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Noise Study Report
DUNE PALMS ROAD LOW WATER CROSSING REPLACEMENT PROJECT
City of La Quinta, Riverside County
08-Riv-Local Assistance
Federal Project Number BLRKS-5433(014)
Prepared for:
City of La Quinta
And
November 2015
Summary
Dune Palms Road is a secondary arterial in the City of La Quinta that provides a
north/south link between residential developments to the north and commercial activity to
the south near the Highway 111 corridor. It is an important connection to schools and
emergency services access to the community. Currently the elevation of the existing
Dune Palms Road low-water crossing causes it to flood during minor rain events making
it impassable. Therefore the City of La Quinta has decided to construct a new bridge to
ensure that all-weather access is maintained.
The new bridge and roadway will be 86 feet wide and a cross section that includes a six-
foot sidewalk on both sides of the bridge, two eight-foot outside shoulders also serving as
bike/golf cart lanes, a 10’ raised median, two eleven-foot travel lanes, and two twelve-
foot travel lanes.
The main purpose of the project is to provide safe access across the Coachella Valley
Storm Water Channel (CVSC) during all-weather events; provide a reliable route for
emergency vehicles, motorists, pedestrians, and bicyclists; and the improved roadway
will achieve the City’s General Plan goals for the corridor.
Land uses within the study area include commercial, residential, church and school. The
area is generally flat with the exception of the existing roadway being within the river
bed. The study area was broken down into two areas.
• Area A: Located on the northeast side of Dune Palms Road between CVSC and
Westward Ho Drive. A mobile home park (Activity Category B) and a church
(Activity Category C-D) are located in this area. This area is generally flat.
Backyards face the street. A four to five foot tall wooden fence shields the
residences in this area. (Refer to Figure 5-1.)
• Area B: Located on the northwest side of Dune Palms Road between CVSC and
Westward Ho Drive. La Quinta High School (Activity Category C-D) is located in
this area. This area is generally flat. No sound barrier or topographical shielding
occurs between the roadway and the high school area. (Refer to Figure 5-1.)
The existing traffic noise in Area A is predicted to be between 55 and 59 dBA L eq (h).
The traffic noise modeling results indicate that traffic noise levels at the church and
residences in Area A are predicted to be in the range of 61 to 65 dBA L eq (h) in the
design-year. The results also indicate that the increase in noise between existing
Dune Palms Road Low Water Crossing Replacement Noise Study Report iii
Summary
conditions and the design-year is predicted to be 4 to 7 dB. Because the noise levels in
the design-year are not predicted to approach or exceed the noise abatement criterion (67
dBA L eq [h]) or result in a substantial increase in noise, no traffic noise impacts are
predicted in Area A.
The church has an interior noise abatement criterion in addition to the exterior criterion,
interior noise must be considered at the church as well. From Table 6 in the FHWA
Highway Traffic Noise Analysis and Abatement Guidance document, the building noise
reduction factor for standard construction with ordinary windows closed is 20 dB. The
interior noise level in the church in the design-year is therefore predicted to be 45 dBA
L eq (h). Because this predicted design-year noise level does not exceed the interior NAC
of 52 dBA Leq(h), no interior traffic noise impacts are predicted at the church.
The existing traffic noise in Area B is predicted to be between 55 and 56 dBA L eq (h).
Levels at the school in Area B are predicted to be 61 dBA L eq (h) in the design-year. The
results also indicate that the increase in noise between existing conditions and the design-
year is predicted to be 5 to 6 dB. Because the noise levels in the design-year are not
predicted to approach or exceed the noise abatement criterion (67 dBA L eq [h]) or result in
a substantial increase in noise, no traffic noise impacts are predicted in Area B.
No traffic noise impacts for the Build Alternative were predicted for Area A and B.
Accordingly, noise abatement does not need to be considered in this project.
During construction of the project, noise from construction activities may intermittently
dominate the noise environment in the immediate area of construction. Noise associated
with construction is controlled by La Quinta’s Municipal Code, Section 6.08.050 and the
General Standard Conditions. No adverse noise impacts from construction are
anticipated because construction would be conducted in accordance with the City’s
Municipal Code. Construction noise would be short-term, intermittent, and
overshadowed by local traffic noise.
Dune Palms Road Low Water Crossing Replacement Noise Study Report iv
Table of Contents
Chapter 1. Introduction ......................................................................................................... 1
1.1. Purpose of the Noise Study Report ......................................................................... 1
1.2. Project Purpose and Need ....................................................................................... 1
1.2.1 Project Purpose ........................................................................................................ 1
1.2.2 Project Need ............................................................................................................ 1
Chapter 2. Project Description .............................................................................................. 4
Chapter 3. Fundamentals of Traffic Noise ............................................................................ 8
3.1. Sound, Noise, and Acoustics .................................................................................. 8
3.1. Frequency ................................................................................................................ 8
3.2. Sound Pressure Levels and Decibels ...................................................................... 8
3.3. Addition of Decibels ............................................................................................... 9
3.4. A-Weighted Decibels .............................................................................................. 9
3.5. Human Response to Changes in Noise Levels ...................................................... 10
3.6. Noise Descriptors .................................................................................................. 11
3.7. Sound Propagation ................................................................................................ 11
3.7.1. Geometric Spreading .............................................................................................. 12
3.7.2. Ground Absorption ................................................................................................. 12
3.7.3. Atmospheric Effects ............................................................................................... 12
3.7.4. Shielding by Natural or Human-Made Features ..................................................... 12
Chapter 4. Federal Regulations and State Policies .............................................................. 14
4.1. Federal Regulations .............................................................................................. 14
4.1.1. 23 CFR 772............................................................................................................. 14
4.1.2. Traffic Noise Analysis Protocol for New Highway Construction and
Reconstruction Projects ......................................................................................... 15
4.2. State Regulations and Policies .............................................................................. 16
4.2.1. California Environmental Quality Act (CEQA) ..................................................... 16
4.2.2. Section 216 of the California Streets and Highways Code ..................................... 17
Chapter 5. Study Methods and Procedures ......................................................................... 18
5.1. Methods for Identifying Land Uses and Selecting Noise Measurement and
Modeling Receiver Locations.................................................................................................... 18
5.2. Field Measurement Procedures ............................................................................. 18
5.2.1. Short-Term Measurements ..................................................................................... 18
5.3. Traffic Noise Levels Prediction Methods ............................................................. 20
5.4. Methods for Identifying Traffic Noise Impacts and Consideration of Abatement 21
Chapter 6. Existing Noise Environment .............................................................................. 23
6.1. Existing Land Uses ............................................................................................... 23
6.2. Noise Measurement Results .................................................................................. 23
6.2.1. Short-Term Monitoring .......................................................................................... 24
Chapter 7. Future Noise Environment, Impacts, and Considered Abatement .................... 25
7.1. Future Noise Environment and Impacts ................................................................ 25
7.2. Preliminary Noise Abatement Analysis ................................................................ 26
