4.10 NOISE - Our Palo Alto 2030

Transcription

COMPREHENSIVE PLAN UPDATE DRAFT EIR
CITY OF PALO ALTO
NOISE
4.10 NOISE
This chapter describes the regulatory framework and existing conditions related to noise sources and the
overall noise environment in Palo Alto, evaluates the potential impacts on the noise environment that could
occur by adopting and implementing the proposed Plan, and evaluates potential impacts of the noise
environment on development under the proposed Plan. The technical data and modeling used to for the
analysis in this chapter are located in Appendix F, Technical Noise Data and Modeling.
4.10.1 ENVIRONMENTAL SETTING
4.10.1.1 OVERVIEW OF NOISE FUNDAMENTALS
Noise Descriptors
Noise is most often defined as unwanted sound that is, loud, unpleasant, unexpected, or otherwise
undesirable. Although sound can be easily measured, the perception of noise and the physical response to
sound complicate the analysis of its impact on people. People judge the relative magnitude of sound
sensation in subjective terms such as “noisiness” or “loudness.”
The following are brief definitions of terminology used in this section:

Sound. A disturbance created by a vibrating object, which when transmitted by pressure waves through
a medium such as air, is capable of being detected by a receiving mechanism, such as the human ear or a
microphone.

Noise. Sound that is loud, unpleasant, unexpected, or otherwise undesirable.

Decibel (dB). A unit-less measure of sound on a logarithmic scale.

A-Weighted Decibel (dBA). An overall frequency-weighted sound level in decibels that
approximates the frequency response of the human ear.

Equivalent Continuous Noise Level (L eq ). The level of a steady sound which, in a stated time
period and at a stated location, has the same A-weighted sound energy as the time-varying sound.

Statistical Sound Level (L n ). The sound level that is exceeded “n” percent of time during a given
sample period. For example, the L 50 level is the statistical indicator of the time-varying noise signal that
is exceeded 50 percent of the time (during each sampling period), which is half of the sampling time,
the changing noise levels are above this value and half of the time they are below it. This is called the
“median sound level.” The L 10 level, likewise, is the value that is exceeded 10 percent of the time (i.e.,
near the maximum) and this is often known as the “intrusive sound level.” The L 90 is the sound level
exceeded 90 percent of the time and is often considered the “effective background level” or “residual
noise level.”
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
Day-Night Sound Level (L dn or DNL). The energy-average of the A-weighted sound levels
occurring during a 24-hour period, with 10 dB added to the sound levels occurring during the period
from 10:00 PM to 7:00 AM.

Community Noise Equivalent Level (CNEL). The energy-average of the A-weighted sound levels
occurring during a 24-hour period, with five dB added to the levels occurring during the period from
7:00 PM to 10:00 PM and 10 dB added to the sound levels occurring during the period from 10:00 PM
to 7:00 AM.
Note: For general community/environmental noise, CNEL and L dn values rarely differ by more than
one dB. As a matter of practice, L dn and CNEL values are considered to be equivalent and are treated as
interchangeable in this assessment.
Characteristics of Sound
Sound is a pressure wave transmitted through the air. It is described in terms of amplitude (measured in
decibels), frequency or pitch (measured in Hertz [Hz] or cycles per second), and duration (measured in
seconds or minutes). The standard unit of measurement of the loudness of sound is the decibel (dB).
Changes of one to three dB are detectable under quiet, controlled conditions and changes of less than
one dBA are usually indiscernible. A three-dB change in noise levels is considered the minimum change that
is detectable with human hearing in outside environments. A change of five dB is readily discernable to most
people in an exterior environment whereas a 10 dBA change is perceived as a doubling (or halving) of the
sound.
The human ear is not equally sensitive to all frequencies. Sound waves below 16 Hz are not heard at all and
are “felt” more as a vibration. Similarly, while people with extremely sensitive hearing can hear sounds as
high as 20,000 Hz, most people cannot hear above 15,000 Hz. In all cases, hearing acuity falls off rapidly
above about 10,000 Hz and below about 200 Hz. Since the human ear is not equally sensitive to sound at all
frequencies, a special frequency dependent rating scale is usually used to relate noise to human sensitivity.
The A-weighted decibel scale (dBA) performs this compensation by discriminating against frequencies in a
manner approximating the sensitivity of the human ear.
Measurement of Sound
Sound intensity is measured through the A-weighted measure to correct for the relative frequency response
of the human ear. That is, an A-weighted noise level deemphasizes low and very high frequencies of sound
similar to the human ear’s de-emphasis of these frequencies.
Unlike linear units such as inches or pounds, decibels are measured on a logarithmic scale, representing
points on a sharply rising curve. This logarithmic scale is used to better account for the large variations in
pressure amplitude (the above range of human hearing, 0 to 140 dBA, represents a ratio in pressures of 100
trillion to one). All noise levels in this study are relative to the industry-standard pressure reference value of
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20 micropascals. Because of the physical characteristics of noise transmission and perception, the relative
loudness of sound does not closely match the actual amounts of sound energy. Table 4.10-1 presents the
subjective effect of changes in sound pressure levels. In practical application, an increase of 10 dB is
ten times more intense than one dB, while 20 dB is 100 times more intense, and 30 dB is 1,000 times more
intense. A sound as soft as human breathing is about ten times greater than zero dB. The decibel system of
measuring sound gives a rough connection between the physical intensity of sound and its perceived
loudness to the human ear. Ambient sounds generally range from 30 dBA (very quiet) to 100 dBA (very
loud).
TABLE 4.10-1
CHANGE IN APPARENT LOUDNESS IN OUTSIDE ENVIRONMENTS
± 3 dB
Threshold of human perceptibility
± 5 dB
Clearly noticeable change in noise level
± 10 dB
Half or twice as loud
± 20 dB
Much quieter or louder
Note: dB = decibel
Source: Bies and Hansen, 2009.
To help relate noise level values to common experience, Table 4.10-2 shows typical noise levels from noise
sources. Sound levels are generated from a source and their decibel level decreases as the distance from that
source increases. Sound dissipates exponentially with distance from the noise source. This phenomenon is
known as “spreading loss.” For a single point source, sound levels decrease by approximately six dB for each
doubling of distance from the source. This drop-off rate is appropriate for noise generated by onsite
operations from stationary equipment or activity at a project site. If noise is produced by a line source, such
as highway traffic, the sound decreases by three dB for each doubling of distance in a hard site environment.
Line source noise in a relatively flat environment with absorptive vegetation decreases by four and onehalf dB for each doubling of distance.
Statistical Sound Level values are typically used to demonstrate compliance for stationary noise sources with
a city’s noise ordinance, as discussed below. Other values typically noted during a noise survey are the L min
and L max . These values represent the minimum and maximum root-mean-square noise levels obtained over
the measurement period.
Because community receptors are more sensitive to unwanted noise intrusion during the evening and at
night, State law and the City of Palo Alto require that, for planning purposes, an artificial dB increment be
added to quiet time noise levels in the Community Noise Equivalent Level (CNEL) or Day-Night Noise
Level (L dn ). The CNEL descriptor requires that an artificial increment of five dBA be added to the actual
noise level for the hours from 7:00 PM to 10:00 PM and 10 dBA for the hours from 10:00 PM to 7:00 AM.
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TABLE 4.10-2
TYPICAL NOISE LEVELS
Common Outdoor Activities
Noise Level
(dBA)
110
Common Indoor Activities
Rock Band
Jet Flyover at 1,000 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
70
Vacuum Cleaner at 10 feet
Noisy Urban Area, Daytime
Commercial Area
Heavy Traffic at 300 feet
Normal speech at 3 feet
60
Large Business Office
Quiet Urban Daytime
50
Dishwasher Next Room
Quiet Urban Nighttime
40
Theater, Large Conference Room (background)
30
Library
Quiet Suburban Nighttime
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, 2009.
The L dn descriptor uses the same methodology except that there is no artificial increment added to the
hours between 7:00 PM and 10:00 PM. Both descriptors give roughly the same 24-hour level with the
CNEL being only slightly more restrictive (i.e., higher).
Psychological and Physiological Effects of Noise
Noise is defined as unwanted sound, and is known to have several adverse effects on people, including
hearing loss, speech and sleep interference, physiological responses, and annoyance. Physical damage to
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human hearing begins at prolonged exposure to noise levels higher than 85 dBA. Exposure to high noise
levels affects our entire system, with prolonged noise exposure in excess of 75 dBA increasing body
tensions, and thereby affecting blood pressure, functions of the heart, and the nervous system. In
comparison, extended periods of noise exposure above 90 dBA could result in permanent hearing damage.
Vibration Fundamentals
Vibration is a trembling, quivering, or oscillating motion of the earth. Like noise, vibration is transmitted in
waves, but in this case through the earth or solid objects. Unlike noise, vibration is typically of a frequency
that is felt rather than heard.
Vibration can be either natural, as in the form of earthquakes, volcanic eruptions, sea waves, or landslides,
or manmade, as from explosions, the action of heavy machinery or heavy vehicles such as trains. Both
natural and manmade vibration may be continuous, such as from operating machinery, or transient, such as
from an explosion. The way in which vibration is transmitted through the earth is called propagation.
Propagation of earthborn vibrations is complicated and difficult to predict because of the endless variations
in the soil through which waves travel. There are three main types of vibration propagation waves: surface,
compression, and shear. Surface waves, or Raleigh waves, travel along the ground’s surface. These waves
carry most of their energy along an expanding circular wave front, similar to ripples produced by throwing a
rock into a pool of water. Compression waves, or P waves, are body waves that carry their energy along an
expanding spherical wave front. The particle motion in these waves is longitudinal (i.e., in a “push-pull”
fashion). P waves are analogous to airborne sound waves. Shear waves, or S waves, are also body waves that
carry energy along an expanding spherical wave front. However, unlike P waves, the particle motion is
transverse or “side-to-side and perpendicular to the direction of propagation.”
As vibration waves propagate from a source, the energy is spread over an ever-increasing area such that the
energy level striking a given point is reduced with the distance from the energy source. This geometric
spreading loss is inversely proportional to the square of the distance. Wave energy is also reduced with
distance as a result of material damping in the form of internal friction, soil layering, and void spaces. The
amount of attenuation provided by material damping varies with soil type and condition as well as the
frequency of the wave.
As with noise, vibration can be described by both its amplitude and frequency. Amplitude may be
characterized in three ways: displacement, velocity, and acceleration. Particle displacement is a measure of
the distance that a vibrated particle travels from its original position and for the purposes of soil
displacement is typically measured in inches or millimeters. Particle velocity is the rate of speed at which
soil particles move in inches per second or millimeters per second. Particle acceleration is the rate of change
in velocity with respect to time and is measured in inches per second or millimeters per second. Typically,
particle velocity (measured in inches or millimeters per second) and/or acceleration (measured in gravities)
are used to describe vibration. Table 4.10-3 presents the human reaction to various levels of peak particle
velocity.
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TABLE 4.10-3
HUMAN REACTION TO TYPICAL VIBRATION LEVELS
Vibration Level Peak
Particle Velocity
(inches/second)
0.006–0.019
Human Reaction
Effect on Buildings
Threshold of perception, possibility of intrusion
Vibrations unlikely to cause damage of any type
0.08
Vibrations readily perceptible
0.10
Level at which continuous vibration begins to
annoy people
0.20
Vibrations annoying to people in buildings
0.4–0.6
Vibrations considered unpleasant by people
subjected to continuous vibrations and
unacceptable to some people walking on
bridges
Recommended upper level of vibration to which
ruins and ancient monuments should be subjected
Virtually no risk of “architectural” (i.e., not
structural) damage to normal buildings
Threshold at which there is a risk to “architectural”
damage to normal buildings with plastered walls and
ceilings
Vibrations at a greater level than normally expected
from traffic, but would cause “architectural”
damage and possibly minor structural damage
Sources: California Department of Transportation, 2004, Transportation- and Construction-Induced Vibration Guidance Manual. California Department of
Transportation, Division of Environmental Analysis, 2002, Transportation Related Earthborne Vibration (Caltrans Experiences). Technical Advisory,
Vibration. TAV-02-01-R9601.
Vibrations also vary in frequency and this affects perception. Typical construction vibrations fall in the 10 to
30 Hz range and usually occur around 15 Hz. Traffic vibrations exhibit a similar range of frequencies;
however, due to their suspension systems, buses often generate frequencies around three Hz at high vehicle
speeds. It is less common, but possible, to measure traffic frequencies above 30 Hz.
Noise- and Vibration-Sensitive Receptors
Certain land uses are particularly sensitive to noise and vibration. These uses include residences, schools,
libraries, churches, nursing homes, hospitals, and open space/recreation areas where quiet environments
are necessary for enjoyment, public health, and safety. Commercial and industrial uses are generally not
considered noise- and vibration-sensitive uses, unless noise and vibration would interfere with their normal
operations and business activities.
Examples of specific noise-sensitive land uses within the City of Palo Alto include the Rinconada Library,
Foothill College, numerous elementary, middle, and high schools, the Palo Alto Veterans Administration
(VA) Hospital, the Palo Alto Medical Foundation, and the large areas of residential land uses. Outside of the
city limits, but within the Sphere of Influence (SOI) boundary, 1 sensitive uses include essentially all of
Stanford University, several residential neighborhoods (near Lucille M. Nixon Elementary School), Stanford
Medical Center, and Lucile Packard Children’s Hospital.
1
Generally bounded by Sand Hill Road on the west, El Camino Real on the north, Page Mill Road on the east, and Junipero Serra
Boulevard on the south.
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4.10.1.2 REGULATORY FRAMEWORK
To limit population exposure to physically and/or psychologically damaging as well as intrusive noise levels,
the federal government, the State of California, various county governments, and most municipalities in the
state have established standards and ordinances to control noise. There are no federal noise or vibration
standards applicable to activities or uses under the jurisdiction of the Palo Alto Comprehensive Plan;
therefore, this analysis only addresses State and local standards.
State Regulations
State of California Code of Regulations
The State of California’s noise insulation standards are codified in the California Code of Regulations
(CCR), Title 24, Building Standards Administrative Code, Part 2, California Building Code (CBC). These
noise standards are applied to new construction in California for the purpose of interior noise compatibility
from exterior noise sources. The regulations specify that acoustical studies must be prepared when noisesensitive structures, such as residential buildings, schools, or hospitals, are located near major transportation
noise sources, and where such noise sources create an exterior noise level of 65 dBA CNEL or higher.
Acoustical studies that accompany building plans must demonstrate that the structure has been designed to
limit interior noise in habitable rooms to acceptable noise levels. For new residential buildings, schools, and
hospitals, the acceptable interior noise limit for new construction is 45 dBA CNEL.
CCR Title 21, Subchapter 6 (Airport Noise Standards) establishes 65 dBA CNEL as the acceptable level of
aircraft noise for persons living in the vicinity of airports. Title 21 applies to airports that have been
designated “noise problem airports,” which includes the San Jose and San Francisco International Airports.
Noise-sensitive land uses in locations where the aircraft exterior noise level exceeds 65 dBA CNEL are
generally incompatible, unless (1) an aviation easement for aircraft noise has been acquired by the airport
proprietor, or (2) the residence is a high-rise apartment or condominium that has an interior CNEL of
45 dBA or less in all habitable rooms despite aircraft noise and an air circulation or air conditioning system,
as appropriate. Assembly Bill (AB) 2776 requires any person who intends to sell or lease residential
properties within an airport influence area to disclose that fact to the person buying the property.
California Noise/Land Use Compatibility Matrix
The California Office of Noise Control has prepared a land use compatibility chart for community noise to
provide urban planners with a tool to gauge the compatibility of land uses relative to existing and future
ambient noise levels. This land use compatibility chart, reproduced below as Table 4.10-4, identifies
“normally acceptable,” “conditionally acceptable,” “normally unacceptable,” and “clearly unacceptable” noise
levels for various land uses.
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TABLE 4.10-4
LAND USE COMPATIBILITY FOR COMMUNITY NOISE ENVIRONMENTS
Land Uses
55
60
CNEL (dBA)
65
70
75
80
Residential: Low Density
Single Family, Duplex, Mobile Homes
Residential: Multiple Family
Transient Lodging, Motels, Hotels
Schools, Libraries, Churches, Hospitals, Nursing Homes
Auditoriums, Concert Halls, Amphitheaters
Sports Arena, Outdoor Spectator Sports
Playgrounds, Neighborhood Parks
Golf Courses, Riding Stables, Water Recreation, Cemeteries
Office Buildings, Businesses, Commercial and Professional
Industrial, Manufacturing, Utilities, Agricultural
Normally Acceptable:
Specified land use is satisfactory based upon the
assumption that any buildings involved are of normal
conventional construction, without any special noise
insulation requirements.
Normally Unacceptable:
New construction or development should generally be
discouraged. If new construction does proceed, a detailed
analysis of the noise reduction requirements must be made
and needed noise insulation features included in the
design.
Conditionally Acceptable:
New construction or development should be
undertaken only after a detailed analysis of the noise
reduction requirements is made and the needed noise
insulation features included in the design. Conventional
construction, but with closed windows and fresh air
supply systems or air conditioning will normally suffice.
Clearly Unacceptable:
New construction or development generally should not
be undertaken.
Source: Office of Noise Control, Guidelines for the Preparation and Content of Noise Elements of the General Plan, 1976. Included in the Governor’s Office
of Planning and Research, California, 2003, General Plan Guidelines, Appendix C.
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A conditionally acceptable designation implies new construction or development should be undertaken only
after a detailed analysis of the noise reduction requirements for each land use is made and needed noise
insulation features are incorporated in the design. By comparison, a normally acceptable designation
indicates that standard construction can occur with no special noise reduction requirements.
Local Regulations
County of Santa Clara General Plan
The EIR Study Area includes the City’s SOI. The SOI—primarily associated with Stanford University and
adjacent residential tracts—is within unincorporated lands of the County of Santa Clara. As such, they are
subject to the County’s General Plan and the County’s Ordinance Code (discussed below).
The Noise section of the Santa Clara County General Plan aims to develop policies that provide for an
environment free from noise which may be hazardous to public health and well-being. The Noise section is
divided into two parts, which address Countywide Issues and Policies, and Rural Unincorporated Issues and
Policies.
The Countywide Issues portion of the Noise section aims to prevent or mitigate unwanted noise, provide
adequate sound buffers, and minimize exposure to airport noise. To achieve land use compatibility, the Plan
includes Noise Compatibility Standards and Recommended Interior Noise Levels, shown in Figure 4.10-1
and Table 4.10-5, respectively.
The noise compatibility levels are defined as follows:

Satisfactory noise levels are those which pose no serious threat to the proposed land use. The ambient
noise level at the site is compatible with the land use category of the proposed project and will not
create annoyance and/or activity interference. Standard construction techniques will be adequate.

