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HomeMy WebLinkAbout04_08_Noise and VibrationCity of South San Francisco Environmental Setting, Impacts, and Mitigation Noise and Vibration 751 Gateway Boulevard Project 4.8-1 September 2020 ICF 0662.19 4.8 Noise and Vibration 4.8.1 Introduction This section describes the environmental and regulatory setting for noise and vibration. It also describes impacts associated with noise and vibration that would result from implementation of the proposed project and mitigation for significant impacts where feasible and appropriate. San Francisco International Airport (SFO) submitted a comment on the Notice of Preparation (NOP). The commenter stated that the project site is outside of the 65 dB community noise equivalent level (CNEL) noise contour and is not within a runway end safety zone. As a result of being located outside of the 65 CNEL contour, the commenter stated that the proposed project would not pose an airport land use compatibility issue related to noise. The commenter also stated that noise impact to any sensitive receptors or nighttime uses associated with the proposed project should be evaluated in the EIR. The proposed project does not propose any nighttime uses or noise-sensitive uses, such as residences; the potential for noise impacts from aircraft activity is evaluated under Impact NOI-3. 4.8.2 Environmental Setting 4.8.2.1 Fundamentals of Environmental Noise Overview of Noise and Sound Noise is commonly defined as unwanted sound that annoys or disturbs people and potentially causes an adverse psychological or physiological effect on human health. Because noise is an environmental pollutant that can interfere with human activities, an evaluation of noise is necessary when considering the environmental impacts of a proposed project. Sound is mechanical energy (i.e., vibration) transmitted by pressure waves over a medium such as air or water. Sound is characterized by various parameters, including the rate of oscillation of sound waves (i.e., frequency), the speed of propagation, and the pressure level or energy content (i.e., amplitude). In particular, the sound pressure level is the most common descriptor for characterizing the loudness of an ambient (i.e., existing) sound level. Although the decibel (dB) scale, which is a logarithmic scale, is used to quantify sound intensity, it does not accurately describe how sound intensity is perceived by human hearing. The human ear is not equally sensitive to all frequencies in the entire spectrum, so noise measurements are weighted more heavily for frequencies to which humans are sensitive in a process called A-weighting, written as dBA and referred to as A-weighted decibels. Table 4.8-1 defines sound measurements and other terminology used in this chapter, and Table 4.8-2 summarizes typical A-weighted sound levels for different noise sources. In general, human sound perception is such that a change in sound level of 1 dB cannot typically be perceived by the human ear, a change of 3 dB is barely noticeable, a change of 5 dB is clearly noticeable, and a change of 10 dB is perceived as doubling or halving the sound level as it increases or decreases, respectively. City of South San Francisco Environmental Setting, Impacts, and Mitigation Noise and Vibration 751 Gateway Boulevard Project 4.8-2 September 2020 ICF 0662.19 Table 4.8-1. Definition of Sound Measurements Sound Measurements Definition Decibel (dB) A unitless measure of sound on a logarithmic scale that indicates the squared ratio of sound pressure amplitude with respect to a reference sound pressure amplitude. The reference pressure is 20 micropascals. A-Weighted Decibel (dBA) An overall frequency-weighted sound level in decibels that approximates the frequency response of the human ear. C-Weighted Decibel (dBC) The sound pressure level in decibels as measured using the C- weighting filter network. The C-weighting is very close to an unweighted or flat response. C-weighting is used only in special cases (i.e., when low-frequency noise is of particular importance). A comparison of the measured A- and C-weighted level gives an indication of low-frequency content. Maximum Sound Level (Lmax) The maximum sound level measured during the measurement period. Minimum Sound Level (Lmin) The minimum sound level measured during the measurement period. Equivalent Sound Level (Leq) The equivalent steady-state sound level that in a stated period of time would contain the same acoustical energy. Percentile-Exceeded Sound Level (Lxx) The sound level exceeded X% of a specific time period. L10 is the sound level exceeded 10% of the time, and L90 is the sound level exceeded 90% of the time. L90 is often considered to be representative of the background noise level in a given area. Day-Night Level (Ldn) The energy average of the A-weighted sound levels occurring during a 24-hour period, with 10 dB added to the A-weighted sound levels occurring during the period from 10:00 p.m. to 7:00 a.m. Community Noise Equivalent Level (CNEL) The energy average of the A-weighted sound levels occurring during a 24-hour period, with 5 dB added to the A-weighted sound levels occurring during the period from 7:00 p.m. to 10:00 p.m. and 10 dB added to the A-weighted sound levels occurring during the period from 10:00 p.m. to 7:00 a.m. Vibration Velocity Level (or Vibration Decibel Level, VdB) The root-mean-square velocity amplitude for measured ground motion expressed in dB. Peak Particle Velocity (Peak Velocity or PPV) A measurement of ground vibration, defined as the maximum speed (measured in inches per second) at which a particle in the ground is moving relative to its inactive state. PPV is usually expressed in inches per second. Frequency: Hertz (Hz) The number of complete pressure fluctuations per second above and below atmospheric pressure. City of South San Francisco Environmental Setting, Impacts, and Mitigation Noise and Vibration 751 Gateway Boulevard Project 4.8-3 September 2020 ICF 0662.19 Table 4.8-2. Typical A-weighted Sound Levels Common Outdoor Activities Noise Level (dBA) Common Indoor Activities —110— Rock band Jet flyover at 1,000 feet —100— Gas lawnmower at 3 feet —90— Diesel truck at 50 feet at 50 mph Food blender at 3 feet —80— Garbage disposal at 3 feet Noisy urban area, daytime Gas lawnmower at 100 feet —70— Vacuum cleaner at 10 feet Commercial area Normal speech at 3 feet Heavy traffic at 300 feet —60— Large business office Quiet urban daytime —50— Dishwasher in next room Quiet urban nighttime —40— Theater, large conference room (background) Quiet suburban nighttime —30— Library Quiet rural nighttime Bedroom at night, concert hall (background) —20— Broadcast/recording studio —10— —0— Source: Federal Transit Administration. 2018. Transit Noise and Vibration Impact Assessment. FTA Report 0123. Available: https://www.transit.dot.gov/sites/fta.dot.gov/files/docs/research-innovation/118131/transit-noise-and- vibration-impact-assessment-manual-fta-report-no-0123_0.pdf. Accessed: May 20, 2020. Different types of measurements are used to characterize the time-varying nature of sound. These measurements include the equivalent sound level (Leq), the minimum and maximum sound levels (Lmin and Lmax), percentile-exceeded sound levels (such as L10, L20), the day-night sound level (Ldn), and the CNEL. Ldn and CNEL values differ by less than 1 dB. As a matter of practice, Ldn and CNEL values are considered to be equivalent and are treated as such. These measurements are defined in Table 4.8-1. For a point source, such as a stationary compressor or a piece of construction equipment, sound attenuates (i.e., lessens in intensity), based on geometry, at a rate of 6 dB per doubling of distance. For a line source, such as free-flowing traffic on a freeway, sound attenuates at a rate of 3 dB per City of South San Francisco Environmental Setting, Impacts, and Mitigation Noise and Vibration 751 Gateway Boulevard Project 4.8-4 September 2020 ICF 0662.19 doubling of distance perpendicular to the source.1 Atmospheric conditions, including wind, temperature gradients, and humidity, can change how sound propagates over distance and can affect the level of sound received at a given location. The degree to which the ground surface absorbs acoustical energy also affects sound propagation. Sound that travels over an acoustically absorptive surface such as grass attenuates at a greater rate than sound that travels over a hard surface such as pavement. The increased attenuation is typically in the range of 1 to 2 dB per doubling of distance. Barriers such as buildings or topographic features that block the line of sight between a source and receiver also increase the attenuation of sound over distance. Community noise environments are generally perceived as quiet when the 24-hour average noise level is below 45 dBA, moderate in the 45 to 60 dBA CNEL range, and loud above 60 dBA CNEL. Very noisy urban residential areas are usually around 70 dBA CNEL. Along major thoroughfares, roadside noise levels are typically between 65 and 75 dBA CNEL. Incremental changes of 3 to 5 dB in the existing 1-hour Leq, or the CNEL, are commonly used as thresholds for an adverse community reaction to a noise increase. However, there is evidence that incremental thresholds in this range may not be sufficiently protective in areas where noise-sensitive uses are located and CNEL is already high (i.e., above 60 dBA). In these areas, limiting noise increases to 3 dB or less is recommended.2 Noise intrusions that cause short-term interior noise levels to rise above 45 dBA at night can disrupt sleep. Exposure to noise levels greater than 85 dBA for 8 hours or longer can cause permanent hearing damage. Noise from Multiple Sources Since sound pressure levels in decibels are based on a logarithmic scale, they cannot be added or subtracted in the usual arithmetical way. Adding a new noise source to an existing noise source, both producing noise at the same level, will not double the noise level. If the difference between two noise sources is 10 dBA or more, the higher noise source will dominate and the resultant noise level will be equal to the noise level of the higher noise source. In general, if the difference between two noise sources is 0 to 1 dBA, the resultant noise level will be 3 dBA higher than the higher noise source, or both sources if they are equal. If the difference between two noise sources is 2 to 3 dBA, the resultant noise level will be 2 dBA above the higher noise source. If the difference between two noise sources is 4 to 10 dBA, the resultant noise level will be 1 dBA higher than the higher noise source. Attenuation of Noise A receptor’s distance from a noise source affects how noise levels attenuate (decrease). Transportation noise sources tend to be arranged linearly such that roadway traffic attenuates at a rate of 3.0 to 4.5 dBA per doubling of distance from the source, depending on the intervening surface (paved or vegetated, respectively). Point sources of noise, such as stationary equipment or construction equipment, typically attenuate at a rate of 6.0 to 7.5 dBA per doubling of distance from 1 California Department of Transportation (Caltrans). 2020. Transportation and Construction Vibration Guidance Manual. April. Available: https://dot.ca.gov/-/media/dot-media/programs/environmental- analysis/documents/env/tcvgm-apr2020-a11y.pdf. Accessed May 20, 2020. 2 Federal Transit Administration (FTA). 