HomeMy WebLinkAbout4 7 Noise
4.7 NOISE
4.7.1 Introduction
This section describes the existing noise conditions for the project area and
potential noise impacts from construction, occupancy, and use of the project.
Regulations and policies affecting the noise environment are described. This
section incorporates information from the 1999 City of South San Francisco
General Plan Noise Element and noise measurements taken by Impact Sciences.
Noise measurement data sheets are provided in Appendix 4.7 of this EIR.
4.7.2 Characteristics of Noise
Noise is usually defined as unwanted sound. It is an undesirable byproduct of
human society's normal day-to-day activities. Sound becomes unwanted when it
interferes with normal activities, when it causes actual physical harm, or when it
has adverse effects on health. The definition of noise as unwanted sound implies
that it has an adverse effect on people and their environment.
Noise is measured on a logarithmic scale of sound pressure level known as a
decibel (dB). The human ear does not respond uniformly to sounds at all
frequencies, being less sensitive to very low and high frequencies than to
medium frequencies that correspond with human speech. The A-weighted noise
level (or scale), which better corresponds to the human ear's subjective
perception of sound levels, has been developed. This A-weighted sound level is
called the "noise level" and is measured in units of dB(A). Because noise is
measured on a logarithmic scale, a doubling of sound energy results in a 3 dB(A)
increase in noise levels. Changes in noise levels of less than 3 dB(A) are not
typically noticed by the human ear (U.S. Department of Transportation 1980).
Changes in noise levels from 3 to 5 dB(A) may be noticed by individuals
extremely sensitive to changes in noise. A 5 dB(A) increase is readily noticeable,
while the human ear perceives a 7 dB(A) increase in sound level to be a doubling
of sound.
Noise sources are classified into two types: (1) point sources, such as pieces of
stationary equipment; and (2) line sources, such as roadways with large numbers
of point sources (motor vehicles). Sound generated by a point source typically
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diminishes (attenuates) at a rate of 6.0 dB(A) for each doubling of distance from
the source to the receptor at an acoustically "hard" site and 7.5 dB(A) at an
acoustically "soft" site (U.S. Department of Transportation 1980). For example, a
60 dB(A) noise level measured at 50 feet from a point source at an acoustically
hard site would be 54 dB(A) at 100 feet from the source and 48 dB(A) at 200 feet
from the source. Sound generated by a line source typically attenuates at a rate
of 3.0 dB(A) and 4.5 dB(A) per doubling of distance from the source to the
receptor for a hard and soft site, respectively (U.S. Department of Transportation
1980). Sound levels can also be attenuated by man-made or natural barriers, as
illustrated in Figure 4.7-1, Noise Attenuation Barriers. Solid walls, berms, or
elevation differences typically reduce noise levels by 5 to 10 dB(A) (U.S.
Department of Transportation 1980). The noise attenuation provided by typical
structures in California is provided below in Table 4.7-1, Outside to Inside
Noise Attenuation, below.
Table 4.7-1
Outside to Inside Noise Attenuation
Building Type
Noise Reduction - dB(A)
Open Closed
Windows Windows
12 25
12 25
20 30
17 25
17 25
20 30
17 25
17 25
Residences
Schools
Churches
Hospitals/Convalescent Homes
Offices
Thea ters
Hotels/Motels
Source: U.S. Department of Transportation 1980
When assessing community reaction to noise, there is an obvious need for a scale
that averages varying noise exposures over time and quantifies the results in
terms of a single number descriptor. Several scales have been developed that
address community noise levels. Those that are applicable to this analysis are
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Sou rce
8'
Deflected Noise
Barrier
" (Ii).
'" $"'0
" ~&.
" "91)/
Receptor
"Barrier Effect" Resulting from Differences in Elevation.
Sou rce
Deflected Noise
"Barrier Effect" Resulting from Typical Soundwall.