Cautionary noise levels are those which could potentially pose a threat to the proposed land use. The
ambient noise level is great enough to require study on the compatibility of the proposed project.
Normal building methods may not be adequate to protect the use.

Critical noise levels are those which probably pose a threat to the proposed land use. The ambient noise
level is severe. The situation requires rigorous analysis of the compatibility of the proposed project with
the ambient noise level at the site. This analysis should include both exterior and interior impacts.
Simple solutions to noise attenuation may not be adequate and uses should be allowed only if they have
been designed for noise reduction by a professional who is competent in sound reduction.
The County includes the following policies to prevent or minimize noise conflicts:

C-HS 24: Environments for all residents of Santa Clara County free from noises that jeopardize their
health and well-being should be provided through measures which promote noise and land use
compatibility.
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Figure 4.10-1
Santa Clara County General Plan Noise Compatibility Standards
Source: Santa Clara County, 1994.

C-HS 25: Noise impacts from public and private projects should be mitigated.

C-HS 26: New development in areas of noise impact (areas subject to sound levels of 55 DNL or
greater) should be approved, denied, or conditioned so as to achieve a satisfactory noise level for those
who will use or occupy the facility (as defined in "Noise Compatibility Standards for Land Use" and
"Maximum Interior Noise Levels For Intermittent Noise").

C-HS 27: Land uses approved by the County and the cities shall be consistent with the adopted policies
of the Santa Clara County Airport Land Use Commission Comprehensive Land Use Plans for specific
airports.
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TABLE 4.10-5
RECOMMENDED MAXIMUM INTERIOR NOISE LEVELS FOR INTERMITTENT NOISE
Use
dBA
Residential
45
Commercial
Hotel-Motel
45
Executive Offices, Conference Rooms
55
Staff Offices
60
Industrial
Offices (same as above)
55-60
Laboratory
60
Machine Shop, Assembly, and Others
75
Mineral Extraction
75
Public or Semi-Public Facility
`
Concert Hall & Legitimate Theater
30
Auditorium, Movie Theater & Church
45
Hospital, Nursing Home & Firehouse (Sleeping Quarters)
45
School Classroom
50
Library
50
Other Public Buildings
55
Source: Santa Clara County, 1994.
The Rural Unincorporated Area Issues portion addresses that sensitive uses in rural areas are subject to noise
from agricultural uses, in addition to traffic and airports. The County includes the following Policies to
minimize noise conflicts in rural areas:

R-HS 1: Significant noise impacts from either public or private projects should be mitigated.


R-HS 2: The County should seek opportunities to minimize noise conflicts in the rural areas.
R-HS 3: New development in areas of noise impact (areas subject to sound levels of 55 DNL or greater)
should be approved, denied, or conditioned so as to achieve a satisfactory noise level for those who will
use or occupy the facility (as defined in "Noise Compatibility Standards for Land Use" and "Maximum
Interior Noise Levels For Intermittent Noise").
In addition, the County includes the following Policy to be consistent with the Airport Land Use
Commission and minimize exposure to airport noise:

R-HS 4: Land uses approved by the County and the cities shall be consistent with the adopted policies of
the Santa Clara County Airport Land Use Commission's Comprehensive Land Use Plan.
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County of Santa Clara Ordinance Code
Exterior Noise Levels
County noise and vibration regulations are set forth in Chapter VIII, Control of Noise andVibration, under
Title B of the Santa Clara County Code. Section B11-152 presents exterior noise level limits for the
County:

Maximum permissible sound levels by receiving land use.

The noise standards for the various receiving land use categories as presented in [Code] Table 3 will
apply to all property within any zoning district.

No person may operate or cause to be operated any source of sound at any location within the
unincorporated territory of the County or allow the creation of any noise on property owned,
leased, occupied or otherwise controlled by the person, which causes the noise level when
measured on any other property either incorporated or unincorporated, to exceed:
- The noise standard for that land use as specified in Table B11-152 for a cumulative period of
more than 30 minutes in any hour; or
- The noise standard plus five dB for a cumulative period of more than 15 minutes in any hour; or
- The noise standard plus 10 dB for a cumulative period of more than five minutes in any hour; or
- The noise standard plus 15 dB for a cumulative period of more than one minute in any hour; or
- The noise standard plus 20 dB or the maximum measured ambient, for any period of time.


If the measured ambient level exceeds that permissible within any of the first four noise limit
categories above, the allowable noise exposure standard will be increased in five dB increments in
each category as appropriate to encompass or reflect the ambient noise level. In the event the
ambient noise level exceeds the fifth noise limit category, the maximum allowable noise level under
the category will be increased to reflect the maximum ambient noise level.

If the noise measurement occurs on a property adjoining a different land use category, the noise
level limit applicable to the lower land use category, plus five dB, will apply.

