appendix e. noise and vibration technical report

178 Pages·2016·6.74 MB·English

APPENDIX E. NOISE AND VIBRATION TECHNICAL REPORT

Environmental Assessment November 2016
South Central Light Rail Extension
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Environmental Assessment November 2016
South Central Light Rail Extension

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Noise and Vibration Technical Report March 2016
Environmental Assessment
South Central Light Rail Extension
EXECUTIVE SUMMARY
This technical report documents the findings of potential noise and vibration impacts for
the proposed South Central Light Rail Extension Project in Phoenix, Arizona. The
technical report and findings are in support of the Environmental Assessment (EA). The
5-mile proposed project, or Build Alternative, would extend the existing Valley Metro
light rail line south of Downtown along Central and 1st Avenues in central Phoenix.
Noise concerns associated with a light rail system include light rail operations; effects
from special trackwork, track curvature, audible warnings and traction power
substations (TPSSs) and construction of the system. Vibration concerns associated with
a light rail system include light rail operations, effects from special trackwork and
construction of the system. More information about light rail noise and vibration
concerns can be found in Section 1.0.
Noise and vibration has been assessed in accordance with guidelines specified in the
Federal Transit Administration (FTA) Noise and Vibration Impact Assessment guidance
manual (FTA Report FTA-VA-90-1003-06, May 2006; also referred to as FTA Guidance
Manual). Specifics of criteria applied can be found in Section 2.0, and specifics of the
prediction methodologies can be found in Section 3.0.
Potential impacts were examined for locations adjacent to the proposed alignment for
both transit operations and construction activities. Noise- and vibration-sensitive land
uses along the alignment include many single- and multifamily residences, hotels,
schools, courthouses, libraries, religious and cultural institutions, a habitat restoration
area and medical facilities. A full list of sensitive receivers and maps showing their
locations can be found in Appendix F.
A noise and vibration measurement program was conducted to characterize the existing
noise and vibration in the project area. The primary existing noise sources in the area
are vehicular traffic along the whole alignment and airplane noise north of Elwood
Street. Normalized to a distance of 25 feet from the near travel lane, 24-hour noise
levels (Ldn) ranged from 69 to 74 dBA; note that the Ldn metric applies penalties for
nighttime noise to properly assess residential land uses. Also at a distance of 25 feet,
short-term (up to 1 hour) noise levels ranged from 68 to 74 dBA Leq, representing the
worst noise hour (highest traffic volumes during free-flowing traffic conditions). More
information about the 2015 conditions can be found in Section 4.0.
The vibration test program included propagation tests to characterize efficiency of
vibration propagation through the ground at several locations along the alignment.
Vibration propagation was found to be very efficient along the whole alignment, with
peak efficiency in the 40 to 50 Hz range. The existing vibration data helped to confirm
the validity of the propagation data. More information about vibration propagation can
be found in Section 4.0.
SUMMARY OF NOISE IMPACT ANALYSIS
This section summarizes the results of the noise impact assessment for the South
Central Light Rail Extension Project (more details can be found in Section 5.0). The
predicted noise levels for light rail operations include the noise from the steel wheels of
the light rail rolling on the steel rails and the noise from special trackwork, train bells as
Noise and Vibration Technical Report ES-1 March 2016
Environmental Assessment
South Central Light Rail Extension
the light rail vehicle (LRV) arrives and departs from stations or passes through an
intersection, crossing gate bells at the roundabouts and TPSS units. The impact
analysis does not include noise from warning horns because they would only be used in
case of emergency. Noise levels from TPSS units were also assessed separately for
nighttime noise at nearby residential properties. The TPSS units are the only ancillary
noise source associated with the project.
The noise-sensitive receivers where potential impact is predicted are presented in
Table ES-1, along with noise limit exceedances and mitigation recommendations.
Impact exceedance is shown as exceedance of a moderate impact level (with severe
impact noted). For the South Central Light Rail Extension Project, mitigation is
recommended for two residential sensitive receiver clusters (FTA Category 2) as
described below. For exceedances less than 1 dB, mitigation is not recommended.