SOURCE: Impact Sciences, Inc. - June 2005
FIGURE 4. 7-1
Noise Attenuation by Barriers and Elevation Differences
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the Equivalent Noise Level (Leq) and the Community Noise Equivalent Level
(CNEL). Leq is the average A-weighted sound level measured over a given time
interval. Leq can be measured over any time period, but is typically measured for
I-minute, IS-minute, I-hour, or 24-hour periods. CNEL is another average A-
weighted sound level measured over a 24-hour time period and is adjusted to
account for some individuals' increased sensitivity to noise levels during the
evening and nighttime hours.
A CNEL noise measurement is obtained by adding S dB(A) to sound levels
occurring during the evening from 7 PM to 10 PM, and 10 dB to sound levels
occurring during the nighttime from 10 PM to 7 AM. The Sand 10 dB
"penalties" are applied to account for peoples' increased sensitivity during the
evening and nighttime hours. The logarithmic effect of these additions is that,
for example, a 60 dB(A) 24-hour Leq would result in a measurement of 66.7 dB(A)
CNEL.
Characteristics of Vibration
Vibration is a unique form of noise in that its energy is carried through structures
and the earth, whereas noise is carried through the air. Thus, vibration is
generally felt and heard. Some vibration effects can be caused by noise (for
example, the rattling of windows from passing trucks).
This phenomenon is related to the coupling of acoustic energy at frequencies that
are close to the resonant frequency of the material being vibrated.
Typically, ground-borne vibration generated by human activity attenuates
rapidly at increasing distances from the source of the vibration. For the purposes
of this document, vibration is described in units of velocity (inches per second)
and is discussed in dB units in order to compress the range of numbers required
to describe vibration.
The effect of vibration on structures and individuals varies depending on soil
type, ground strata, and receptor location. Sensitivity to vibration varies from
person to person. Peak velocities of 0.01 inches per second root-mean-square
(RMS) are not generally noticeable, while velocities of 0.1 inches per second RMS
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can be troublesome to persons near the vibration source. Damage to structures
can occur above 0.04 inches per second RMS.
Traffic Noise
The level of traffic noise depends on three primary factors: (1) the volume of the
traffic; (2) the speed of the traffic; and (3) the number of trucks in the flow of
traffic. Generally, the loudness of traffic noise is increased by heavier traffic
volumes, higher speeds, and a greater number of trucks. Vehicle noise is a
combination of the noise produced by the engine, exhaust, and tires.
Train Noise
Train noise is a combination of different noise sources such as propulsion
mechanisms, machinery and auxiliary equipment, wheel-rail interaction, and
vehicle-body vibrations. Train noise is a unique noise source that constitutes a
single pass-by event per train.
4.7.3 Existing Conditions
The project site is located in an industrial and commercial environment, east of
u.s. 101, a major freeway corridor, between Oyster Point Boulevard and East
Grand Avenue. Background noise from vehicles on the freeway and on
surrounding roadways contributes to the existing noise levels for the project site.
In addition, Southern Pacific Railroad (SPRR) operates a major line with two
railroad tracks that run parallel to u.s. 101 on the eastern side, and is
approximately 0.5 mile from the project site. Caltrain operates approximately 68
commuter trains each day through South San Francisco and SPRR freight trains
also use the line.
The nearest airport to the project site is the San Francisco International Airport
(SFO), located approximately 2 miles south of the project site. SFO averages
approximately 2,300 takeoffs and landings per day and about 28,000 operations
per year. Air traffic is comprised primarily of private air carriers that range from
small private jets to large, four-engine international commercial jets. The project
site is under one of the planned departure routes, the Shoreline Departure Route
for aircraft operating on Runway 28. This route frequently takes aircraft over or
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near the project site, under full take-off power. This area is exposed to a higher
volume of single-event noise levels than other areas of the City. According to the
San Mateo County Airport Land Use Commission, the project site is within the
65 db CNEL noise contour for the airport.
4.7.3.1
Sensitive Receptors
Whether a sound is considered unpleasant depends on the individual who hears
the sound and the setting and circumstances under which the sound is heard.