If for any reason the alleged offending noise source cannot be shutdown, the ambient noise must be
estimated by performing a measurement in the same general area of the source but at a sufficient
distance that the noise from the source is at least 10 dB below the ambient in order that only the
ambient level be measured. If the difference between the ambient and the noise source is five to
10 dB, then the level of the ambient itself can be reasonably determined by subtracting a onedecibel correction to account for the contribution of the source.
Correction for character of sound. In the event the alleged offensive noise contains a steady, audible
tone such as a whine, screech or hum, or contains music or speech conveying informational content, the
standard limits set forth in [Code] Table 3 will be reduced by five dB.
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Interior Noise Levels
Section B11-153 includes interior noise level limits for multifamily dwellings. The standard is 35 dBA from
10 PM to 7 AM, and 45 dBA from 7 AM to 10 PM. Noise levels must not exceed:
 The noise standard for a cumulative period of more than five minutes in any hour; or
 The noise standard plus five dB for a cumulative period of more than one minute in any hour; or
 The noise standard plus 10 dB or the maximum measured ambient, for any period of time.
Also, if the measured ambient level exceeds that permissible within any of the noise limit categories above,
the allowable noise exposure standard will be increased in five-dB increments in each category as
appropriate to reflect the ambient noise level. Additionally, if the alleged offensive noise contains a steady,
audible tone such as a whine, screech or hum, or contains music or speech conveying information content,
the standard limits will be reduced by five dB.
Construction
Construction that creates a noise disturbance across a residential or commercial property line is prohibited
between 7 PM and 7 AM Monday through Saturday, and at any time on Sundays or holidays. Exceptions are
made for emergency work and variances. In addition to restrictions on hours of operation, maximum
construction noise levels at affected properties will not exceed those listed in [Code] Tables 4 and 5, where
technically and economically feasible.
Vibration
Subsection B11-154 b) prohibits the operation of any device that creates a vibrating effect that endangers or
injures the safety or health of human beings or animals; annoys or disturbs a person of normal sensitivities;
or endangers or injures personal or real properties.
The above County of Santa Clara policies and regulations would apply to areas outside of the City of Palo
Alto boundaries, but within the City’s SOI; principally, Stanford University and the residential area north of
Junipero Serra Boulevard and west of Page Mill Road.
City of Palo Alto Municipal Code
The Palo Alto Municipal Code regulates noise primarily through the Noise Ordinance, which comprises
Chapter 9.10 of the Code, under Title 9, Public Peace, Morals, and Safety. The Municipal Code contains
additional specific and general provisions relating to noise. Most notably, the Municipal Code contains
performance standards for Multiple Family, Commercial, Manufacturing, and Planned Community
Districts. Beyond the noise ordinance and performance standards, the Municipal Code contains additional
miscellaneous references to noise.
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The primary function of the Palo Alto noise ordinance is to establish limits on the generation of noise on
different land uses, such that adjacent properties or dwelling units do not receive excessive noise. For
residential uses, a violation of the ordinance would occur if a particular noise caused the ambient noise level
within an adjacent property or unit to increase by six or more decibels. For commercial and industrial
properties, a violation occurs at an increase of eight or more decibels, and for public properties this
threshold is 15 decibels. Within certain limits, the ordinance allows exceptions for sound performances,
special events, and warning devices, such as car horns. The ordinance also allows general exceptions during
the daytime (which is defined differently depending on the day of the week), provided that the overall level
of noise from a particular source is less than 70 dBA at a distance of 25 feet or greater.
The noise ordinance also creates certain exceptions for noise from construction, while still generally
limiting most construction activity to the hours of 8:00 AM to 6:00 PM Monday through Friday and
9:00 AM to 6:00 PM on Saturday. Nevertheless, construction activities and noise must meet certain
standards including:
 Adhering to maximum noise levels from individual pieces of equipment,
 Avoiding exceptionally high noise levels on adjacent properties,
 Maintaining a valid construction permit, and
 Posting informational signage about construction hours and the noise ordinance itself.
Similar regulations also apply to other equipment used by the City and City employees, as well as residential
power equipment.
The noise ordinance also serves to regulate a number of other activities and pieces of equipment that can be
major sources of noise. The noise ordinance includes limits on both the amount of noise that may be
generated by leaf blowers 2 and the hours during which a leaf blower may be used (Palo Alto Municipal Code
Chapter 9.10.060(f)). 3 Similarly, the ordinance places limits on the maximum noise levels and hours of
operation for street sweeping activities, refuse collection, public parking lot cleaning, and business district
street cleaning (Palo Alto Municipal Code Chapter 9.10.060(g), Palo Alto Municipal Code Chapter
9.10.060(h), and Palo Alto Municipal Code Chapter 9.10.060(k)). For aural warning devices (which are
required by law to protect the health, safety, and welfare of the community), the sound emissions from such
2
"Leaf blower" means any portable machine used to blow leaves, dirt, and other debris off sidewalks, driveways, lawns, or other surfaces
(per Municipal Code Chapter 9.10.020).
3
A leaf blower must bear an affixed manufacturer's label indicating (a) the model number of the leaf blower and (b) the noise level
emissions are less than 65 dBA (measured at 50 feet from the blower and using methodologies from the American National Standard Institute
(ANSI)). All leaf blowers must be operated with all originally-installed muffler(s) and extension tube(s), as supplied by the manufacturer. No
leaf blowers are to be operated within a residential zone outside of 9:00 AM to 5:00 PM (Monday through Friday) or 10:00 AM to 4:00 PM
(Saturday). No leaf blowers are to be operated within a non-residential zone outside of 8:00 AM to 6:00 PM (Monday through Friday) or 10:00
AM to 4:00 PM (Saturday). No leaf blowing operations are permitted on Sundays, regardless of land use. The use of leaf blowers powered by
an internal combustion engine is not allowed within a residential zone. Commercial leaf blower operators must have a certificate from the Chief
of Police verifying the successful completion of leaf blower training courses for all operators. The blowing of leaves on public streets, sidewalks,
business-district parking lots, and the Municipal Golf Course is allowed between 4:00 AM and 8:00 AM (in addition to the above restrictions),
as long as the aforementioned noise level emissions and labeling requirements are also met.
4.10-14
FEBRUARY 5, 2016
CITY OF PALO ALTO
NOISE
devise cannot not produce a noise level more than three dBA above the standard or minimum level
stipulated by law (Palo Alto Municipal Code Chapter 9.10.060(i)).
Certain exceptions are permitted by the noise ordinance, but these are fairly limited and are made at the
discretion of the City Manager and/or City Council. The noise ordinance provides a general exception for
emergencies and also offers the potential for an exception permit. The noise ordinance allows an exception
permit to be granted by the City Manager when meeting the other requirements of the ordinance can be
shown to be “impractical or unreasonable,” but only if appropriate conditions are included to minimize the
“public detriment” resulting from the exception. Decisions by the City Manager in this regard may be
appealed to the City Council (Palo Alto Municipal Code Chapter 9.10.070).
Beyond the noise ordinance itself, the Palo Alto Municipal Code contains noise and vibration performance
criteria that serve to limit the generation and/or reception of noise by particular land uses (Palo Alto
Municipal Code Chapter 18.23.060). The general intent of these regulations is to protect residential and
other sensitive land uses from excessive noise and vibration. For Multiple Family, Commercial,
Manufacturing, and Planned Community Districts, the Municipal Code seeks to reduce noise from parking
and loading areas, refuse collection areas, and common HVAC (heating, ventilation, and air conditioning)
and mechanical equipment. Prescribed approaches to limiting noise from these sources include various
screening techniques, as well as strategically locating the noise sources to minimize perception of noise.
Projects are required to demonstrate their compliance using acoustic measurements and analysis.
Additionally, the performance standards seek to protect residential development from excessive noise by
requiring certain siting, building, and other noise reduction techniques. The guidelines recognize that key
sources of noise potentially impacting new residential development include major roadways, industrial or
commercial operations, and equipment or activities associated with the residential development itself. To
address potential noise impacts, the guidelines recommend engineered approaches, such as berms,
soundwalls, fencing, and other screening techniques, as well as siting approaches, which serve to spatially
isolate residential units and major noise sources from one another. Finally, the guidelines recommend
operational approaches that serve to limit noise from residential, commercial, and/or industrial activity.
Similar to the standards adopted for the districts discussed above, the Palo Alto Municipal Code also adopts
standards and guidelines for low-density and single-family residential districts (Palo Alto Municipal Code
Chapter 18.12.020(l)), as well as additional standards for multiple-family residential districts (Palo Alto
Municipal Code Chapter 18.23.060). The Municipal Code establishes standards for the location and
screening of stationary equipment, requiring that such techniques be sufficient to ensure that any noise from
the equipment meets the requirements of the Noise Ordinance itself. For multiple-family residential
districts, the Municipal Code requires that open space areas be protected and/or buffered from noise
generated by adjacent streets and commercial uses, as feasible. Additionally, commercial uses, such as
neighborhood-serving uses, in multiple-family residential districts must demonstrate that they would not
generate excessive noise and are implementing appropriate measures to limit the generation of noise.
PLACEWORKS
4.10-15
CITY OF PALO ALTO
NOISE
Beyond these primary regulations and standards, the Municipal Code also contains a number of more minor,
miscellaneous standards. These include provisions that: protect stream corridors from noise-generating
equipment; require parking and loading areas to be designed to minimize noise impacts to adjacent uses;
require shock-mounting for permanent appliances in certain instances; and limit noise from devices that
amplify sound. A number of other provisions mention the need to limit excessive noise. A complete listing
of noise-related provisions of the Municipal Code is included in Appendix F.
4.10.1.3 EXISTING CONDITIONS
Like many urban areas, Palo Alto’s noise environment is dominated by transportation-related noise,
including car and truck traffic, and trains. US 101 is the largest source of traffic noise in Palo Alto, with
other highways and major roadways contributing as well. These include El Camino Real, Oregon
Expressway, Foothill Expressway, Interstate 280 (I-280), Embarcadero Road, San Antonio Road, Middlefield
Road, University Avenue, Page Mill Road, and Alma Street, among others. Noise along all of these roadways
is generated by private cars, trucks, buses, and other types of vehicles.
Caltrain also runs through the center of Palo Alto and makes significant contributions to the noise
environment of the city.
Air traffic makes only a modest contribution to the noise environment of Palo Alto; primarily due to the
relatively large distances to the nearest major airports, which are the San Francisco, San Jose, and Oakland
International Airports. San Jose International is the closest major airport to Palo Alto, located 13 miles
southeast of Palo Alto. San Francisco International and Metropolitan Oakland International are a bit farther
northwest, at 18 and 20 miles respectively. All distances are from the approximate geographic center of Palo
Alto. Beyond these major public airports, the City of Palo Alto owns and operates the Palo Alto Airport
(KPAO), a relatively small public air facility which primarily serves single-engine, general aviation (GA)
aircraft. 4 There is one standalone heliport located within the EIR Study Area. Stanford University operates
one heliport (15CA), which is located at Stanford University Hospital adjacent to the Stanford Campus near
Quarry Road and Campus Drive. Additional information on public and private airports, airfields, and
heliports is contained in the discussions of Impacts NOISE-9 and NOISE-10 below.
Activities associated with industrial, commercial, and residential uses also contribute substantially to the
noise environment of Palo Alto. For all of these uses, stationary equipment, such as HVAC systems,
represents a significant source of noise. Activities such as deliveries and refuse collection also contribute to
the noise generated by land uses in Palo Alto. In some areas, such as Downtown Palo Alto, direct noise from
conversation, dining, and other human activity also contributes strongly to the noise environment.
4
Information from AirNav.com at http://www.airnav.com/airport/KPAO, accessed December 23, 2015.
4.10-16
FEBRUARY 5, 2016
CITY OF PALO ALTO
NOISE
Noise Measurements
Existing ambient noise levels were measured at 18 sites around Palo Alto to document representative noise
levels at a variety of locations characterized by different land uses, development intensities, traffic levels,
and typical nearby activities found in Palo Alto. These locations are shown on Figure 4.10-2. 5
Short-term noise level measurements were taken at 16 locations for a minimum period of 15 minutes
during the daytime on Tuesday, April 8 and Wednesday, April 9, 2014, between the hours of 9 AM and 8 PM.
Long-term noise level measurements were taken at two locations for a period of 24 hours between April 8
and 9, 2014. 6 Short-term noise measurements serve as a snapshot of noise levels at a particular time and
location, offering a sense of how other, similar locations might experience noise during comparable times of
day. Long-term noise level measurements serve to provide a broader picture of how noise levels vary over
the course of a full day, helping to put the short-term measurements in a broader temporal context. As
representative samples of noise levels at a variety of locations during typical weekday conditions under fair
weather settings (as is consistent with industry standard practices), both long- and short-term
measurements serve to indicate where excessive noise may be an existing or future issue for existing or new
land uses.
Noise levels were measured using a Larson-Davis Model 820 sound level meter, which satisfies the American
National Standards Institute for Type One general environmental noise measurement instrumentation.
Adherence to this standard ensures that noise measurements taken are accurate by way of consistency with
technical standards; such standards guarantee that different pieces of equipment could be relied upon to
return consistent results when measuring the same physical phenomena. The sound level meter and
microphone were mounted on a tripod five feet above the ground and equipped with a windscreen during
all short-term measurements. For long-term measurements, the microphone and windscreen were attached
to available objects, at a height between four and six feet, as dictated by conditions in the field.
The sound level meters were programmed to record noise levels with the “slow” time constant and using the
“A” weighting filter network. Meteorological conditions during the measurement periods were favorable
and were noted to be representative of typical conditions for the season. Generally, conditions included
clear to partly cloudy skies, daytime temperatures of approximately 57 to 80 degrees Fahrenheit (°F), and
less than five-mile-per-hour (mph) winds. The short- and long-term noise measurement locations are
described below.
5
Figure 4.10-2 is an updated version of Figure 9-2 in the Existing Conditions Report that was published in 2014. Note that Figure 9-2 in
the 2014 Existing Conditions Report incorrectly transposed the labeling for measurements locations LT-1 and LT-2. This has been corrected in
Figure 4.10-2.
6
It is believed that little has substantively changed in the city regarding characteristic community noise environments since these
measurements were conducted. Thus, while being several months old, these data are considered to still be valid as representative samples of
noise conditions in the study area.
PLACEWORKS
4.10-17
COMPREHENSIVE PLAN UPDATE EIR
CITY OF PALO ALTO
NOISE
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Figure 4.10-2
Noise Monitoring Locations and Sensitive Land Uses
CITY OF PALO ALTO
NOISE
Short-Term Noise Measurement Locations
Noise levels at the short-term measurement locations ranged from a minimum of 53.2 dBA L eq at
Location 1 (Sierra Court at St. Francis Drive) to a maximum of 72.6 dBA L eq at Location 6 (Alma Street and
Seale Avenue), with an average L eq of 62.8 dBA, and the majority of locations falling between 60 and 70
dBA L eq . Noise levels tended to be higher adjacent to major roadways, in close proximity to Caltrain tracks,
and in busy business districts. Noise was higher in these areas due to high traffic, the sound of passing trains,
and high levels of human activity. Short-term measurements indicate that Oregon Expressway and Caltrain
rail corridor are among the most significant noise sources in Palo Alto. Detailed descriptions and
quantitative data for all short-term monitoring locations are included in Appendix F of this Draft EIR.
Long-Term Noise Measurement Locations
Noise levels at the long-term measurement locations ranged from a minimum of 44 dBA L eq during the
1:00 AM hour at Location 2 (East Meadow Drive and East Meadow Circle) to a maximum of 60.5 dBA L eq
during the 11:00 AM hour at Location 1 (Cambridge Avenue and Park Boulevard). Overall, Long-term
Location 1 had a 24-hour L dn of 59.8 dBA, and Location 2 had a 24-hour L dn of 55.7 dBA. Noise levels
tended to be lower during nighttime hours and highest during the morning rush hour and midday period.
Long-term measurements indicate that overall diurnal patterns of noise in Palo Alto match what one would
expect for a typical mid-sized urban area. Detailed descriptions and quantitative data for all long-term
monitoring locations are included in Appendix F of this Draft EIR.
Table 4.10-6 summarizes the results of both the short- and long-term noise monitoring.
Principal Noise Sources in Palo Alto
On-Road Vehicles
Freeways that run along the city’s northeastern and southwestern boundaries are US 101 and I-280,
respectively. El Camino Real (State Route 82) runs northwest to southeast across the middle of the city. In
addition to the previously mentioned highways, major roadways running northwest to southeast through
Palo Alto include Junipero Serra Boulevard, Alma Street, and Middlefield Road. Major northeast to
southwest roadways include San Antonio Road, Arastradero Road, East Charleston Road, Oregon
Expressway, Page Mill Road, Embarcadero Road, University Avenue, and Sand Hill Road. Together, these
highways and streets comprise the major roads in the City of Palo Alto. Figure 4.10-3 shows existing noise
contours for the City of Palo Alto, including the roadways referenced above. Noise generated by on-road
vehicles, including acceleration, movement, and engine revving is accounted for by the roadway noise
models, which are based on Federal Transit Authority (FTA) methodologies and standard assumptions about
vehicle mix and noise levels.
PLACEWORKS
4.10-19
CITY OF PALO ALTO
NOISE
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Figure 4.10-3
Existing Noise Contours
CITY OF PALO ALTO
NOISE
TABLE 4.10-6
NOISE MONITORING SUMMARY
Monitoring
Location
Location Description
Start Time (Duration)
Noise Level
ST-1
Sierra Court (at St. Francis Drive)
9:50 AM (15 min)
53.2 dBA L eq
ST-2
University Avenue and Bryant Street
1:46 PM (15 min)
65.9 dBA L eq
ST-3
Middlefield Road and Embarcadero Road
10:48 AM (15 min)
68.2 dBA L eq
ST-4
Arastradero Road and Foothill Expressway
2:13 PM (15 min)
60.8 dBA L eq
ST-5
El Camino Real and Ventura Avenue
6:22 PM (15 min)
67.8 dBA L eq
ST-6
Alma Street and Seale Avenue
4:38 PM (15 min)
72.6 dBA L eq
ST-7
South California Avenue and Hanover Street
5:10 PM (15 min)
56.7 dBA L eq
ST-8
Edgewood Drive near Newell Road
9:10 AM (15 min)
53.4 dBA L eq
ST-9
Middlefield Road and Montrose Avenue
10:24 AM (15 min)
61.7 dBA L eq
ST-10
East Meadow Drive (near Waverly Street)
2:55 PM (15 min)
60.6 dBA L eq
ST-11
Terman/Donald Drive and Arastradero Road
1:40 PM (15 min)
66.7 dBA L eq
ST-12
Channing Avenue, Boyce Avenue, and Guinda Street
11:32 AM (15 min)
56.5 dBA L eq
ST-13
Middlefield Road and Channing Avenue
11:14 AM (15 min)
65.0 dBA L eq
ST-14
Louis Road and Sycamore Drive
9:38 AM (15 min)
58.7 dBA L eq
ST-15
Oregon Expressway and Ross Road
9:03 AM (15 min)
68.6 dBA L eq
ST-16
El Camino Real and Del Medio Avenue
6:50 PM (15 min)
68.1 dBA L eq
LT-1
Cambridge Avenue and Park Boulevard
8:04 PM (24 hrs)
59.8 dBA L dn
LT-2
East Meadow Drive and East Meadow Circle
7:30 PM (24 hrs)
55.7 dBA L dn
Notes: min = minutes; hrs = hours. Noise measurement results printouts included in Appendix F of this Draft EIR. Noise Measurements taken by
PlaceWorks on April 8 and 9, 2014.
Train Noise
The Caltrain right-of-way is the one major rail line that traverses Palo Alto, bisecting the city along its short
northwest-southeast axis. The Caltrain tracks run in the area between El Camino Real and Alma Road,
entering the city at San Francisquito Creek/Sand Hill Road and exiting to Los Altos at San Antonio Road.
Caltrain runs on a double track throughout its entire length through Palo Alto, and its right-of-way is owned
and administered by the Peninsula Corridor Joint Powers Board. Palo Alto is served by two Caltrain stations
along this line, and though there are currently 86 weekday daily stops at the Palo Alto station (either
northbound or southbound) and only 53 daily stops at the California Avenue Station (either northbound or
southbound), more than 90 trains pass either north or south through Palo Alto on a daily basis during the
PLACEWORKS
4.10-21
CITY OF PALO ALTO
NOISE
work week. 7 The sheer number of diesel-powered commuter train pass-bys ensures that the activity along
the Caltrain railway contributes significantly to the ambient noise environment of nearby areas of Palo Alto
and these Caltrain pass-by noise contributions are included in the existing noise contour map (of Figure
4.10-3). 8 Freight trains make limited use of the Caltrain corridor, with one daily round trip through Palo
Alto during nighttime hours. 9
Future plans for the Caltrain corridor include the Caltrain Modernization Program for electrifying the
existing corridor between San Francisco and San Jose (through Palo Alto). Modernization – scheduled to be
operational by 2020 – will allow Caltrain to operate quieter, cleaner, faster, and/or more frequent train
service to more riders. Increased capacity and improved service will help Caltrain meet increasing ridership
demand and alleviate local and regional traffic congestion. It should be noted, additionally, that Scenarios 3
and 4 of the proposed Plan include Caltrain operations in a below-grade trench under Meadow Drive and
Charleston Road to separate the existing Caltrain tracks from the roadways (both in anticipation of possible
future High Speed Rail service and to alleviate existing safety and traffic congestion issues ). In addition to
the commuter-focused improvements, the Caltrain Modernization Program will help prepare the corridor
to eventually accommodate California’s statewide high-speed rail service, which is planned for 2029. 10
Caltrain and high-speed rail (HSR) will primarily share Caltrain’s existing tracks, operating on a blended
system. 11
The operations of the California HSR system are still in the planning and development stages. As such, there
is a lack of detailed HSR information, such as final alignment drawings, operations schedules, 12 and
equipment specifications. However, some generalized interpretations can be presented concerning HSR
operations noise. The total wayside noise generated by a high-speed train pass-by consists of several
individual noise-generating mechanisms, each with its own characteristics of source location, strength,
frequency content, directivity, and speed dependence. These noise sources can be generalized into three
major regimes: 13
 Regime I. Propulsion or machinery noise.
 Regime II. Mechanical noise resulting from wheel-rail interactions and/or guideway vibrations.
 Regime III. Aerodynamic noise resulting from airflow moving past the train, including the pantograph. 14
7
Train movement information principally found at: http://www.caltrain.com/schedules/PDF_Schedules.html, accessed on June 18,
2015 and October 30, 2015.
8
It should be noted, though, that the Caltrain railway noise contributions overlap the nearby and parallel Alma Street roadway noise
contributions and are not visually distinguishable at the scale of this city-wide presentation.
9
Peninsula Corridor Join Powers Board, 2014, Draft Peninsula Corridor Electrification Project Environmental Impact Report, page 3.1429 (Figure 3.14-7).
10
Information from http://www.caltrain.com/projectsplans/CaltrainModernization.html, accessed on October 29, 2015.
11
Information from http://www.caltrain.com/projectsplans/CaltrainModernization/BlendedSystem.html, accessed on October 29,
2015.
12
Lipkin, Boris. Deputy Director of Business Analytics and Commercial Implementation, California High Speed Rail Authority. Personal
communication with Seung Hong, PlaceWorks. July 3, 2015. This email primarily focuses on operations in and around Gilroy, California. Per
this email correspondence, specific train schedules have not been developed yet.
13
Federal Railroad Administration, United States Department of Transportation, 2012, High-Speed Ground Transportation Noise and Vibration
Impact Assessment, DOT/FRA/ORD-12/15.
14
The pantograph is the telescopic structure that picks up electrical current from the overhead wires.
4.10-22
FEBRUARY 5, 2016
CITY OF PALO ALTO
NOISE
The significance of these different regimes is that, for a given train, there are three distinct speed ranges in
which one sound source contributes most to the total noise level. For a conventional train with a maximum
speed of up to approximately 125 mph, propulsion and mechanical noise are sufficient to describe the total
wayside noise. For a high-speed train, the aerodynamic noise component begins to be an important factor
when the train speed exceeds approximately 160 mph. In general, electrically-powered HSR operations
would produce lower noise and vibration levels in Regime I (the low-speed regime), as compared with lowfrequency noise generated by diesel powered engines. Generally, noise levels increase only slightly with
increases in speed (below 40 mph) for this regime. 15 Further, fan noise tends to dominate the noise
spectrum in the frequency bands near 1,000 Hz and cooling fan noise tends to be constant with respect to
train speed, which makes fans the dominant noise when a train is stopped in a station. 16 Regime II, (the
medium-speed regime) covers a wide range of operations—from approximately 50 or 60 mph all the way
up to approximately 150 or 160 mph (which is the transition to Regime III). For Regime II, mechanical
noise generation results from the effects of wheel-rail interaction, guideway structural vibrations, and
vehicle-body vibrations. For both conventional trains and HSRs, wheel/rail interaction is the primary noise
source. Fortunately, as this source is low to the ground, it can be shielded with noise barriers for at-grade
operations. Propulsion and rolling noise (discussed above) are generally sufficient to describe the total noise
of most train operations up to speeds of approximately 160 mph for steel-wheeled trains. Above this speed
(i.e., in Regime III and only applicable to HSR systems), aerodynamic noise sources tend to dominate the
radiated noise levels. For HSR, significant noise is generated at speeds of approximately 180 mph, depending
on the magnitude of the mechanical/structural noise.
Note that neither the Caltrain Modernization Program nor the development of the California HSR system is
part of the proposed Plan that is the subject of this EIR. Associated environmental impacts for these two rail
projects are not included herein (since such impact analyses have been or will be conducted separately by
the respective rail authorities).
Heliports
There is only one standalone heliport located within the City of Palo Alto. Stanford University operates one
heliport, which is located at Stanford University Hospital adjacent to the Stanford Campus near Quarry
Road and Campus Drive. The nearest residential uses are located approximately 1,400 feet to the west of
the heliport. The next nearest heliport is located approximately eight miles to the southeast of Palo Alto, in
the city of Santa Clara.
Aircraft Noise
There are several medium to large airports in the general region around the city. At the nearest points
within city limits, Palo Alto is located approximately 2.6 miles to the west of Moffett Federal Airfield
15
Hatch Mott MacDonald, 2011, Station Area Noise/Vibration Analysis. Prepared for the City of Gilroy.
Federal Railroad Administration, United States Department of Transportation, September 2012, High-Speed Ground Transportation Noise
and Vibration Impact Assessment, DOT/FRA/ORD-12/15.
16
PLACEWORKS
4.10-23
CITY OF PALO ALTO
NOISE
(KNUQ), six miles to the southeast of San Carlos Airport (KSQL), 10 miles to the northwest of the San
Jose International Airport (SJC), 15 miles to the southeast of San Francisco International Airport (SFO), and
17 miles to the south of Oakland International Airport (OAK). At these relatively large distances, all areas of
the City of Palo Alto are miles outside of the pertinent 65 dBA CNEL noise contour of all of these airports.
Of particular concern to the citizens of Palo Alto, however, are over-flights associated with SFO and how
those aircraft operations may have changed over time, resulting in changing/worsening noise effects. 17
While people around airports do, indeed, hear and respond to separate aircraft over-flight events (that
commonly last for only a minute or two), the standard metric used for community impact assessment is the
CNEL metric (which is a 24-hour energy-averaged sound level). The 24-hour CNEL noise value for any
given airport or heliport includes the contributions from all the separate aircraft over-flight events, but also
includes the sound levels for times between the fly-overs, which are much quieter than when an aircraft is
overhead. Thus, an airport’s CNEL levels will be several decibels quieter than for a single over-flight event
(that many people may find to be annoying or a nuisance). The use of the CNEL metric is required by statute
for general plan noise elements, by Title 24 for interior noise levels, and per FAA regulations (see the
discussion above under State Regulations in Section 4.10.1.2 for additional information about applicable
exterior [65 dBA CNEL] and interior [45 dBA CNEL] noise level standards regarding aircraft noise). This
Draft EIR uses the mandated noise metric in the consideration of potential aircraft-related noise impacts
(i.e., exterior noise level from aircraft exceeding 65 dBA CNEL and interior noise levels from aircraft
exceeding 45 dBA CNEL in high-rise apartment or condominium facilities are generally considered as
incompatible).
In addition to these large and medium-sized regional airports, the City of Palo Alto owns and operates the
Palo Alto Airport (KPAO), a relatively small public air facility which primarily serves general aviation uses.
Noise contours from the aircraft using this airport have been incorporated into the existing citywide
contours shown in Figure 4.10-3. Additional small airports in the vicinity include the Hayward Executive
Airport (KHWD), 14 miles away, and the Half Moon Bay Airport (KHAF), 18 miles away. Although Palo
Alto does receive some noise from aircraft using these facilities, the EIR Study Area does not fall within the
airport land use planning areas/airport influence areas, runway protection zones, or the identified noise
contours of any airport other than Palo Alto Airport.
With respect to the Palo Alto Airport, a Comprehensive Land Use Plan (CLUP) was adopted in November
2008 18 by the Santa Clara County Airport Land Use Commission (ALUC) 19 and provides guidance related to
the placement of land uses near the Palo Alto Airport. Specifically, the CLUP seeks to protect the public
from adverse effects of aircraft noise, to ensure that people and facilities are not concentrated in areas
susceptible to aircraft accidents, and to ensure that no structures or activities adversely affect navigable
airspace. Based on the noise contours presented in the Palo Alto Airport CLUP, within Palo Alto only
17
Information from http://www.paloaltoonline.com/news/2015/08/26/study-aims-to-bring-data-to-palo-altos-loud-debate-overairplane-noise, accessed on October 29, 2015.
18
At the time of the preparation of the ALUC document, Palo Alto Airport was owned and operated by the County of Santa Clara.
19
Santa Clara County Airport Land Use Commissions, 2008, Palo Alto Airport Comprehensive Land Use Plan.
4.10-24
FEBRUARY 5, 2016
CITY OF PALO ALTO
NOISE
airport and golf course (Palo Alto Municipal Golf Course) land uses fall within the Palo Alto Airport’s 60
dBA noise contour.
Stationary Source Noise
Stationary sources of noise may occur from all types of land uses. Palo Alto is mostly developed with
residential, commercial, mixed-use, institutional, and some light industrial uses. Commercial uses can
generate noise from HVAC systems, loading docks, trash compactors, and other sources. Industrial uses may
generate noise from HVAC systems, loading docks, and machinery required for manufacturing processes.
Any excessive noise generated by commercial uses is generally short-term and intermittent, since noise
sources such as loading/unloading, ventilation systems, and waste disposal are not constant. Industrial uses
may generate noise on a more continual basis, or intermittently, depending on the processes and types of
machinery involved. In addition to on-site mechanical equipment, which generates stationary noise,
warehousing and industrial land uses generate substantial truck traffic that results in additional sources of
noise on local roadways in the vicinity of industrial operations.
For Palo Alto, many of the area’s limited industrial operations are located in the far eastern reaches of the
city near San Antonio Road and East Charleston Road, and are usually separated from sensitive uses, such as
residences, by either major roads or some degree of buffering. In both cases, this added distance serves to
decrease the noise perceived by these receptors and, in the case of major roads, the noise from the roads was
generally observed to exceed that from the industrial uses. Residential areas with the greatest potential to be
impacted by noise from industrial operations include those lying to the northeast and southeast of the
intersection of East Charleston Road and San Antonio Road, and those along the northern end of Adobe
Creek.
Additional office and research and development uses are located in the area generally bounded by South
California Avenue, Page Mill Road, Foothill Expressway, the Bol Park Bike Path, Chimalus Drive, Lambert
Avenue, Alma Street, and North California Avenue. These uses have the potential to have some degree of
noise impact upon nearby sensitive receptors at the edges of this area. Such impacts would vary depending
on the specific uses, with truck deliveries, HVAC, and other mechanical equipment being the primary
sources of noise.
Construction Noise
Construction activity also contributes to the noise environment of Palo Alto; however such activities are
typically temporary, occurring in any one location for only a limited period of time. Larger or multi-phase
construction projects may contribute to the noise environment of a particular location for a more extended
period of time. Public infrastructure that requires ongoing maintenance may also result in ongoing noise
impacts, though usually not at a constant location.
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4.10-25
CITY OF PALO ALTO
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Public Facility Noise
Outdoor activities that occur on school campuses and in parks throughout the city generate noticeable levels
of noise in the vicinity of these campuses and facilities. While it is preferable to have schools located within a
residential setting to support the neighborhood, noise generated on both the weekdays (from physical
education classes and sports programs) and weekends (from use of the fields and stadiums by youth
organizations) can elevate community noise levels.
4.10.2 STANDARDS OF SIGNIFICANCE
Appendix G of the California Environmental Quality Act (CEQA) Guidelines contains standards of
significance for the evaluation of a project’s impacts. Section 15064.7 of the CEQA Guidelines encourages
each public agency to develop and publish its own thresholds of significance that the agency uses in
evaluating the significance of environmental effects for projects in its jurisdiction. The City of Palo Alto
prepared its Environmental Criteria Used by the City of Palo Alto in 2007. In determining which standards of
significance to use for evaluating the noise impacts of the proposed Plan, Appendix G of the CEQA
Guidelines and the City’s published environmental criteria were considered. As part of this review, some of
the City’s criteria were determined to be relevant to the environmental review of specific development
projects but not appropriate for the review of a broad policy document such as the Comp Plan (see
Appendix B for more information on the City’s thresholds), and some criteria were added for consistency
with the CEQA Guidelines. Based on this consideration, the analysis in Section 4.8.3 uses the following
standards of significance. The proposed Plan would result in a significant noise impact if it would:

Cause the average 24-hour noise level (L dn ) to increase by 5.0 decibels (dB) or more in an existing
residential area, even if the L dn would remain below 60 dB.

Cause the L dn to increase by three dB or more in an existing residential area, thereby causing the L dn in
the area to exceed 60 dB.

Cause an increase of three dB or more in an existing residential area where the L dn currently exceeds
60 dB.

Result in indoor noise levels for residential development to exceed an L dn of 45 dB.

Expose persons to or generate excessive groundbome vibrations or groundbome noise levels.

Expose people to noise levels in excess of established State standards.

Exposure of people to or generation of noise levels in excess of standards established in the General
Plan or the Municipal Code, or applicable standards of other agencies.

A substantial temporary or periodic increase in ambient noise levels in the project vicinity above levels
existing without the project.
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FEBRUARY 5, 2016
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NOISE

For a project located within an airport land use plan or, where such a plan has not been adopted, within
two miles of a public airport or public use airport, would the project expose people residing or working
in the project area to excessive noise levels.

For a project within the vicinity of a private airstrip, would the project expose people residing or
working in the project area to excessive noise levels.
4.10.3 IMPACT DISCUSSION
The remaining sections of this chapter provide an analysis of the potential project impacts, including impacts
from growth expected to occur during the life of the proposed Plan, as well as cumulative noise impacts that
could occur as a result of the implementation of the proposed Plan when combined with projects outside of
Palo Alto.
NOISE-1
Implementation of the proposed Plan would have the potential to cause the
average 24-hour noise level (L dn ) to increase by 5.0 decibels (dB) or more in
an existing residential area, even if the L dn would remain below 60 dB. (Less
than Significant – Scenario 1; Potentially Significant and Mitigable –
Scenarios 2, 3, and 4)
Summary: In general, all four scenarios include varying levels of development that aim to facilitate different
paces of residential and commercial growth throughout the city. As stated in Section 3.4.1 of Chapter 3,
Project Description, of this Draft EIR, Palo Alto is largely built out and the current Comp Plan land use map
(shown in Figure 3-3 in Chapter 3 of this Draft EIR), is likely to remain unchanged with the proposed Plan.
As described below, regarding long-term operational noise, Scenario 1 would result in a less-than-significant
impact while Scenarios 2, 3, and 4 would result in a potentially significant impact, requiring mitigation.
Regarding transportation-related noise, all four scenarios would result in less-than-significant impacts
associated with roadway noise and potentially significant impacts associated with aircraft and railway noise.
Implementation of the proposed Plan would have a significant impact if it results in a substantial permanent
increase in ambient noise levels in the project vicinity above levels existing without the Plan. According to
the City of Palo Alto’s Environmental Criteria Used by the City of Palo Alto (prepared in 2007), a project in the
City of Palo Alto would cause a significant impact if: it would cause the L dn to increase by five dB or more in
an existing residential area; it would cause the L dn to increase by three dB or more in an existing residential
area and cause the L dn in the area to exceed 60 dB; or it would cause the L dn to increase by three dB or more
in an existing residential area where the L dn currently exceeds 60 dB. Note that three dB is the smallest
increase in loudness perceptible by the human ear, and increases of five dB or greater are easily noticed. 20
However, the implementation of the proposed Plan and changes in the ambient noise environment would
occur over a period of more than 15 years (i.e., build-out horizon of 2030).
20
Bies, David and Hansen, Colin, 2009, Engineering Noise Control: Theory and Practice, Fourth Edition, New York: Spoon Press.
PLACEWORKS
4.10-27
CITY OF PALO ALTO
NOISE
Applicable Regulations:
 California Code of Regulations, Title 24, Building Standards
 Palo Alto Municipal Code: Chapter 9.10, Noise
Long-Term Operational Noise
A portion of the substantial permanent increases to ambient noise levels that could result from
implementation of the proposed Plan would be attributable to ongoing operations on land uses developed
under the plan. Residential, open space, and most passive recreational land uses (i.e., trails, rests areas,
picnic areas) are generally not associated with substantial permanent increases in ambient noise. In the case
of these land uses, very specific sources of noise, such as lawn equipment or social gatherings, would be the
most likely source of excessive noise. Addressing impacts from these noise sources would be handled via the
pertinent chapters of Palo Alto’s Municipal Code. In addition, development projects that are subject to
CEQA review would be evaluated based on the City’s Environmental Criteria Used by the City of Palo Alto,
which assess whether a project would cause the L dn to increase by five dB or more in an existing residential
area; cause the L dn to increase by three dB or more in an existing residential area and cause the L dn in the
area to exceed 60 dB; or cause the L dn to increase by three dB or more in an existing residential area where
the L dn currently exceeds 60 dB. Noise sources associated with residential, open space, and passive
recreational land uses are generally not sufficiently frequent or sustained so as to result in permanent
substantial increases to ambient noise levels. Instead, substantial permanent increases in ambient noise levels
would be most likely to result from development of commercial, industrial, mixed-use, and certain
institutional or active recreational land uses (i.e., ball fields, skate-parks, dog parks).
Scenario 1
Under Scenario 1, the noise-related portions of the existing Comprehensive Plan (in particular, Policies
N-56 through N-61, and related programs) would serve to prevent or mitigate substantial permanent
increase to ambient noise levels from long-term operations. Key provisions of these policies include, among
others: limits on hours of operation, site planning, setbacks, soundwalls, landscaping and, in particular,
project level review to ensure compliance with indoor/outdoor noise standards for sensitive uses. Together,
these policies would serve to ensure that the development of new land uses under Scenario 1 would not
result in substantial permanent increases in the ambient noise level in the project vicinity, and the impact in
this regard would be less than significant.
Scenarios 2, 3, and 4
Under Scenarios 2, 3, and 4, as under Scenario 1, existing Comprehensive Plan land use designations would
remain unchanged, with the exception of the Fry’s Electronics site, which may be redesignated under
Scenario 4. However, because the proposed Plan development is still in process, it has not yet been decided
which policies would be adopted as part of the proposed Plan under these scenarios. Therefore, the impact
would be potentially significant, requiring mitigation.
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NOISE
Transportation-Related Noise
Roadway Noise
As a result of implementation of the proposed Plan and ongoing regional growth, it is anticipated that there
would be substantial permanent increases to the ambient noise levels throughout Palo Alto, and that these
increases would primarily result from increases to transportation-related noise, especially that of automobile
traffic. However, these increases are not expected to meet or exceed the City’s thresholds and, thus, would
not result in a significant impact.
Tables 4.10-7 through 4.10-10 show major roadway segments in Palo Alto with estimated increases in the
ambient noise level at a distance of 50 feet from the roadway centerline for each of the four scenarios. As
shown in Tables 4.10-7 through 4.10-10, none of the segments would experience a significant increase (i.e.,
plus five dB) in traffic noise levels under any of the scenarios.
To summarize the traffic-related noise environments, Table 4.10-11 compares the CNEL increases for the
four scenarios. As shown in Table 4.10-11, all of the projected increases are at or below one and one-half dB
and, thus, none of the four scenarios would result in significant increases (i.e., plus five dB) in ambient noise
levels for any of the roadway segments. None of the segment CNEL increases differ by more than 0.2 dBA
between any of the scenarios. Therefore, the four scenarios would each have approximately the same impact
on roadway noise level increases, and none of the scenarios would result in a significant impact.
Given the high degree of similar results, all four scenarios would have indistinguishable graphical
representations for the future conditions noise contour map. As such, the CNEL contour map shown in
Figure 4.10-4 would apply to all four scenarios. This map includes the contributions from traffic flows on
the freeways through the city. In that respect, it is important to note that US 101 and I-280 will not
experience significant noise level increases as a result of the project. Current average daily traffic on US 101
in Palo Alto is approximately 230,000 trips and on I-280 at Page Mill Road is approximately 110,000
trips. 21 US 101 and I-280 are major thoroughfares for Santa Clara County, and only a small amount of those
trips are due to Palo Alto traffic. Any increase in the number of Palo Alto trips due to the project would have
a negligible effect on the overall traffic volumes. Thus, project-related traffic on the freeways through the
city would not be significant.
21
Caltrans, 2014, http://traffic-counts.dot.ca.gov/, accessed on October 21, 2015. Note that 2014 data is the most recent data that is
available on the Caltrans website. Specifically, Caltrans gathers daily data, aggregates it over an entire year, then divides by 365 to get a yearbased, daily average. Thus, they only have posted data that includes 2014 operations and 2015 data is still being gathered.
PLACEWORKS
4.10-29
CITY OF PALO ALTO
NOISE
TABLE 4.10-7
INCREASES TO AMBIENT NOISE LEVELS ALONG MAJOR ROADWAY SEGMENTS – SCENARIO 1
Ambient Noise Level at 50 feet from
Roadway Centerline CNEL dBA
Existing
Conditions
70.8
Scenario 1
Conditions
71.9
Increase
(dBA)
1.1
Sand Hill Road to Page Mill Road
74.9
75.7
0.8
Page Mill Road to San Antonio Road
74.2
75.2
1.0
Page Mill Road
I-280 to El Camino Real
71.6
72.1
0.5
Arastradero Road
64.3
65.8
1.5
Alma Street
University Avenue to San Antonio Road
70.4
71.2
0.8
Middlefield Road
63.1
63.4
0.3
University Avenue
El Camino Real to US 101
64.9
65.1
0.2
Embarcadero Road
66.4
67.6
1.2
Oregon Expressway
71.1
71.3
0.2
Roadway
Sand Hill Road
Segment
El Camino Real
Charleston Road
El Camino Real to San Antonio Road
63.2
64.4
1.2
San Antonio Road
Foothill Expressway/
Junipero Serra Boulevard
71.8
72.0
0.2
Sand Hill Road to Arastradero Road
70.0
71.4
1.4
Source: Hexagon Transportation Consultants, Inc., 2015; PlaceWorks, 2015.
TABLE 4.10-8
Existing
Conditions
70.8
Scenario 2
Conditions
72.0
Increase
(dBA)
1.2
74.9
75.7
0.8
74.2
75.1
0.9
Page Mill Road
71.6
72.0
0.4
Arastradero Road
64.3
65.7
1.4
Alma Street
70.4
71.2
0.8
Middlefield Road
63.1
63.1
0.0
University Avenue
64.9
65.1
0.2
Embarcadero Road
66.4
67.5
1.1
Oregon Expressway
71.1
71.1
0.0
Charleston Road
63.2
64.2
1.0
San Antonio Road
Foothill Expressway/
Junipero Serra Boulevard
71.8
72.0
0.2
70.0
71.3
1.3
Roadway
Sand Hill Road
El Camino Real
Segment
4.10-30
FEBRUARY 5, 2016
CITY OF PALO ALTO
NOISE
TABLE 4.10-9
Existing
Conditions
70.8
Scenario 3
Conditions
72.0
Increase
(dBA)
1.2
74.9
75.7
0.8
74.2
75.1
0.9
Page Mill Road
71.6
72.1
0.5
Arastradero Road
64.3
65.8
1.5
Alma Street
70.4
71.2
0.8
Middlefield Road
63.1
63.1
0.0
University Avenue
64.9
65.1
0.2
Embarcadero Road
66.4
67.6
1.2
Oregon Expressway
71.1
71.2
0.1
Charleston Road
63.2
64.3
1.1
San Antonio Road
Foothill Expressway
/Junipero Serra Boulevard
71.8
72.0
0.2
70.0
71.4
1.4
Roadway
Sand Hill Road
Segment
El Camino Real
TABLE 4.10-10
Existing
Conditions
70.8
Scenario 4
Conditions
71.9
Increase
(dBA)
1.1
74.9
75.8
0.9
74.2
75.2
1.0
Page Mill Road
71.6
72.2
0.6
Arastradero Road
64.3
65.7
1.4
Alma Street
70.4
71.2
0.8
Middlefield Road
63.1
63.2
0.1
University Avenue
64.9
65.2
0.3
Embarcadero Road
66.4
67.7
1.3
Oregon Expressway
71.1
71.3
0.2
Charleston Road
63.2
64.4
1.2
San Antonio Road
Foothill Expressway
/Junipero Serra Boulevard
71.8
71.9
0.1
70.0
71.4
1.4
Roadway
Sand Hill Road
El Camino Real
Segment
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4.10-31
CITY OF PALO ALTO
NOISE
TABLE 4.10-11
INCREASES TO AMBIENT NOISE LEVELS ALONG MAJOR ROADWAY SEGMENTS – COMPARISON
Increase in Ambient Noise Level at 50 Feet
from Roadway Centerline CNEL dBA
Scenario 1
Scenario 2
Scenario 3
Scenario 4
1.1
1.2
1.2
1.1
0.8
0.8
0.8
0.9
1.0
0.9
0.9
1.0
Page Mill Road
0.5
0.4
0.5
0.6
Arastradero Road
1.5
1.4
1.5
1.4
Alma Street
0.8
0.8
0.8
0.8
Middlefield Road
0.3
0.0
0.0
0.1
University Avenue
0.2
0.2
0.2
0.3
Embarcadero Road
1.2
1.1
1.2
1.3
Oregon Expressway
0.2
0.0
0.1
0.2
Charleston Road
1.2
1.0
1.1
1.2
San Antonio Road
0.2
0.2
0.2
0.1
Foothill Expessway/Junipero
Serra Boulevard
1.4
1.3
1.4
1.4
Roadway
Segment
Sand Hill Road
El Camino Real
Airport/Heliport Noise
Airport noise results are also shown in Figure 4.10-4 and would be the same for all four scenarios. Because
Palo Alto has only one heliport at Stanford University Hospital, and Palo Alto Airport, notable increases in
ambient noise levels from air traffic are not anticipated. However, encroachment of land uses near these
aircraft facilities, along with unknown future operations patterns, could potentially result in unacceptable
aircraft-related noise environments from one or both of these Palo Alto-based facilities. That is, aircraft
operations may cause the L dn to increase by five dB or more in an existing residential area. Thus, future
aircraft-related conditions would have the potential to result in a significant impact under all four scenarios,
requiring mitigation. As discussed above in the Existing Conditions section, noise from medium or large
airports in the region (including Moffett Airfield, San Carlos Airport, San Jose Airport, Oakland
International Airport, and San Francisco International Airport) would not contribute to this determination
of impact significance, with respect to CEQA evaluations, as the relevant noise characteristics of these
facilities are many miles outside of the EIR Study Area.
4.10-32
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NOISE
Notes:
The difference in roadway noise contours between the four scenarios is no more than 0.2 dB
on any segment. This is well below the threshold of distinguishability for community noise.
Additionally, this difference would not be visible on a noise contour map at this citywide scale.
Therefore, all four scenarios are represented on a single map.
Map includes estimated contributions for CalTrain operations from available information
at www.CalTrain.com.
S A N
F R A N C I S C O
B A Y
Railway noise contours generally overlap roadway noise contours
from the adjacent and parallel Alma Street traffic flows.
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65 dBA CNEL contour
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0
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1
Caltrain Stations
Highways
Railroads
City Limit
Sphere of Influence
Figure 4.10-4
2030 Noise Contours
CITY OF PALO ALTO
NOISE
Railway Noise
Railway noise results are also shown in Figure 4.10-4 and would be the same for all four scenarios. With a
single railway alignment through the city, railway operations – primarily focusing on the Caltrain pass-bys as
the freight movements are relatively insubstantial in comparison – are not anticipated to notably increase
community noise levels, except in the immediate vicinity of the rail lines. Noise from the railway generally
is comparable to and overlaps with noise from the adjacent and parallel roadway contributions from Alma
Street traffic flows. Future increases in the number and frequency of railway operations, as a result of the
Caltrain Modernization Program, would result in higher noise level contributions near the rail lines, but
these increases would be offset, to some unknown extent, by the use of electrified and updated equipment
that would have quieter overall noise emissions than the current fleet of trains. 22 Additionally, under
Scenarios 3 and 4, grade-separation trenching configurations would be implemented. The Caltrain
operations would be in a below-grade trench under Meadow Drive and Charleston Road to separate the
existing Caltrain tracks from the roadways (both in anticipation of possible future High Speed Rail service
and to alleviate existing safety and traffic congestion issues). As a result, the scenarios preclude the use of
warning horns on the trains or warning signals at the roadway crossings. The entrenchment of train
operations, along with the lack of warning sounds, would be a noise reduction benefit for Scenarios 3 and 4.
However, since a definitive assessment of either the operations increases or the improvement decreases
cannot be made at this time, future railway operations, could potentially result in unacceptable rail-related
noise environments. That is, railway operations may cause the L dn to increase by five dB or more in an
existing residential area. This would have the potential to result in a significant impact, requiring mitigation
under all four scenarios.
In summary, for long-term operational noise, noise impacts would be less than significant for Scenario 1. The
long-term operational noise impacts for Scenarios 2, 3, and 4 would be potentially significant, requiring
mitigation. Impacts associated with roadway noise, railways, and aircrafts would be less-than-significant under
all four scenarios.
Significance before Mitigation: For long-term operational noise, substantial permanent increases in
ambient noise levels would be most likely to result from development of commercial, industrial, mixed-use,
and certain institutional or active recreational land uses (i.e., ball fields, skate-parks, dog parks). The
associated noise impacts would be less than significant for Scenario 1. The associated noise impacts for
Scenarios 2, 3, and 4 would be potentially significant, requiring mitigation. For roadway-related, railwayrelated, and aircraft-related noise, all four scenarios would result in less-than-significant noise impacts.
22
Additional information on the Caltrain Modernization Program – presented here for reference purposes since Caltrain operations are
not under the purview of this Comprehensive Plan Update – may be found at:
http://www.caltrain.com/Assets/Peninsula+Rail+Program/Electrification+2025/Caltrain_Electrification_EA-FEIR_Vol-I_July_2009WEB.pdf; accessed 6/18/15 and 10/30/15.
4.10-34
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Mitigation Measures
Mitigation Measure NOISE-1a: The following policies and programs, or equally effective language,
shall be included in the proposed Plan to ensure that long-term operational noise under Scenarios 2, 3,
and 4 would not result in significant increases in average 24-hour noise levels.