• A potential moderate impact with an exceedance of 3 dB is predicted for receiver
cluster SB-42, two residences on the southbound side just north of the Western
Canal. This impact is caused by the nearby special trackwork just north of the
Central Avenue/Baseline Road station. Installing a low-impact frog for the special
trackwork would eliminate the impact. Low-impact frogs can reduce noise levels by
creating a smoother transition through the gap in the rails at the special trackwork.
Examples of low-impact frogs include moveable point frogs, spring-rail frogs,
monoblock frogs or flange-bearing frogs (refer to Appendix G for more information).
• A potential severe impact with predicted levels meeting the severe limit (and
exceeding the moderate limit by 5 dB) occurs at receiver cluster NB-13, two
residences on the northbound side near the intersection of Central Avenue/
Raymond Street. This impact is caused by nearby special trackwork and a nearby
TPSS unit. Mitigation for both the special trackwork and the TPSS unit is necessary
to eliminate the impact. A low-impact frog is recommended for the special trackwork.
To mitigate the noise from the TPSS unit, it should be strategically located within the
site, with the major noise source, the cooling fans, being as far from the residences
as possible. If the TPSS unit is located within the parcel as far as feasible and
oriented with the cooling fans facing away from the sensitive receivers, the predicted
noise level could be reduced to below the applicable threshold. The cooling fans on
the TPSS unit should be facing east or south and be located more than 50 feet from
the nearest residence to reduce the predicted noise levels to below the impact
threshold (when combined with the low-impact frog). If there is not much flexibility on
where to locate the unit within the parcel, a sound enclosure should be built around
the TPSS unit to reduce noise levels at sensitive receivers; the sound enclosure
would need to reduce noise by 3.4 dB, which is attainable with a proper design of
the enclosure (appropriately considers the cooling fan height above ground). Since
only five of the six TPSS locations being evaluated will be chosen, it may be
possible to eliminate this location as an option and thus remove the TPSS unit as a
sound source for nearby receivers.
Note that for all predictions and mitigation recommendations, it is assumed that the
track and wheels would be maintained in a state of good repair (that is, rail corrugations
and wheel flats would be minimized through maintenance procedures—rail grinding and
wheel truing).
Noise and Vibration Technical Report ES-2 March 2016
Environmental Assessment
South Central Light Rail Extension
Also note that potential wheel squeal would be addressed for the infrequent,
nonrevenue train movements at the following locations with track curvature:
1st Avenue/McKinley Street, Central Avenue/McKinley Street, Central Avenue/Jefferson
Street, 1st Avenue/Sherman Street and Central Avenue/Sherman Street. Wheel squeal
is minimized with friction control. Two approaches to friction control are (1) applying a
friction modifier to the rail head and/or the wheel tread or (2) applying lubricant to the
gauge face of the rail or the wheel flange. Valley Metro vehicles are equipped with a
lubrication system and are used on all track curvatures. All new light rail vehicles will
also be equipped with a lubrication system. There are no revenue service train
movements through low-radius curves.
TABLE ES-1: SUMMARY OF PREDICTED NOISE IMPACTS
AND MITIGATION FOR LIGHT RAIL OPERATIONS
Amount
FTA # Impacted
Sensitive Exceeds
Coaft Leganodry IDa Desc.b Receiver FTA Impact wUitnhiotsu t ReMcoitmigmateionndde d
Location Threshold
Uses Mitigation
(dB)c
Category 1 — — — — — —
Use low-impact frog for
7–13 E special trackwork at
NB-13 SF Raymond 5e 2 Raymond St; strategic
Street placement/orientation of
TPSS unit
7252 S
Category 2
Central
Ave, Use low-impact frog for
SB-42 SF 1st row, 3 2 special trackwork in the
and 7246 vicinity of Western Canal
S Central
Ave
Category 3 — — — — — —
a ID identifies sensitive receivers as shown in the maps in Appendix F. NB = northbound side, SB = southbound side.
b SF = single-family
c Moderate limit exceedance.
d Mitigation not recommended for exceedances less than 1 dB.
e This exceedance qualifies as a severe impact.

The South Central Light Rail Extension Project would involve some physical roadway
changes and bus headway changes. Also, traffic volume differences are predicted for
the Build and No-Build Alternatives. Evaluating changes with the Federal Highway
Administration (FHWA) Traffic Noise Model (TNM), it is concluded that traffic changes
would result in minimal or negligible sound level differences. As a result, these changes
are not included in the project noise predictions.
