4.11 NOISE. A. Existing Conditions

Transcription

1 4.11 NOISE This chapter describes the regulatory framework and existing ambient noise conditions in and around the project site. This chapter also evaluates the potential noise impacts of the project, including cumulative impacts. A. Existing Conditions This section describes the methodology used for measuring noise as well as the existing noise environment within the vicinity of the project site. The project site is located in a suburban area and is, therefore, influenced by several surrounding noise sources. 1. Characteristics of Sound Noise is generally defined as unwanted sound. Noise consists of any sound that may produce physiological or psychological damage and/or interfere with communication, work, rest, recreation, and sleep. To the human ear, sound has two significant characteristics: pitch and loudness. Pitch is the number of complete vibrations or cycles per second of a wave that results in the range of tone from high to low. Loudness is the strength of a sound that describes a noisy or quiet environment, and it is measured by the amplitude of the sound wave. Loudness is determined by the intensity of the sound waves combined with the reception characteristics of the human ear. Sound intensity refers to how hard the sound wave strikes an object, which in turn produces the sound s effect. This characteristic of sound can be precisely measured with instruments. The analysis of a project defines the noise environment of the project area in terms of sound intensity and its effects on adjacent sensitive land uses. a. Measurement of Sound Sound intensity is measured through the A-weighted scale to correct for the relative frequency response of the human ear. That is, an A-weighted noise level de-emphasizes low and very high frequencies of sound similar to the human ear s de-emphasis of these frequencies. Unlike linear units such as inches or pounds, decibels are measured on a logarithmic scale, representing

2 points on a sharply rising curve. Table contains a list of typical acoustical terms and definitions. Table shows representative outdoor and indoor noise levels in units of dba. A decibel (db) is a unit of measurement which indicates the relative intensity of a sound. The 0 point on the db scale is based on the lowest sound level that the healthy, unimpaired human ear can detect. Changes of 3 db or less are only perceptible in laboratory environments. Audible increases in noise levels generally refer to a change of 3 db or more, as this level has been found to be barely perceptible to the human ear in outdoor environments. Sound levels in db are calculated on a logarithmic basis. An increase of 10 db represents a 10-fold increase in acoustic energy, while 20 db is 100 times more intense, 30 db is 1,000 times more intense. Each 10-dB increase in sound level is perceived as approximately a doubling of loudness. As noise spreads from a source, it loses energy so that the farther away the noise receiver is from the noise source, the lower the perceived noise level would be. Geometric spreading causes the sound level to attenuate or be reduced, resulting in a 6 db reduction in the noise level for each doubling of distance from a single point source of noise to the noise sensitive receptor of concern. There are many ways to rate noise for various time periods, but an appropriate rating of ambient noise affecting humans also accounts for the annoying effects of sound. Equivalent continuous sound level (Leq) is the total sound energy of time varying noise over a sample period. However, the predominant rating scales for human communities in the State of California are the Leq, the community noise equivalent level (CNEL), and the day-night average level (Ldn) based on A-weighted decibels (dba). CNEL is the time varying noise over a 24-hour period, with a 5 dba weighting factor applied to the hourly Leq for noises occurring from 7:00 p.m. to 10:00 p.m. (defined as relaxation hours) and 10 dba weighting factor applied to noise occurring from 10:00 p.m. to 7:00 a.m. (defined as sleeping hours). Ldn is similar to the CNEL

3 TABLE DEFINITIONS OF ACOUSTICAL TERMS Term Decibel, db Frequency, Hz A-Weighted Sound Level, dba L01, L10, L50, L90 Equivalent Continuous Noise Level, Leq Community Noise Equivalent Level, CNEL Day/Night Noise Level, Ldn Lmax, Lmin Definitions A unit of level that denotes the ratio between two quantities proportional to power; the number of decibels is 10 times the logarithm (to the base 10) of this ratio. Of a function periodic in time, the number of times that the quantity repeats itself in one second (i.e., number of cycles per second). The sound level obtained by use of A-weighting. The A- weighting filter de-emphasizes the very low and very high frequency components of the sound in a manner similar to the frequency response of the human ear and correlates well with subjective reactions to noise. All sound levels in this report are A-weighted, unless reported otherwise. The fast A-weighted noise levels equaled or exceeded by a fluctuating sound level for 1 percent, 10 percent, 50 percent, and 90 percent of a stated time period. The level of a steady sound that, in a stated time period and at a stated location, has the same A-weighted sound energy as the time varying sound. The 24-hour A-weighted average sound level from midnight to midnight, obtained after the addition of five decibels to sound levels occurring in the evening from 7:00 p.m. to 10:00 p.m. and after the addition of 10 decibels to sound levels occurring in the night between 10:00 p.m. and 7:00 a.m. The 24-hour A-weighted average sound level from midnight to midnight, obtained after the addition of 10 decibels to sound levels occurring in the night between 10:00 p.m. and 7:00 a.m. The maximum and minimum A-weighted sound levels measured on a sound level meter, during a designated time interval, using fast time averaging