While performing certain tasks, people expect and accept certain sounds that are
considered unpleasant under other circumstances. For example, if a person
works in an office, sounds from printers, copiers, telephones, and keyboards are
generally acceptable and not considered unduly unpleasant or unwanted. By
comparison, when resting or relaxing, these same sounds may be less tolerable.
Because individuals' tolerance for noise varies by setting, some land uses are
more sensitive to changes in the noise environment. Residences, motels and
hotels, schools, libraries, churches, hospitals, nursing homes, auditoriums, parks,
and outdoor recreation areas are generally more sensitive to noise than are
commercial and industrial land uses. In the vicinity of the project site, sensitive
receptors include several hotels approximately 0.5 mile to 1 mile away from the
site and the future child care facility located across the street from the project site
on Allerton Avenue.
4.7.3.2 Existing On-Site and Off-Site Noise Levels
Noise measurements were taken at two locations on the project site. These noise
level measurements were used to assess the existing noise environment and to
calibrate the noise prediction models that were used to help identify any
potential noise impacts.
Noise Measurement Locations and Results
One long-term measurement and one short-term measurement were taken on the
project site to determine the existing ambient background noise levels. These
locations are shown on Figure 4.7-2, Noise Monitoring Locations. These noise
level measurements were used to assess the existing noise environment and to
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calibrate noise prediction models that were used to help identify any potential
noise impacts to sensitive receptors.
Short- Term Noise Measurement
Table 4.7-2, Existing Short-Term Noise Data Summary, identifies the location
and results of the short-term measurement. This measurement was taken for 15
minutes during the PM peak hour. Based on the results, the existing ambient Leq
noise levels for the project site was 61.0 dB(A) Leq.
Table 4.7-2
Existing Short-Term Noise Data Summary
Located on the southeast portion of the site 40 feet
from the centerline of Allerton Ave.
Traffic noise along Allerton
Avenue.
Source: Impact Sciences 2007
Long Term Noise Measurement Location and Results
Noise levels at the second location were recorded for a period of 24 hours to
obtain long-term noise data. The location and measurements are summarized
below in Table 4.7-3, Existing Long-Term Noise Data Summary.
This noise measurement was located along Allerton Avenue, in a portion of the
project site where the project would add a majority of traffic to the existing
conditions through the addition of three driveways.This long-term noise
measurement location was approximately 70 feet from the centerline of Forbes
Boulevard and measured 68 dB(A) CNEL.
As described in Chapter 3.0, Project Description, three driveways would be
added to the project site. These driveways would be located along Allerton
Avenue and would represent the main access points to the project site and the
proposed parking structure. It is assumed that most of the vehicle traffic using
these driveways would originate from Forbes Boulevard, with the remaining
traffic originating from East Grande Avenue.
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Noise Monitoring Locations I
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Table 4.7-3
Existing Long-Term Noise Data Summary
Located on the northeast corner of the site approximately
70 feet from the centerline of Forbes Blvd.
Source: Impact Sciences 2007
Off-Site Noise Levels
Using existing data on traffic volumes, vehicle mix, and roadway measurements,
the existing CNEL values were calculated for areas with sensitive receptors
around the project site. This analysis estimated ambient noise levels only along
those roadway segments that contained the proposed child care facility and
hotels. For roadway segments with hotels, the modeled sound level is at the face
of the building closest the roadway; sound levels at frequent use areas that do
not face onto the roadway (e.g., swimming pools, lounge areas, playgrounds,
etc.) would be lower. All other uses in the project vicinity are not considered
sensitive receptors. Table 4.7-4, Existing Off-Site Noise Levels summarizes the
CNEL values for the roadway segments that contain sensitive receptors. Off-site
values for Allerton Avenue and Forbes Boulevard correspond to the noise
measurements taken on the project site. This confirms that the noise
measurements represent the existing noise environment for the project site.