2018. Transit Noise and Vibration Impact Assessment. FTA Report 0123. Available: https://www.transit.dot.gov/sites/fta.dot.gov/files/docs/research-innovation/118131/transit- noise-and-vibration-impact-assessment-manual-fta-report-no-0123_0.pdf. Accessed: May 20, 2020. City of South San Francisco Environmental Setting, Impacts, and Mitigation Noise and Vibration 751 Gateway Boulevard Project 4.8-5 September 2020 ICF 0662.19 the source, depending on the intervening surface.3 For example, a sound level of 80 dBA at 50 feet from the noise source will be reduced to 74 dBA at 100 feet, 68 dBA at 200 feet, and so on, based on the 6 dB point source reduction over a non-absorptive surface (e.g. pavement instead of vegetation). Noise levels can also be attenuated by “shielding” or providing a barrier between the source and the receptor. With respect to interior noise levels, noise attenuation effectiveness depends on whether windows are closed or open. Based on the U.S. Environmental Protection Agency’s (EPA’s) national average, closed windows reduce noise levels by approximately 25 dBA and open windows reduce noise levels by about 15 dBA.4 Noise-Sensitive Land Uses Noise-sensitive land uses are generally defined as locations where people reside or where the presence of unwanted sound could adversely affect the use of the land. Noise-sensitive land uses typically include single- and multi-family residential areas, health care facilities, lodging facilities, and schools. Noise-sensitive land uses where people typically sleep are typically more sensitive to noise during nighttime hours (when people are typically sleeping). Recreational areas where quiet is an important part of the environment as well as some commercial areas, such as outdoor restaurant seating areas, can also be considered sensitive to noise. Overview of Ground-borne Vibration Ground vibration consists of rapidly fluctuating motions or waves with an average motion of zero. Vibration is an oscillatory motion through a solid medium in which the motion’s amplitude can be described in terms of displacement, velocity, or acceleration. Several different methods are typically used to quantify vibration amplitude; one is peak particle velocity (PPV) and another is root mean square (RMS) velocity. PPV is defined as the maximum instantaneous positive or negative peak of the vibration wave. RMS velocity is defined as the average of the squared amplitude of the signal. Vibration is typically measured in inches per second or millimeters per second. Operation of heavy construction equipment, particularly pile-driving equipment and other impact devices (e.g., pavement breakers), creates seismic waves that radiate along the surface of and downward into the ground. These surface waves can be felt as ground vibration. Vibration from the operation of this type of equipment can result in effects that range from annoyance for people to damage for structures. Variations in geology and distance result in different vibration levels, including different frequencies and displacements. In all cases, vibration amplitudes decrease with increased distance. Perceptible ground-borne vibration is generally limited to areas within a few hundred feet of construction activities. As seismic waves travel outward from a vibration source, they cause rock and soil particles to oscillate. The actual distance that these particles move is usually only a few ten-thousandths to a few thousandths of an inch. The rate or velocity (in inches per second) at which these particles move is the commonly accepted descriptor of vibration amplitude, referred to as PPV. 3 The 1.5-dBA variation in attenuation rate (6 dBA vs. 7.5 dBA) can result from ground-absorption effects, which occur as sound travels over soft surfaces such as soft earth or vegetation (7.5 dBA attenuation rate) versus hard ground such as pavement or very hard-packed earth (6 dBA rate) (U.S. Housing and Urban Development, The Noise Guidebook, 1985, p. 24. Available online at: https://www.hudexchange.info/onecpd/assets/File/Noise- Guidebook-Chapter-4.pdf. Accessed May 20, 2020.) 4 U.S. Environmental Protection Agency, 1974. Information on Levels of Environmental Noise Requisite to Protect Public Health and Welfare with an Adequate Margin of Safety, Appendix B, Table B-4, p. B-6, March 1974. City of South San Francisco Environmental Setting, Impacts, and Mitigation Noise and Vibration 751 Gateway Boulevard Project 4.8-6 September 2020 ICF 0662.19 Vibration amplitude attenuates over distance. This is a complex function of how energy is imparted into the ground and the soil or rock conditions through which the vibration is traveling. The following equation is used to estimate the vibration level at a given distance for typical soil conditions.5 PPVref is the reference PPV at 25 feet (Table 4.8-3). PPV = PPVref x (25/Distance)1.5 Table 4.8-3. Vibration Source Levels for Construction Equipment Equipment PPV at 25 Feet PPV at 50 Feet PPV at 75 Feet PPV at 80 Feet PPV at 100 Feet Auger drill 0.089 0.0315 0.0171 0.016 0.011 Hoe ram 0.089 0.0315 0.0171 0.016 0.011 Large bulldozer 0.089 0.0315 0.0171 0.016 0.011 Loaded trucks 0.076 0.0269 0.0146 0.013 0.010 Jackhammer 0.035 0.0124 0.0067 0.006 0.004 Small bulldozer 0.003 0.0011 0.0006 0.001 0.0004 Source: Federal Transit Administration. 2018. Transit Noise and Vibration Impact Assessment. FTA Report 0123. Available: https://www.transit.dot.gov/sites/fta.dot.gov/files/docs/research-innovation/118131/transit-noise-and- vibration-impact-assessment-manual-fta-report-no-0123_0.pdf. Accessed: May 20, 2020. Table 4.8-3 summarizes typical vibration levels generated by construction equipment at the reference distance of 25 feet and other distances, as determined with use of the attenuation equation above.6 Tables 4.8-4 and 4.8-5 summarize the guidelines developed by the California Department of Transportation (Caltrans) for damage and annoyance potential from the transient and continuous vibration that is usually associated with construction activity. The activities that are typical of continuous vibration include the use of excavation equipment, static compaction equipment, tracked vehicles, vehicles on a highway, vibratory pile drivers, pile-extraction equipment, and vibratory compaction equipment. The activities that are typical of single-impact (transient) or low-rate, repeated impact vibration include the use of drop balls, blasting, and the use of impact pile drivers, “pogo stick” compactors, and crack-and-seat equipment.7 4.8.2.2 Existing Noise Environment Regional and Local Setting The project site is in the City of South San Francisco in northern San Mateo County. The project site is served by Gateway Boulevard as the primary arterial road, fed by Oyster Point Boulevard (running east to west) to the north and East Grand Avenue (running east to west) to the south. In addition, the project site is approximately 0.5 mile north of the South San Francisco Caltrain station and approximately 0.2 mile east of U.S. 101. SFO is approximately 2 miles south of the project site. 5 Federal Transit Administration. 2018. Transit Noise and Vibration Impact Assessment. FTA Report 0123. Available: https://www.transit.dot.gov/sites/fta.dot.gov/files/docs/research-innovation/118131/transit- noise-and-vibration-impact-assessment-manual-fta-report-no-0123_0.pdf. Accessed: May 20, 2020. 6 California Department of Transportation. 2020. Transportation and Construction Vibration Guidance Manual. April. Available: https://dot.ca.gov/-/media/dot-media/programs/environmental- analysis/documents/env/tcvgm-apr2020-a11y.pdf. Accessed May 20, 2020. 7 Ibid. City of South San Francisco Environmental Setting, Impacts, and Mitigation Noise and Vibration 751 Gateway Boulevard Project 4.8-7 September 2020 ICF 0662.19 Table 4.8-4. Vibration Damage Potential Threshold Criteria Guidelines Structure and Condition Maximum PPV (inches per second) Transient Sources Continuous/Frequent Intermittent Sources Extremely fragile historic buildings, ruins, ancient monuments 0.12 0.08 Fragile buildings 0.2 0.1 Historic and some old buildings 0.5 0.25 Older residential structures 0.5 0.3 New residential structures 1.0 0.5 Modern industrial/commercial buildings 2.0 0.5 Source: California Department of Transportation. 2020. Transportation and Construction Vibration Guidance Manual. April. Available: https://dot.ca.gov/-/media/dot-media/programs/environmental-analysis/documents/env/tcvgm- apr2020-a11y.pdf. Accessed May 20, 2020. Note: Transient sources create a single, isolated vibration event (e.g., blasting or the use of drop balls). Continuous/frequent intermittent sources include impact pile drivers, pogo-stick compactors, crack-and-seat equipment, vibratory pile drivers, and vibratory compaction equipment. Table 4.8-5. Vibration Annoyance Potential Criteria Guidelines Human Response Maximum PPV (inches per second) Transient Sources Continuous/Frequent Intermittent Sources Barely perceptible 0.04 0.01 Distinctly perceptible 0.25 0.04 Strongly perceptible 0.9 0.10 Severe 2.0 0.4 Source: California Department of Transportation. 2020. Transportation and Construction Vibration Guidance Manual. April. Available: https://dot.ca.gov/-/media/dot-media/programs/environmental-analysis/documents/env/tcvgm- apr2020-a11y.pdf. Accessed May 20, 2020. Note: Transient sources create a single, isolated vibration event (e.g., blasting or the use of drop balls). Continuous/frequent intermittent sources include impact pile drivers, pogo-stick compactors, crack-and-seat equipment, vibratory pile drivers, and vibratory compaction equipment. Existing Uses at the Project Site The project site is located in the Gateway Campus, an area with primarily commercial and office uses. The project site is bounded by a commercial and office building (901 Gateway Boulevard) and a surface parking lot to the north, Gateway Boulevard to the east, a surface parking lot to the south, and commercial and office buildings to the west. Existing Noise-Sensitive Uses in the Vicinity There are no residential land uses located within 1,000 feet of the project site; the nearest residential land uses are located along Airport Boulevard, over 1,200 feet from the project site. Two hotels, Larkspur Landing and Hilton Garden Inn, are within 600 and 900 feet of the main project construction areas, respectively, and the Gateway Child Development Center Peninsula is approximately 1,000 feet from the main project construction areas. However, the Gateway Child Development Center Peninsula is approximately 670 feet from the nearest project construction area, which would be at the southern terminus of the site and include repaving and curb work, as well as some landscaping activities. This City of South San Francisco Environmental Setting, Impacts, and Mitigation Noise and Vibration 751 Gateway Boulevard Project 4.8-8 September 2020 ICF 0662.19 construction area is approximately 300 feet from the Larkspur Landing Hotel and 400 feet from the Hilton Garden Inn. The project site is in the Gateway Specific Plan Area, which includes a variety of commercial (including hotel and childcare) and R&D land uses. As shown in Figure 3-3 in Chapter 3, Project Description, of this draft EIR, the parcels in the vicinity of the project site are zoned Gateway Specific Plan District (GSPD). Existing Noise Levels The existing ambient noise environment at the project site is characteristic of an urban environment (e.g., highway and local traffic, aircraft overflights, commercial noise sources). Traffic noise from vehicles traveling on surrounding streets and freeways (e.g., U.S. 101) is typically the dominant noise source in urban areas. Traffic noise is the primary source contributing to ambient noise levels at the project site. In addition to traffic noise, noise from aircraft overflights traveling to or from SFO, approximately 2 miles south of the project site, is sometimes audible at the project site. The Caltrain right-of-way is located along the western boundary of the Gateway Campus. Thus, intermittent Caltrain noise also contributes to the noise environment in the project area. As discussed above, traffic noise is the primary source contributing to ambient noise levels in the project vicinity. Thus, to estimate existing ambient noise levels at and around the project site, existing traffic noise levels in the project area were modeled based on traffic data provided by Fehr & Peers. Refer to Table 4.8-6 for modeled existing noise levels along roadway segments within approximately 0.5 mile of the project site. 4.8.3 Regulatory Framework 4.8.3.1 State California Code of Regulations California Code of Regulations Title 24, part 2, Sound Transmission, establishes minimum noise insulation standards to protect persons within new hotels, motels, dormitories, long-term care facilities, apartment houses, and dwellings other than single-family residences. Under this regulation, interior noise levels attributable to exterior noise sources cannot exceed 45 dB in any habitable room. The noise metric is either the Ldn or the CNEL. Compliance with Title 24 interior noise standards occurs during the permit review process and generally protects a proposed project’s users from existing ambient outdoor noise levels. If determined necessary, a detailed acoustical analysis of exterior wall and window assemblies may be required. 