7.2.1. Area A .................................................................................................................... 26
7.2.2. Area B ..................................................................................................................... 27
Chapter 8. Construction Noise ............................................................................................ 28
Chapter 9. References ......................................................................................................... 30
Appendix A Traffic Data ................................................................................................... 31
Appendix B Predicted Future Noise Levels and Noise Barrier Analysis .......................... 34
Appendix C Supplemental Data ......................................................................................... 36
Dune Palms Road Low Water Crossing Replacement Noise Study Report v
List of Tables
List of Figures
Figure 1-1. Project Vicinity.............................................................................................. 2
Figure 1-2. Project Location ........................................................................................... 3
Figure 2-1. Dune Palms Road Project Location and Study Area..................................... 6
Figure 5-1. Analysis Areas and Noise Monitoring Positions .......................................... 19
List of Tables
Page
Table 3-1. Typical A-Weighted Noise Levels ................................................................ 10
Table 6-1. Summary of Short-Term Measurements ...................................................... 24
Table 6-3. Comparison of Measured to Predicted Sound Levels in the TNM Model .... 24
Table 8-1. Construction Equipment Noise .................................................................... 28
Table A-1. Traffic Data for Existing Conditions ............................................................. 32
Table A-2. Traffic Data for Design Year No-Project Conditions .................................... 32
Table A-3. Traffic Data for Design Year with Project Conditions ................................... 33
Table B-1. Predicted Future Noise and Barrier Analysis ................................................ 35
Dune Palms Road Low Water Crossing Replacement Noise Study Report vi
List of Abbreviated Terms
CEQA California Environmental Quality Act
CFR Code of Federal Regulations
CNEL
CVSC
Community Noise Equivalent Level
Coachella Valley Storm Water Channel
dB Decibels
FHWA Federal Highway Administration
Hz Hertz
kHz Kilohertz
L dn Day-Night Level
L eq Equivalent Sound Level
L eq(h) Equivalent Sound Level over one hour
L max Maximum Sound Level
LOS Level of Service
L xx Percentile-Exceeded Sound Level
mPa micro-Pascals
mph miles per hour
NAC noise abatement criteria
NADR Noise Abatement Decision Report
NEPA National Environmental Policy Act
NSR Noise Study Report
Protocol Caltrans Traffic Noise Analysis Protocol for New Highway Construction,
Reconstruction, and Retrofit Barrier Projects
SPL sound pressure level
TeNS Caltrans’ Technical Noise Supplement
TNM 2.5 FHWA Traffic Noise Model Version 2.5
Dune Palms Road Low Water Crossing Replacement Noise Study Report vii
Chapter 1. Introduction
1.1 Purpose of the Noise Study Report
The purpose of this Noise Study Report (NSR) is to evaluate noise impacts and
abatement under the requirements of Title 23, Part 772 of the Code of Federal
Regulations (23 CFR 772) “Procedures for Abatement of Highway Traffic Noise.” 23
CFR 772 provides procedures for preparing operational and construction noise studies
and evaluating noise abatement considered for federal and Federal-aid highway projects.
According to 23 CFR 772.3, all highway projects that are developed in conformance with
this regulation are deemed to be in conformance with Federal Highway Administration
(FHWA) noise standards. Compliance with 23 CFR 772 provides compliance with the
noise impact assessment requirements of the National Environmental Policy Act (NEPA).
The Caltrans Traffic Noise Analysis Protocol for New Highway Construction,
Reconstruction, and Retrofit Barrier Projects (Protocol) (Caltrans 2011) provides Caltrans
policy for implementing 23 CFR 772 in California. The Protocol outlines the
requirements for preparing noise study reports. Noise impacts associated with this
project under the California Environmental Quality Act (CEQA) are evaluated separately
in the project’s environmental document.
1.2 Project Purpose and Need
1.2.1 Project Purpose
The purpose of the project is to replace the existing low-water crossing spanning the
Coachella Valley Storm Water Channel (CVSC) at Dune Palms Road with an all-weather
access. The proposed improvements will accomplish the following in the project area:
• Provide safe access across the CVSC (Whitewater River) during all-weather
events
• Provide reliable route for emergency vehicles, motorists, pedestrians, and
bicyclists
• Achieve the City’s General Plan goals for the corridor
1.2.2 Project Need
Dune Palms Road serves a vital access for emergency services within the project area, as
well as for La Quinta High, John Glen Middle and Amelia Earhart Elementary Schools. It
also provides connectivity of the city residential development north of the Channel with
Dune Palms Road Low Water Crossing Replacement Noise Study Report 1
Chapter 1 Introduction
the Highway 111 commercial corridor located south of the CVSC (Figure 1-1 and
Figure 1-2).
Figure 1-1. Project Vicinity Map
[Dune Palms Road Low Water Crossing Replacement Noise Study Report 2
Chapter 1 Introduction
Figure 1-2. Project Location Map
The CVSC conveys storm water runoff from the surrounding mountains as well as
developed areas within the Coachella Valley. The elevation of the existing Dune Palms
Road low-water crossing causes it to flood during minor rain events (2-year frequency)
and results in full street closure and detour of both vehicle and pedestrian traffic. In the
interest of public health and safety, and in response to community concerns regarding
frequent closures of the low-water crossing, the City of La Quinta has determined that
replacement of the low-water crossing with a new bridge is needed to ensure that all-
weather access is maintained. The Dune Palms Road low-water crossing is the last
remaining low-water crossing of the CVSC within the City.
[Dune Palms Road Low Water Crossing Replacement Noise Study Report 3
Chapter 2. Project Description
Existing Conditions
The existing roadway crosses the CVSC at the channel grade. The roadway width is 68
feet at the crossing, and consists of one northbound and two southbound through lanes,
eight foot wide walkway area along the western edge, and an eight foot shoulder along
the eastern edge of the road; and no median. The existing roadway approach south of the
crossing consists of one northbound and two southbound through lanes. The northern
roadway approach consists of one through lane in each direction. The transition from one
to two lanes in the southbound direction occurs at the midpoint of the channel crossing.
Dune Palms Road approximately one-quarter mile north of the channel low-water
crossing and just south of the project limits is a four lane roadway with a median. The
roadway section just north of the crossing will be widened as part of an approved City
project (City Project Number 2009-04 per the City’s current CIP). The City widening
project was originally with a Mitigated Negative Declaration under CEQA in April 2010.
Proposed Improvements
The project proposes to remove the existing low-water crossing of Dune Palms Road at
the CVSC in the City of La Quinta, Riverside County. The crossing will be replaced with
a 480 feet long and 86 feet wide four-span bridge. The bridge typical section consists of
six-foot sidewalk on both sides of the bridge, two (2) eight-foot outside shoulders also
serving as bike/golf cart lanes, a 10 foot raised median, two (2) eleven-foot travel lanes,
and two (2) twelve-foot travel lanes.
The proposed configuration will be consistent with the existing four lane roadway section
to the south, and the City’s current improvement project to the north (City Project
Number 2009-04), which will widen Dune Palms Road from two to four lanes with a
median and left turn lanes.
The proposed improvements will include reconstruction of the north and south bridge
approaches to accommodate the significant raised profile of the roadway. In order to
match the roadway section on the south side of the bridge, the project’s construction
limits will be extended to just north of Highway 111. On the north side of the bridge, the
project construction limits will be extended to include a vacant lot immediately north of
the project limits. The vacant lot is owned by the City and will be offered by the City in
Dune Palms Road Low Water Crossing Replacement Noise Study Report 4
Chapter 2 Project Description
the bidding documents to be used for storage and construction staging by the contractor
for the construction of this project.
As a part of the bridge construction, concrete slope protection will be installed along the
north side of the channel. Additionally, minor removal and replacement of slope
protection will be required on the south side of channel west of the proposed bridge and
extension of slope protection approximately 300 feet downstream of the proposed bridge.
The slope protection is needed for scour countermeasures. As a result of the proposed
cast-in-place drilled shaft bridge construction, scour protection within the bottom of the
channel should not be required.