Table 4.7-4
Existing Off-Site Noise Levels
Allerton Avenue (Forbes Blvd. and East Grand Ave.)
Gateway Blvd. (Oyster Point Blvd and East Grand Ave.)
Oyster Point Blvd. (Gateway Blvd. and Eccles Ave.)
Airport Blvd. (Sister Cities Blvd. and Miller Ave.)
East Grand Ave. (101 Off-ramp and Grand Overcross)
Forbes Blvd. (Eccles Ave. and Allerton Ave.)
60.3
64.3
69.3
65.4
65.0
67.3
Source: Impact Sciences 2007
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4.7.3.3
Noise Standards
The City of South San Francisco utilizes the CNEL scale as the criterion for
assessing industrial and commercial land uses with transportation-related noise
sources. The City has set an interior noise standard of 45 dB(A) CNEL and an
exterior noise standard of 70 dB(A) CNEL for commercial uses, 75 dB(A) CNEL
for industrial land uses, and 65 dB(A) CNEL for schools (e.g., daycare) and
hotels.
The City of South San Francisco General Plan standards are derived from
standards contained in the General Plan Guidelines, a publication of the
California Office of Planning and Research. These standards are used by many
California cities and counties. The Noise Element includes standards for land
use compatibility for community noise exposure. Table 4.7-5, Land Use
Compatibility for Community Noise Environment, shows the exterior noise
exposure levels for the various land use categories in the City of South San
Francisco.
Construction Noise
Construction noise represents a short-term impact on ambient noise levels.
Noise generated by construction equipment, including trucks, graders,
bulldozers, concrete mixers, and portable generators can reach high levels.
Grading activities typically represent one of the highest-potential sources for
noise impacts. The most effective method of controlling construction noise is by
limiting the hours of construction to normal weekday working hours. The City
restricts construction to the hours of 8:00 AM to 8:00 PM during the week.
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Table 4.7-5
Land Use Compatibility for Community Noise Environment
Residential - Low Density Single
Family, Duplex, Mobile Homes
Residential- Multifamily
Transient Lodging - Motels, Hotels
Schools, Libraries, Churches,
Hospitals, Nursing Homes
Auditorium, Concert Halls,
Amphitheaters
Sports Arena, Outdoor Spectator
Sports Areas
Playgrounds, Neighborhood Parks
Golf Courses, Riding Stables, Water
Recreation, Cemeteries
Office Buildings, Business
Commercial, and Professional
Industrial, Manufacturing, Utilities,
and Agriculture (P A)
Source: Urban Crossroads 2006a
Normally Acceptable
Conditionally Acceptable
Normally Unacceptable
Clearly Unacceptable
Vibration Standards
The City of South San Francisco does not address vibration in either the City
Ordinance or in the Noise Element of the City of South San Francisco General
Plan. There are no Federal Highway Administration (FHW A) or state standards
for vibration. According to Caltrans' "Transportation Related Earthborne
Vibrations," the traditional view has been that highway traffic and construction
vibrations pose no threat to buildings and structures and do not cause annoyance
at a level above discomfort.
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The U.S. Department of Transportation Federal Transit Administration (FTA)
provides criteria for acceptable levels of ground-borne vibration for various
types of special buildings that are sensitive to vibration. Criteria for
environmental impact from ground-borne vibration and noise are based on the
maximum levels of a single event. Criteria describe observed human reaction to
various peak levels of vibration in the vertical direction at various frequent and
infrequent vibration levels. Traffic is considered frequent, but for train impacts
the infrequent event limit is considered more appropriate because the locomotive
event lasts only a few seconds. These criteria are used by Caltrans to evaluate
the severity of vibration problems.
4.7.4 Regulatory Considerations
Plans and policies that pertain to the noise conditions affecting and affected by
the project include: (1) the City of South San Francisco Noise Ordinance (Sections
8.32.020, 8.32.030, and 8.32.040 of the Municipal Code); (2) the City of South San
Francisco General Plan Noise Element; (3) the East of 101 Area Plan; (4) the
California Environmental Quality Act (CEQA) Guidelines, Appendix G, Significant
Effects; and (5) the State of California, Department of Health Services,
Environmental Health Division Guidelines for Noise and Land Use Compatibility.