4.8.3.2 Regional Comprehensive Airport Land Use Compatibility Plan8 Refer to Section 4.10.3, Hazards and Hazardous Materials, of this draft EIR for a discussion of the 2012 SFO Airport Land Use Compatibility Plan (ALUCP). Noise associated with airport and aircraft operations is considered one of the main areas of important concern for airport land use commissions, especially in highly urbanized areas like the Bay Area. 8 C/CAG. 2012. Comprehensive Airport Land Use Compatibility Plan for the Environs of San Francisco International Airport. November 2012. Available: https://ccag.ca.gov/wp-content/uploads/2014/10/Consolidated_CCAG_ ALUCP_November-20121.pdf. Accessed: March 27, 2020. City of South San Francisco Environmental Setting, Impacts, and Mitigation Noise and Vibration 751 Gateway Boulevard Project 4.8-9 September 2020 ICF 0662.19 Table 4.8-6. Modeled Existing Noise Levels within 0.5 mile of the Project Site Roadway Segment Existing Noise Level (dBA Ldn) Airport Boulevard North of Sister Cities Boulevard 65.4 Airport Boulevard South of Sister Cities Boulevard 64.1 Airport Boulevard North of Grand Avenue 65.3 Airport Boulevard South of Grand Avenue 65.5 Sister Cities Boulevard East of Airport Boulevard 69.3 Sister Cities Boulevard West of Airport Boulevard 68.8 Oyster Point Boulevard East of Dubuque Avenue 66.2 Oyster Point Boulevard West of Dubuque Avenue 69.1 Oyster Point Boulevard East of Gateway Boulevard 69.0 Oyster Point Boulevard West of Gateway Boulevard 69.9 Gateway Boulevard South of Oyster Point Boulevard 66.0 Gateway Boulevard North of East Grand Avenue 65.2 Gateway Boulevard South of East Grand Avenue 65.3 East Grand Avenue East of Gateway Boulevard 68.8 East Grand Avenue West of Gateway Boulevard 68.1 Grand Avenue East of Airport Boulevard 67.1 Grand Avenue West of Airport Boulevard 64.5 Dubuque Avenue South of Oyster Point Boulevard 67.9 Dubuque Avenue South of U.S. 101 Ramps 61.6 Note: Due to the COVID-19 shelter-in-place orders that were in effect at the time of the draft EIR preparation, existing noise levels were modeled based on traffic data for year 2019 rather than based on noise measurements taken in the field. Traffic noise is usually the dominant source of overall ambient noise in urban areas, and field work conducted during the shelter-in-place orders would not accurately capture typical traffic noise levels (with schools and many businesses closed and many people working remotely). Thus, the modeled traffic noise levels provide a reasonable approximation for typical ambient noise levels in the vicinity of the project site. In addition, the modeled traffic noise levels for the project area are generally similar to measured pre-COVID-19 noise levels for other projects in the area, including the 499 Forbes Boulevard Office Project EIR and the 201 Haskins Way Project Draft EIR. Source: Traffic volumes provided by Fehr & Peers. Modeling conducted using a spreadsheet based on the Federal Highway Administration (FHWA) Traffic Noise Model (TNM), version 2.5 at a fixed distance of 50 feet from the roadway centerline. . According to the 2012 SFO ALUCP, the Airport Influence Area (AIA), which is the geographic area that is subject to the land use compatibility considerations identified in the ALUCP, is divided into two areas: Area A and Area B. Area A encompasses all of San Mateo County and the incorporated cities within it. Area B roughly follows the noise compatibility and safety zone contours. Consistent with Title 14 of the Code of Federal Regulations (CFR) Part 77, the 2012 SFO ALUCP establishes height restrictions within specific contours of airport facilities throughout Area A and Area B. The project site is located within both Area A and Area B. City of South San Francisco Environmental Setting, Impacts, and Mitigation Noise and Vibration 751 Gateway Boulevard Project 4.8-10 September 2020 ICF 0662.19 The 2012 SFO ALUCP has four primary areas of concern, two of which pertain to noise, as listed below. 1. Aircraft Noise Impact Reduction: To reduce the potential number of future airport area residents who could be exposed to noise impacts from airport and aircraft operations. 2. Over-flight Notification: To establish an area within which aircraft flights to and from the airport occur frequently enough and at a low enough altitude to be noticeable by sensitive residents. Within this area, real estate disclosure notices shall be required, pursuant to state law. According to the 2012 SFO ALUCP, the project site is not located within the CNEL 65 dB noise contour9 or any safety zones.10 4.8.3.3 Local South San Francisco General Plan The 1999 General Plan for the City of South San Francisco (City) provides a vision for long-range physical and economic development of the City, provides strategies and specific implementing actions, and establishes a basis for judging whether specific development proposals and public projects are consistent with the City’s plans and policy standards. The General Plan contains a Noise Element, which is intended to ensure compliance with state requirements and promote a comprehensive, long-range program of achieving acceptable noise levels throughout the City. The General Plan includes the following policies applicable to noise and vibration. • Policy 9-I-7: Where site conditions permit, require noise buffering for all noise-sensitive development subject to noise generators producing noise levels greater than 65 dB CNEL. This noise attenuation method should avoid the use of visible sound walls, where practical. • Policy 9-I-8: 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 generators. Local plans, policy actions, or development activities within SFO’s 65 dB CNEL contour require the approval of the San Mateo County Airport Land Use Commission (ALUC) prior to local permit issuance. To assist this process, the ALUC has established noise/land use compatibility standards as the basis of plan review, which are included in the City’s General Plan Noise Element (see Table 9.2-1). The City also applies these standards in its review of development applications located within the 65 dB CNEL boundary. The standards are shown below in Table 4.8.7. As previously noted, the project site is located outside of the 65 dB CNEL boundary. South San Francisco Municipal Code Chapter 8.32, Noise Regulations, contains the noise regulations of the South San Francisco Municipal Code. The code’s quantitative noise limits and construction noise regulations are described below. 9 Exhibit IV-5, Noise Compatibility Zones in the 2012 SFO ALUCP. 10 Exhibit IV-2, Airport Influence Area B – Land Use Policy Action/Project Referral Area in the 2012 SFO ALUCP. City of South San Francisco Environmental Setting, Impacts, and Mitigation Noise and Vibration 751 Gateway Boulevard Project 4.8-11 September 2020 ICF 0662.19 Table 4.8-7. General Plan Land Use Criteria for Noise-Impacted Areas Land Use CNEL Range General Land Use Criteria Residential Less than 65 65 to 70 Over 70 Satisfactory; no special insulation requirements Development requires analysis of noise reduction requirements and insulation as needed Development should not be undertaken Commercial Less than 70 70 to 80 Over 80 Satisfactory; no special insulation requirements Development requires analysis of noise reduction requirements and insulation as needed Airport-related development only; special noise insulation should be provided Industrial Less than 75 75 to 85 Over 85 Satisfactory; no special insulation requirements Development requires analysis of noise reduction requirements and insulation as needed Airport-related development only; special noise insulation should be provided Open Less than 75 Over 75 Satisfactory; no special insulation requirements Avoid uses involving concentrations of people or animals Source: South San Francisco General Plan, Noise Element. Table 4.8-8 specifies the maximum permissible sound levels to be generated by any property within the City according to Section 8.32.030 of the City’s Noise Ordinance. The maximum allowable level is determined by the land use category of the receiving property and is measured on any receiving property. All references to dB in the code use the A-weighting scale. All land uses within the Gateway Specific Plan Area are governed by noise thresholds of 65 dBA during the daytime hours of 7 a.m. to 10 p.m. and 60 dBA during the nighttime hours of 10 p.m. to 7 a.m. Table 4.8-8. City of South San Francisco Noise Level Standards Land Use Category Time Period Noise Level (dB)a R-E, R-1 and R-2 zones or any single-family or duplex residential in a specific plan district 10:00 p.m.—7:00 a.m. 7:00 a.m.—10:00 p.m. 50 60 R-3 and D-C zones or any multiple-family residential or mixed residential/commercial in any specific plan district 10:00 p.m.—7:00 a.m. 7:00 a.m.—10:00 p.m. 55 60 C-1, P-C, Gateway and Oyster Point Marina specific plan districts or any commercial use in any specific plan district 10:00 p.m.—7:00 a.m. 7:00 a.m.—10:00 p.m. 60 65 M-1, P-1 Anytime 70 Source: Table 8.32.030 of the South San Francisco Municipal Code a The noise level standard for each land use for a cumulative period of more than thirty minutes in any hour (L50). Standards increase for durations less than 15 minutes per hour. If the measured ambient level for any area is higher than the standard set in the City Municipal Code, then the threshold is 5 dB above the measured ambient level. Section 20.300.010(F) of the South San Francisco Municipal Code states that no vibration shall be produced that is transmitted through the ground and is discernible without the aid of instruments by a reasonable person at the lot lines of the site. Vibration from temporary construction, demolition, and vehicles that enter and leave the subject parcel (e.g., construction equipment, trains, trucks) are exempt from this standard. City of South San Francisco Environmental Setting, Impacts, and Mitigation Noise and Vibration 751 Gateway Boulevard Project 4.8-12 September 2020 ICF 0662.19 Section 8.32.050 (d) of the South San Francisco Municipal Code identifies a special provision that allows construction activities with a City permit between the hours of 8:00 a.m. to 8:00 p.m. on weekdays, 9:00 a.m. to 8:00 p.m. on Saturdays, and 10:00 a.m. to 6:00 p.m. on Sundays and holidays. Other hours may be authorized by obtaining a permit, provided the construction meets at least one of the following requirements. • No individual piece of equipment shall produce a noise level exceeding 90 dB at a distance of 25 feet. If the device is housed within a structure or trailer on the property, the measurement shall be made outside the structure at a distance as close to 25 feet from the equipment as possible. • The noise level at any point outside of the property plane of the project shall not exceed 90 dB. Gateway Specific Plan The Gateway