The project will also include the following additional improvements:
• Railing Architectural treatment. The bridge design will incorporate railing
architectural treatment as required by the City’s standard design.
• Integration of a regional Bike/Pedestrian/NEV corridor (CV Link). The
Coachella Valley Association of Governments (CVAG) and the communities
within the Coachella Valley are working together on the implementation of a
regional Bike/Pedestrian/NEV corridor (CV Link) along Whitewater River
and Coachella Valley Storm Water Channel. The project design will be
consistent with these plans by allowing for the integration of a trail under
crossing within the southern slope protection, which also includes a trail
connector to the pedestrian and bike facilities proposed along Dune Palms
Road in the project area.
• Utility Relocation. The project will also require utility relocations for
overhead electrical distribution lines (Imperial Irrigation District facility),
adjustment to both water valve can and lids and the manhole covers, minor
12” ductile iron pipe water main relocations at each bridge abutment, and
relocation of both a 12” and 18” sewer line at the northern bridge abutment.
Right-of-Way Requirements
The project will require right-of-way acquisition on the northeast and southeast corners of
the proposed bridge. The existing development at the northeast corner of the proposed
bridge consists of a Mobile Home Park with one single family home. Some of the mobile
homes adjacent to the Dune Palms Road are encroaching within the street right of way.
The project may require the acquisition of the single-family residence and relocation of
Dune Palms Road Low Water Crossing Replacement Noise Study Report 5
Chapter 2 Project Description
two mobile homes residents. The project will be designed to avoid and minimize
relocation impacts of the mobile homes. At the southeast corner of the crossing, the
existing parcel is currently an undeveloped commercial parcel. Acquisition for the
vacant parcel will consist of a strip acquisition parallel with Dune Palms Road.
Temporary Construction Bypass
The existing roadway will be modified to construct a temporary bypass road. The
temporary bypass will allow for staged construction of the bridge, and maintaining
vehicle and pedestrian access at all times. Temporary and short term access impact may
occur during construction, and will require coordination with property owners, the public,
and other stakeholders.
Noise Study Area
The study area for this project includes the segment of Dune Palms Road between
Highway 111 and Westward Ho Drive/Blackhawk Way. The study also includes the two
signalized intersections on either side of this segment of Dune Palms Road that is being
reconstructed. The study intersections and segment are shown in Figure 2-1 and listed
below.
Figure 2-1: Dune Palms Road Project Location and Study Area
Dune Palms Road Low Water Crossing Replacement Noise Study Report 6
Chapter 2 Project Description
1. Dune Palms Road and Westward Ho Drive/Blackhawk Way
2. Dune Palms Road and Highway 111
This report presents the analysis of the following three study scenarios:
• Existing Conditions – operation of the intersections and roadway segment with
existing traffic volumes
• Future 2040 No-Build Conditions – operation of the intersections and roadway
segment with future traffic volumes and existing roadway geometrics (i.e. number
of lanes)
• Future 2040 Build Conditions – operation of the intersection and roadway
segment with future traffic volumes and proposed roadway reconstructions
geometrics
Dune Palms Road Low Water Crossing Replacement Noise Study Report 7
Chapter 3. Fundamentals of Traffic Noise
The following is a brief discussion of fundamental traffic noise concepts. For a detailed
discussion, please refer to Caltrans’ Technical Noise Supplement (TeNS) (Caltrans
2013), a technical supplement to the Protocol that is available on Caltrans Web site
(http://www.dot.ca.gov/hq/env/noise/pub/TeNS_Sept_2013B.pdf).
3.1. Sound, Noise, and Acoustics
Sound can be described as the mechanical energy of a vibrating object transmitted by
pressure waves through a liquid or gaseous medium (e.g., air) to a hearing organ, such as
a human ear. Noise is defined as loud, unexpected, or annoying sound.
In the science of acoustics, the fundamental model consists of a sound (or noise) source, a
receptor, and the propagation path between the two. The loudness of the noise source
and obstructions or atmospheric factors affecting the propagation path to the receptor
determines the sound level and characteristics of the noise perceived by the receptor. The
field of acoustics deals primarily with the propagation and control of sound.
3.1. Frequency
Continuous sound can be described by frequency (pitch) and amplitude (loudness). A
low-frequency sound is perceived as low in pitch. Frequency is expressed in terms of
cycles per second, or Hertz (Hz) (e.g., a frequency of 250 cycles per second is referred to
as 250 Hz). High frequencies are sometimes more conveniently expressed in kilohertz
(kHz), or thousands of Hertz. The audible frequency range for humans is generally
between 20 Hz and 20,000 Hz.
3.2. Sound Pressure Levels and Decibels
The amplitude of pressure waves generated by a sound source determines the loudness of
that source. Sound pressure amplitude is measured in micro-Pascals (mPa). One mPa is
approximately one hundred billionth (0.00000000001) of normal atmospheric pressure.
Sound pressure amplitudes for different kinds of noise environments can range from less
than 100 to 100,000,000 mPa. Because of this huge range of values, sound is rarely
expressed in terms of mPa. Instead, a logarithmic scale is used to describe sound
pressure level (SPL) in terms of decibels (dB). The threshold of hearing for young
people is about 0 dB, which corresponds to 20 mPa.
Dune Palms Road Low Water Crossing Replacement Noise Study Report 8
Chapter 3 Fundamentals of Traffic Noise
3.3. Addition of Decibels
Because decibels are logarithmic units, SPL cannot be added or subtracted through
ordinary arithmetic. Under the decibel scale, a doubling of sound energy corresponds to
a 3-dB increase. In other words, when two identical sources are each producing sound of
the same loudness, the resulting sound level at a given distance would be 3 dB higher
than one source under the same conditions. For example, if one automobile produces an
SPL of 70 dB when it passes an observer, two cars passing simultaneously would not
produce 140 dB—rather, they would combine to produce 73 dB. Under the decibel scale,
three sources of equal loudness together produce a sound level 5 dB louder than one
source.
3.4. A-Weighted Decibels
The decibel scale alone does not adequately characterize how humans perceive noise.
The dominant frequencies of a sound have a substantial effect on the human response to
that sound. Although the intensity (energy per unit area) of the sound is a purely physical
quantity, the loudness or human response is determined by the characteristics of the
human ear.
Human hearing is limited in the range of audible frequencies as well as in the way it
perceives the SPL in that range. In general, people are most sensitive to the frequency
range of 1,000–8,000 Hz, and perceive sounds within that range better than sounds of the
same amplitude in higher or lower frequencies. To approximate the response of the
human ear, sound levels of individual frequency bands are weighted, depending on the
human sensitivity to those frequencies. Then, an “A-weighted” sound level (expressed in
units of dBA) can be computed based on this information.
The A-weighting network approximates the frequency response of the average young ear
when listening to most ordinary sounds. When people make judgments of the relative
loudness or annoyance of a sound, their judgments correlate well with the A-scale sound
levels of those sounds. Other weighting networks have been devised to address high
noise levels or other special problems (e.g., B-, C-, and D-scales), but these scales are
rarely used in conjunction with highway-traffic noise. Noise levels for traffic noise
reports are typically reported in terms of A-weighted decibels or dBA. Table 3-1
describes typical A-weighted noise levels for various noise sources.