4.7.4.1
City of South San Francisco Noise Ordinance
The City has established noise standards by adopting amendments to its
Municipal Code. Chapter 8 regarding Health and Welfare addresses noise
regulations. Section 8.32.020 defines sound level and noise level, giving specific
information on how noise monitoring is to be conducted. Section 8.32.030
defines the maximum permissible sound levels for various land use categories.
The information contained in this section is summarized below in Table 4.7-6,
City of South San Francisco Noise Level Standards.
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Table 4.7-6
City of South San Francisco Noise Level Standards
R-E, R-l and R-2 zones or any
single-family or duplex residential
in a specific plan district
R-3 and D-C zones or any multiple-
family residential or mixed
residential/commercial in any
specific plan district
C-l, P-C, Gateway and Oyster Point
Marina specific plan districts or any
commercial use in any specific plan
district
M-l, P-l
Source: Urban Crossroads 2006a
10 PM-7 AM
7 AM-I0 PM
50
60
10 PM-7 AM
7 AM-I0 PM
55
60
10 PM-7 AM
7 AM-I0 PM
60
65
Anytime
70
4.7.4.2
City of South San Francisco General Plan
The City of South San Francisco General Plan's primary objective related to noise
is to protect public health and welfare and to work to adopt mitigation and to
lower average noise standards. The General Plan provides goals, policies, and
programs to help meet these objectives. A list of project-related policies is
provided below:
Policy 9-G-1
Policy 9-]-1
Policy 9-]-2
Policy 9-]-4
Protect public health and welfare by eliminating or minimizing
the effects of existing noise problems, and by preventing
increased noise levels in the future.
Work to adopt a pass-by (single-event) noise standard to
supplement the current 65 dB(A) CNEL average noise level
standard as the basis for aircraft noise abatement programs.
Work to adopt a lower average noise standard for aircraft-based
mitigation and land use controls.
Ensure that new noise-sensitive land uses, including schools,
hospitals, churches, and homes, in areas near roadways
identified as impacting sensitive receptors by producing noise
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4.7.4.3
4.7.4.4
levels greater than 65 dB(A) CNEL, incorporate mitigation
measures to ensure that interior noise levels do not exceed 45
dB(A) CNEL.
Policy 9-1-7
Require the control of noise at source through site design,
building design, landscaping, hours of operation, and other
techniques, for new developments deemed to be noise
gener a tors.
East of 101 Area Plan
The East of 101 Area Plan Noise Element establishes policies to provide
acceptable noise levels for anticipated land uses. Similar to the General Plan, the
acceptable interior noise levels for the project site area should not exceed 45
dB(A). Additionally, this plan serves to encourage commercial, office and
research and development uses in the plan area. This would lead to a decrease
in noise due to reduced volumes of medium and heavy trucks and increased
passenger vehicle traffic.
California Department of Health Services
The State of California, Department of Health Services, Environmental Health
Division has published recommended guidelines for mobile source noise and
land use compatibility. Each jurisdiction is required to consider these guidelines
when developing its General Plan Noise Element and determining the acceptable
noise levels within its community. The City has considered these guidelines
when preparing the Noise Element of the City of South San Francisco General
Plan.
4.7.5 Consistency with Applicable Regulations
The project would be consistent with all local regulations regarding noise levels
and mitigation measures. The project would not exceed the exterior noise level
for the given land use designation. Additionally, the project would implement
construction materials that would ensure that the interior noise standard would
be met in both buildings on the project site.