Specific Plan covers the portion of the East of 101 Area Plan from east of the Caltrain tracks to the eastern boundary of the parcels along the east side of Gateway Boulevard and the area between Oyster Point Boulevard and Grand Avenue on the northern and southern boundaries. The Specific Plan is “intended to provide for various commercial and research and development land uses integrated by consistent development standards.” The Gateway Specific Plan includes the following construction standards and open space standards applicable to noise. • Construction Standard 1(c): Noise Abatement. (1) Buildings shall be designed and oriented on the Site to reduce interior noise levels within the Buildings caused by on-site activities or by adjacent highways, roads, flight paths or rail facilities to a level complying with all then applicable federal, state, and local health and safety requirements. Noise generated on a Site during construction or in areas outside completed Buildings shall be minimized as necessary to avoid creation of a nuisance. (2) All construction contracts for any work to be performed on a Site shall require the contractor to comply with all applicable federal, state and local governmental requirements relating to noise limitations on construction vehicles and equipment. East of 101 Area Plan The East of 101 Area Plan, which was adopted in 1994 and most recently amended in 2016, sets forth specific land use policies for the East of 101 Area. The City interprets the East of 101 Area Plan as a design-level document. Per Policy IM-5, the Gateway Specific Plan is not affected by the land use regulations of the East of 101 Area Plan. Therefore, the policies in the General Plan Noise Element are the guiding policies and supersede all Noise Element policies set forth in Chapter 9 of the East of 101 Area Plan. Nonetheless, the East of 101 Area Plan contains the following goals and policies applicable to noise. • Goal 6.1: Encourage the development of land uses which will be compatible with the noise environment of the East of 101 Area. • Goal 6.2: Provide guidelines for noise attenuation for hotel and office uses in the East of 101 Area. • Policy NO-2: Office and retail developments in the East of 101 Area shall be designed so that the calculated hourly average noise levels during the daytime does not exceed an Leq of 45 dBA, and instantaneous maximum noise levels do not exceed 60 dBA. • Policy NO-4: New development shall be designed so that the average noise level resulting from the new development does not exceed an Leq of 60 dBA at the nearest open space or recreational area. City of South San Francisco Environmental Setting, Impacts, and Mitigation Noise and Vibration 751 Gateway Boulevard Project 4.8-13 September 2020 ICF 0662.19 4.8.4 Impacts and Mitigation Measures 4.8.4.1 Significance Criteria Based on Appendix G of the CEQA Guidelines, the proposed project would have a noise and vibration impact if it would: • Generate a substantial temporary or permanent increase in ambient noise levels in the vicinity of the project in excess of standards established in the local general plan or noise ordinance, or applicable standards of other agencies; • Generate excessive ground-borne vibration or ground-borne noise levels; or • For a project located within the vicinity of a private airstrip or 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, expose people residing or working in the project area to excessive noise levels. 4.8.4.2 Approach to Analysis This noise and vibration impact analysis evaluates the temporary noise and vibration increases associated with project construction and demolition activities, traffic noise associated with project- related changes in traffic patterns, and operational noise generated by sound-generating equipment and onsite activities. Construction and Demolition Noise The construction schedule, a list of construction equipment expected to be used for each construction stage, and construction equipment operating details were provided by the project sponsor. Noise impacts associated with onsite demolition and construction were evaluated using construction equipment noise data in the Federal Highway Administration (FHWA) Roadway Construction Noise Model (RCNM). The data include the A-weighted Lmax, measured at a distance of 50 feet from the construction equipment and the utilization factors for the equipment. The utilization factor is the percentage of time each piece of construction equipment is typically operated at full power over the specified time period. It is used to estimate Leq values from Lmax values. For example, the Leq value for a piece of equipment that operates at full power over 50 percent of the time is 3 dB less than the Lmax value.11 Construction noise levels of typical equipment from the FHWA RCNM user guide were compared to the applicable construction noise thresholds during daytime hours. For construction outside of these daytime hours, the FHWA RCNM the noise calculation methods were used to estimate reasonable worst-case noise from the loudest two pieces of equipment proposed for use during a single construction phase. Estimated construction noise levels were compared against the maximum permissible sound levels according to Section 8.32.030 of the City’s Noise Ordinance, which are identified in Table 4.8-8. For this analysis, Leq is considered a reasonable proxy for assessing noise against the L50 standards12 in Table 4.8-8. 11 Federal Highway Administration (FHWA). 2006. FHWA Roadway Construction Noise Model User’s Guide. FHWA- HEP-05-054. January. Available: https://www.gsweventcenter.com/Draft_SEIR_References/2006_01_Roadway_ Construction_Noise_Model_User_Guide_FHWA.pdf. Accessed: May 20, 2020. 12 L50 is the noise level standard for each land use for a cumulative period of more than 30 minutes in any hour. City of South San Francisco Environmental Setting, Impacts, and Mitigation Noise and Vibration 751 Gateway Boulevard Project 4.8-14 September 2020 ICF 0662.19 Traffic Noise During Operation Noise impacts associated with increased traffic volumes generated by the proposed project were evaluated for the following conditions, which are described in Section 4.9, Transportation and Circulation, of this draft EIR. l Existing Conditions l Existing Plus Project Conditions l Cumulative Conditions l Cumulative Plus Project Conditions Quantitative modeling of traffic noise that may be generated by the proposed project was conducted using a spreadsheet that was based on the FHWA TNM version 2.5. The spreadsheet calculates the traffic noise level at a fixed distance from the centerline of a roadway based on the traffic volume, roadway speed, and vehicle mix, which is predicted to occur under each condition. Traffic volumes were provided by Fehr & Peers and traffic noise levels were modeled to estimate potential traffic noise increases along the major vehicle access routes resulting from project implementation. A reasonable default vehicle mix (i.e., the proportion of automobiles, trucks, buses, and other vehicles) was used in the model, and were based on guidance from Fehr & Peers; roadway speeds were obtained from Google Earth StreetView. Traffic noise was evaluated in terms of how project-related noise increases could affect existing noise-sensitive land uses. As discussed above, a change of 3 dB is barely noticeable, a change of 5 dB is clearly noticeable, and a change of 10 dB is perceived as doubling or halving the sound level as it increases or decreases. The City’s noise regulations and guidance documents do not include a specific threshold that pertains to traffic noise impacts from implementation of a project. The following criteria to determine potential project-related traffic noise impacts. A project impact related to traffic noise would be identified if: • A 5 dBA or greater increase in traffic noise resulting from project implementation occurs, if the future noise level is within the normally acceptable range (CNEL 65 dBA or less for residences and childcare; CNEL 70 dBA or less for offices and retail). • A 3 dBA or greater increase in traffic noise resulting from project implementation occurs, if future noise level is above the normally acceptable range. A cumulative impact related to traffic noise would be identified if: • A 5 dBA or greater increase in traffic noise from existing to cumulative with project conditions occurs, if the future noise level is within the normally acceptable range (CNEL 65 dBA or less for residences and childcare; CNEL 70 dBA or less for offices and retail; CNEL 75 dBA or less for industrial land uses) AND the project’s contribution is cumulatively considerable (greater than 1 dBA). • A 3 dBA or greater increase in traffic noise from existing to cumulative with project conditions occurs, if future noise level is above the normally acceptable range AND the project’s contribution is cumulatively considerable (greater than 1 dBA). City of South San Francisco Environmental Setting, Impacts, and Mitigation Noise and Vibration 751 Gateway Boulevard Project 4.8-15 September 2020 ICF 0662.19 Stationary Source Noise During Operation Operational noise impacts associated with proposed onsite activities and stationary sources of noise were evaluated based on the proposed site plan layout and the types of noise-generating equipment and activities that are anticipated under the proposed project. In accordance with applicable South San Francisco Municipal Code noise thresholds, the proposed mechanical equipment may not result in noise levels at nearby land uses in the Gateway Specific Plan Area in excess of 65 dBA during the hours of 7:00 a.m. to 10:00 p.m. or in excess of 60 dBA during the hours of 10:00 p.m. to 7:00 a.m. Noise at various distances from point sources (e.g., stationary operational equipment such as generators and heating and cooling equipment) was estimated using point-source attenuation of 6 dB per doubling of distance. The South San Francisco Municipal Code also provides if measured ambient noise levels are higher than the standards set forth Table 4.8-8, generated noise levels may exceed measured ambient noise levels by up to 5 dB. For purposes of this analysis, the thresholds outlined in Table 4.8-8, which are more conservative, are used. 4.8.4.3 Impact Evaluation Impact NOI-1: The proposed project would not generate a substantial temporary or permanent increase in ambient noise levels in the vicinity of the project in excess of standards established in the local general plan or noise ordinance, or applicable standards of other agencies. (Less than Significant with Mitigation) Construction Equipment Noise Construction and demolition activities for the proposed project would include demolishing a surface parking lot, constructing a new building, undertaking various site improvements, and providing utility infrastructure. Construction of the proposed project, if the related entitlements are approved by the City, would begin in 2020 and occur over approximately 18 months, with an anticipated completion date in 2021. Construction and demolition activities would generate noise and temporarily increase noise levels onsite and at nearby land uses. The level of noise generated would depend on the types of construction equipment used, the timing and duration of noise-generating activities, and the distance between construction noise sources and noise-sensitive receptors. Potential construction noise impacts are typically more substantial when construction occurs during noise-sensitive times of the day (i.e., early morning, evening, or nighttime hours) in areas immediately adjoining noise- sensitive land uses or for extended periods of time. Construction Noise Impacts During Daytime Hours As described in Regulatory Framework, construction activities in the City that are authorized by a valid City permit are generally allowed on weekdays