Dune Palms Road Low Water Crossing Replacement Noise Study Report 9
Chapter 3 Fundamentals of Traffic Noise
Table 3-1. Typical A-Weighted Noise Levels
Common Outdoor Activities Noise Level
(dBA) Common Indoor Activities
— 110 — Rock band
Jet fly-over at 1000 feet
— 100 —
Gas lawn mower at 3 feet
— 90 —
Diesel truck at 50 feet at 50 mph Food blender at 3 feet
— 80 — Garbage disposal at 3 feet
Noisy urban area, daytime
Gas lawn mower, 100 feet — 70 — Vacuum cleaner at 10 feet
Commercial area Normal speech at 3 feet
Heavy traffic at 300 feet — 60 —
Large business office
Quiet urban daytime — 50 — Dishwasher next room
Quiet urban nighttime — 40 — Theater, large conference room (background)
Quiet suburban nighttime
— 30 — Library
Quiet rural nighttime Bedroom at night, concert hall (background)
— 20 —
Broadcast/recording studio
— 10 —
Lowest threshold of human hearing — 0 — Lowest threshold of human hearing
Source: Caltrans 2013.
3.5. Human Response to Changes in Noise Levels
As discussed above, doubling sound energy results in a 3-dB increase in sound.
However, given a sound level change measured with precise instrumentation, the
subjective human perception of a doubling of loudness will usually be different than what
is measured.
Under controlled conditions in an acoustical laboratory, the trained, healthy human ear is
able to discern 1-dB changes in sound levels, when exposed to steady, single-frequency
(“pure-tone”) signals in the midfrequency (1,000 Hz–8,000 Hz) range. In typical noisy
environments, changes in noise of 1 to 2 dB are generally not perceptible. However, it is
widely accepted that people are able to begin to detect sound level increases of 3 dB in
typical noisy environments. Further, a 5-dB increase is generally perceived as a
distinctly noticeable increase, and a 10-dB increase is generally perceived as a doubling
of loudness. Therefore, a doubling of sound energy (e.g., doubling the volume of traffic
on a highway) that would result in a 3-dB increase in sound, would generally be
perceived as barely detectable.
Dune Palms Road Low Water Crossing Replacement Noise Study Report 10
Chapter 3 Fundamentals of Traffic Noise
3.6. Noise Descriptors
Noise in our daily environment fluctuates over time. Some fluctuations are minor, but
some are substantial. Some noise levels occur in regular patterns, but others are random.
Some noise levels fluctuate rapidly, but others slowly. Some noise levels vary widely,
but others are relatively constant. Various noise descriptors have been developed to
describe time-varying noise levels. The following are the noise descriptors most
commonly used in traffic noise analysis.
• Equivalent Sound Level (L eq ): L eq represents an average of the sound energy
occurring over a specified period. In effect, L eq is the steady-state sound level
containing the same acoustical energy as the time-varying sound that actually occurs
during the same period. The 1-hour A-weighted equivalent sound level (L eq [h]) is
the energy average of A-weighted sound levels occurring during a one-hour period,
and is the basis for noise abatement criteria (NAC) used by Caltrans and FHWA.
• Percentile-Exceeded Sound Level (L xx ): Lxx represents the sound level exceeded
for a given percentage of a specified period (e.g., L 10 is the sound level exceeded
10% of the time, and L90 is the sound level exceeded 90% of the time).
• Maximum Sound Level (L max ): L max is the highest instantaneous sound level
measured during a specified period.
• Day-Night Level (L dn ): Ldn is the energy average of A-weighted sound levels
occurring over a 24-hour period, with a 10-dB penalty applied to A-weighted sound
levels occurring during nighttime hours between 10 p.m. and 7 a.m.
• Community Noise Equivalent Level (CNEL): Similar to Ldn , CNEL is the energy
average of the A-weighted sound levels occurring over a 24-hour period, with a 10-
dB penalty applied to A-weighted sound levels occurring during the nighttime hours
between 10 p.m. and 7 a.m., and a 5-dB penalty applied to the A-weighted sound
levels occurring during evening hours between 7 p.m. and 10 p.m.
3.7. Sound Propagation
When sound propagates over a distance, it changes in level and frequency content. The
manner in which noise reduces with distance depends on the following factors.
Dune Palms Road Low Water Crossing Replacement Noise Study Report 11
Chapter 3 Fundamentals of Traffic Noise
3.7.1. Geometric Spreading
Sound from a localized source (i.e., a point source) propagates uniformly outward in a
spherical pattern. The sound level attenuates (or decreases) at a rate of 6 decibels for
each doubling of distance from a point source. Highways consist of several localized
noise sources on a defined path, and hence can be treated as a line source, which
approximates the effect of several point sources. Noise from a line source propagates
outward in a cylindrical pattern, often referred to as cylindrical spreading. Sound levels
attenuate at a rate of 3 decibels for each doubling of distance from a line source.
3.7.2. Ground Absorption
The propagation path of noise from a highway to a receptor is usually very close to the
ground. Noise attenuation from ground absorption and reflective-wave canceling adds to
the attenuation associated with geometric spreading. Traditionally, the excess attenuation
has also been expressed in terms of attenuation per doubling of distance. This
approximation is usually sufficiently accurate for distances of less than 200 feet. For
acoustically hard sites (i.e., sites with a reflective surface between the source and the
receptor, such as a parking lot or body of water,), no excess ground attenuation is
assumed. For acoustically absorptive or soft sites (i.e., those sites with an absorptive
ground surface between the source and the receptor, such as soft dirt, grass, or scattered
bushes and trees), an excess ground-attenuation value of 1.5 decibels per doubling of
distance is normally assumed. When added to the cylindrical spreading, the excess
ground attenuation results in an overall drop-off rate of 4.5 decibels per doubling of
distance.
3.7.3. Atmospheric Effects
Receptors located downwind from a source can be exposed to increased noise levels
relative to calm conditions, whereas locations upwind can have lowered noise levels.
Sound levels can be increased at large distances (e.g., more than 500 feet) from the
highway due to atmospheric temperature inversion (i.e., increasing temperature with
elevation). Other factors such as air temperature, humidity, and turbulence can also have
significant effects.
3.7.4. Shielding by Natural or Human-Made Features
A large object or barrier in the path between a noise source and a receptor can
substantially attenuate noise levels at the receptor. The amount of attenuation provided
by shielding depends on the size of the object and the frequency content of the noise
source. Natural terrain features (e.g., hills and dense woods) and human-made features
(e.g., buildings and walls) can substantially reduce noise levels. Walls are often
Dune Palms Road Low Water Crossing Replacement Noise Study Report 12
Chapter 3 Fundamentals of Traffic Noise
constructed between a source and a receptor specifically to reduce noise. A barrier that
breaks the line of sight between a source and a receptor will typically result in at least 5
dB of noise reduction. Taller barriers provide increased noise reduction. Vegetation
between the highway and receptor is rarely effective in reducing noise because it does not
create a solid barrier.
Dune Palms Road Low Water Crossing Replacement Noise Study Report 13
Chapter 4. Federal Regulations and State
Policies
This report focuses on the requirements of 23 CFR 772, as discussed below.
4.1. Federal Regulations
4.1.1. 23 CFR 772
23 CFR 772 provides procedures for preparing operational and construction noise studies
and evaluating noise abatement considered for federal and Federal-aid highway projects.
Under 23 CFR 772.7, projects are categorized as Type I, Type II, or Type III projects.
