Studio (teaching facility) 250 Commuter V-18 Tufts Bray Labs 350 Green Line V-19 Tufts Curtis Hall c Green Line Commuter V-20 Brooking Street 250 Commuter V-21 Horace Street Total Length of Track Vibration Isolation (feet) Total Cost of Mitigation (if Ballast Mats or Resiliently-Supported Ties) Total Cost of Mitigation (if Resilient Fasteners) Green Line Commuter 11,500 (23,250 track-feet) $4.2 million $7.0 million a Mitigation included to reduce airborne noise. b Mitigation required on near Green Line track (outbound to Union Square, 600 feet), Green Line track (inbound to Lechmere Station, 500 feet) where on retained fill and the Green Line maintenance yard lead track (350 feet) where on retained fill. c Mitigation is required for ground-borne noise. Vibration measurements of existing commuter trains indicate that maximum vibration occurs in the 50-Hz one-third octave band at Morton Avenue, Aldrich Street and Tufts Science and Technology Center. At the Cedar Street measurement site, maximum vibration was generated in the 80-Hz one-third octave band. At Horace Street, Nashua Street, Pearl Street Apartments and Richdale Avenue, maximum vibration from 65

72 MBTA Green Line Extension Project commuter trains was generated in the 25 and 31.5-Hz one-third octave bands. These measurements indicate that vibration mitigation should be effective down to the 50-Hz band at many locations and down to the 25 Hz-band at a few locations. A vibration reduction goal for mitigation measures, such as ballast mats, resiliently-supported ties or resilient fasteners, will be specified in the bid documents. The designbuild contractor will incorporate suitable mitigation measures into the Proposed Action to achieve the mitigation goal. Special trackwork (turnouts and crossovers) cause local increase in vibration levels of up to 10 VdB. In addition to the locations of proposed vibration mitigation shown above, relocating special trackwork (turnouts and crossovers) away from sensitive receptors or using specially-engineered trackwork (flangebearing or moveable-point frogs) would minimize potential vibration impact at some locations. Table 22 provides a summary of existing crossovers and turnout locations that are recommended for speciallyengineered trackwork or relocation. Table 22. Potential vibration mitigation measures for crossovers and turnouts Special Trackwork Location (Civil Station No.) Location Type of Special Trackwork Rail Line A Alston Street Number 8 Double Crossover Green Line B Aldrich Street Turnout Commuter C Pembroke Court Number 8 Double Crossover Green Line D Henderson Street Turnout Commuter E Hinckley Street Crossover Commuter F Charles E Ryan Road Crossover Commuter G Murdock Street Crossover Commuter H Murdock Street Crossover Commuter I Tufts Bacon Hall Number 8 Double Crossover Green Line J Brickbottom Artists Buildings (South Facade) Turnout Green Line K Horace Street Turnout Green Line Table 23 shows the summary of vibration-sensitive receptors that would be exposed to impact with and without vibration mitigation. Prior to mitigation, vibration impact is projected at 92 single-family and multi-family residential buildings and at four institutional buildings (Tufts Science and Technology Center, Tufts Bacon Hall, Tufts Bray Labs and Outside the Line Artist s Studio). With mitigation, there would be 34 residual impacts to residential properties and one residual impact to the Tufts Science and Technology Center for the potential impact to vibration-sensitive equipment. Although future vibration levels are expected to be at or below existing levels at these locations with mitigation, they are considered residual impacts since future levels would still be above the vibration criteria with mitigation. Table 23. Summary of potential vibration impact prior to and with mitigation Residential Buildings Impacted Institutional Buildings Impacted Prior to Mitigation With Mitigation Prior to Mitigation With Mitigation a 1 b a Institutional buildings include the Tufts Science and Technology Center, Tufts Bacon Hall, Tufts Bray Labs and Outside the Lines Studio. b Residual impact would occur at Tufts Science and Technology Center for potential impact to vibrationsensitive equipment. 66 January, 2011 HMMH Report No

73 Environmental Assessment Noise and Vibration Technical Report 7.4 Construction Vibration Mitigation To mitigate potential vibration impact from construction activities, the following measures will be applied where feasible: Using alternative construction methods to minimize the use of impact and vibratory equipment (e.g. pile drivers and compactors) Truck routes that minimize exposure to sensitive receptors and maintaining smooth roadway surfaces Avoiding nighttime construction in residential neighborhoods 67