between the hours of 8:00 a.m. and 8:00 p.m., on Saturdays between the hours of 9:00 a.m. and 8:00 p.m., and on Sundays and holidays between the hours of 10:00 a.m. and 6:00 p.m. (or at such other hours as may be authorized by the permit) if they meet at least one of two outlined noise limitations. Construction would be allowed during the daytime hours specific on the permit as long as noise from each individual piece of equipment is limited to 90 dB at a distance of 25 feet or as long as combined construction noise at any point outside of the property plane of the project does not exceed 90 dB. City of South San Francisco Environmental Setting, Impacts, and Mitigation Noise and Vibration 751 Gateway Boulevard Project 4.8-16 September 2020 ICF 0662.19 Noise levels for the equipment proposed for project construction are provided in Table 4.8-9. As shown, noise from each individual piece of equipment proposed for project construction would not be expected to exceed 90 dBA Leq at a distance of 25 feet. For this reason, construction that takes place during daytime hours defined by the South San Francisco Municipal Code would not conflict with local construction noise regulations and this impact would be less than significant. No mitigation measures are required. Table 4.8-9. Noise from Equipment Proposed for Project Construction (Leq) Construction Stage Equipment Type Noise at 25 Feet (Leq) Site Preparation and Demolition Excavator 83 Crusher 89 Dump Truck 78 Foundation Installation Excavator 83 Dump Truck 78 Concrete Mixer Truck 81 Concrete Pump Truck 80 Building Structure Construction Crane 79 Welder 76 Man lift 74 Gradall 85 Exterior and Roof Buildout Mobile Crane 79 Construction Noise Impacts Outside of Daytime Hours Outside of the daytime hours specified by the City permit, construction noise would be regulated by Section 8.32.030 of the City of South San Francisco Municipal Code (Table 4.8-8). The project site is in the Gateway Specific Plan District (GSPD) per the City Municipal Code. Noise at in this district are is limited to the same noise level standard regardless of the type of land use. For example, both a hotel and an office building in the district would be governed by the same noise standard of 60 dBA during the nighttime hours of 10:00 p.m. to 7:00 a.m. and 65 dBA during the daytime hours of 7:00 a.m. to 10:00 p.m. Project construction would typically occur Monday through Friday, between 7:00 a.m. and 5:00 p.m., although some work is anticipated to occur on Saturdays between 9:00 a.m. and 8:00 p.m. or on Sundays between 10:00 a.m. and 6:00 p.m. Between the hours of 7:00 and 8:00 a.m., construction noise in the City is restricted to the more stringent general noise standard criteria of 65 dBA rather than the individual equipment threshold or property line construction noise threshold of 90 dBA. Therefore, the reasonable worst-case combined construction noise must be estimated to determine potential construction noise impacts between 7:00 and 8:00 a.m. To estimate the reasonable worst-case combined construction noise levels from the use of construction equipment during project construction, this analysis assumes the three loudest pieces of equipment proposed for a single construction stage would operate concurrently in the same general location on the project site. The screening analysis determined that the site preparation and demolition stage, during which a dump truck, crusher and excavator could all operate simultaneously, would have the potential to produce the highest sound level of all construction City of South San Francisco Environmental Setting, Impacts, and Mitigation Noise and Vibration 751 Gateway Boulevard Project 4.8-17 September 2020 ICF 0662.19 stages. Table 4.8-10 identifies the combined noise level (both Lmax and Leq) from operation of these three pieces of construction equipment and the anticipated reasonable worst-case noise levels during project construction at various distances from the project site. Table 4.8-10. Combined Project Construction Noise Levels at Various Distances from 7:00 to 8:00 am (Lmax and Leq)a Source Data Maximum Sound Level (dBA) Utilization Factor (%) Leq Sound Level (dBA) Construction Stage: Site Preparation and Demolition Source 1: Dump truck— Sound level (dBA) at 50 feet = 76 40 72.0 Source 2: Excavator— Sound level (dBA) at 50 feet = 81 40 77.0 Source 3: Crusher— Sound level (dBA) at 50 feet = 87 40 83.0 Calculated Data All Sources Combined—Lmax sound level (dBA) at 50 feet = 88 Lmax All Sources Combined—Leq sound level (dBA) at 50 feet = 84 Leq Distance Between Source and Receiver (feet) Geometric Attenuation (dB)b Calculated Lmax Sound Level (dBA)c Calculated Leq Sound Level (dBA) c 25 6 94 90 45d 1 89 85 50 0 88 84 100 -6 82 78 200 -12 76 72 400 -18 70 66 500 -20 68 64 600 -22 67 63 900 -25 63 59 Source: Federal Highway Administration (FHWA). 2006. FHWA Roadway Construction Noise Model User’s Guide. FHWA-HEP-05-054. January. Available: https://www.gsweventcenter.com/Draft_SEIR_References/ 2006_01_Roadway_Construction_Noise_Model_User_Guide_FHWA.pdf. Accessed: May 20, 2020. Notes: a This analysis is to estimate construction noise from activities that occur outside of the standard daytime construction hours defined by the municipal code (e.g. between the hour of 7:00 and 8:00 a.m.). b Geometric attenuation based on 6 dB per doubling of distance. c This calculation does not include the effects, if any, of local shielding or ground attenuation from walls, topography, or other barriers that may reduce sound levels further. d Bolded results: Results at 45 feet are bolded because 45 feet is the approximate distance to the nearest existing land uses to project construction areas (701 Gateway Boulevard and 901 Gateway Boulevard). City of South San Francisco Environmental Setting, Impacts, and Mitigation Noise and Vibration 751 Gateway Boulevard Project 4.8-18 September 2020 ICF 0662.19 The nearest existing land uses to project construction areas are the buildings at 701 Gateway and 901 Gateway, which are both located approximately 45 feet from project construction areas. As shown in Table 4.8-11, the reasonable worst-case combined construction noise is expected to be approximately 85 dBA Leq at a distance of 45 feet. Construction activities are proposed during the hours of 7:00 and 8:00 a.m. weekdays, which is outside of the normal construction hours outlined in the South San Francisco Municipal Code and construction noise during this hour could be in excess of the 65 dBA threshold at the nearest noise-sensitive land use. Therefore, construction that takes place between 7:00 and 8:00 a.m. on weekdays could conflict with local construction noise regulations and this impact would be significant. Table 4.8-11. Combined Project Construction Noise Levels at Various Distances During Nighttime Concrete Pours (Lmax and Leq) Source Data Maximum Sound Level (dBA) Utilization Factor (%) Leq Sound Level (dBA) Construction Condition: Nighttime Concrete Pour Source 1: Concrete mixer truck— Sound level (dBA) at 50 feet = 79 90 75.0 Source 2: Concrete mixer truck— Sound level (dBA) at 50 feet = 79 90 75.0 Source 3: Concrete pump truck— Sound level (dBA) at 50 feet = 81 80 74.0 Calculated Data All Sources Combined—Lmax sound level (dBA) at 50 feet = 85 Lmax All Sources Combined—Leq sound level (dBA) at 50 feet = 84 Leq Distance Between Source and Receiver (feet) Geometric Attenuation (dB)a Calculated Lmax Sound Level (dBA)b Calculated Leq Sound Level (dBA) b 45 c 1 85 85 50 0 85 84 100 -6 79 78 200 -12 73 72 300 -16 69 68 400 -18 66 66 450 -19 65 65 500 -20 65 64 600 -22 63 62 Notes: a Geometric attenuation based on 6 dB per doubling of distance. b This calculation does not include the effects, if any, of local shielding or ground attenuation from walls, topography, or other barriers that may reduce sound levels further. c Bolded = results: Results at 45 feet are bolded because 45 feet is the approximate distance to the nearest existing land uses to project construction areas (701 Gateway Boulevard and 901 Gateway Boulevard). City of South San Francisco Environmental Setting, Impacts, and Mitigation Noise and Vibration 751 Gateway Boulevard Project 4.8-19 September 2020 ICF 0662.19 In addition to the daytime construction activities proposed for the project that may begin prior to the 8:00 a.m. standard construction start time, approximately 15 instances of nighttime construction work would occur for concrete pours. Nighttime construction would begin approximately at 4:00 a.m. and be completed by 5:00 p.m. Between the hours of 4:00 a.m. and 7:00 a.m., construction noise must comply with the nighttime noise standard of 60 dBA. Between the hour of 7:00 a.m. and 8:00 a.m., construction noise must comply with the daytime noise standard of 65 dBA. The loudest pieces of equipment required for a nighttime concrete pour would be two concrete mixer trucks and a concrete pump truck. Table 4.8-11 presents the potential noise levels during simultaneous operation the three loudest pieces equipment that would operate during nighttime concrete pours at various distances from the project site. As shown in Table 4.8-11, noise levels from two concrete mixer trucks and a concrete pump truck are estimated to be approximately 85 dBA Leq at a distance of 45 feet. Therefore, noise from concrete pour activities would exceed the City’s 60 dBA nighttime noise standard at the nearest land use. There are no residential land uses near the project site. However, the nearest noise- sensitive land use where people typically sleep is the Larkspur Landing Hotel, which is located approximately 600 feet from areas where nighttime concrete pour activities could occur. At a distance of 600 feet, noise levels from two concrete mixer trucks and a concrete pump truck are estimated to be approximately 62 dBA Leq. Although noise may be further attenuated at this distance from intervening features, or may be reduced if the concrete pour activities occur in the northern portion of the project site and at greater distances from this hotel, this estimated noise level exceeds the nighttime threshold of 60 dBA. For these reasons, during the nighttime hours of 4:00 a.m. to 7:00 a.m. and during the daytime, but non-standard, hour of 7:00 a.m. to 8:00 a.m., noise from concrete pouring activities would potentially exceed the local standard, and impacts would be significant. Therefore, Mitigation Measure NOI-1, Construction Noise Control Plan to Reduce Noise Outside of the Standard Construction Hours in the City of South San Francisco, which includes measures to reduce noise from construction activity during non-standard construction hours, would be implemented to reduce impacts from construction-related noise. Consequently, the impact from construction- generated noise that could occur during the 7:00 a.m. to 8:00 a.m. hour before standard construction noise hours begin and during the 15 occurrences of nighttime concrete pours (which would start at 4:00 a.m.) would be less than significant with mitigation. Mitigation Measure NOI-1: Construction Noise Control Plan to Reduce Noise Outside of the Standard Construction Hours in the City of South San Francisco The project sponsor and/or the contractor(s) for the proposed project shall obtain a permit to complete work outside of the standard construction hours outlined in the City Municipal Code. In addition, the project sponsor and/or the contractor(s) for the proposed project shall develop a construction noise control plan to reduce noise levels to within the City’s daytime and nighttime noise standards. Specifically, the plan shall demonstrate that noise from construction activities that occur daily between 7:00 and 8:00 a.m. weekdays and Saturday will comply with the applicable City noise limit of 65 dBA at the nearest existing land use, and construction activities that occur between 10:00 p.m. and 