Policy: Encourage the location of land uses in areas with compatible noise environments. Use the
guidelines in the table “Land Use Compatibility for Community Noise Environment” to determine
compatibility.
- For exterior noise, the guideline for “normally acceptable” noise levels in residential areas is an
L dn of 60 dBA. This level is a guideline for the design and location of future development and a
goal for the reduction of noise in existing development. However, 60 dBA L dn is a guideline
which cannot necessarily be reached in all residential areas within the constraints of economic
or aesthetic feasibility. This guideline will be primarily applied where outdoor use is a major
consideration (e.g., backyards in single-family housing developments and recreational areas in
multiple-family housing projects). Where the City determines that providing an L dn of 60 dBA
or lower outdoors is not feasible, the noise level in outdoor areas intended for recreational use
should be reduced to as close to the standard as feasible through project design.
- For interior noise, the requirements of the State of California Building Standards Code (Title
24) and the Noise Insulation Standards (Title 25) are extended to all new dwelling units in Palo
Alto. Specifically, interior levels for all habitable rooms must not exceed an Ldn of 45 dBA in all
new dwelling units in Palo Alto.
- Noise exposure(s) should be determined from a) more detailed noise exposure studies, or b)
area-specific or project-specific noise measurements, as appropriate. Noise contour maps in this
plan can be used as a preliminary screening tool in determining approximate noise exposure.
- Prior to the initial development application for future developments near noise-sensitive land
uses, the applicant shall submit an acoustical analysis by an acoustical engineer demonstrating
projected compliance with the Comprehensive Plan, the Noise Ordinance, and the State
building code. The analysis shall be based on acoustical readings, equipment specifications,
architectural designs (even if preliminary), and any proposed sound reduction/insulation
measures, such that the pertinent land use compatibility, interior environments, and projectrelated noise emissions can be demonstrated to comply with prescribed city, county, and state
noise standards.

Policy: The City may require proposals to reduce noise impacts of development on adjacent
properties through appropriate means including, but not limited to, the following:
- Construct noise walls when compatible with aesthetic concerns.
- Screen and control noise sources such as parking, outdoor activities, and mechanical
equipment.
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- Increase setbacks for noise sources from adjacent dwellings.
- Whenever possible, retain fences, walls, or landscaping that serve as noise buffers although
design, safety, and other impacts must be addressed.
- Use soundproofing materials and double-glazed windows.
- Control hours of operation, including deliveries and trash pickup, to minimize noise impacts.

Program: Update the Noise Ordinance to provide for clear interpretation of the regulations, and to
review the appropriateness of existing standards. Strictly enforce the Noise Ordinance.
Mitigation Measure NOISE-1b: The following policy, or equally effective language, shall be
included in the proposed Plan to ensure that aircraft noise under all four scenarios would not result in
significant increases in average 24-hour noise levels.
The following new policy shall be adopted as part of the proposed Plan. The wording of this policy may
change as long as the revised policy is equally effective in mitigating potential aircraft noise impacts:

Policy: Ensure compliance with the airport related land use compatibility standards for community
noise environments by prohibiting incompatible land use development within the 60 dBA CNEL
noise contours of the Palo Alto airport.
Mitigation Measure NOISE-1c: The following policies, or equally effective language, shall be
included in the proposed Plan to ensure that railway noise under all four scenarios would not result in
significant increases in average 24-hour noise levels.

Policy: Minimize noise spillover from rail related activities into adjacent residential or noisesensitive areas.