• FHWA defines a Type I project as a proposed federal or federal-aid highway
project for the construction of a highway on a new location or the physical
alteration of an existing highway which significantly changes either the horizontal
or vertical alignment of the highway. The following projects are also considered
to be Type I projects:
• The addition of a through-traffic lane(s). This includes the addition of a through-
traffic lane that functions as a high-occupancy vehicle (HOV) lane, high-
occupancy toll (HOT) lane, bus lane, or truck climbing lane,
• The addition of an auxiliary lane, except for when the auxiliary lane is a turn lane,
• The addition or relocation of interchange lanes or ramps added to a quadrant to
complete an existing partial interchange,
• Restriping existing pavement for the purpose of adding a through traffic lane or
an auxiliary lane,
• The addition of a new or substantial alteration of a weigh station, rest stop, ride-
share lot, or toll plaza.
If a project is determined to be a Type I project under this definition, the entire project
area as defined in the environmental document is a Type I project.
A Type II project is a noise barrier retrofit project that involves no changes to highway
capacity or alignment. A Type III project is a project that does not meet the
Dune Palms Road Low Water Crossing Replacement Noise Study Report 14
Chapter 4 Federal Regulations and State Policies
classifications of a Type I or Type II project. Type III projects do not require a noise
analysis.
Under 23 CFR 772.11, noise abatement must be considered for Type I projects if the
project is predicted to result in a traffic noise impact. In such cases, 23 CFR 772 requires
that the project sponsor “consider” noise abatement before adoption of the final NEPA
document. This process involves identification of noise abatement measures that are
reasonable, feasible, and likely to be incorporated into the project, and of noise impacts
for which no apparent solution is available.
Traffic noise impacts, as defined in 23 CFR 772.5, occur when the predicted noise level
in the design-year approaches or exceeds the NAC specified in 23 CFR 772, or a
predicted noise level substantially exceeds the existing noise level (a “substantial” noise
increase). 23 CFR 772 does not specifically define the terms “substantial increase” or
“approach”; these criteria are defined in the Protocol, as described below.
Table 4-1 summarizes NAC corresponding to various land use activity categories.
Activity categories and related traffic noise impacts are determined based on the actual or
permitted land use in a given area.
4.1.2. Traffic Noise Analysis Protocol for New Highway Construction and
Reconstruction Projects
The Protocol specifies the policies, procedures, and practices to be used by agencies that
sponsor new construction or reconstruction of federal or Federal-aid highway projects.
The Protocol defines a noise increase as substantial when the predicted noise levels with
project implementation exceed existing noise levels by 12 dBA or more. The Protocol
also states that a sound level is considered to approach an NAC level when the sound
level is within 1 dB of the NAC identified in 23 CFR 772 (e.g., 66 dBA is considered to
approach the NAC of 67 dBA, but 65 dBA is not).
The Technical Noise Supplement to the Protocol provides detailed technical guidance for
the evaluation of highway traffic noise. This includes field measurement methods, noise
modeling methods, and report preparation guidance.
Dune Palms Road Low Water Crossing Replacement Noise Study Report 15
Chapter 4 Federal Regulations and State Policies
Table 4-1. Activity Categories and Noise Abatement Criteria (23 CFR 772)
Activity
Category
Activity
L eq [h]1 Evaluation Location Description of Activities
A 57 Exterior Lands on which serenity and quiet are of extraordinary
significance and serve an important public need and where the
preservation of those qualities is essential if the area is to
continue to serve its intended purpose.
B2 67 Exterior Residential.
C2 67 Exterior Active sport areas, amphitheaters, auditoriums, campgrounds,
cemeteries, day care centers, hospitals, libraries, medical
facilities, parks, picnic areas, places of worship, playgrounds,
public meeting rooms, public or nonprofit institutional
structures, radio studios, recording studios, recreation areas,
Section 4(f) sites, schools, television studios, trails, and trail
crossings.
D 52 Interior Auditoriums, day care centers, hospitals, libraries, medical
facilities, places of worship, public meeting rooms, public or
nonprofit institutional structures, radio studios, recording
studios, schools, and television studios.
E 72 Exterior Hotels, motels, offices, restaurants/bars, and other developed
lands, properties, or activities not included in A–D or F.
F Agriculture, airports, bus yards, emergency services,
industrial, logging, maintenance facilities, manufacturing,
mining, rail yards, retail facilities, shipyards, utilities (water
resources, water treatment, electrical), and warehousing.
G Undeveloped lands that are not permitted.
1 The L eq (h) activity criteria values are for impact determination only and are not design standards for noise
abatement measures. All values are A-weighted decibels (dBA).
2 Includes undeveloped lands permitted for this activity category.
4.2. State Regulations and Policies
4.2.1. California Environmental Quality Act (CEQA)
Noise analysis under the California Environmental Quality Act (CEQA) may be required
regardless of whether or not the project is a Type I project. The CEQA noise analysis is
completely independent of the 23 CFR 772 analysis done for NEPA. Under CEQA, the
baseline noise level is compared to the build noise level. The assessment entails looking
at the setting of the noise impact and then how large or perceptible any noise increase
would be in the given area. Key considerations include: the uniqueness of the setting, the
sensitive nature of the noise receptors, the magnitude of the noise increase, the number of
residences affected, and the absolute noise level
Dune Palms Road Low Water Crossing Replacement Noise Study Report 16
Chapter 4 Federal Regulations and State Policies
The significance of noise impacts under CEQA are addressed in the environmental
document rather than the NSR. Even though the NSR (or noise technical memorandum)
does not specifically evaluate the significance of noise impacts under CEQA, it must
contain the technical information that is needed to make that determination in the
environmental document.
4.2.2. Section 216 of the California Streets and Highways Code
Section 216 of the California Streets and Highways Code relates to the noise effects of a
proposed freeway project on public and private elementary and secondary schools.
Under this code, a noise impact occurs if, as a result of a proposed freeway project, noise
levels exceed 52 dBA-L eq (h) in the interior of public or private elementary or secondary
classrooms, libraries, multipurpose rooms, or spaces. This requirement does not replace
the “approach or exceed” NAC criterion for FHWA Activity Category E for classroom
interiors, but it is a requirement that must be addressed in addition to the requirements of
23 CFR 772.
If a project results in a noise impact under this code, noise abatement must be provided to
reduce classroom noise to a level that is at or below 52 dBA-Leq (h). If the noise levels
generated from freeway and roadway sources exceed 52 dBA-L eq (h) prior to the
construction of the proposed freeway project, then noise abatement must be provided to
reduce the noise to the level that existed prior to construction of the project.
Dune Palms Road Low Water Crossing Replacement Noise Study Report 17
Chapter 5. Study Methods and Procedures
5.1. Methods for Identifying Land Uses and Selecting Noise
Measurement and Modeling Receiver Locations
A field investigation was conducted to identify land uses that could be subject to traffic
and construction noise impacts from the proposed project. Existing land uses in the
project area were categorized by land use type and Activity Category as defined in Table
4-1, and the extent of frequent human use. As stated in the Protocol, noise abatement is
only considered where frequent human use occurs and where a lowered noise level would
be of benefit. Although all land uses are evaluated in this analysis, the focus is on
locations of frequent human use that would benefit from a lowered noise level.
Accordingly, this impact analysis focuses on locations with defined outdoor activity
areas, such as residential backyards and common use areas at multi-family residences.
The geometry of the project relative to nearby existing and planned land uses was also
identified.
Short-term measurement locations were selected to represent each major developed area
within the project area. Also, short-term measurement locations were selected to serve as
representative modeling locations.
5.2. Field Measurement Procedures
A field noise study was conducted in accordance with recommended procedures in TeNS.
The following is a summary of the procedures used to collect short-term and long term
sound level data.