7:00 a.m. will comply with the applicable City noise limit of 60 dBA at the nearest existing land use. Measures to help reduce noise from construction activity during non-standard construction hours to these levels shall be incorporated into this plan and may include, but are not limited to, the following. City of South San Francisco Environmental Setting, Impacts, and Mitigation Noise and Vibration 751 Gateway Boulevard Project 4.8-20 September 2020 ICF 0662.19 l Require all construction equipment be equipped with mufflers and sound control devices (e.g., intake silencers and noise shrouds) that are in good condition (at least as effective as those originally provided by the manufacturer) and appropriate for the equipment. l Maintain all construction equipment to minimize noise emissions. l Locate construction equipment as far as feasible from adjacent or nearby noise-sensitive receptors. l Require all stationary equipment be located to maintain the greatest possible distance to the nearby existing buildings, where feasible. l Require stationary noise sources associated with construction (e.g., generators and compressors) in proximity to noise-sensitive land uses to be muffled and/or enclosed within temporary enclosures and shielded by barriers, which can reduce construction noise by as much as 5 dB. l Use noise-reducing enclosures around noise-generating equipment during nighttime/non- standard daytime hours. Prohibit the use of impact tools (e.g., jack hammers) during these hours. l Prohibit idling of inactive construction equipment for prolonged periods during nighttime hours (i.e., more than 2 minutes). l Advance notification shall be provided to surrounding land uses disclosing the construction schedule, including the various types of activities that would be occurring throughout the duration of the construction period. l The construction contractor shall provide the name and telephone number of an on-site construction liaison. If construction noise is found to be intrusive to the community (complaints are received), the construction liaison shall investigate the source of the noise and require that reasonable measures be implemented to correct the problem. l Use electric motors rather than gasoline- or diesel-powered engines to avoid noise associated with compressed air exhaust from pneumatically powered tools during nighttime hours. Where the use of pneumatic tools is unavoidable, an exhaust muffler on the compressed air exhaust could be used; this muffler can lower noise levels from the exhaust by about 10 dB. External jackets on the tools themselves could be used, which could achieve a reduction of 5 dB. Construction Haul Truck Noise Haul trucks and material delivery trucks would be used to transport materials to and from the site during project construction. According to the project sponsor, the maximum number of trucks that would travel to and from the site in a given hour would be 22 trucks. This would occur during the concrete pours for the project. Note that this is a reasonable worst-case maximum, and for most construction activities, truck trips would be somewhat spread out throughout the day and there would be fewer per-hour trips than this number. The City’s Municipal Code does not include a specific threshold that pertains to construction haul truck noise. However, and as discussed above, a change of 3 dB is considered barely noticeable by the human ear. Therefore, anticipated loudest-hour haul truck noise was assessed to determine if a 3 dB increase over ambient noise levels would occur. City of South San Francisco Environmental Setting, Impacts, and Mitigation Noise and Vibration 751 Gateway Boulevard Project 4.8-21 September 2020 ICF 0662.19 The City has published general truck routes in the City,13 but the routes of trucks during project construction is not known with certainty at this time. Based on the City’s general truck routes, the closest access to the U.S. 101 is located northeast of the project site. It is likely that trucks would travel to the project site via U.S. 101, then travel east on Oyster Point Boulevard after exiting the freeway, and turning south on Gateway Boulevard to access the project site. Along this route, there are only commercial and office land uses, which are not typically considered sensitive to noise. Noise in these areas is already somewhat elevated from the nearby U.S. 101 freeway and other local roadways, as well. Existing worst-hour traffic noise modeling was conducted to estimate the peak-hour Leq noise level along these two segments. Existing traffic noise from vehicles traveling on Oyster Point Boulevard east of Dubuque Avenue was modeled to be approximately 70.3 dBA Leq during the peak hour, and traffic noise from vehicles traveling along Gateway Boulevard south of Oyster Point was modeled to be 66.6 dBA Leq during the worst-case peak hour. The addition of 22 trucks to these two segments would increase noise to approximately 70.7 and 67.4 dBA Leq respectively, which equates to an approximately 0.4 and 0.9 dB increase along these segments. A less than 3 dB increase in noise would occur (with a change of 3 dB considered barely noticeable); thus, temporary noise increases from project haul and materials delivery trucks in the project vicinity would be less than significant. Traffic Noise As discussed in Section 4.9, Transportation and Circulation, of this draft EIR, implementation of the proposed project would lead to an increase in traffic in the vicinity of the project site. Quantitative modeling of traffic noise increases resulting from project implementation was conducted using a spreadsheet that is based on the FHWA TNM version 2.5. As shown in Table 4.8-12, project-related noise increases on roadway segments in the project vicinity range from 0 to 0.5 dB. Project-related traffic noise would not result in a 5 dBA or greater increase in areas where future noise level are within the normally acceptable range, and would not result in a 3 dBA or greater increase in areas where future noise level are above the normally acceptable range. Thus, project-related traffic noise impacts would be less than significant. Heating, Ventilation, and Air Conditioning, and Mechanical Equipment Noise The proposed heating, ventilation, and air conditioning (HVAC) systems and mechanical equipment for the proposed project would include two chillers and three boilers to serve the heating and cooling needs in the building, which would be located in a rooftop penthouse. Nine pumps would also be located in the penthouse. Four air-handling units, two cooling towers and six large exhaust fans would also be located on the roof behind a screen. Noise generated by equipment located in the mechanical equipment room or the rooftop penthouse would be attenuated somewhat by the walls of the equipment room. A reasonably conservative assumption of 10 dB of reduction was applied to all equipment located inside the equipment room. The rooftop screen may not be as tall as the height of the equipment and there would be a gap at the 13 City of South San Francisco. 2020. Truck Routes. Available: https://www.google.com/maps/d/viewer? mid=1ePU1NiJj2omRVWwagk4bBUKU9t58-Y0K&ll=37.649158157197135%2C-122.40959426201982&z=14. Accessed: July 28, 2020. City of South San Francisco Environmental Setting, Impacts, and Mitigation Noise and Vibration 751 Gateway Boulevard Project 4.8-22 September 2020 ICF 0662.19 Table 4.8-12. Modeled Traffic Noise Impacts on Existing Land Uses Roadway Segment Existing No Project (dB Ldn) Existing Plus Project (dB Ldn) Project- related Increasea (dB) Airport Boulevard North of Sister Cities Boulevard 65.4 65.4 0.0 Airport Boulevard South of Sister Cities Boulevard 64.1 64.1 0.0 Airport Boulevard North of Grand Avenue 65.3 65.3 0.0 Airport Boulevard South of Grand Avenue 65.5 65.5 0.0 Sister Cities Boulevard East of Airport Boulevard 69.3 69.3 0.0 Sister Cities Boulevard West of Airport Boulevard 68.8 68.8 0.0 Oyster Point Boulevard East of Dubuque Avenue 66.2 66.2 0.0 Oyster Point Boulevard West of Dubuque Avenue 69.1 69.1 0.0 Oyster Point Boulevard East of Gateway Boulevard 69.0 69.0 0.0 Oyster Point Boulevard West of Gateway Boulevard 69.9 70.0 0.2 Gateway Boulevard South of Oyster Point Boulevard 66.0 66.5 0.5 Gateway Boulevard North of East Grand Avenue 65.2 65.5 0.3 Gateway Boulevard South of East Grand Avenue 65.3 65.5 0.1 East Grand Avenue East of Gateway Boulevard 68.8 68.8 0.0 East Grand Avenue West of Gateway Boulevard 68.1 68.2 0.1 Grand Avenue East of Airport Boulevard 67.1 67.2 0.1 Grand Avenue West of Airport Boulevard 64.5 64.6 0.1 Dubuque Avenue South of Oyster Point Boulevard 67.9 68.0 0.1 Dubuque Avenue South of U.S. 101 Ramps 61.6 61.7 0.0 Source: Traffic volumes provided by Fehr & Peers. Modeling conducted using a spreadsheet based on the FHWA TNM version 2.5 at a fixed distance of 50 feet from the roadway centerline. Notes: a Existing plus project values minus existing no project values. bottom of the screen to allow for exhaust and ventilation. Noise from equipment located behind the rooftop screen may be reduced slightly by the screen; however, noise is not typically substantially reduced unless a screen is solid with no gaps or openings and is at least as tall as the equipment. Therefore, although some attenuation may be achieved from the rooftop screen, no noise attenuation is assumed in this analysis for noise sources located on the roof behind the rooftop equipment screen. According to the project sponsor, custom air handling units, such as the four air handlers proposed for the project, can produce sound levels in the range of about 65 to 70 dBA at 50 feet, depending on the size of the unit. The proposed cooling towers would generate a noise level of approximately 78 dBA at 50 feet. The heat recovery chillers would generate a noise level of 65 dBA at 50 feet without accounting for any attenuation, a typical boiler generates a sound power level in the range of 96 to 99 dBA,14 which equates to a noise level of 64 to 67 dBA at 50 feet. 14 Hoover and Keith. 2000. Noise Control for Buildings, Manufacturing Plants, Equipment, and Products. Houston, TX. City of South San Francisco Environmental Setting, Impacts, and Mitigation Noise and Vibration 751 Gateway Boulevard Project 4.8-23 September 2020 ICF 0662.19 Pumps can generate noise levels at 50 feet of approximately 81 dBA, and the types of exhaust/ventilation fans proposed for the project can generate noise levels at 50 feet of approximately 77 dBA, according to the project sponsor. Based on these source noise levels, combined noise from three boilers, two chillers, and nine pumps located in a mechanical penthouse and two cooling towers, four air handling units, and six exhaust fans located behind a mechanical equipment screen at a distance of 50 feet could be up to approximately 88dBA, conservatively assuming all equipment was operational simultaneously and relatively close to one another. The nearest existing land use to the proposed building is 701 Gateway Boulevard. The proposed building would be located approximately 100 feet from 701 Gateway Boulevard. Based on the source noise levels and operational assumptions described above, noise from the HVAC system and equipment at a distance of 100 feet is conservatively estimated to be approximately 84 dBA. The next closest land use, 901 Gateway boulevard, is located approximately 160 feet from the proposed building. Noise from the rooftop equipment at a distance of 160 feet would be approximately 80 dBA. As described previously, all land uses within the GSPD are governed by the same municipal code noise thresholds of 65 dBA during the daytime hours of 7:00 a.m. to 10:00 p.m. and 60 dBA during the nighttime hours of 10:00 p.m. to 7:00 a.m. with respect to noise generated by stationary sources. Thus, the proposed rooftop HVAC system and equipment noise may exceed the