Policy: Reduce impacts from noise and ground borne vibrations associated with rail operations by
requiring that future development of habitable buildings address the following:
- Be sited at least 100 feet from the centerline of the tracks whenever feasible.
- Interior noise level of up to 45 dBA Ldn, with windows closed must be ensured through
structural design. For habitable buildings located within 100 feet from the centerline of railroad
tracks, developments shall provide a detailed noise impact analysis, prepared by a qualified
acoustical consultant technician, demonstrating that noise and ground borne vibration issues
associated with rail operations have been adequately addressed (i.e., by building siting or
construction techniques). This study must demonstrate that an interior noise level of 45 dBA
Ldn will not be exceeded with windows closed.
- Provide a detailed vibration impact analysis, prepared by a qualified acoustical consultant,
demonstrating that ground-borne vibration levels will not exceed 72 VdB (relative to
one microinch/sec) at residential buildings or 65 VdB at buildings with vibration-sensitive uses.
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Significance after Mitigation: Less than Significant.
NOISE-2
Implementation of the proposed Plan would not cause the L dn to increase
by three dB or more in an existing residential area, thereby causing the L dn
in the area to exceed 60 dB. (Potentially Significant and Mitigable – All Four
Scenarios)
Summary: This impact threshold is closely related to that of NOISE-1. As such, traffic flows within the EIR
Study Area would not markedly change with any of the four scenarios so as to exceed this impact threshold.
However, rail-related and aircraft-related operations may result in potentially significant impacts under all
four scenarios. In addition, while Scenario 1 would result in a less-than-significant impact associated with
long-term operational noise, Scenarios 2, 3, and 4 would result in a potentially significant impact, requiring
mitigation.
Scenario 1
Please see the discussion, results, and conclusions presented under Impact NOISE-1. The noise-related
portions of the existing Comprehensive Plan (in particular, Policies N-56 through N-61, and related
programs) would serve to prevent or mitigate substantial permanent increase to ambient noise levels from
long-term operations. Therefore, development of new land uses under Scenario 1 would not result in
substantial permanent increases in the ambient noise level in the project vicinity, such that L dn would
increase by three dB, causing the L dn in an area to exceed 60 dB, and the impact in this regard would be less
than significant.
As is the case with the threshold for Impact NOISE-1, development of new land uses under the proposed
Plan would not result in substantial permanent increases in the ambient noise level in the project vicinity,
such that L dn would increase by three dB, causing the L dn in an area to exceed 60 dB (please see the full
discussions, results, and conclusions presented under Impact NOISE-1). However, because the proposed
Plan development is still in process, it has not yet been decided which policies would be adopted under
these scenarios to guide development and help to prevent significant noise impacts. Therefore, the impact
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Roadway Noise
As discussed under Impact NOISE-1, there would be no project-related increases in L dn levels within the
EIR Study Area that would be greater than 1.5 dB. Specifically, as shown in Tables 4.10-7 through 4.10-10
(above), none of the segments would experience a significant increase (i.e., more than three dB) in traffic
noise levels under any of the scenarios. Since none of the roadway segments would have noise level increases
of three dB or more for any scenario, roadway, US 101, and I-280 noise level increases due to the project
would be negligible, and impacts due to traffic noise increases would not be significant under any of the
scenarios.
Aircraft/Heliport Noise
Please see the discussion, results, and conclusions presented under Impact NOISE-1. Development of new
land uses under all four scenarios may result in encroachment of land uses near aircraft facilities. In addition,
because of the unknown nature of future operations patterns, unacceptable aircraft-related noise
environments could potentially exist. That is, aircraft operations may cause the L dn to increase by three dB
or more in an existing residential area and which would cause the L dn in the area to be pushed above 60
dBA. Thus, future aircraft-related conditions could result in a significant impact, requiring mitigation, under
all four scenarios. As discussed above in the Existing Conditions section, noise from medium or large
airports in the region (including Moffett Airfield, San Carlos Airport, San Jose Airport, Oakland
International Airport, and San Francisco International Airport) would not contribute to this determination
of impact significance, with respect to CEQA evaluations, as the relevant noise characteristics of these
facilities are many miles outside of the EIR Study Area.
Railway Noise
Please see the discussion, results, and conclusions presented under Impact NOISE-1. Future changes in the
number and frequency of railway operations, as a result of the Caltrain Modernization Program, would
result in higher noise level contributions near the rail lines, but these increases would be offset, to some
unknown extent, by the use of electrified and updated equipment that would have quieter overall noise
emissions than the current fleet of trains. In addition, under Scenarios 3 and 4, grade-separation trenching
configurations would be implemented (both in anticipation of possible future High Speed Rail service and to
alleviate existing safety and traffic congestion issues), which would provide a noise reduction benefit for
Scenarios 3 and 4. However, since a definitive assessment of either the operations increases or the
improvement decreases can be made at this time, future railway operations may cause the L dn to increase by
three dB or more in an existing residential area and which would cause the L dn in the area to be pushed
above 60 dBA. Thus, future rail-related conditions could result in a significant impact, requiring mitigation
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In summary, for long-term operational noise, substantial permanent increases in ambient noise levels would
be less than significant for Scenario 1. For Scenarios 2, 3, and 4 the impact would be potentially significant,
requiring mitigation. For impacts associated with roadways, all four scenarios would result in less-thansignificant noise impacts. For impacts associated with railways and aircrafts, all four scenarios would have
potentially significant noise impacts, requiring mitigation.
associated noise impacts would be less than significant for Scenario 1. The associated noise impacts for
Scenarios 2, 3, and 4 would be potentially significant, requiring mitigation. For roadway-related noise, all
four scenarios would result in less than significant noise impacts. However, for railway-related and aircraftrelated noise, all four scenarios could have potentially significant noise impacts, requiring mitigation.
Mitigation Measures
Mitigation Measure NOISE-2: Implement Mitigation Measures NOISE-1a, NOISE-1b, and
NOISE-1c.
NOISE-3
Implementation of the proposed Plan would have the potential to cause an
increase of three dB or more in an existing residential area where the L dn
currently exceeds 60 dB. (Potentially Significant and Mitigable – All Four
Scenarios)
Summary: This impact threshold is closely related to that of NOISE-1. As such, traffic flows within the EIR
Study Area would not markedly change with any of the four scenarios so as to exceed this impact threshold.
However, rail-related and aircraft-related operations may result in potentially significant impacts under all
four scenarios. In addition, while Scenario 1 would result in a less-than-significant impact associated with
long-term operational noise, Scenarios 2, 3, and 4 would result in a potentially significant impact, requiring
mitigation.
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Scenario 1
Please see the discussion, results, and conclusions presented under Impact NOISE-1. The noise-related
portions of the existing Comprehensive Plan (in particular, Policies N-56 through N-61, and related
programs) would serve to prevent or mitigate substantial permanent increase to ambient noise levels from
long-term operations. Therefore, development of new land uses under Scenario 1 would not result in
substantial permanent increases in the ambient noise level in the project vicinity, such that L dn would
increase by three dB in a residential area that already exceeds 60 dB. The impact in this regard would be less
than significant.
As is the case with the threshold for Impact NOISE-1, development of new land uses under the proposed
Plan would not result in substantial permanent increases in the ambient noise level in the project vicinity,
such that L dn would increase by three dB in a residential area that already exceeds 60 dB (please see the full
discussions, results, and conclusions presented under Impact NOISE-1). However, because the proposed
Plan development is still in process, it has not yet been decided which policies would be adopted under
these scenarios to guide development and help to prevent significant noise impacts. Therefore, the impact
Roadway Noise
As discussed under Impact NOISE-1, there would be no project-related increases in L dn levels within the
EIR Study Area that would be greater than 1.5 dB. Specifically, as shown in Tables 4.10-7 through 4.10-10
(above), none of the segments would experience a significant increase (i.e., more than three dB) in traffic
noise levels under any of the scenarios. Since none of the roadway segments would have noise level increases
of three dBA or more for any scenario, roadway, US 101, and I-280 noise level increases due to the project
would be negligible, and impacts due to traffic noise increases would not be significant under any of the
scenarios.
Aircraft/Heliport Noise
Please see the discussion, results, and conclusions presented under Impact NOISE-1. Development of new
land uses under all four scenarios may result in encroachment of land uses near aircraft facilities. In addition,
because of the unknown nature of future operations patterns, aircraft operations may cause the L dn to
increase by three dB or more in an existing residential area which is already exceeding 60 dBA L dn . Thus,
future aircraft-related conditions could result in a significant impact, requiring mitigation, under all four
scenarios. As discussed above in the Existing Conditions section, noise from medium or large airports in the
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region (including Moffett Airfield, San Carlos Airport, San Jose Airport, Oakland International Airport, and
San Francisco International Airport) would not contribute to this determination of impact significance, with
respect to CEQA evaluations, as the relevant noise characteristics of these facilities are many miles outside
of EIR Study Area.
Railway Noise
Please see the discussion, results, and conclusions presented under Impact NOISE-1. Future changes in the
number and frequency of railway operations, as a result of the Caltrain Modernization Program, would
result in higher noise level contributions near the rail lines, but these increases would be offset, to some
unknown extent, by the use of electrified and updated equipment that would have quieter overall noise
emissions than the current fleet of trains. In addition, under Scenarios 3 and 4, grade-separation trenching
configurations would be implemented (both in anticipation of possible future High Speed Rail service and to
alleviate existing safety and traffic congestion issues), which would provide a noise reduction benefit for
Scenarios 3 and 4. However, since a definitive assessment of either the operations increases or the
improvement decreases can be made at this time, future railway operations could potentially result in the
L dn to increase by three dB or more in an existing residential area which is already exceeding 60 dBA L dn .
Thus, future rail-related conditions could result in a significant impact, requiring mitigation under all four
scenarios.
In summary, for long-term operational noise, substantial permanent increases in ambient noise levels would
be less than significant for Scenario 1. For Scenarios 2, 3, and 4, the impact would be potentially significant,
requiring mitigation. For impacts related to roadways, all four scenarios would result in less-than-significant
noise impacts. However, for impacts related to railways and aircrafts, all four scenarios would have potentially
significant noise impacts, requiring mitigation.
associated noise impacts would be less than significant for Scenario 1 and potentially significant for Scenarios
2, 3, and 4. For roadway-related noise, all four scenarios would result in less-than-significant noise impacts.
However, for railway-related and aircraft-related noise, all four scenarios could have potentially significant
noise impacts, requiring mitigation. .
Mitigation Measures
Mitigation Measure NOISE-3: Implement Mitigation Measures NOISE-1a, NOISE-1b, and
NOISE-1c.
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NOISE-4
Implementation of the proposed Plan would have the potential to result in
indoor noise levels for residential development to exceed an L dn of 45 dB.
(Significant and Mitigable – Scenario 1; Potentially Significant and
Mitigable – Scenarios 2, 3, and 4)
Summary: As described below, project-specific acoustical analysis would be required under all four
scenarios to ensure that impacts are less than significant. Therefore, impacts would be significant or
potentially significant, requiring mitigation, for all four scenarios.
 Title 21, Subchapter 6, of the California Code of Regulations
 Palo Alto Municipal Code, Chapter 9.10, Noise
 Palo Alto Municipal Code, Chapter 18.23.060, Noise and Vibration
Citywide and SOI Discussion
Standards for interior noise environments in the City of Palo Alto are currently determined using: the Land
Use Noise Compatibility Guidelines (which are established in the Natural and Urban Environment and
Safety Element of the existing Comprehensive Plan), as well as by the interior noise standards set by the
Title 24 of the State Building Code. The former is predicated on an assumed, nominal exterior-to-interior
noise level reduction for typical residential architectural elements (with doors and windows being in their
closed position). 23 The latter is a defined interior limit that the State of California has judged to be
appropriate for community-wide quality of life. These city-focused guidelines are generally consistent with
the information in the corresponding County Element and Code. Under all four scenarios, new
development would be required to adhere to Title 24 requirements.
Scenario 1
Under Scenario 1, the existing Land Use Noise Compatibility Standards included in the noise portion of
Natural Environment Chapter of the existing Comprehensive Plan would be maintained. No changes would
be made on the County Compatibility Standards (since they are not under the purview of the City). While
Chapter 18.23.060 of the Palo Alto Municipal Code requires the submittal of an acoustical analysis report
for selected new projects, this Code requirement is aimed at showing compliance regarding noise emissions
from one property onto adjoining/nearby properties (per Chapter 9.10). As such, Chapter 18.23.060 does
not speak to land use compatibility, which is typically addressed in a city’s Noise Element. For the City of
Palo Alto in particular, however, existing Comprehensive Plan policies do not require acoustical analyses to
demonstrate compliance with applicable noise compatibility standards. Therefore, new policies would be
23
That is, for an exterior environment of 65 dBA CNEL and assuming a nominal – and conservative – reduction value of 20 dB, the
interior environment would be 45 dBA CNEL. Typically, noise reduction values (with closed windows and doors) in the range of 24 to 25 dB
are commonly used in environmental impact assessments.
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needed to ensure that such impacts would be less than significant. Absent these policies, the impact would
therefore be considered significant, requiring mitigation.
The Natural Environment Chapter of the existing Comprehensive Plan currently contains policies that are
generally intended to minimize community noise impacts as well as to facilitate the juxtaposition of
compatible land uses with respect to noise intrusions. However, because the proposed Plan development is
still in process, it has not yet been decided which policies would be adopted under Scenarios 2, 3, and 4 and
therefore it is unknown whether and how the City’s Land Use Compatibility Standards and noise-related
policies would be maintained or revised. Additionally, as with Scenario 1, one or more new policies
regarding acoustical studies—aimed at ensuring land use compatibility—would be needed to ensure that
such impacts would be less than significant. Therefore, the impact is potentially significant, requiring
mitigation for Scenarios 2, 3, and 4.
Site-Specific Discussion
The EIR Study Area encompasses a geographically large expanse and includes a diversity of noise
environments (from both land uses and roadways). For this reason, it is not feasible to discuss site-level noise
impacts in these special areas within the EIR Study Area, in the absence of information about specific
proposed development projects.
Nevertheless, it can be generally stated that, under all four scenarios, as the proposed Plan allows
development and redevelopment activities throughout the EIR Study Area, all areas within the EIR Study
Area have the potential to receive some amount of noise from both highways and major arterials. Because all
portions of the EIR Study Area are at least partly located in close proximity to major arterial(s) or a
highway, it is likely that there are areas where development would require special noise-insulating features
or construction techniques. Therefore, for individual sites located within the EIR Study Area, additional
project-level acoustical analysis would be necessary to demonstrate consistency with applicable land use
compatibility requirements and interior noise standards.
Although the various project sites may be affected in different ways or to different degrees by noise from
major arterials and/or freeways, project-level acoustical analyses, at a minimum, would need to examine
portions of individual housing sites nearest to major transportation corridors to measure current, 24-hour
ambient noise levels and determine appropriate site design and/or construction techniques for noise
attenuation. Since the existing Comp Plan policies do not require acoustical analyses to demonstrate
compliance with applicable noise compatibility standards and since Chapter 18.23.060 of the Municipal
Code does not focus on land use compatibility in its requirements for acoustical studies, new policies would
be needed to ensure that such impacts would be less than significant. Therefore, the impact would be
potentially significant, requiring mitigation under all four scenarios.
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Significance before Mitigation: Development under all four scenarios may result in interior noise
environments in excess of the pertinent building standards requirements. Interior noise impacts were found
to be significant under Scenario 1 and potentially significant under Scenarios 2, 3, and 4. For all scenarios,
the proposed Plan should include one or more policies regarding acoustical analyses for land use
compatibility.
Mitigation Measures
Mitigation Measure NOISE-4a: The following policies and programs, or equally effective language,
shall be included in the proposed Plan to ensure that future development under all four scenarios would
not result in indoor noise levels that exceed acceptable levels in residential development.

Policy: Encourage the location of land uses in areas with compatible noise environments. Use the
guidelines in the table “Land Use Compatibility for Community Noise Environment” to determine
compatibility.
- For exterior noise, the guideline for “normally acceptable” noise levels in residential areas is an
L dn of 60 dBA. This level is a guideline for the design and location of future development and a
goal for the reduction of noise in existing development. However, 60 dBA L dn is a guideline
which cannot necessarily be reached in all residential areas within the constraints of economic
or aesthetic feasibility. This guideline will be primarily applied where outdoor use is a major
consideration (e.g., backyards in single family housing developments and recreational areas in
multiple family housing projects). Where the City determines that providing an L dn of 60 dBA
or lower outdoors is not feasible, the noise level in outdoor areas intended for recreational use
should be reduced to as close to the standard as feasible through project design.
- For interior noise, the requirements of the State of California Building Standards Code (Title
24) and the Noise Insulation Standards (Title 25) are extended to all new dwelling units in Palo
Alto. Specifically, interior levels for all habitable rooms must not exceed an Ldn of 45 dBA in all
new dwelling units in Palo Alto.

4.10-44
- Noise exposure(s) should be determined from (a more detailed noise exposure studies, or (b)
on area-specific or project-specific noise measurements, as appropriate. Noise contour maps in
this plan can be used as a preliminary screening tool in determining approximate noise
exposure.
Prior to the initial development application for future developments near noise-sensitive land uses,
the applicant shall submit an acoustical analysis by an acoustical engineer demonstrating projected
compliance with the Comprehensive Plan, the Noise Ordinance, and the State building code. The
analysis shall be based on acoustical readings, equipment specifications, architectural designs (even
if preliminary), and any proposed sound reduction/insulation measures, such that the pertinent
land use compatibility, interior environments, and project-related noise emissions can be
demonstrated to comply with prescribed city, county, and state noise standards.
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
Policy: For all future residential projects greater than four dwelling units that are proposed to be
within the 65 dBA L dn noise contours, as depicted on current Comprehensive Plan mapping, an
acoustical analysis prepared by a qualified acoustical consultant shall be submitted to the City as part
of the entitlement review application. As part of the above acoustical analysis, require that projects
include appropriate layout, structural, and/or architectural design features to ensure meeting the
interior noise standards of the City and State codes.
Mitigation Measure NOISE-4b: The Land Use Noise Compatibility Guidelines established in the
current Comprehensive Plan shall be maintained under all four scenarios.
NOISE-5
Implementation of the proposed Plan would have the potential to expose
persons to or generate excessive ground-borne vibration or ground-borne
noise levels. (Significant and Mitigable – Scenario 1; Potentially Significant
and Mitigable – Scenarios 2, 3, and 4)
Summary: As described below, under all four scenarios, project-specific review and new policies would be
needed to ensure that impacts would be less than significant. Therefore, impacts would be significant or
potentially significant, requiring mitigation for all four scenarios.
CEQA does not specify quantitative thresholds for what is considered “excessive” vibration or groundborne
noise, nor does the City of Palo Alto establish any such thresholds. The City of Palo Alto Municipal Code
does specify that “All uses within 150 feet of a residential property should be operated as not to generate
vibration discernible without instruments at or beyond the lot line upon which the source is located or
within adjoining enclosed space if more than one establishment occupies a structure” (Palo Alto Municipal
Code Chapter 18.23.060), but the Code does not set a specific numeric threshold.
In the City of Palo Alto, groundborne vibration can be related to (a) short-term impacts from construction
activities or (b) on-going impacts related to operation of a permanent land use (such as a commercial or
industrial facility) or (c) on-going impacts related to rail pass-bys. These three types of groundborne
vibration situations are discussed below.
 Palo Alto Municipal Code, Chapter 18.23.060
Short-Term Construction-Related Vibration Impacts
The effect on buildings in the vicinity of a construction site varies depending on soil type, ground strata, and
receptor-building construction. The results from vibration can range from no perceptible effects at the
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lowest vibration levels, to low rumbling sounds and perceptible vibrations at moderate levels, to slight
structural damage at the highest levels. Vibration from construction activities rarely reaches the levels that
can damage structures, but groundborne vibration and groundborne noise can reach perceptible and audible
levels in buildings that are close to the construction site. Table 4.10-12 lists vibration levels for construction
equipment.
As shown in Table 4.10-12, vibration generated by construction equipment has the potential to be
substantial. Significant vibration impacts may occur from construction activities associated with new
development under the proposed Plan. Under all four scenarios, the proposed Plan would allow an increase
in development intensity in certain areas, in the absence of information about specific development
proposals.
Construction would be localized and would occur intermittently for varying periods of time. Without
specific development details, it is not possible to quantify potential construction vibration impacts. Grading
and demolition activity typically generate the highest vibration levels during construction. Except for pile
driving, maximum vibration levels measured at a distance of 25 feet from an individual piece of typical
construction equipment do not exceed the thresholds for human annoyance for industrial uses, nor the
thresholds for architectural damage.
Methods to reduce vibration during construction would include the use of smaller equipment, use of wellmaintained equipment, use of static rollers instead of vibratory rollers, and drilling of piles as opposed to
pile driving. Methods to reduce human impacts of vibration from construction include limitations on
construction hours and/or guidelines for the positioning of vibration-generating construction equipment.
Since perception of vibrations varies between individuals, it is necessary to establish a quantitative threshold
that reflects levels of vibration typically capable of causing perception, annoyance, or damage. For the
purpose of this analysis and consistent with common practice in the industry, the standards adopted by the
FTA to evaluate vibration from construction equipment are utilized.
According to the FTA Noise and Vibration Impact Guidelines (2006), vibrations generated by projectrelated construction activities exceeding 0.2 peak particle velocity (PPV) in inches per second (in/sec) 24
would be strong enough to cause vibration-induced architectural damage to typical wood-framed buildings.
Similarly, vibration-induced annoyance at nearby residential structures may be experienced when projectrelated construction activities exceed the FTA’s daytime vibration criteria of 78 VdB (vibration decibel with
a reference of 1 micro-inch/second).
24
This is predicated on the receptor building being a non-engineered timber or masonry building; per FTA manual guidelines. The 0.2
PPV threshold is approximately equivalent to an RMS velocity level of 94 VdB with respect to one micro-inch/second (and assuming a typical
crest factor of four).
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TABLE 4.10-12
GROUNDBORNE VIBRATION LEVELS FOR CONSTRUCTION EQUIPMENT
Approximate Velocity
Level at 25 Feet
(VdB)
Approximate RMSa
Velocity at 25 Feet
(inch/sec)
Pile Driver (Impact) Upper Range
112
1.518
Pile Driver (Impact) Lower Range
104
0.644
Pile Driver (Sonic) Upper Range
105
0.734
Pile Driver (Sonic) Lower Range
93
0.170
Large Bulldozer
87
0.089
Caisson Drilling
87
0.089
Jackhammer
79
0.035
Small Bulldozer
58
0.003
Loaded Trucks
86
0.076
78 to 90b
—
—
0.2 to 0.5c
Equipment
FTA Criteria – Human Annoyance (Daytime)
FTA Criteria – Structural Damage
a. RMS velocity calculated from vibration level (VdB) using the reference of 1 micro-inch/second.
b. Depending on affected land use. For residential 78 VdB, for offices 84 VdB, workshops 90 VdB.
c. Depending on affected building structure, for timber and masonry buildings 0.2 in/sec, for reinforced-concrete, steel, or timber 0.5 in/sec.
Source: Federal Transit Administration, Transit Noise, and Vibration Impact Assessment, 2006.
Overall, vibration impacts related to construction would be short-term, temporary, and generally restricted
to the areas in the immediate vicinity of active construction equipment. Construction would be localized
and would occur intermittently for varying periods of time. Because specific, project-level information is
not available at this time, it is not possible to quantify the construction vibration impacts at specific sensitive
receptors. Therefore, individual project review would be needed to ensure appropriately reduced vibration
impacts arising from construction. Therefore, the impact could be significant, requiring mitigation under all
four scenarios.
On-Going Operations Vibration Impacts
Development that would be allowed under all four scenarios may result in long-term, operations-related
vibration impacts to sensitive receptors if sensitive land uses, such as residential, educational facilities,
hospitals, or places of worship, were to be located in close proximity to industrial land uses that could have
equipment with the potential to generate significant vibration levels. None of the four scenarios include
changes to the City’s Comprehensive Plan land use map, with the exception of Scenario 4, which may
redesignate the Fry’s Electronics site. Under all four scenarios, there would continue to be limited areas of
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the EIR Study Area where residential or other sensitive land uses would interface with light industrial
operations under the Comprehensive Plan land use designations.
Despite the potential for vibration impacts from the juxtaposition of sensitive land uses and land uses with
the potential to generate vibration, measures such as appropriate setbacks, buffers and use restrictions, can
largely eliminate these impacts. As discussed above, vibration impacts are highly dependent on a variety of
localized factors, including geology, soil conditions, and building construction techniques. However, in most
cases, vibration attenuates relatively rapidly with distance, making setbacks and buffering particularly
effective approaches to avoid vibration impacts. Moreover, high levels of vibration are usually associated with
heavy industrial uses. The light industrial uses of the sort that would continue to be permitted in Palo Alto
under the proposed Plan are very rarely associated with vibration that is sufficiently intense or sustained so
as to cause either human discomfort or architectural/structural damage.
Although there are no State or federal regulations to limit perception of vibration by sensitive receptors, the
proposed Plan would continue Municipal Code provisions that would employ the previously mentioned
strategies to prevent vibration impacts. More specifically, Chapter 18.23.060 of the Municipal Code
contains general restrictions regarding the generation of vibration that is perceptible without instruments at
the lot line of the receiving property. However, under all four scenarios, new policies would be needed to
ensure that buildout of land uses allowed by the proposed Plan would not result in the perception by
sensitive receptors of excessive vibration (and noise).
Scenario 1
Under Scenario 1, the policies and programs of the existing Comprehensive Plan would be maintained and
new policies would not be adopted. Because existing policies are not sufficient to ensure that on-going
vibration impacts from operation of land uses would be less than significant, Scenario 1 would result in a
significant impact, requiring mitigation.
Because the proposed Plan development is still in process, it has not yet been decided which policies will be
adopted under Scenarios 2, 3, and 4 and therefore it is unknown whether proposed Plan policies would
address and prevent on-going vibration impacts from operation of land uses. Therefore, the impact is
potentially significant for Scenarios 2, 3, and 4.
On-Going Railway Pass-By Vibration Impacts
Development allowed by the proposed Plan may result in long-term, vibration impacts if sensitive land uses
(such as residential, educational facilities, hospitals, or places of worship) were allowed to be developed in
close proximity to existing railways. As discussed above, the effect on sensitive receptors in the vicinity of a
railway depends on soil type, ground strata, and receptor-building construction, as well as on the type of rail
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system (i.e., commuter, rapid transit, light rail, heavy freight, and/or high-speed rail) 25, the locomotive and
railcar loading, the auxiliary equipment, the condition of the tracks, and the pass-by speed. While vibration
impacts related to rail pass-bys would be short-term, temporary, and generally restricted to the areas in the
immediate vicinity of a railway, vibration effects from on-going rail pass-bys could be objectionable. These
vibration effects can range from no perceptible effects at the lowest vibration levels, to low rumbling sounds
and perceptible vibrations at moderate levels, to slight structural damage at the highest levels. Vibration
from rail pass-bys rarely reaches the levels that can damage structures, but groundborne vibration and
groundborne noise can reach perceptible and audible levels in buildings that are close to railways. As such,
appropriate setbacks, buffers, and/or other measures can largely eliminate these impacts since these basic
techniques are particularly effective approaches to avoid vibration impacts. However, additional efforts
would be needed to ensure that no new development of vibration-sensitive uses would be allowed.
Specifically, individual project review would be needed to ensure appropriately reduced vibration impacts
arising from rail pass-bys. Therefore, the impact could be significant, requiring mitigation under all four
scenarios.
In summary, temporary construction-related vibration would be potentially significant under all four
scenarios, requiring mitigation. For long-term operational vibration, project-related impacts would be
significant for Scenario 1 and potentially significant for Scenarios 2, 3, and 4. For impacts related to railway
vibration, all four scenarios could have potentially significant impacts, requiring mitigation. There would be
no impacts related to either roadway or aircraft facilities under any of the scenarios.
Significance before Mitigation: Development under all four scenarios may result in groundborne
vibration levels above the pertinent industry standards and City guidelines. Temporary construction-related
vibration would be potentially significant under all four scenarios, requiring mitigation. For long-term
operational vibration, project-related impacts would be significant for Scenario 1 and potentially significant
for Scenarios 2, 3, and 4, requiring mitigation. For railway-related vibration, all four scenarios could have
potentially significant vibration impacts, requiring mitigation. There would be no impacts related to either
roadway or aircraft facilities.
Mitigation Measures
Mitigation Measure NOISE-5a: The following policies, or equally effective language, shall be
included in the proposed Plan to ensure that future development under all four scenarios would not
result in significant construction-related vibration impacts.

