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SVM Project List SEPTA | |
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5.9 NOISE AND VIBRATION5.9.1 REGULATORY SETTING AND METHODOLOGYThere are no federal or state noise and vibration standards for rail transit operations. The FTA has guidelines which recommend noise and vibration levels for human comfort, annoyance avoidance, and structural damage avoidance. The noise and vibration impact predictions in this analysis were derived using the FTA guidance manual, Transit Noise and Vibration Impact Assessment, dated April 1995. Please note that horns, bells, whistles, and other warning devices produce a form of noise intended to be heard for safety reasons. Because sound level limits on these sources would interfere with their function, FTA has not set standards or criteria on these devices.Exhibit 5.9-1 FTA Noise Impact Criteria [PDF], excerpted from FTA's report, illustrates the specific noise levels above which a rail project is considered to have impact. The SVM impact analysis compares estimates of existing noise and vibration levels and predictions of future levels to identify potential impacts for each mode/power source used in the six build alternatives. The presence of active freight and commuter rail operations along the majority of the alignment is a key element of the existing noise and vibration environments. To characterize the existing environments, a limited amount of noise and vibration monitoring was performed to help calibrate the estimates of existing noise and vibration levels. 5.9.2 NOISEPerceptible transit noise associated with the project could include: 1) Commuter rail and light rail operations; 2) Bus operations associated with intermodal facilities, and 3) Automobiles at park-and-ride facilities. Table 5.9-1 identifies some of the most common sources of noise generated from transit operations.The basic noise unit of measurement for transit noise is the A-weighted sound level (dBA). It describes the noise level experienced by a receptor at any moment in time. Typical community A-weighted environmental noise levels range from 45 dBA to 85dBA, where 45 is quiet and 85 is very loud. Exhibit 5.9-2 Typical Noise Levels [PDF] illustrates some typical levels by land use and human activity. Noise levels concerning activity patterns for urban, suburban, and residential environments are shown in Exhibit 5.9-3 Correlation Between Statistical Noise Level and Human Activity Patterns. The letters dB stand for "decibels" and refer to the general strength of the noise. The letter "A" indicates that the sound has been filtered to reduce the strength of very low and very high frequency sounds, much as the human ear does. On average, each A-weighted sound level increase of 10 decibels corresponds to a doubling of subjective loudness. That is, a sound level of 70 decibels is perceived as being twice as loud as a sound at 60 decibels. Noise level changes of 3 dBA or less are not generally noticeable by most humans. Transit noise impact metrics are typically described with two terms. An Hourly Equivalent Level, abbreviated as Leq(h), is an hourly measure that accounts for moment-to-moment fluctuations in A-weighted sound levels due to all sound sources during the hour combined. The descriptor for cumulative 24-hour exposure is the Day-Night Sound Level, abbreviated as Ldn, a 24-hr measure that integrates the moment-to-moment fluctuations in dBA-levels for a 24-hour period. Ldn is used for any location where persons potentially receiving the sound will be sleeping. As most people are more easily disturbed by noise during nighttime hours when both background noise is lower and people are sleeping, noises during this period (10:00 PM to 7:00 AM) are weighted with an additional 10dBA. The FTA has developed noise impact criteria, which describe the noise environment considered acceptable for a given situation. These criteria are a function of land use category and existing noise exposure. The three land use categories are defined below:
5.9.2.1 AFFECTED ENVIRONMENT (NOISE)Due to the existing use of most of the project alignment by freight or commuter trains, 24-hour noise level monitoring was performed at four representative locations adjacent to the alignment. Refer to Exhibit 5.9-4 Time History for Noise Locations N1 Through N4 [PDF]. Based on these measurements, current levels of rail traffic, and general land use conditions (by municipality), ambient noise levels were projected for each municipality along the alignment. Using these baseline conditions and factoring in modal/power generation alternatives and running schedules, noise levels associated with the build alternatives were developed. Continuous noise monitoring was performed over a 24-hour period at four locations along the proposed project alignment. Locations, existing