daytime and nighttime thresholds outlined in the South San Francisco Municipal Code and impacts from mechanical equipment noise would be significant. Therefore, Mitigation Measure NOI-2, Operational Noise Study to Determine Attenuation Measures to Reduce Noise from Project Mechanical Equipment, would ensure the project’s mechanical equipment is selected and located to comply with the City’s Noise Ordinance. Consequently, the noise impact from the mechanical equipment would be less than significant with mitigation. Mitigation Measure NOI-2: Operational Noise Study to Determine Attenuation Measures to Reduce Noise from Project Mechanical Equipment Once equipment models and design features to attenuate noise have been selected, the project sponsor shall conduct a noise analysis to estimate actual noise levels of project-specific mechanical equipment, including heating and cooling equipment (such as boilers, chillers, cooling towers, and exhaust fans), to reduce potential noise impacts resulting from project mechanical equipment. Feasible methods to reduce noise below the significance threshold include, but are not limited to, selecting quieter equipment, siting equipment further from the roofline, and/or enclosing all equipment in a mechanical equipment room designed to reduce noise. This analysis shall be conducted, and its results and reduction methods provided to the City, prior to the issuance of building permits. The analysis shall be prepared by persons qualified in acoustical analysis and/or engineering and shall demonstrate with reasonable certainty that the mechanical equipment selected for the project and the attenuation features incorporated into project design would ensure noise from these equipment do not result in noise at the nearest existing land use of 65 dBA Leq during the daytime and 60 dBA Leq during the nighttime. The project sponsor shall incorporate all recommendations from the acoustical analysis necessary to ensure that noise sources would meet applicable requirements of the noise ordinance into the building design and operations. City of South San Francisco Environmental Setting, Impacts, and Mitigation Noise and Vibration 751 Gateway Boulevard Project 4.8-24 September 2020 ICF 0662.19 Emergency Generator Noise The project proposes the installation of one diesel 1,250-kilowatt (kW) emergency generator in the project loading and service yard. The generator would be equipped with a level 3 enclosure, which would reduce noise levels somewhat from generator operations. Periodic testing of the generator would be completed; testing is anticipated to consist of one test per week for 30 to 45 minutes per test at a load of 100 percent for up to 50 hours per year maximum. Other than testing, the generator would only operate during emergencies. Typically, generator noise during emergencies is exempt from local noise standards. During testing, generator noise must comply with the local standards. Section 8.32.030 of the City’s Noise Ordinance specifies maximum permissible sound levels to be generated by any property within the City. The maximum allowable level is determined by the land use category of the receiving property and is measured on any receiving property. In the GSPD, noise generated during daytime hours is limited to 65 dBA and noise generated during nighttime hours is limited to 60 dBA at nearby receptors. Operation of the proposed generator equipped with a level 3 enclosure could result in noise levels of 75 dBA at a distance of 7 meters, or approximately 23 feet. The nearest existing building to the proposed service yard, which is where the generator would be located, is the building at 701 Gateway, approximately 150 feet from the proposed generator location within the service yard. At a distance of 150 feet, noise from generator testing would be reduced to 59 dBA Leq. Noise from generator testing at other nearby buildings would be even lower because they are all located farther than 150 feet from the proposed generator location. Noise from generator testing would not result in noise levels of greater than the 65 dBA daytime and 60 dBA nighttime thresholds at the nearest receptors; thus, noise impacts from generator testing would be less than significant. Impact NOI-2: The proposed project would not generate excessive ground-borne vibration or ground-borne noise levels. (Less than Significant) Damage to Structures Construction of the proposed project would require equipment that could generate ground-borne vibration; however, most of the proposed equipment types generate relatively low vibration levels. Typical vibration levels associated with heavy-duty construction equipment at a reference distance of 50 feet are shown in Table 4.8-13. No pile drivers or hoe rams are proposed for project construction. The proposed pieces of equipment for project construction with the greatest potential to generate vibration are ground-disturbing equipment such as an excavator and a Gradall. These pieces of equipment typically generate vibration levels similar to that of a large bulldozer. A large bulldozer would generate vibration levels of approximately 0.037 PPV inches per second at a distance of 45 feet. The existing structures located within and adjacent to the project site appear to be relatively modern and are not expected to be particularly susceptible to vibration-related damage. The nearest existing structures to project construction activities are the buildings at 701 Gateway Boulevard and 901 Gateway Boulevard; both buildings are located approximately 45 feet from the nearest project construction areas. These structures would likely be categorized as a modern industrial/commercial building, according to the Caltrans vibration damage criteria shown in Table 4.8-4. These types of buildings have a vibration threshold for continuous or frequent/intermittent vibration sources (such as construction) of 0.5 PPV inches per second. City of South San Francisco Environmental Setting, Impacts, and Mitigation Noise and Vibration 751 Gateway Boulevard Project 4.8-25 September 2020 ICF 0662.19 Therefore, a large bulldozer would generate vibration over ten times below this level at a distance of 45 feet and potential vibration-related damage impacts from project construction would be less than significant. Annoyance-related Vibration Impacts Regarding annoyance-related vibration impacts, a significant vibration impact related to sleep disturbance could occur when nighttime construction activities generate vibration levels that are strongly perceptible at locations where people sleep for a prolonged period of time. There are no residential land uses near the project site, so sleep-disturbance related vibration impacts would not occur. The nearest residential land uses are located over 1,200 feet from the project site, the nearest hotel (Larkspur Landing) is located approximately 600 feet from the main project construction areas, and 300 feet from the southern portion of the project site where paving, curb work and landscaping activities may occur. The nearest childcare use (Gateway Child Development Center Peninsula) is located approximately 670 feet from the nearest project construction area (the southern portion of the site where paving and landscaping work is proposed). Sleep disturbances from vibration only occur if residences are located very close to ground-disturbing construction activities that occur at night. For example, vibration levels may exceed Caltrans Vibration Annoyance Criteria’s distinctly perceptible level of 0.04 PPV inches per second within 50 feet of an operating auger drill or large bulldozer, or the strongly perceptible criteria of 0.1 PPV inches per second at 25 feet for this equipment. Construction activity involving these types of equipment is not proposed for nighttime hours, and residences are located much farther than these distances from project construction areas. However, it is possible that construction vibration during daytime hours could result in disturbances to nearby office or research-related buildings. If vibration levels are in excess of the Caltrans Vibration Annoyance Criteria’s distinctly perceptible level of 0.04 PPV inches per second, annoyance-related impacts could be significant. The nearest existing structures to project construction activities are the buildings at 701 Gateway Boulevard and 901 Gateway Boulevard; both buildings are located approximately 45 feet from the nearest project construction areas. To provide a conservative assumption, vibration levels at a distance of 45 feet from construction activity were modeled to assess potential annoyance-related vibration impacts. As described above, the pieces of construction equipment likely to generate the most vibration are an excavator and a Gradall. These would generate vibration levels similar to that of a large bulldozer. At a distance of 45 feet, a large bulldozer would generate a vibration level of approximately 0.037 PPV inches per second. This is below the Caltrans vibration annoyance criteria’s distinctly perceptible level of 0.04 PPV inches per second. In addition, the construction equipment would usually operate farther than 45 feet from the nearby occupied buildings. Therefore, annoyance-related vibration impacts would be less than significant. Impact NOI-3: The proposed project would not expose people residing or working in the project area to excessive noise levels for a project located within the vicinity of a private airstrip or an airport land use plan or, were such a plan has not been adopted, within two miles of a public airport or public use airport. (No Impact) SFO is approximately 2 miles south of the project site. According to the 2012 SFO ALUCP, the project site is not located within the CNEL 65 decibel noise contour.15 In addition, there are no private airstrips within the vicinity of the project site. For these reasons, there would be no impact related to aircraft activity noise from public airports and private airstrips. 15 Exhibit IV-5, Noise Compatibility Zones in the 2012 SFO ALUCP. City of South San Francisco Environmental Setting, Impacts, and Mitigation Noise and Vibration 751 Gateway Boulevard Project 4.8-26 September 2020 ICF 0662.19 4.8.4.4 Cumulative Impacts Impact C-NOI-1: The proposed project would not result in a cumulatively considerable contribution to the generation of a substantial temporary or permanent increase in ambient noise levels in the vicinity of the project site in excess of standards established in a local general plan or noise ordinance or applicable standards of other agencies. (Less than Significant with Mitigation) The cumulative geographic context for noise and vibration varies, depending on the source of the noise or vibration. Specifically, the geographic context for cumulative construction noise impacts typically encompasses cumulative projects within no more than 1,000 feet of the project site. Beyond 1,000 feet, the contributions of noise from the construction of other projects would be greatly attenuated through both distance and intervening structures, and their contribution would be expected to be minimal. The cumulative context for stationary-source noise impacts, such as noise effects from HVAC or other mechanical equipment, and for vibration effects from construction activities is generally smaller than this distance (a few hundred feet at most). Finally, cumulative impacts related to vehicular traffic noise are based on overall forecast average daily traffic along roadway segments near the project site, which includes traffic increases from all growth within the project area, as predicted in the traffic model. The cumulative projects within 0.5 mile of the project site are described in Section 4.1.5, Approach to Cumulative Impact Analysis, of this draft EIR and shown in Figure 4.1-1. Construction Noise Construction noise is a localized impact that reduces