5.2.1. Short-Term Measurements
Short-term monitoring was conducted at three locations on Tuesday, April 7, 2015, using
an Bruel & Kjaer Model BK2238 Precision Type 1 sound level meters (serial numbers
2160297). The calibration of the meter was checked before and after the measurement
using an Bruel & Kjaer Model BK4230 calibrator (serial number 1351753).
Measurements were taken over a 15-minute period at each site. Short-term monitoring
was conducted at Activity Category B land uses. The short-term measurement locations
are identified in Figure 5-1.
[Dune Palms Road Low Water Crossing Replacement Noise Study Report 18
Chapter 5 Study Methods and Procedures
Figure 5-1. Analysis Areas and Noise Monitoring Positions
AREA - A
AREA - B
Westward Ho Drive
Whitewater River Dune Palms RoadM5
M2
M3
M4
M1
ST-3
ST-2
ST-1
0 125 250 375 500Feet
Legend
Model Site
Measurement Site
Dune Palms Road Low Water Crossing Replacement Noise Study Report 19
Chapter 5 Study Methods and Procedures
During the short-term measurements, field staff attended each meter. Minute-to-minute
L eq values collected during the measurement period (typically 15 minutes in duration)
were logged manually, and dominant noise sources observed during each individual 1-
minute period were also identified and logged. Using this approach, those minutes when
traffic noise was observed to be a dominant contributor to noise levels at a given
measurement location could be distinguished from one-minute noise levels where other
non-traffic noise sources (such as aircraft and lawn equipment) contributed significantly
to existing noise levels.
Traffic on Dune Palm Road was classified and counted during short-term noise
measurements. Vehicles were classified as automobiles, medium-duty trucks, or heavy-
duty trucks. An automobile was defined as a vehicle with two axles and four tires that
are designed primarily to carry passengers. Small vans and light trucks were included in
this category. Medium-duty trucks included all cargo vehicles with two axles and six
tires. Heavy-duty trucks included all vehicles with three or more axles. The posted
speed on Dune Palm Road ranged between 25 and 40 mph.
5.3. Traffic Noise Levels Prediction Methods
Traffic noise levels were predicted using the FHWA Traffic Noise Model Version 2.5
(TNM 2.5). (Use the current applicable model version.) TNM 2.5 is a computer model
based on two FHWA reports: FHWA-PD-96-009 and FHWA-PD-96-010 (FHWA 1998a,
1998b). Key inputs to the traffic noise model were the locations of roadways, traffic mix
and speed, shielding features (e.g., topography and buildings), noise barriers, ground
type, and receptors. Three-dimensional representations of these inputs were developed
using CAD drawings, aerials, and topographic contours provided by the Bengal
Engineering, Inc.
Traffic noise was evaluated under existing conditions, design-year no -project conditions,
and design-year conditions with the project alternative. Loudest-hour traffic volumes,
vehicle classification percentages, and traffic speeds under existing and design-year
(2040) conditions were provided by Parsons Brinckerhoff (Traffic Analysis Report,
March 2015) for input into the traffic noise model. The highest average traffic volumes
on Dune Palms Road are predicted to occur during the AM peak hour; therefore AM peak
hour traffic volumes were used in the model. Tables A-1 to A-3 in Appendix A
summarize the traffic volumes and assumptions used for modeling existing and design-
year conditions with and without the project alternative.
Dune Palms Road Low Water Crossing Replacement Noise Study Report 20
Chapter 5 Study Methods and Procedures
To validate the accuracy of the model calculations, TNM 2.5 was used to compare
measured traffic noise levels to modeled noise levels at field measurement locations. For
each receptor, traffic volumes counted during the short-term measurement periods were
normalized to 1-hour volumes. These normalized volumes were assigned to the
corresponding project area roadways to simulate the noise source strength at the
roadways during the actual measurement period. Modeled and measured sound levels
were then compared to determine the accuracy of the model and if additional adjustment
of the model was necessary.
5.4. Methods for Identifying Traffic Noise Impacts and
Consideration of Abatement
Traffic noise impacts are considered to occur at receptor locations where predicted
design-year noise levels are 12 dB or more greater than existing noise levels, or where
predicted design-year noise levels approach or exceed the NAC for the applicable activity
category. Where traffic noise impacts are identified, noise abatement must be considered
for reasonableness and feasibility as required by 23 CFR 772 and the Protocol.
According to the Protocol, abatement measures are considered acoustically feasible if a
minimum noise reduction of 5 dB at impacted receptor locations is predicted with
implementation of the abatement measures. In addition, barriers should be designed to
intercept the line-of-sight from the exhaust stack of a truck to the first tier of receptors, as
required by the Highway Design Manual, Chapter 1100. Other factors that affect
feasibility include topography, access requirements for driveways and ramps, presence of
local cross streets, utility conflicts, other noise sources in the area, and safety
considerations.
The overall reasonableness of noise abatement is determined by the following three
factors:
• The noise reduction design goal.
• The cost of noise abatement.
• The viewpoints of benefited receptors (including property owners and
residents of the benefited receptors).
The Caltrans’ acoustical design goal is that a barrier must be predicted to provide at least
7 dB of noise reduction at one benefited receptor. This design goal applies to any receptor
and is not limited to impacted receptors.
Dune Palms Road Low Water Crossing Replacement Noise Study Report 21
Chapter 5 Study Methods and Procedures
The Protocol defines the procedure for assessing reasonableness of noise barriers from a
cost perspective. Based on 2014 construction costs an allowance of $71,000 is provided
for each benefited receptor (i.e., receptors that receive at least 5 dB of noise reduction
from a noise barrier). The total allowance for each barrier is calculated by multiplying
the number of benefited receptors by $71,000. The allowance should be adjusted annually
based on the published Caltrans Construction Price Index (CPI) and a base 2011
allowance of $55,000. If the estimated construction cost of a barrier is less than the total
calculated allowance for the barrier, the barrier is considered reasonable from a cost
perspective. The viewpoints of benefits receptors are determined by a survey that is
typically conducted after completion of the noise study report. The process for
conducting the survey is described in detail in the Protocol.
The noise study report identifies traffic noise impacts and evaluates noise abatement for
acoustical feasibility. It also reports information that will be used in the reasonableness
analysis including if the 7 dB design goal reduction in noise can be achieved and the
abatement allowances. The noise study report does not make any conclusions regarding
reasonableness. The feasibility and reasonableness of noise abatement is reported in the
Noise Abatement Decision Report.
Dune Palms Road Low Water Crossing Replacement Noise Study Report 22
Chapter 6. Existing Noise Environment
6.1. Existing Land Uses
A field investigation was conducted to identify land uses that could be subject to traffic
and construction noise impacts from the proposed project. The following land uses were
identified in the project area:
• Single-family residences: Activity Category B
• Places of worship: Activity Category C (exterior), Activity Category D (interior)
• School: Activity Category C (exterior), Activity Category D (interior)
• Commercial retail uses: Activity Category F
Although all developed land uses are evaluated in this analysis, noise abatement is only
considered for areas of frequent human use that would benefit from a lowered noise level.
Accordingly, this impact analysis focuses on locations with defined outdoor activity
areas, such as residential backyards and common use areas at multi-family residences.
Land uses in the project area are identified in Figure 5-1.
• Area A: Located on the northeast side of Dune Palms Road between CVSC and
Westward Ho Drive. A mobile home park (Activity Category B) and a church
(Activity Category C-D) is located in this area. This area is generally flat.
Backyards face the street. A five to six foot tall wooden fence shields the residences
in this area. (Refer to Figure 5-1.)