Policy: Require a detailed construction noise impact analysis, prepared by a qualified acoustical
consultant, for all projects that require discretionary approval and that are located within 100 feet of
25
Future HSR-related vibration levels will be minimized by adhering to standards for new track construction, as well as standards for ongoing maintenance aimed at achieving smooth wheel and track surfaces. Both the initial smooth track and on-going maintenance are required for
successful high-speed rail operation and would be the responsibility of the California High Speed Rail Authority to implement. Under that
premise, the condition of the HSR right-of-way rails and wheels are expected to be smoother than current, non-HSR tracks and wheels. Thus,
the HSR system would be less likely to produce vibrational energy into the new track bed than would existing Caltrain operations.
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any noise sensitive land uses. If impacts are identified, require a noise monitoring plan to be
prepared and submitted prior to the issuance of construction permits. This plan shall identify the
monitoring locations, durations and regularity, the instrumentation to be used, and the appropriate
noise control measures that will be incorporated to ensure compliance with the noise ordinance.

Policy: Continue to prioritize construction noise limits around sensitive receptors.
Mitigation Measure NOISE-5b: Implement Mitigation Measure NOISE-1c.
NOISE-6
Implementation of the proposed Plan would have the potential to expose
people to noise levels in excess of established State standards. (Potentially
Significant and Mitigable – All Four Scenarios)
Summary: As described below, project-level acoustical analysis would be necessary under all four scenarios
to demonstrate consistency with applicable land use compatibility requirements and interior noise
standards. Therefore, the impact would be potentially significant, requiring mitigation under all four
scenarios.
Standards for interior noise environments in the City of Palo Alto are currently determined primarily
through the Land Use Noise Compatibility Guidelines (which are established in the Natural and Urban
Environment and Safety Element of the existing Comprehensive Plan), as well as by the interior noise
standards set by the Title 24 of the State Building Code. As discussed under Impact NOISE-4 (above), under
the proposed Plan, in areas where noise levels exceed those that are normally acceptable for a particular
land use, new policies would be needed to ensure that interior noise environments would comply with the
45 dBA L dn State standard. As future development occurs under all four scenarios, project-level acoustical
analyses would be necessary to demonstrate consistency with applicable land use compatibility requirements
(per Impact NOISE-4) and interior noise standards (per Impact NOISE-6). Since the existing
Comprehensive Plan policies do not require acoustical analyses to demonstrate compliance with applicable
noise compatibility standards (neither exterior nor interior), new policies would be needed to ensure that
such impacts would be less than significant. Therefore, the impact would be potentially significant, requiring
mitigation under all four scenarios.
Significance before Mitigation: Development under all four scenarios may result in interior noise
environments in excess of the pertinent state building standards requirements. Interior noise impacts were
found to be potentially significant under all four scenarios. For all scenarios, the proposed Plan should
include one or more policies regarding acoustical analyses for land use compatibility.
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Mitigation Measures
Mitigation Measure NOISE-6: Implement Mitigation Measures NOISE-4a and NOISE-4b.
NOISE-7
Implementation of the proposed Plan would have the potential to result in
the exposure of persons to or generation of noise levels in excess of
standards established in the local General Plan or noise ordinance, or
applicable standards of other agencies. (Potentially Significant and
Mitigable – All Four Scenarios)
Summary: None of the scenarios propose specific development projects that would be certain to exceed
applicable noise thresholds. In addition, none of the scenarios would include changes to County regulations
that would affect compliance with noise regulations within the SOI. However, under all four scenarios,
without project-level acoustical impact analyses, future projects allowed by the proposed Plan could be
inconsistent with applicable noise requirements in City and State standards. Therefore, the impact would be
potentially significant, requiring mitigation under all four scenarios for future development within the city.
Citywide Discussion
Standards for noise generation and exposure in the City of Palo Alto are determined primarily through the
Comprehensive Plan Land Use Noise Compatibility Guidelines; Chapters 9.10 and 18.23.060 of the Palo
Alto Municipal Code; as well as by the interior noise standards set by the Title 24 of the State Building
Code. In addition to the guidelines for land use noise compatibility, the City of Palo Alto’s Municipal Code
noise limits by use are defined in terms of the amount by which the noise level exceeds the local ambient
level, and this regulatory approach would continue under the proposed Project. Therefore, there are three
subsequent criteria, based on applicable standards and regulations, which may be applied to determine
impacts within the City of Palo Alto under this significance threshold. Each of these is analyzed in greater
detail below.

Criterion 1: Development of any land use in an area that is characterized by an exterior L dn which
indicates that the establishment of that land use in the area would be “clearly unacceptable,” pursuant to
the Land Use Noise Compatibility Guidelines continued under the proposed Plan.
Analysis: Under Scenario 1, the Land Use Noise Compatibility Guidelines in the existing
Comprehensive Plan would be maintained. Therefore, Scenario 1 would comply with this criterion.
Because the proposed Plan development is still in process, it has not yet been decided which policies and
guidelines of the existing Comprehensive Plan would be maintained under Scenarios 2, 3, and 4 .
Therefore, there could be a significant impact and these scenarios would require mitigation to ensure
consistency with this criterion.
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
Criterion 2: Development of a new land use that would result in adjacent properties experiencing
short- or long-term ambient noise levels that exceed levels permitted under Chapters 9.10 and
18.23.060 of the Palo Alto Municipal Code.
Analysis: None of the scenarios proposed amendments to Chapters 9.10 or 18.23.060 of the Palo Alto
Municipal Code. However, under all four scenarios, project-level acoustical analysis would be necessary
to demonstrate that new development would comply with applicable City Code requirements (Chapter
18.23.060) and would not contribute to excessive noise at existing sensitive receptors. With the absence
of such acoustical analyses in the existing City of Palo Alto Comprehensive Plan, there could be a
significant impact and these scenarios would require mitigation to ensure consistency with this
criterion.

Criterion 3: Development of new residential or other noise-sensitive land uses such that those new
uses would experience an indoor L dn exceeding 45 dBA.
Analysis: Prevention of excessive interior noise levels would need to be achieved through the
performance of acoustical analysis in noisy areas, which would help determine what, if any, noise
attenuating features are necessary to achieve the 45 dBA L dn interior noise standard. As individual
projects are proposed under the proposed Plan, project-specific acoustical analysis would be needed to
demonstrate compliance. With the absence of such acoustical analyses in the existing City of Palo Alto
Comprehensive Plan, there could be a significant impact and all four scenarios would require mitigation
to ensure consistency with this criterion.
SOI Discussion
Standards for noise generation and exposure outside of the city limit, but within the SOI, would be covered
by County of Santa Clara standards. Similar to the City standards, County standards are determined
primarily through the County Land Use Noise Compatibility Guidelines; Chapter VIII, Control of Noise and
Vibration, under Title B of the Santa Clara County Code (mainly Section B11-152); as well as by the interior
noise standards set by the Title 24 of the State Building Code. While the County’s General Plan – like the
City’s Comprehensive Plan – establishes the guidelines for land use noise compatibility based on exterior
sound levels, the County’s General Plan extends their standards by also promoting recommended maximum
interior noise levels for intermittent noise. In addition to these exterior and interior guidelines for land use
noise compatibility, the County of Santa Clara’s Code establishes noise limits for both exterior and interior
spaces. Both the County’s policy and regulatory approaches would continue under the proposed Project.
Therefore, there are three subsequent criteria, based on applicable standards and regulations, which may be
applied to determine impacts in the SOI under this significance threshold. Each of these is analyzed in
greater detail below.

Criterion 4: Development of any land use in an area that is characterized by an exterior L dn which
indicates that the establishment of that land use in the area would be “cautionary” or “critical,” as defined
in the County’s Land Use Noise Compatibility Guidelines. The associated text for these definitions
include mention of requiring “study on the compatibility of the proposed project” (for “cautionary”
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determinations) and requiring “rigorous analysis of the compatibility of the proposed project with the
ambient noise level at the site” (for “critical” determinations), but there are no detailed characterizations
for what a “study” or a “rigorous analysis” would entail. Beyond the exterior guidelines, every reasonable
effort should be made to follow the County’s recommended maximum interior noise levels (for
intermittent noise). Neither of the County exterior or interior noise standards would be subject to
changing under any of the four scenarios.
Analysis: Since the County’s Land Use Noise Compatibility Guidelines would not change under the
proposed Plan, these exterior and interior noise compatibility standards would be followed under all
four scenarios. None of the scenarios would include changes to the County’s Land Use Noise
Compatibility Guidelines. Therefore, none of the scenarios would result in an impact.

Criterion 5: Development of a new land use that would result in adjacent properties experiencing
short- or long-term ambient noise levels that exceed levels permitted under Chapter VIII of the Santa
Clara County Code.
Analysis: None of the scenarios proposed amendments to Chapter VIII of the Santa Clara County
Code. Therefore, development in the county would continue to follow the Santa Clara County Code.
Because none of the scenarios would include changes to the County Code, none of the scenarios would
result in an impacts.