rail use, land use, Ldn, and Leq (maximum and minimum) are presented in Table 5.9-3.The data obtained from the monitoring illustrate the influence of existing rail traffic on noise levels. The monitoring station at Lorane (N3) (all monitoring stations were positioned within 40 feet of the nearest active track), a suburban residential area in Exeter Township, had the highest Ldn and hourly Leq. These levels were higher than a mixed industrial and high density residential area of urban Reading. Over 30 freight trains, some of them having multiple locomotives and 120 or more railcars, pass through Lorane each day, many of them during nighttime hours. Noise levels adjacent to SEPTA's Wynnefield station (N1) (20 electric-commuter trains per day) and at Otterbein (N2) (low density residential and institutional, with a few relatively short freight trains per day) are substantially lower. Noise levels for existing conditions at three distance intervals (50-, 150-, and 300-feet) from the track were developed for each municipality along the alignment, using land use, railroad use, and monitoring data and the FTA guidance manual (see Table 5.9-4). Consistent with the monitoring data, estimated noise levels are highest in those communities with heavy freight train traffic and lowest in suburban areas with electric commuter rail or no rail traffic. 5.9.2.2 ENVIRONMENTAL CONSEQUENCES (NOISE IMPACTS)Station AreasNoise impacts associated with station areas are not directly assessed as increased noise associated with vehicular traffic generally results in noise increase of 3 dBA or less. Train-generated noise is the major element of the station area noise environment. No-Build Alternative It is unlikely that there would be direct noise impacts due to the No-Build Alternative. If anything, the increased roadway automobile traffic loads on existing roads would be offset by reduced operating speeds, because one factor offsets the other with regard to noise generation. TSM Alternative The bus elements of the TSM would have negligible affect on noise receptors. The park-and-ride lots associated with this alternative are either adjacent to exit ramps of US Route 422, in urban areas, or adjacent to the heavily trafficked rail alignment. Even a 50 percent increase in vehicular traffic around a parking area would result in an increase of 3 dBA or less from ambient conditions. The extension of electric commuter rail service to Port Kennedy from Norristown will not cause an impact due to the high level of existing freight traffic on this portion of the alignment. Build Alternatives The predicted noise impacts associated with the build alternatives are a function of five factors:
Exeter Township was chosen to represent areas of the alignment with high levels of existing freight train traffic. Addition of commuter rail or light rail traffic will result in no increase in computed noise impacts, due to the high, existing freight train traffic-induced noise levels. Whitemarsh was chosen to represent relatively quiet suburban communities with existing commuter rail traffic. Noise impacts at a distance of 50 and 100 feet from a residence would be characterized as severe for diesel commuter rail and 50 feet for light rail. In those areas with relatively moderate or existing noise impacts, severe noise impacts result from one or more modes/propulsion systems at varying distances less than 100 feet from the nearest track. Table 5.9-6 lists the estimated number of residences that may encounter severe noise impacts associated with the proposed project. Due to increased frequency of service, severe noise impacts associated with the light rail alternatives (5E, 5ET, and 6) are concentrated along the existing R6 Norristown line between the Whitemarsh/Philadelphia boundary and Ivy Ridge where there are 19 homes within 50 feet of the alignment. Severe noise impacts for the diesel commuter rail alternatives (1D and 2D) would result in 32 severe impacts in Phoenixville and Upper Providence. Alternative 2D would result in 40 additional severe noise impacts in Lower Merion. 5.9.2.3 MITIGATION (NOISE)When impacts fall in the severe impact range, their mitigation depends on a variety of factors including:
No direct noise impacts are associated with the No-Build, and as a result, mitigations will not be necessary. TSM The FHWA guidelines indicate that noise abatement should be considered when predicted traffic noise levels substantially exceed the existing noise levels. A substantial increase is considered typically to be 10 or more dB. This level of increase is not expected. Consequently, no mitigation measures would be proposed for the TSM Alternative. Construction mitigation measures are discussed in Section 5.17. Build Alternatives FTA guidance indicates that two federal agencies, the Department of Housing and Urban Development (HUD) and the Federal Aviation Administration (FAA), consider above 65 Ldn to be incompatible with residential use. Factors such as the number of noise-sensitive sites, the increase compared to existing noise levels, and cost are considered in evaluating mitigation measures. The majority of the severe noise impacts are associated with the Alternatives 1D and 2D, which would use diesel commuter. Selection of a different alternative would substantially reduce impacts. Noise barriers are a commonly used form of mitigation. During Preliminary Engineering all locations with severe noise impacts will be evaluated in detail to confirm the severity of the impact and to assess specific mitigation alternatives. The use of horns accounts for many of these severe impacts. The impacts due to the horns are considered unavoidable for safety reasons. Recent FTA research on grade crossing safety has shown that at grade crossings used by freight trains, the accident rate is higher if local ordinances ban sounding horns except in emergencies. Grade crossing safety is of primary importance, and the blowing of horns at grade crossings will be a part of SVM's operations. During preliminary and final engineering the SVM team will work with local municipalities and residents to develop and implement mitigation that minimize noise impacts. 5.9.3 VIBRATION5.9.3.1 AFFECTED ENVIRONMENT (VIBRATION)Vibration event monitoring results for four locations along the alignment are presented in Table 5.9-7. Monitoring points were 30-60 feet from the track. During times of no rail activity vibration levels were less than 50 VdB (The threshold of perceptibility for the average person is 65VdB.) Measured vibration event levels ranged from 61 to 81 vibration decibels (VdB). Freight train induced events ranged from 70 to 81 VdB. Rail speeds varied from about 20 to 50 miles per hour.Predicted existing vibration levels with distance from the tracks for those segments of the proposed alignment with existing rail traffic are presented in Table 5.9-8 for representative locations. Higher predicted levels west of Norristown are due to the influence of continued freight rail service on vibration levels. For those areas of the proposed alignment without existing rail traffic, vibration levels are assumed to be on the order of 50 VdB. At distances beyond 50 feet of the track, existing vibration levels throughout the length of the alignment are within FTA's 80 VdB criterion for "infrequent events" (70 or less trains per day). 5.9.3.2 CONSEQUENCES (VIBRATION)No-Build AlternativeAs the No-Build Alternative does not include any changes in passenger rail traffic anywhere along the alignment and rubber-tired roadway vehicles do not generate perceptible ground-borne vibration levels, the No-Build Alternative will not generate any vibration-related impacts. TSM Alternative An increase in the number of commuter rail trains on existing track between Ivy Ridge and Philadelphia via Cynwyd will not significantly impact the vibration environment as the existing vibration levels as close as 50 feet from the track are within both the "infrequent" and "frequent" FTA vibration criteria guidance. The introduction of commuter rail from Port Kennedy to Norristown will be within an area of existing freight train traffic. Vibration levels will be unchanged and the FTA "infrequent criterion will continue to apply. The restoration of electric commuter rail service between Cynwyd and Ivy Ridge will increase vibration levels in a portion of Lower Merion Township. Maximum vibration levels will be within the FTA criterion at 50 feet from the track. Build Alternatives The introduction of diesel or electric commuter rail or electric light rail in those areas of the alignment currently having freight traffic will not increase maximum vibration levels. However, as the total number of rail vibration events will exceed 70 for all locations between Norristown and Perkiomen Junction and Cromby and Klapperthal Junction, the more restrictive vibration threshold of 72 VdB will apply. Vibration will be perceptible in some homes, but no homes or other occupied buildings are expected to be impacted with excessive vibration levels. In areas with existing commuter train traffic or no rail traffic of any type, the increase to more than 70 vibration events per day will not result in any impacts. Vibration levels at 50 feet will be perceptible in places, but are projected to be within the FTA 72 VdB criterion. 5.9.3.3 MITIGATIONAlthough no significant vibration impacts are expected to occur, owners of buildings adjacent to the alignment should be contacted during preliminary engineering to document any buildings having occupant-perceived vibration levels. Vibration monitoring and structural inspection should be performed where appropriate.
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