• Area B: Located on the northwest side of Dune Palms Road between CVSC and
Westward Ho Drive. La Quinta High School (Activity Category C-D) is located in
this area. This area is generally flat. No sound barrier or topographical shielding
occurs between the roadway and the high school area. (Refer to Figure 5-1.)
6.2. Noise Measurement Results
The existing noise environment in the project area is characterized below based on short-
term noise monitoring that was conducted.
Dune Palms Road Low Water Crossing Replacement Noise Study Report 23
Chapter 6 Existing Noise Environment
6.2.1. Short-Term Monitoring
Table 6-1 summarizes the results of the short-term noise monitoring conducted in the
project area.
Table 6-1. Summary of Short-Term Measurements
Position Address Area Land Uses Start
Time
Duration
(minutes)
Measured
L eq Autos Medium
Trucks
Heavy
Trucks
Observed
Speed
(mph)
ST-1 46300
Dune
Palms Rd
A Church 11:00
a.m.
15 59.4 119 4 0 30
ST-2 46400
Dune
Palms Rd
#58
A Residential 11:30
a.m.
15 56.0 120 3 0 30
ST-3 46500
Dune
Palms Rd
A Residential 12:00
a.m.
15 69.4 155 9 0 40
Note: Refer to Figure 5-1 for measurement locations and boundaries of each area.
TNM 2.5 was used to compare measured traffic noise levels to modeled noise levels at
field measurement locations. Table 6-3 compares measured and modeled noise levels at
each measurement location (see Figure 5-1). The predicted sound levels are within 1 dB
of the measured sound levels for ST-1 and ST-2 and are, therefore, considered to be in
reasonable agreement with the measured sound levels. Measurement site ST-3 was 3.4
dBA higher that what was measured. The existing roadway within the riverbed is graded
with vertical grooves to assist with drainage. However, the grooves create a rough texture
on the roadway which increases the tire noise. A +3.0 K-factor will be added to the
existing and No Build option.
Table 6-3. Comparison of Measured to Predicted
Sound Levels in the TNM Model
Measurement
Position
Measured Sound
Level (dBA)
Predicted Sound
Level (dBA)
Measured minus
Predicted (dB)
ST-1 59.4 59.0 + 0.4
ST-2 56.0 55.8 + 0.2
ST-3 67.4 64.0 + 3.4
Table B-1 in Appendix B presents existing noise levels at each receptor.
Dune Palms Road Low Water Crossing Replacement Noise Study Report 24
Chapter 7. Future Noise Environment,
Impacts, and Considered
Abatement
7.1. Future Noise Environment and Impacts
Table B-1 in Appendix B summarizes the traffic noise modeling results for existing
conditions and design-year conditions with and without the project. Predicted design-
year traffic noise levels with the project are compared to existing conditions and to
design-year no-project conditions. The comparison to existing conditions is included in
the analysis to identify traffic noise impacts as defined under 23 CFR 772. The
comparison to no-project conditions indicates the direct effect of the project.
As stated in the TeNS, modeling results are rounded to the nearest decibel before
comparisons are made. In some cases, this can result in relative changes that may not
appear intuitive. An example would be a comparison between calculated sound levels of
64.4 and 64.5 dBA. The difference between these two values is 0.1 dB. However, after
rounding, the difference is reported as 1 dB.
Modeling results in Appendix B, Table B-1, indicate the following:
Area A
The traffic noise modeling results in Table B-1 indicate that traffic noise levels at the
church and residences in Area A are predicted to be in the range of 61 to 65 dBA L eq (h)
in the design-year. The results also indicate that the increase in noise between existing
conditions and the design-year is predicted to be 4 to 7dB. Because the predicted noise
levels in the design-year are not predicted to approach or exceed the noise abatement
criterion (67 dBA L eq [h]) or result in a substantial increase in noise, no traffic noise
impacts are predicted in Area A.
Because the church has an interior noise abatement criterion in addition to the exterior
criterion, interior noise must be considered at the church as well. From Table 6 in the
FHWA Highway Traffic Noise Analysis and Abatement Guidance document, the
building noise reduction factor for standard construction with ordinary windows closed is
20 dB. The interior noise level in the church in the design-year is therefore predicted to
be 45 dBA L eq (h). Because this predicted design-year noise level does not exceed the
Dune Palms Road Low Water Crossing Replacement Noise Study Report 25
Chapter 7 Future Noise Environment, Impacts, and Considered Abatement
interior NAC of 52 dBA Leq(h), no interior traffic noise impacts are predicted at the
church.
Area B
The traffic noise modeling results in Table B-1 indicate that traffic noise levels at school
in Area B are predicted to be 61 dBA L eq (h) in the design-year. The results also indicate
that the increase in noise between existing conditions and the design-year is predicted to
be 5 to 6 dB. Because the predicted noise levels in the design-year are not predicted to
approach or exceed the noise abatement criterion (67 dBA L eq [h]) or result in a
substantial increase in noise, no traffic noise impacts are predicted in Area B.
7.2. Preliminary Noise Abatement Analysis
Noise abatement is considered where noise impacts are predicted in areas of frequent
human use that would benefit from a lowered noise level. According to 23 CFR
772(13)(c) and 772(15)(c), federal funding may be used for the following abatement
measures:
• Construction of noise barriers, including acquisition of property rights, either
within or outside the highway right-of-way.
• Traffic management measures including, but not limited to, traffic control devices
and signing for prohibition of certain vehicle types, time-use restrictions for
certain vehicle types, modified speed limits, and exclusive lane designations.
• Alteration of horizontal and vertical alignments.
• Acquisition of real property or interests therein (predominantly unimproved
property) to serve as a buffer zone to preempt development which would be
adversely impacted by traffic noise.
• Noise insulation of Activity Category D land use facilities listed in Table 1. Post-
installation maintenance and operational costs for noise insulation are not eligible
for Federal-aid funding.
7.2.1. Area A
No traffic noise impacts are predicted for Area A. Accordingly, noise abatement does not
need to be considered in this area.
Dune Palms Road Low Water Crossing Replacement Noise Study Report 26
Chapter 7 Future Noise Environment, Impacts, and Considered Abatement
7.2.2. Area B
No traffic noise impacts are predicted for Area A. Accordingly, noise abatement does not
need to be considered in this area.
Dune Palms Road Low Water Crossing Replacement Noise Study Report 27
Chapter 8. Construction Noise
During construction of the project, noise from construction activities may intermittently
dominate the noise environment in the immediate area of construction. Noise associated
with construction is controlled by La Quinta’s Municipal Code, Section 6.08.050 and the
General Standard Conditions, “Noise Control,” which states the following:
It is a nuisance and it is unlawful, for any person to be engaged or employed, or
for any person to cause any other person to be engaged or employed, in any work
of construction, erection, alteration, repair, addition to, or improvement to realty,
except between the hours set forth as follows:
October 1th through April 30th Monday – Friday 7:00 AM – 5:30 PM
Saturday 8:00 AM – 5:00 PM
Sunday & Holidays None
May 1st through September 30th Monday – Friday 6:00 AM – 7:00 PM
Saturday 8:00 AM – 5:00 PM
Sunday & Holidays None
Equip an internal combustion engine with the manufacturer-recommended
muffler. Do not operate an internal combustion engine on the job site without the
appropriate muffler.
Table 8-1 summarizes noise levels produced by construction equipment that is commonly
used on roadway construction projects. Construction equipment is expected to generate
noise levels ranging from 70 to 90 dB at a distance of 50 feet, and noise produced by
construction equipment would be reduced over distance at a rate of about 6 dB per
doubling of distance.