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75 Appendix A Measurement Site Photographs Figure 25. Long-term noise Site 1-39 Horace St. Somerville, MA Figure 26. Long-term noise Site 2 5 Alston St. Somerville, MA A-1

76 Figure 27. Long-term noise Site Medford St. Somerville, MA Figure 28. Long-term noise Site 4 34 Richdale Ave. Somerville, MA A-2 January, 2011 HMMH Report No

77 Figure 29. Long-term noise Site 5-86 Vernon St. Somerville, MA Figure 30. Long-term noise Site 6-95 Boston Ave. Somerville, MA A-3

78 Figure 31. Long-term noise Site 7-7/9 Winchester Pl. Somerville, MA Figure 32. Long-term noise Site Burget Ave. Medford, MA A-4 January, 2011 HMMH Report No

79 Figure 33. Long-term noise Site 9-76 Orchard St. Medford, MA Figure 34. Long-term noise Site 11 - Brickbottom Artists Buildings Northeast Façade Somerville, MA A-5

80 Figure 35. Long-term noise Site 12 - Brickbottom Artists Buildings South Façade Somerville, MA Figure 36. Short-term noise Site 1 - Water Street (Hampton Inn Hotel) Cambridge, MA A-6 January, 2011 HMMH Report No

81 Figure 37. Short-term noise Site 2 - Brickbottom Artists Buildings South Façade Somerville, MA Figure 38. Short-term noise Site Somerville Ave. Somerville, MA A-7

82 Figure 39. Short-term noise Site 4-2 Charlestown St. Somerville, MA Figure 40. Short-term noise Site 5-45 Aldrich St. Somerville, MA A-8 January, 2011 HMMH Report No

83 Figure 41. Short-term noise Site 6-81 Hinckley St. Somerville, MA Figure 42. Short-term noise Site 7 - Colby St. (Tufts University) Medford, MA A-9

84 Figure 43. Short-term noise Site 8 - End of Water St. Cambridge, MA Figure 44. Short-term noise Site 9 - Archstone Phase II Cambridge, MA A-10 January, 2011 HMMH Report No

85 Figure 45. Force density measurement site for Green Line trains (near Beaconsfeld Stop on D Branch) Figure 46. Vibration propagation measurement Site V-1 at 200 Innerbelt Road, Somerville MA A-11

86 Figure 47. Vibration propagation measurement Site V-2 at 20 Vernon St. Somerville, MA Figure 48. Vibration propagation measurement Site V-3a at Tufts University Alumni Field Somerville, MA A-12 January, 2011 HMMH Report No

87 Figure 49. Vibration measurement Site V-3b at Tufts University (commuter trains) Figure 50. Vibration measurement Site V-4 at Archstone Phase II Development parcel A-13

88 Figure 51. Vibration measurement Site V-5 at Horace Street Figure 52. Vibration measurement Site V-6 at Aldrich Street A-14 January, 2011 HMMH Report No

89 Figure 53. Vibration measurement Site V-7 at Pearl Street Apartments Figure 54. Vibration measurement Site V-8 at Richdale Avenue A-15

90 Figure 55. Vibration measurement Site V-9 at Nashua Street Figure 56. Vibration measurement Site V-10 at Cedar Street A-16 January, 2011 HMMH Report No

91 Figure 57. Vibration measurement Site V-11 at Morton Avenue Figure 58. Vibration measurement Site V-12 at Tufts Science and Technology Center A-17

92 Figure 59. Sound insulation measurement site at Glass Factory Condominiums Figure 60. Sound insulation measurement site at Hampton Inn Hotel A-18 January, 2011 HMMH Report No

93 Figure 61. Sound insulation measurement site at Brickbottom Artists Buildings (Cannery East) Figure 62. Sound insulation measurement site at Brickbottom Artists Buildings (Cannery East and West) A-19

94 Figure 63. Sound insulation measurement site at Pearl Street Apartments Figure 64. Sound insulation measurement site at Visiting Nurses Association A-20 January, 2011 HMMH Report No

95 Figure 65. Sound insulation measurement site at Tufts Science and Technology Center Figure 66. Sound insulation measurement site at Outside the Lines Studio A-21