The park-and-ride lots to be used for the project consist of one at Broadway
Road/Central Avenue, one near Fremont Road/Central Avenue (near the proposed
Baseline Road/Central Avenue station) and two existing lots along Baseline Road, one
east of Central Avenue and the other west of Central Avenue. Applying FTA
Noise and Vibration Technical Report ES-3 March 2016
Environmental Assessment
South Central Light Rail Extension
procedures, it is predicted that the park-and-ride lot noise at Broadway Road/Central
Avenue is far below the existing noise, resulting in no increase in noise at the
surrounding receivers. For the park-and-ride lot near Fremont Road/Central Avenue, it
was determined that all lot noise levels were below existing noise levels. When the lot
noise level was close to the existing noise level, further analysis was done that showed
the lot noise does not contribute to potential project noise impacts for the nearby
receivers. For the existing lots on Baseline Road, no substantial change to current use
is anticipated as a result of the project. Therefore, these lots require no further
consideration of noise impact.
Although the proposed project includes planned improvements to the facilities at the
existing site for the Operations and Maintenance Center, east of Phoenix Sky Harbor
International Airport and southwest of the intersection of the Grand Canal and
Loop 202, no receivers in the vicinity are sensitive to noise and vibration impacts. As a
result, no noise or vibration impacts are predicted.
In summary, with implementation of mitigation where needed, the proposed project
would not result in exceedances of the applicable noise criteria thresholds. Therefore,
the project would have no significant adverse noise impact.
SUMMARY OF VIBRATION IMPACT ANALYSIS
This section summarizes the results of the vibration impact assessment for the South
Central Light Rail Project (more details can be found in Section 5.0). The vibration-
sensitive receivers where impact is predicted are presented in Table ES-2. Below is a
summary of the predicted impacts and recommended mitigation.
Impacts are predicted at two multifamily residential receivers Downtown, including the
Palomar Hotel and Barrister Place. Groundborne noise and vibration impacts are
predicted because of the proximity of the track (approximately 20 feet) as well as the
presence of special trackwork. The Barrister Place building is currently vacant, but is
planned for a multiuse redevelopment that will include a residential component.
If it is not possible to relocate either the track or the special trackwork farther away from
the Palomar Hotel or Barrister Place, then the recommended mitigation for the Palomar
Hotel and Barrister Place is installation of isolated slab track. The design consists of a
concrete slab supported by a continuous elastomeric support mat. This design is
capable of attenuation greater than 10 dB at frequencies of 25 Hz and higher.
A less than 1 VdB exceedance of the vibration criteria threshold is anticipated for three
single-family homes at cluster NB-07 on Central Avenue. A less than 1 dB exceedance
of the groundborne noise criteria is also expected at the Arizona Summit Law School
(NB-A) and the Maricopa County Courthouse (NB-B). At these locations, a rail boot, a
resilient material between the rail and the receiver, is the recommended mitigation
measure. The most common design for embedded track on modern light rail systems is
to use a rubber boot around the rail with the rail and boot embedded in concrete. The
standard-booted embedded track system is relatively stiff and does not provide much
isolation. However, several suppliers have developed embedded track systems that
incorporate much softer rubber elements. Where relatively limited vibration attenuation
is required, one of these systems would provide sufficient vibration attenuation.
Noise and Vibration Technical Report ES-4 March 2016
Environmental Assessment
South Central Light Rail Extension
The proposed project is expected to exceed the vibration impact levels at the Salvation
Army Adult Rehabilitation Center (NB-C) by less than 1 VdB and the groundborne noise
threshold levels by approximately 10 dB. The recommended mitigation is to install a rail
boot and a low-impact frog (described more in the next paragraph).
For all other sensitive uses presented in Table ES-2, installation of low-impact frogs at
the nearby special trackwork, such as loops and crossovers, is the recommended
measure to mitigate groundborne noise and/or vibration impacts at these locations. The
gaps in the rail associated with standard frogs can cause vibration levels to increase by
up to 10 decibels. Low-impact frogs can reduce vibration levels by creating a smoother
transition through the gap in the rails at the special trackwork. Examples of low-impact
frogs include monoblock frogs, flange-bearing frogs, moveable point frogs or spring rail
frogs. Where possible, special trackwork may also be relocated farther away from the
receiver. More information on low-impact frogs is included in Appendix G.