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4.7.6 Impacts and Mitigation
4.7.6.1 Significance Criteria
In accordance with Appendix G of the CEQA Guidelines (Environmental
Checklist Form) and City of South San Francisco environmental guidelines,
implementation of the project could have a significant effect on the environment
if it would:
. Result in exposure of persons to, or generation of, noise levels in excess of
standards established in the local General Plan or noise ordinance;
. Result in a substantial temporary or periodic, or permanent increase in
ambient noise levels in the project vicinity above levels existing without the
project; or
. Result in exposure of persons to, or generation of, excessive ground-borne
vibration or ground-borne noise levels.
Additionally, the CEQA Guidelines do not define the specific level at which
temporary and permanent increases in ambient noise are considered
"substantial." As discussed previously in this section, a noise level increase of 3
dB(A) is barely perceptible to most people, a 5 dB(A) increase is readily
noticeable, and a difference of 10 dB(A) would be perceived as a doubling of
loudness. Based on this information, this EIR has used a 3 dB(A) CNEL increase
as the basis for determining a significant noise impact.
Noise Issues Not Discussed Further
The project involves development of campus-style office and research and
development uses that would be similar in nature to those already in the vicinity
of the project site. Project operation would not generate ground-borne noise or
vibration at levels that would expose people or structures to risk of harm. The
project site is over 2,000 feet from the Caltrain tracks and u.s. 101. Passenger
trains, such as Caltrain, generally do not create vibration levels that would
expose people or structures to harm. Additionally, because the tracks and
freeway are over 2,000 feet from the project site, any vibration created by the
trains would attenuate before it reached the project site. Therefore,
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implementation of the project would result in less than significant impacts from
ground-borne noise or vibration.
4.7.6.2 Project Impacts
Impact 4.7-1: Implementation of the project would result in less than
significant noise impacts to uses proposed within the project
site. (L TS)
Future users of the site would be exposed to a number of different noise sources,
located both on and off the project site. The main noise source would be
associated with increased vehicle traffic generated by development of the
proposed project. As described previously in this section, a total of three
driveways would be constructed along the Allerton Avenue portion of project
site. These driveways would be in addition to the existing driveway located
along the Forbes Boulevard portion of the site. Traffic entering the project site
would terminate at either one of the outdoor parking areas, or the proposed
parking structure. Delivery vehicles entering the site would use one of the three
Allerton Avenue access points. Workers and visitors to the site would be
exposed to these noise sources while in the parking area until entering the
buildings on site.
Additionally, the San Francisco International Airport is located south of the
project site. The City's Noise Element (1999) contains existing and future (2006)
airport noise contours associated with the airport, which indicate that the project
site is located outside of the 65 dB(A) existing and future noise contours.
Due to the proposed land use and the project's proximity to the San Francisco
International Airport, exterior noise exposure would not be considered
significant to future users on the site.
Interior noise levels are regulated by the City of South San Francisco. As
described previously, there is a 45 dB(A) CNEL interior noise standard for the
proposed use which would be met through the use of standard construction
materials for the proposed buildings and compliance with noise requirements
described in the East of 101 Area Plan. Although there would be a slight increase
in exterior noise from the proposed project, approximately 0.2 dB(A) CNEL, this
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would not prevent the interior noise level standard from being met. Therefore,
this would be considered a less than significant impact.
Mitigation Measure: None required.
Impact 4.7-2: Implementation of the project would result in less than
significant impacts to off-site sensitive noise receptors. (L TS)
Industrial uses predominantly surround the project site. While there are no
residential uses in the surrounding area, a child care facility is planned for
construction adjacent to the project site along Allerton Avenue. There are also
several hotels near u.s. 101. The child care facility and hotels are considered
sensitive receptors to unwanted noise. Therefore, the discussion below focuses
on potential noise impacts to these off-site receptors.