Table 8-1. Construction Equipment Noise
Equipment Maximum Noise Level (dBA at 50 feet)
Scrapers 89
Bulldozers 85
Heavy Trucks 88
Backhoe 80
Pneumatic Tools 85
Concrete Pump 82
Source: Federal Transit Administration, 2006. See
also: http://www.fhwa.dot.gov/environment/noise/construction_noise/handbook/handbook09.cfm
Dune Palms Road Low Water Crossing Replacement Noise Study Report 28
Chapter 9 References
No adverse noise impacts from construction are anticipated because construction would
be conducted in accordance with La Quinta’s Municipal Code, Section 6.08.050 and the
General Standard Conditions. Construction noise would be short-term, intermittent, and
overshadowed by local traffic noise.
Dune Palms Road Low Water Crossing Replacement Noise Study Report 29
Chapter 9 References
Chapter 9. References
Caltrans. 2013. Technical Noise Supplement. September. Sacramento, CA:
Environmental Program, Noise, Air Quality, and Hazardous Waste Management
Office. Sacramento, CA. Available:
(http://www.dot.ca.gov/hq/env/noise/pub/TeNS_Sept_2013B.pdf).
———. 2011. Traffic Noise Analysis Protocol for New Highway Construction,
Reconstruction, and Retrofit Barrier Projects. May. Sacramento, CA. Available:
(http://www.dot.ca.gov/hq/env/noise/pub/ca_tnap_may2011.pdf).
Caltrans. 2013. Transportation and Construction Vibration Guidance Manual.
September. Sacramento, CA: Environmental Program, Noise, Air Quality, and
Hazardous Waste Management Office. Sacramento, CA. Available:
(http://www.dot.ca.gov/hq/env/noise/pub/TCVGM_Sep13_FINAL.pdf)
Federal Highway Administration. 2011. Highway Traffic Noise: Analysis and
Abatement Guidance. December. Washington D.C. FHWA-HEP-10-025.
Available:
(http://www.fhwa.dot.gov/environment/noise/regulations_and_guidance/analysis_
and_abatement_guidance/revguidance.pdf)
———. 1998a. FHWA Traffic Noise Model, Version 1.0 User’s
Guide. January. FHWA-PD-96-009. Washington D.C.
———. 1998b. FHWA Traffic Noise Model, Version 1.0. February. FHWA-PD-96-
010. Washington D.C.
———. 2006. Roadway Construction Noise Model. February, 15, 2006. Available:
(http://www.fhwa.dot.gov/environment/noise/construction_noise/rcnm/).
Federal Transit Administration. 2006. Transit Noise and Vibration Impact Assessment.
(DOT-T-95-16.) Office of Planning, Washington, DC. Prepared by Harris Miller
Miller & Hanson, Inc. Burlington, MA.
Dune Palms Road Low Water Crossing Replacement Noise Study Report 30
Appendix A Traffic Data
Dune Palms Road Low Water Crossing Replacement Noise Study Report 31
Table A-1. Traffic Data for Existing Conditions
Segment Number
of Lanes
Total
Volume PM
Peak Hour
Volume
Auto Medium Trucks Heavy Trucks Speed
(A/MT/HT
) % Volume % Volume % Volume
Mainline
NB Dune Palms
Road
Between Hwy 111 and
Westward Ho Drive 1 299 94.8% 283 5.0% 15 0.2% 1 30/30/30
SB Dune Palms
Road
Between Hwy 111 and
Westward Ho Drive 2 305 97.8% 298 2.0% 6 0.2% 1 30/30/30
Table A-2. Traffic Data for Design Year (2040) No-Project Conditions
Segment Number
of Lanes
Total
Volume PM
Peak Hour
Volume
Auto Medium Trucks Heavy Trucks
Speed % Volume % Volume % Volume
Mainline
NB Dune Palms
Road
Between Hwy 111 and
Westward Ho Drive 1 1166 94.8% 1106 5.0% 58 0.2% 2 30/30/30
SB Dune Palms
Road
Between Hwy 111 and
Westward Ho Drive 2 1294 97.8% 1266 2.0% 26 0.2% 3 30/30/30
Dune Palms Road Low Water Crossing Replacement Noise Study Report 32
Table A-3. Traffic Data for Design Year (2040) with Project Conditions
Segment Number
of Lanes
Total
Volume PM
Peak Hour
Volume
Auto Medium Trucks Heavy Trucks
Speed % Volume % Volume % Volume
Mainline
NB Dune Palms
Road
Between Hwy 111 and
Westward Ho Drive 2 1166 94.8% 1106 5.0% 58 0.2% 2 30/30/30
SB Dune Palms
Road
Between Hwy 111 and
Westward Ho Drive 2 1294 97.8% 1266 2.0% 26 0.2% 3 30/30/30
Dune Palms Road Low Water Crossing Replacement Noise Study Report 33
Appendix B Predicted Future Noise Levels
and Noise Barrier Analysis
Dune Palms Road Low Water Crossing Replacement Noise Study Report 34
Table B-1. Predicted Future Noise and Barrier Analysis Receptor I.D. Area Barrier I.D. Land Use Number of Dwelling Units Address Existing Noise Level Leq(h), dBA SR-26 Future Worst Hour Noise Levels - L eq (h), dBA Design Year Noise Level without Project Leq(h), dBA Design Year Noise Level with Project Leq(h), dBA Design Year Noise Level without Project minus Existing Conditions Leq(h), dBA Design Year Noise Level with Project Minus No Project Conditions Leq(h), dBA Activity Category (NAC) Impact Type Noise Prediction with Barrier, Barrier Insertion Loss (I.L.), and
Number of Benefited Receptors (NBR)
6 feet 8 feet 10 feet 12 feet 14 feet 16 feet Leq(h) I.L. NBR Leq(h) I.L. NBR Leq(h) I.L. NBR Leq(h) I.L. NBR Leq(h) I.L. NBR Leq(h) I.L. NBR ST-1 A - Church 1 46300 Dune
Palms Drive 59 65 65 6 0 C (67) None – – – – – – – – – – – – – – – – – –
M2 A - Residential 2 46400 Dune
Palms Drive 54 60 61 6 1 B (67) None – – – – – – – – – – – – – – – – – –
ST-2 A NB-1 Residential 2 46400 Dune
Palms Drive 58 63 64 5 1 B (67) None – – – – – – – – – – – – – – – – – –
M1 A NB-1 Residential 2 46400 Dune
Palms Drive 54 60 61 6 1 B (67) None – – – – – – – – – – – – – – – – – –
ST-3^ A NB-1 Residential 2 46400 Dune
Palms Drive 65 71 PROPERTY ACQUISITION
M5 A NB-1 Residential 1 46400 Dune
Palms Drive 59 65 63 6 -2 B (67) None – – – – – – – – – – – – – – – – – –
M3 B - School None
79255
Westward Ho
Drive
56 62 61 6 -1 C (67) None – – – – – – – – – – – – – – – – – –
M4 B - School None
79255
Westward Ho
Drive
55 61 61 6 0 C (67) None – – – – – – – – – – – – – – – – – –
Note: All NAC are exterior unless note. A/E= Future noise conditions approach or exceed the Noise Abatement Criteria; SI = Substantial Increase
^ Property Acquisition.
[Dune Palms Road Low Water Crossing Replacement Noise Study Report 35
Appendix C Supplemental Data
Dune Palms Road Low Water Crossing Replacement Noise Study Report 36
Site 1
Site 2
Site 3