as distance from the noise source increases. In addition, intervening features (e.g., buildings) between construction areas and nearby noise- sensitive land uses result in additional noise attenuation by providing barriers that break the line of sight between noise-generating equipment and sensitive receptors. These barriers can block sound wave propagation and somewhat reduce noise at a given receiver. The only cumulative project located with 1,000 feet of the proposed project is 475 Eccles Avenue (Cumulative Project No. 16). The project was entitled in August of 2016. However, at this time, it is unknown when construction will begin. Construction activities for the project could coincide with construction activities for the 475 Eccles Avenue Project. The project site is located approximately 630 feet from the closest edge of the project site for the 475 Eccles Avenue Project. At this distance, construction noise would diminish substantially. For example, as shown in Table 4.8-10, worst-case project construction noise at a distance of 600 feet from the loudest proposed project construction activities would be approximately 64 dBA Leq. This noise level is typical of an urban area, such as the area where these two projects would be located. Project construction would also occur mostly during the standard daytime hours for construction, as defined by the South San Francisco Municipal Code. During these hours, construction noise restrictions are less stringent, and nearby receptors are considered to be less sensitive to noise. In addition, there are no residences or land uses that are typically considered noise-sensitive located between the project site and the 475 Eccles Avenue Project. Furthermore, numerous buildings are located between the two sites, which would provide shielding and further attenuate noise from construction activities and would reduce the likelihood of construction noise from these two projects combining. Thus, it is unlikely that construction activities from these two projects would combine to expose the same receptors to excessive construction noise. For these reasons, the proposed project, in combination with other past, City of South San Francisco Environmental Setting, Impacts, and Mitigation Noise and Vibration 751 Gateway Boulevard Project 4.8-27 September 2020 ICF 0662.19 present, and reasonably foreseeable future projects, would not result in a significant cumulative noise impact during construction. The cumulative impact would be less than significant. No mitigation is required. Operational Noise Traffic Noise To determine the potential cumulative noise impacts in the project area, traffic volumes from the existing scenario were compared to the 2040 with-project scenario. If a cumulative traffic noise impact is anticipated along a given roadway segment (i.e., a 3 dB in increase between existing and cumulative no project conditions), then the proposed project’s contribution to that impact must be assessed. If the project would contribute 3 dB to the overall increase, the project’s cumulatively considerable contribution to the cumulative impact would be significant. Table 4.8-13 shows cumulative traffic noise increases and includes an analysis of potential impacts along roadway segments near the project site. There were no segments identified where a 5 dB increase in noise would occur in areas where future noise levels would below the acceptable range. However, as shown in Table 4.8-13, significant cumulative impacts in areas where future noise levels are above the acceptable range (e.g., a 3 dB increase from existing to cumulative plus project conditions) were modeled to occur along seven modeled roadway segments. The cumulative impact would be significant. However, the proposed project’s incremental increase to these potential cumulative impacts would be between 0 and 0.2 dB. Therefore, the proposed project’s contribution to the cumulative impact would be less than cumulatively considerable. HVAC Noise In general, most operational sources of noise do not generate noise that is perceptible far beyond the edge of a project site. HVAC noise from the proposed project would be localized and would attenuate rapidly with distance. The nearest cumulative project, the project at 475 Eccles Avenue (Cumulative Project 16), is located approximately 630 feet east of the project site. There are no residences or land uses that are typically considered noise-sensitive located between the two projects. However, the applicable noise thresholds for all land uses in the GSPD are the same regardless of the type of use (i.e., 60 dBA during nighttime hours and 65 dBA during daytime hours). As described under Impact NOI-1, unattenuated noise from rooftop heating and cooling equipment could result in excessive noise levels in the project vicinity with an estimated combined noise level of 90 dBA at a distance of 50 feet from the proposed equipment. The approximate halfway distance between the two project sites is approximately 315 feet. An existing occupied office structure is at this location. At a distance of 315 feet, unattenuated HVAC noise from the project site would be in the range of approximately 74 dBA. Assuming the cumulative project at 475 Eccles Avenue uses similar heating and cooling equipment, noise from the cumulative project could also elevate ambient noise levels at this common receptor. Should both projects expose a single receptor to the same noise levels from heating and cooling equipment, the overall combined noise level would be approximately 3 dB higher than the HVAC noise from a single project. Although it is not easily perceptible, a 3 dB increase in noise is considered to be barely perceptible by the average healthy human ear. A perceptible increase in noise at a common receptor could occur if both projects had unattenuated HVAC noise; thus, the cumulative noise impact from HVAC equipment would be significant. With implementation of Mitigation Measure NOI-2, Operational Noise Study to Determine Attenuation Measures to City of South San Francisco Environmental Setting, Impacts, and Mitigation Noise and Vibration 751 Gateway Boulevard Project 4.8-28 September 2020 ICF 0662.19 Reduce Noise from Project Mechanical Equipment, project-related impacts would be reduced to less-than-significant levels, and the contribution of the project to the potential cumulative impact would be less than cumulatively considerable with mitigation. Emergency Generator Noise The nearest cumulative project, the project at 475 Eccles Avenue (Cumulative Project No. 16), is located approximately 630 feet east of the project site. There are no residences or land uses that are typically considered noise-sensitive located between the two projects. As discussed under Impact NOI-1, noise from the testing of the emergency generator would not be expected to exceed the daytime or nighttime noise thresholds in the City at a distance of 150 feet (noise from project generator testing was estimated to be up to 59 dBA Leq at this distance). Assuming the cumulative project at 475 Eccles Avenue includes an emergency generator, noise from the cumulative project could also elevate ambient noise levels at this common receptor. However, emergency generator testing typically occurs very intermittently (e.g., up to once per week for a period of 30 to 45 minutes for the proposed project) and, thus, it is unlikely that testing of the emergency generator for the proposed project would occur concurrently with the generator testing at 475 Eccles Avenue. Even if testing were to occur simultaneously, the distance between the two generators would be great enough ensure that noise levels would not combine to expose a given individual receptor to increased cumulative noise from generator testing. Thus, the cumulative noise impact related to emergency generator testing would be less than significant. Impact C-NOI-2: The proposed project, in combination with past, present, and reasonably foreseeable future projects, would not expose persons to or generate excessive ground-borne vibration or ground-borne noise levels. (Less than Significant) Vibration impacts are based on instantaneous PPV levels. Thus, since impacts only consider the peak vibration levels, worst-case ground-borne vibration levels from construction are generally determined by whichever individual piece of equipment generates the highest peak vibration level. Unlike the analysis for average noise levels, in which noise levels of multiple pieces of equipment can be combined to generate a maximum combined noise level, instantaneous peak vibration levels do not combine in this way. Vibration from multiple construction sites, even if they are close to one another, would not be expected to combine to raise the maximum PPV level. For this reason, the cumulative impact of construction vibration from multiple construction projects near one another (or even adjacent to one another) would generally not combine to increase PPV vibration levels. Thus, the cumulative geographic context for vibration is highly localized. The cumulative projects within 0.5 mile of the project site are described in Section 4.1.5, Approach to Cumulative Impact Analysis, of this draft EIR and shown in Figure 4.1-1. The nearest cumulative project, the project at 475 Eccles Avenue (Cumulative Project No. 16), is located approximately 630 feet east of the project site. At this distance, peak vibration levels resulting from construction of the project would not be expected to combine with vibration effects from the construction of the 475 Eccles Avenue Project if they were to be under construction simultaneously. Therefore, cumulative ground-borne vibration impacts related to both potential damage and annoyance would be less than significant. City of South San Francisco Environmental Setting, Impacts, and Mitigation Noise and Vibration 751 Gateway Boulevard Project 4.8-29 September 2020 ICF 0662.19 Table 4.8-13. Modeled Cumulative Traffic Noise Impacts Roadway Segment Existing No Project (dB Ldn) Cumulative No Project (dB Ldn) Cumulative Plus Project (dB Ldn) Cumulative Plus Project Minus Existing (dB) Potential Cumulative Impact? Cumulative Plus Project Minus Cumulative No Project (dB) Cumulatively Considerable Increase? Airport Boulevard North of Sister Cities Boulevard 65.4 67.0 67.0 1.6 No 0.0 N/A Airport Boulevard South of Sister Cities Boulevard 64.1 65.2 65.2 1.1 No 0.0 N/A Airport Boulevard North of Grand Avenue 65.3 68.0 68.0 2.7 No 0.0 N/A Airport Boulevard South of Grand Avenue 65.5 67.2 67.3 1.8 No 0.0 N/A Sister Cities Boulevard East of Airport Boulevard 69.3 71.0 71.1 1.7 No 0.0 N/A Sister Cities Boulevard West of Airport Boulevard 68.8 69.4 69.4 0.6 No 0.0 N/A Oyster Point Boulevard East of Dubuque Avenue 66.2 67.3 67.3 1.1 No 0.0 N/A Oyster Point Boulevard West of Dubuque Avenue 69.1 70.8 70.8 1.7 No 0.0 N/A Oyster Point Boulevard East of Gateway Boulevard 69.0 72.4 72.4 3.4 Yes 0.0 No Oyster Point Boulevard West of Gateway Boulevard 69.9 73.0 73.0 3.2 Yes 0.1 No Gateway Boulevard South of Oyster Point Boulevard 66.0 69.4 69.6 3.6 Yes 0.2 No Gateway Boulevard North of East Grand Avenue 65.2 67.6 67.7 2.5 No 0.1 N/A Gateway Boulevard South of East Grand Avenue 65.3 69.3 69.3 4.0 Yes 0.1 No East Grand Avenue East of Gateway Boulevard 68.8 72.0 72.0 3.2 Yes 0.0 No East Grand Avenue West of Gateway Boulevard 68.1 71.5 71.5 3.3 Yes 0.0 No Grand Avenue East of Airport Boulevard 67.1 71.2 71.2 4.1 Yes 0.0 No Grand Avenue West of Airport Boulevard 64.5 66.1 66.2 1.7 No 0.0 N/A Dubuque Avenue South of Oyster Point Boulevard 67.9 69.6 69.7 1.8 No 0.1 N/A Dubuque Avenue South of U.S. 101 Ramps 61.6 61.8 61.8 0.2 No 0.0 N/A Note: N/A indicates that there would be no potential cumulative impact and, thus, no cumulatively considerable increase attributable to the proposed project. 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