Table 4.7-7, Project Off-Site Noise Contributions, shows a comparison of the
noise conditions under project buildout (2015) with both the proposed project
and no project. These noise contours were developed using the FHWA Highway
Noise Prediction Model with traffic volumes that were obtained from the Traffic
Impact Analysis (see Appendix 4.7). As shown in Table 4.7-7, all roadway
segments that contain sensitive receptors, including the planned child care
facility, would experience increased noise levels ranging from 0.0 dB(A) CNEL to
0.8 dB(A) CNEL. As discussed in Subsection 4.7.2, changes in sound levels
between 3 dB(A) and 5 dB(A) may be noticed by some individuals. The City of
South San Francisco uses that threshold in that an increase in ambient noise level
of 3 dB(A) or more in an area that results in an overall noise level exceeding 65
dB(A) is considered a significant impact. An increase of less than 3 dB(A) is not
considered significant. Therefore, the project would have less than significant
impacts to off-site sensitive receptors.
Mitigation Measure: None required.
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Table 4.7-7
Project Off-Site Noise Contributions in dB(A) (2015)
Allerton A venue 59.8 60.6 0.8 NO
(Forbes Blvd. and East Grand Ave.)
Gateway Blvd. 64.0 64.0 0.0 NO
(Oyster Point Blvd and East Grand Ave.)
Oyster Point Blvd. 70.5 70.6 0.1 NO
(Gateway Blvd. and Eccles Ave.)
Airport Blvd. 66.3 66.3 0.0 NO
(Sister Cities Blvd. and Miller Ave.)
East Grand Ave. 64.5 64.7 0.2 NO
(101 Off-ramp and Grand Overcross)
Forbes Blvd. 67.5 67.7 0.2 NO
(Eccles Ave. and Allerton Ave.)
Source: Impact Sciences 2007
Impact 4.7-3: The project would result in temporary or periodic noise
impacts associated with construction activities. (S)
The U.S. Environmental Protection Agency (EP A) has compiled data regarding
the noise-generating characteristics of specific types of construction equipment.
These are shown in Table 4.7-8, Noise Levels of Typical Construction
Equipment. As shown, noise levels generated by heavy construction equipment
can range from approximately 68 dB(A) to noise levels in excess of 100 dB(A)
when measured at 50 feet. Field measurements show that construction noise
levels generated by commonly used grading equipment (i.e., loaders, graders,
and trucks) typically do not exceed those levels shown in Table 4.7-8. However,
these noise levels would diminish rapidly with distance from the construction
site at a rate of approximately 6 dB(A) per doubling of distance. For example, a
noise level of 68 dB(A) measured at 50 feet from the noise source to the receptor
would be reduced to 62 dB(A) at 100 feet from the source to the receptor, and
would be further reduced to 56 dB(A) at 200 feet from the source to the receptor.
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4.7 Noise
Table 4.7-8
Noise Levels of Typical Construction Equipment
Air Compressor
Backhoe
Concrete Pump
Concrete Vibrator
Truck Crane
Dozer
Generator
Loader
Paver
Pneumatic Tools
Pile Driver
Water Pump
Power Hand Saw
Shovel
Trucks
81
85
82
76
88
87
78
84
88
85
100
76
78
82
88
71
80
80
70
80
83
71
80
80
75
NA
71
70
80
83
Quieted equipment can be designed with enclosures, mufflers, or other noise-reducing features.
Source: u.s. Environmental Protection Agency (EP A). "Noise from Construction Equipment and operations, Building Equipment, and Home
Appliances. /I 1971.
Development of the project site would occur in two staggered phases, beginning
with the construction of Building B. Construction of Building A would begin
approximately 1 year later, with each construction phase taking approximately
70 weeks to complete. Construction of the parking structure would coincide
with the completion of Building B.
The proposed Genentech child care facility could experience periodic noise
increases due to project construction, depending on construction timing for the
two projects. All other sensitive receptors would not experience any increase in
exterior noise due to project construction given their significant distance from the
site.