Criterion 6: Development of new residential or other noise-sensitive land uses such that those new
uses would experience an indoor L dn exceeding 45 dBA.
Analysis: None of the scenarios would include changes to the development regulations within the
county. Therefore, none of the scenarios would result in an impact.
Site-Specific Discussion
The EIR Study Area encompasses a geographically large expanse and includes a diversity of noise
environments (from both land uses and roadways). For this reason, it is not feasible to discuss site-level noise
impacts in these special areas in the absence of information about specific proposed development projects.
Nevertheless, it can be generally stated that all study areas have the potential to receive some amount of
noise from both highways and major arterials. Because all of the study areas are at least partly located in
close proximity to major arterial(s) or a highway, it is likely that there are portions of all study areas where
development would require special noise-insulating features or construction techniques. Therefore, for
individual sites located within all study areas, additional project-level acoustical analyses would be necessary
to demonstrate consistency with applicable land use compatibility requirements and interior noise
standards. Although the various project sites may be affected in different ways or to different degrees by
noise from major arterials and/or freeways, project-level analysis, at a minimum, would need to examine
portions of individual housing sites nearest to major transportation corridors to measure current, 24-hour
ambient noise levels and determine appropriate site design and/or construction techniques for noise
attenuation. Since the existing Comprehensive Plan policies do not require acoustical analyses to
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demonstrate compliance with applicable noise compatibility standards and since Chapter 18.23.060 of the
Municipal Code does not focus on land use compatibility in its requirements for acoustical studies, new
policies would be needed to ensure that such impacts would be less than significant. Therefore, the impact
could be significant, requiring mitigation under all four scenarios.
In summary, all four scenarios would result in potentially significant citywide and project-specific impacts,
with the single exception of Scenario 1, which would result in a less-than-significant impact (per Criterion 1).
Within the SOI, there would be no impact.
 Title 21, Subchapter 6, of the California Code of Regulations
 Palo Alto Municipal Code, Chapter 9.10, Noise
 Palo Alto Municipal Code, Chapter 18.23.060, Noise and Vibration
 Santa Clara County General Plan, Land Use Noise Compatibility Guidelines
 Santa Clara County Code, Section B11-152
Significance before Mitigation: Development under all four scenarios may result in community noise
environments in excess of the pertinent Comprehensive Plan, Municipal Code, and/or State building
requirements. This pertains to citywide and project-specific development, with the single exception of
Scenario 1, which would maintain compliance with the pertinent Comprehensive Plan Land Use
Compatibility Guidelines (per Criterion 1). Since none of the scenarios of the proposed Plan would change
any requirements under the County of Santa Clara General Plan or Code, there would be no impact under
the proposed Plan for areas outside of the city limits, but within the Plan’s SOI area.
Mitigation Measures
Mitigation Measure NOISE-7: Implement Mitigation Measures NOISE-1a, NOISE-1b, NOISE-1c,
NOISE-4a, and NOISE-4b.
NOISE-8
Implementation of the proposed Plan could result in a potentially
substantial temporary or periodic increase in ambient noise levels in the
project vicinity above levels existing without the project. (Potentially
Significant and Mitigable – All Four Scenarios)
Summary: As described below, under all four scenarios it is possible that certain construction activities
would lead to substantial temporary or periodic increases to ambient noise levels. Therefore, impacts under
all four scenarios would be potentially significant, requiring mitigation.
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Implementation of the proposed Plan would have a significant impact if it would result in a substantial
temporary or periodic increase in ambient noise levels in the project vicinity above levels existing without
the Plan.
Noise from construction equipment and various construction-related activities is frequently a cause of
temporary or periodic increases in ambient noise levels. Table 4.10-13, below, shows typical noise levels
generated by commonly used construction equipment. Although the noise ordinance would serve to reduce
noise generation from construction equipment, it is likely that in certain cases these and other available
methods to reduce noise would be inadequate to prevent a significant impact.
TABLE 4.10-13
Construction
Equipment
CONSTRUCTION EQUIPMENT NOISE EMISSION LEVELS
Typical Noise Level
(dBA) at 50 Feet
Construction
Equipment
Typical Noise Level
(dBA) at 50 Feet
Air Compressor
81
Pile-Driver (Impact)
101
Backhoe
80
Pile-Driver (Sonic)
96
Ballast Equalizer
82
Pneumatic Tool
85
Ballast Tamper
83
Pump
76
Compactor
82
Rail Saw
90
Concrete Mixer
85
Rock Drill
98
Concrete Pump
71
Roller
74
Concrete Vibrator
76
Saw
76
Crane, Derrick
88
Scarifier
83
Crane, Mobile
83
Scraper
89
Dozer
85
Shovel
82
Generator
81
Spike Driver
77
Grader
85
Tie Cutter
84
Impact Wrench
85
Tie Handler
80
Jack Hammer
88
Tie Inserter
85
Loader
85
Truck
88
Paver
89
Source: Federal Transit Administration, Transit Noise, and Vibration Impact Assessment, 2006.
Palo Alto Municipal Code Chapter 9.10.060 serves to regulate noise from construction and related activities
in Palo Alto. The ordinance allows construction between the hours of 8:00 AM and 6:00 PM, Monday
through Friday, and between 9:00 AM and 6:00 PM on Saturday. Construction is prohibited on Sundays and
federal holidays. In addition to restrictions on hours of activity, no individual piece of construction
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equipment may generate noise in excess of 110 dBA at a distance of 25 feet, and the noise level outside of
the property may not exceed 110 dBA.
Although the regulations of the Municipal Code would serve to reduce noise generation during construction
activities, it is possible that certain construction activities under all four scenarios may lead to substantial
temporary or periodic increases to ambient noise levels. Therefore, impacts from temporary or periodic
increases to ambient noise levels would be potentially significant, requiring mitigation.
 Palo Alto Municipal Code, Chapter 9.10.060, Special Provisions.
Significance before Mitigation: Since it is possible that certain construction activities under all four
scenarios may lead to substantial temporary or periodic increases to ambient noise levels which would result
in potentially significant impacts.
Mitigation Measures
Mitigation Measure NOISE-8: The following policies, or equally effective language, shall be
included in the proposed Plan to ensure that future development under all four scenarios would not
result in significant impacts to sensitive receptors from construction noise and vibration.

Policy: Require a detailed construction noise and vibration impact analysis, prepared by a qualified
acoustical consultant, for all projects that require discretionary approval and that are located within
100 feet of any noise- and/or vibration-sensitive land uses.
- If noise impacts are identified, require a noise monitoring plan to be prepared and submitted
prior to the issuance of construction permits. This plan shall identify the noise monitoring
locations, durations and regularity, the instrumentation to be used, and the appropriate noise
control/mitigation measures that will be incorporated to ensure compliance with the noise
ordinance.
- If projected daytime vibration levels exceed 90 VdB (relative to one microinch/sec) at
workshop uses, 84 VdB at offices uses, 78 VdB at residential uses, or the limits for VC-A through
VC-E uses shown in the FTA manual, 26 a vibration mitigation plan is to be prepared and
submitted prior to the issuance of construction permits.

Policy: Continue to prioritize construction noise and vibration limits around sensitive receptors.
26
These are found in Chapter 8 of the FTA manual (2006 edition), Table 8-3 “Interpretation of Vibration Criteria for Detailed Analysis”.
Uses VC-A through VC-E are for vibration-sensitive equipment such as optical microscopes, electron microscopes, and lithography equipment.
The associated limits range from 66 to 42 VdB, respectively.
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Significance after Mitigation: Less than Significant. The policies of the proposed Plan would serve
to minimize temporary or periodic increases to ambient noise. With preparation of a detailed analysis
and implementation of a monitoring plan, project construction noise and vibration impacts at sensitive
receptors would be significantly reduced. After implementation of the new policies, impacts from
temporary or periodic increases to ambient noise levels, would be less than significant.
NOISE-9
For a project located within an airport land use plan or, where such a plan
has not been adopted, within two miles of a public airport or public use
airport, the project would not expose people residing or working in the
project area to excessive noise levels. (Less than Significant– All Four
Scenarios)
Summary: As described below, under all four scenarios only airport and golf course land uses would fall
within the Palo Alto Airport’s 60 dBA noise contour. Therefore, the impact would be less than significant
The City of Palo Alto owns and operates the Palo Alto Airport (KPAO), a relatively small public air facility
which primarily serves single-engine, general aviation (GA) aircraft. 27 Noise contours from the aircraft
using this airport have been incorporated into the existing citywide contours shown in Figure 4.10-3. At the
nearest points within city limits, Palo Alto is located approximately 2.6 miles to the west of Moffett Federal
Airfield (KNUQ), six miles to the southeast of San Carlos Airport (KSQL), 10 miles to the northwest of the
San Jose International Airport (SJC), 15 miles to the southeast of San Francisco International Airport (SFO),
and 17 miles to the south of Oakland International Airport (OAK). Additional small airports in the vicinity
include the Hayward Executive Airport (KHWD), 14 miles away, and the Half Moon Bay airport (KHAF),
18 miles away. At these relatively large distances, all areas of the City of Palo Alto are miles outside of the
pertinent 65 dBA CNEL noise contour of all of these airports, so their contributions would not influence
the 2030 citywide contours (in Figure 4.10-4).
Although Palo Alto does receive some noise from aircraft using these facilities, the Palo Alto city limit does
not fall within the airport land use planning areas/airport influence areas, runway protection zones, or the
identified 65 dBA CNEL noise contours of any airport other than Palo Alto Airport (discussed further
below). Since all areas of the City of Palo Alto are well below the pertinent 65 dBA CNEL noise level
impact threshold for out-of-city airports, 28 public airport noise impacts would be less than significant.
27
Information from AirNav.com at http://www.airnav.com/airport/KPAO ; accessed 12/23/15.
The standard metric used for community impact assessment is the 24-hour CNEL metric and the 65 dBA CNEL level; as required by
statute for general plan noise elements, Title 24 for interior noise levels, and per FAA regulations (see the discussion above under State
Regulations in section 4.10.1.2 for additional information about applicable exterior and interior noise level standards regarding aircraft noise).
This DEIR used the mandated noise metric in the consideration of potential aircraft-related noise impacts.
28
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The Palo Alto Airport CLUP was adopted in November 2008 29 by the Santa Clara County ALUC 30 and
provides guidance related to the placement of land uses near the Palo Alto Airport. Specifically, the CLUP
seeks to protect the public from adverse effects of aircraft noise, to ensure that people and facilities are not
concentrated in areas susceptible to aircraft accidents, and to ensure that no structures or activities adversely
affect navigable airspace. Based on the noise contours presented in the Palo Alto Airport CLUP, within the
EIR Study Area only airport and golf course land uses fall within the Palo Alto Airport’s 60 dBA noise
contour. Therefore, the impact due to noise levels produced by public airports – both within and outside of
the EIR Study Area – would be less than significant.
 None
Significance before Mitigation: Since all areas of the City of Palo Alto are well below the pertinent 65
dBA CNEL noise level impact threshold, 31 out-of-city public airport noise impacts would be less than
significant. Further, since only airport property and the golf course – neither of which are noise-sensitive
land uses – are between the airport’s 60 and 65 dBA CNEL noise contours, within-city public airport noise
impacts would also be less than significant.
NOISE-10
For a project within the vicinity of a private airstrip, the project would not
expose people residing or working in the project area to excessive noise
levels. (Less than Significant– All Four Scenarios)
Summary: As described below, due to the small number of flights operating at private airstrips /heliports,
as well as the distance from these uses to the nearest noise-sensitive receptors, noise level impacts under all
four scenarios would be less than significant.
There is only one standalone heliport located within the EIR Study Area. Specifically, Stanford University
operates a heliport (15CA), which is located at Stanford University Hospital adjacent to the Stanford
Campus near Quarry Road and Campus Drive. The nearest residential uses are located approximately
1,400 feet to the west of the heliport. The next nearest heliport – McCandless Towers Heliport (CL86) – is
located approximately eight miles to the southeast of Palo Alto, in Santa Clara County.
At the nearest points within city limits, Palo Alto is located approximately 2.6 miles to the west of Moffett
Federal Airfield (KNUQ). This is the only private airport within 20 miles of Palo Alto.
29
At the time of the preparation of the ALUC document, Palo Alto airport was owned and operated by the County of Santa Clara.
Santa Clara County Airport Land Use Commissions, 2008, Palo Alto Airport Comprehensive Land Use Plan.
31
The standard metric used for community impact assessment is the 24-hour CNEL metric and the 65 dBA CNEL level; as required by
statute for general plan noise elements, Title 24 for interior noise levels, and per FAA regulations (see the discussion above under State
Regulations in section 4.10.1.2 for additional information about applicable exterior and interior noise level standards regarding aircraft noise).
This Draft EIR uses the mandated noise metric in the consideration of potential aircraft-related noise impacts.
30
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Due to the small number of flights operating at these private airstrips or heliports, coupled with the
distances to the nearest noise-sensitive receptors within the EIR Study Area, the noise level impacts due to
operations at these facilities would be less than significant.
 None
Significance before Mitigation: With relatively large distances to the nearest noise-sensitive receptors
within the EIR Study Area and with relatively few flights operating at private airstrips or heliports, noise
level impacts due to operations at these facilities would be less than significant.
4.10.4 CUMULATIVE IMPACTS
NOISE-11
Implementation of the proposed Plan, in combination with past, present,
and reasonably foreseeable projects, may result in significant cumulative
impacts with respect to noise. (Potentially Significant and Mitigable – All
Four Scenarios)
Summary: Cumulative impacts would be less than significant for all scenarios for foreseeable traffic-related
noise, since cumulative impacts were inherently accounted for in the assessments under Impacts NOISE-1,
NOISE-2, and NOISE-3. However, due to uncertain future development details near pertinent railway and
airport facilities, as well as unknown noise emissions characteristics of these rail- and air-related services,
cumulative community noise levels could be potentially significant, requiring mitigation for all four
scenarios.
The analysis of the proposed Plan, discussed above, addresses cumulative impacts with regard to noise, as
well as groundborne noise and vibration. Although multiple simultaneous nearby noise sources may, in
combination, result in higher overall noise levels, this effect is captured and accounted for by the ambient
noise level metrics which form the basis of the Standards of Significance for noise analysis. Any
measurement of sound or ambient noise, whether for the purpose of evaluating land use compatibility,
establishing compliance with exterior and interior noise standards, or determining point-source violations
of a noise ordinance, necessarily will incorporate noise from all other nearby perceptible sources.
Additionally, although noise attenuation is influenced by a variety of topographical, meteorological, and
other factors, noise levels decrease relatively rapidly with distance, and vibration impacts decrease even
more rapidly. Therefore, site-level cumulative noise or vibration impacts across city boundaries occur only
infrequently. The City of Palo Alto shares borders with other incorporated communities and similarly
urbanized areas, which makes cross-border cumulative noise and vibration impacts possible. Nevertheless,
given the Municipal Code requirements discussed above, it is unlikely that operations-related noise would,
in combination with noise sources from adjacent cities, result in cumulative noise impacts. Additionally,
because any noise measurements taken in conjunction with Municipal Code requirements would necessarily
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account for noises received from outside the boundaries of the City of Palo Alto, the ongoing
implementation of these policies and regulations under the proposed project would serve to prevent sitebased cumulative noise impacts.
Similarly, the traffic-related noise levels developed for the proposed Plan include and account for regional
travel patterns as they affect traffic levels in Palo Alto. Noise contours were based upon both existing and
projected future traffic volumes that incorporate cumulative regional effects and trends. Existing noise
contours were derived from traffic volumes based on counts of current traffic, and these traffic counts
inherently include cumulative traffic, as generated by regional trips. With regard to future noise, projected
noise contours were determined using projected 2030 traffic volumes; these data account for growth both
within the EIR Study Area under the proposed Plan, as well as anticipated regional growth. The future noise
modeling which served as the foundation for the overall Project analysis was therefore based on future,
cumulative conditions. Therefore, Impact NOISE-3 encompasses and addresses cumulative noise impacts
from implementation of the proposed Plan. As discussed under Impacts NOISE-1, NOISE-2, and NOISE-3,
buildout of the proposed Plan would remain within the City of Palo Alto’s Environmental Criteria Used by the
City of Palo Alto (of 2007) and impacts due to cumulative traffic noise increases would be less than significant.
However, the development of the Caltrain Modernization Program and the California HSR network
(discussed above in Section 4.10.1.3)—while aimed at improving both the state’s overall transportation
infrastructure and doing so with quieter technologies (as compared to current, diesel-driven rail systems)
—may result in increases in the community noise environment within parts of Palo Alto. That is, the
projected increases in ridership for Caltrain, coupled with the addition of HSR operations, may offset the
quieter technologies afforded by electric-driven systems such that these railway operations, overlaid onto
traffic and general community noise sources, may expose people to noise levels in excess of established City
and/or State standards. As noted above, there is currently a lack of detailed information about both future
electrified Caltrain or HSR operations and, as a result, a definitive conclusion about future noise levels
cannot be made at this time. Lastly, it should also be kept in mind that neither the Caltrain Modernization
Program, nor the development of the California HSR system are part of this proposed Plan and the
associated environmental impacts for these two rail projects in the cumulative setting are not included
herein (since such impact analyses have been or will be conducted separately by the respective rail
authorities). Nonetheless, cumulative impacts from future regional growth and future railway
development/improvement programs could result in community noise levels that may be potentially
significant.
Likewise, uncertain or unknown factors with respect to future land use development around or operations
associated with local airports, could potentially result in unacceptable aircraft-related noise environments
from one or both of the Palo Alto-based aircraft facilities (i.e., Stanford University Medical Center Heliport
and Palo Alto Airport). Thus, future aircraft-related conditions, in combination with cumulatively rising
noise environments from non-aircraft sources, could result in a potentially significant impact under all four
scenarios. As with the project-focused assessments discussed in Impacts NOISE-1, NOISE-2, and NOISE-3,
noise from medium or large airports in the region (including Moffett Airfield, San Carlos Airport, San Jose
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NOISE
Airport, Oakland International Airport, and San Francisco International Airport) – while being audible and
potentially annoying or intrusive to some people – would not contribute to cumulative impacts with respect
to CEQA evaluations, as the relevant noise characteristics of these facilities are many miles outside of the
EIR Study Area.
 None
Significance before Mitigation: Since the traffic-related noise levels developed for the proposed Plan
included and accounted for regional travel patterns as they affect traffic levels in Palo Alto, the assessment
under Impact NOISE-3 inherently encompassed and addressed cumulative noise impacts from
implementation of the proposed Plan. As such, impacts due to cumulative traffic noise increases would be
less than significant. However, uncertain or unknown factors with respect to future land use development,
operations, and/or regional growth associated with both railway development/improvement programs and
local (public and private) airport activities could result in cumulative community noise levels that may be
potentially significant under all four scenarios.
Mitigation Measures
Mitigation Measure NOISE-11a: Implement Mitigation Measure NOISE-1c.
Mitigation Measure NOISE-11b: The following programs, or equally effective language, shall be
included in the proposed Plan to preclude overall community noise impacts that are in excess of
established State and/or City standards.

Program: Encourage the Joint Powers Board to pursue technologies to reduce train whistle noise in
communities served by Caltrain.

Program: Evaluate changing at-grade rail crossings so that they qualify as Quiet Zones based on
Federal Railroad Administration (FRA) rules and guidelines in order to mitigate the effects of train
horn noise without adversely affecting safety at railroad crossings.
Mitigation Measure NOISE-11c: City of Palo Alto staff and officials shall participate in and
contribute to the environmental impact assessment of future Caltrain and HSR development programs
for railway operations within the city’s SOI.
Significance after Mitigation: Less than Significant. The policies of the proposed Plan (Mitigation
Measure NOISE-11a and NOISE-11b), coupled with the vigilance of the City regarding future railway
development (Mitigation Measure NOISE-11c) would serve to minimize the possibility for communitywide ambient noise increases due to cumulative sources. After implementation of the new policies and
Mitigation Measures, impacts from cumulative noise increases would be less than significant.
PLACEWORKS
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4.10 NOISE - Our Palo Alto 2030

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