With implementation of the recommended mitigation where needed, the proposed
project would not result in exceedances of the applicable groundborne noise or vibration
criteria thresholds. Therefore, the project would have no significant adverse
groundborne noise or vibration impacts.
TABLE ES-2: SUMMARY OF PREDICTED VIBRATION IMPACTS
AND APPLICABLE MITIGATION AT RESIDENTIAL RECEIVERS
GBV GBN
Mitigation,
(VdB) (dBA)
Sensitive Feet Total
IDa Desc.b RLoeccaetivioenr mit dict mit dict ReMcoitmigmateionnd ed BEdegyoen odf MLeitniggathti oonf
Li re Li re Building
P P
Hotel Palomar Isolated slab
NB-01 HT 72 78 44 53 65
Phoenix track
Barrister Place
(potential
480
multiuse Isolated slab
NB-02 MF 72 77 43 53 65
redevelopment track
with residential
component)
1001–1009
NB-07 SF 72 72c 50 47 Rail boot 60 280
S Central Ave
3716 S Central
SB-11 SF 72 74 51 48 Low-impact frog — —
Ave
S Central Ave
and W Cody Dr,
SB-23 SF 72 75 50 49 Low-impact frog — —
1st and 2nd
rows
7252 S Central
Ave, 1st row,
SB-42 SF 72 76 51 50 Low-impact frog — —
and 7246 S
Central Ave
NB-A SC Arizona Summit 78 66 40 40c Rail boot 55 210
Law School
Noise and Vibration Technical Report ES-5 March 2016
Environmental Assessment
South Central Light Rail Extension
TABLE ES-2: SUMMARY OF PREDICTED VIBRATION IMPACTS
AND APPLICABLE MITIGATION AT RESIDENTIAL RECEIVERS
GBV GBN
Mitigation,
(VdB) (dBA)
Sensitive Feet Total
IDa Desc.b RLoeccaetivioenr mit dict mit dict ReMcoitmigmateionnd ed BEdegyoen odf MLeitniggathti oonf
Li re Li re Building
P P
Maricopa
NB-B Court County Justice 78 67 41 41c Rail boot 40 230
Courts
Salvation Army Low-impact
NB-C MD Adult Rehab 78 78c 43 53 frog, 65 480
Center Rail boot
Revealed Word
NB-G CH 78 78c 52 52c Low-impact frog — —
Church
Phoenix
SB-N SC Collegiate 78 82 52 57 Low-impact frog — —
Academy
a ID identifies sensitive receivers as shown in the maps in Appendix F. NB = northbound side, SB = southbound side.
b SF = single-family residential, MF = multifamily residential, Court = government courthouse, MD = medical center,
CH = church, SC = school
c Levels are reported to the nearest decibel. These numbers represent fractional exceedances of less than 1 dB (still
considered an impact).

Note that historic structures that do not fall into the FTA land use categories are not
included in the assessment for vibration impact from light rail operations. The vibration
impact thresholds are based on annoyance, and the primary concern for historic
structures is the risk of damage. The recommended limit in the FTA Guidance Manual
for buildings extremely susceptible to damage is 90 VdB, which is 18 decibels higher
than the limit for Category 2 (residential) land uses. Vibration from light rail operations
will be well below the limit for buildings extremely susceptible to damage at all historic
resources.
In summary, with implementation of mitigation where needed, the proposed project
would not result in exceedances of the applicable groundborne noise or vibration criteria
thresholds. Therefore, the project would have no significant adverse groundborne noise
or vibration impact.
SUMMARY OF CONSTRUCTION NOISE AND VIBRATION IMPACT ANALYSIS
Construction Noise
Construction noise levels were predicted using estimates of the types of equipment
likely to be used during the noisiest periods of track construction. The predicted
construction noise level exceeds the FTA impact threshold for construction noise by
4 decibels at 50 feet. Given that some residences in the project area are within 50 feet
of the alignment, construction noise impacts are likely unless the contractor is required
to implement noise control measures when working near residences.
Noise and Vibration Technical Report ES-6 March 2016
Environmental Assessment
South Central Light Rail Extension