Currently, under Section 8.32.050(d) of the City's Municipal Code, construction
activities are limited to between the hours of 8:00 AM to 8:00 PM on weekdays,
9:00 AM to 8:00 PM on Saturdays, and 10:00 AM to 6:00 PM on Sundays and
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4.7 Noise
holidays. Construction noise would be of short-term duration and would not
present any long-term impacts on the project site or the surrounding area but
could temporarily elevate noise levels in the project vicinity. However, the
proposed project would comply with SSFMC Section 8.32.050(d) and therefore,
the impact from construction would be less than significant. To further reduce
this impact, Mitigation Measures 4.7-1 through 4.7-4 have been included to
reduce the construction noise impact associated with both construction phases to
a less than significant level.
Mitigation Measure 4.7-1: The construction contractor shall locate stationary
noise sources as far from existing sensitive receptors as possible. If stationary
sources must be located near existing receptors, they shall be muffled and
enclosed within temporary sheds or other structures.
Mitigation Measure 4.7-2: The construction contractor shall implement feasible
noise controls to minimize equipment noise impacts on nearby sensitive
receptors. Feasible noise controls shall include improved mufflers, equipment
redesign, use of intake silencers, ducts, engine enclosures, and acoustically-
attenuating shields or shrouds. Noise controls can reduce noise levels at 50 feet
by 1 dB(A) to 16 dB(A), depending on the type of equipment.
Mitigation Measure 4.7-3: Equipment used for construction shall be
hydraulically or electrically-powered impact tools (e.g., jackhammers) whenever
possible to avoid noise associated with compressed air exhaust from
pneumatically-powered tools. Where use of a pneumatically-powered tool is
unavoidable, an exhaust muffler on the compressed air exhaust shall be used. (A
muffler could lower noise levels from exhaust by up to 10 dB(A)). External
jackets on the tools themselves shall be used when feasible, resulting in a
reduction of up to 5 dB(A).
Mitigation Measure 4.7-4: The construction contractor shall implement
appropriate additional noise reduction measures such as shutting off idling
equipment and notifying adjacent businesses in advance of construction work.
The City shall also require that prior to demolition and grading activities, signs
must be posted with a phone number for information and noise complaints.
Impact After Mitigation: Less than significant.
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4.7 Noise
4.7.7 Cumulative Impacts
Cumulative development in South San Francisco would increase traffic volumes
but would decrease the amount of heavy and medium trucks in the vehicle mix.
This would increase noise levels at some areas of the City and decrease noise
levels at others given the change in future land uses. Table 4.7-9, Cumulative
Off-Site Noise Contributions in dB (A), shows the existing and projected
cumulative (2015) roadway noise levels adjacent to the project area with sensitive
receptors. Noise levels at all roadway segments would remain below 75 dB(A)
CNEL, which is considered acceptable for industrial uses and generally below 70
dB(A) CNEL, which is considered acceptable for business and commercial uses
such as offices. As shown, some roadway segments would experience a slight
decrease in noise volumes and others would increase, depending upon location
of land uses.
The project's contribution on all roadway segments studied under cumulative
conditions would not exceed 0.8 dB(A), which would be inaudible. Therefore,
the project's contribution to cumulative impacts would not be considerable.
Table 4.7-9
Cumulative Off-Site Noise Contributions in dB(A)
Allerton A venue 60.3 59.8 60.6 -0.5 [0.8] NO
(Forbes Blvd. and East Grand Ave.)
Gateway Blvd.
(Oyster Point Blvd and East Grand 64.3 64.0 64.0 -0.3[0.0] NO
Ave.)
Oyster Point Blvd. 69.3 70.5 70.6 1.2[0.1] NO
(Gateway Blvd. and Eccles Ave.)
Airport Blvd. 65.4 66.3 66.3 0.9[0.0] NO
(Sister Cities Blvd. and Miller Ave.)
East Grand Ave. 65.0 64.5 64.7 -0.5 [0.2] NO
(101 Off-ramp and Grand Overcross)
Forbes Blvd. 67.3 67.5 67.7 0.2[0.2] NO
(Eccles Ave. and Allerton Ave.)
Source: Impact Sciences 2007
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