4 S T A T E O F C A L I F O R N I A / S A N T A C L A R A C O U N T Y TABLE DEFINITIONS OF ACOUSTICAL TERMS (CONTINUED) Term Definitions The all encompassing noise associated with a given environment at a specified time, usually a composite of Ambient Noise Level sound from many sources at many directions, near and far; no particular sound is dominant. The noise that intrudes over and above the existing ambient noise at a given location. The relative intrusiveness of a sound depends upon its amplitude, Intrusive duration, frequency, and time of occurrence and tonal or informational content as well as the prevailing ambient noise level. Source: Handbook of Acoustical Measurements and Noise Control, scale, but without the adjustment for events occurring during the evening relaxation hours. CNEL and Ldn are within one dba of each other and are normally exchangeable. The noise adjustments are added to the noise events occurring during the more sensitive hours. Typical A-weighted sound levels from various sources are described in Table Other noise rating scales of importance when assessing the annoyance factor include the maximum noise level (Lmax), which is the highest exponential time averaged sound level that occurs during a stated time period. The noise environments discussed in this analysis are specified in terms of maximum levels denoted by Lmax for short-term noise impacts. Lmax reflects peak operating conditions, and addresses the annoying aspects of intermittent noise. Noise standards in terms of percentile exceedance levels, Ln, are often used together with the Lmax for noise enforcement purposes. When specified, the percentile exceedance levels are not to be exceeded by an offending sound over a stated time period. For example, the L10 noise level represents the level exceeded ten percent of the time during a stated period. The L50 noise level represents the median noise level. Half the time the noise level exceeds this level, and half the time it is less than this level. The L90 noise level represents the noise level exceeded 90 percent of the time and is considered the lowest

5 TABLE TYPICAL A-WEIGHTED SOUND LEVELS Noise Source A-Weighted Sound Level in Decibels Noise Environments Near Jet Engine 140 Deafening Civil Defense Siren 130 Threshold of pain Hard Rock Band 120 Threshold of feeling Accelerating Motorcycle at a Few Feet Away Pile Driver; Noisy Urban Street/Heavy City Traffic Ambulance Siren; Food Blender 110 Very loud 100 Very loud 95 Very loud Garbage Disposal 90 Very loud Freight Cars; Tractors/ Agricultural Equipment at 50 Feet Pneumatic Drill; Vacuum Cleaner 85 Loud 80 Loud Busy Restaurant 75 Moderately loud Near Freeway Auto Traffic 70 Moderately loud Average Office 60 Moderate Suburban Street 55 Moderate Light Traffic; Soft Radio Music in Apartment 50 Quiet Large Transformer 45 Quiet Average Residence Without Stereo Playing 40 Faint Soft Whisper 30 Faint Rustling Leaves 20 Very faint Human Breathing 10 Very faint Source: Compiled by LSA Associates, Inc.,

6 noise level experienced during a monitoring period. It is normally referred to as the background noise level. For a relatively steady noise, the measured Leq and L50 are approximately the same. Noise impacts can be described in three categories. The first is audible impacts that refer to increases in noise levels noticeable to humans. Audible increases in noise levels generally refer to a change of 3.0 dba or greater, since, as described earlier, this level has been found to be barely perceptible in exterior environments. The second category, potentially audible, refers to a change in the noise level between 1.0 and 3.0 dba. This range of noise levels has been found to be noticeable only in laboratory environments. The last category is changes in noise level of less than 1.0 dba that are inaudible to the human ear. Only audible changes in existing ambient or background noise levels are considered potentially significant. b. Physiological Effects of Noise Physical damage to human hearing begins at prolonged exposure to noise levels higher than 85 dba. Exposure to high noise levels affects our entire system, with prolonged noise exposure in excess of 75 dba increasing body tensions, and thereby affecting blood pressure, functions of the ear, and the nervous system. In comparison, extended periods of noise exposure above 90 dba would result in permanent cell damage. When the noise level reaches 120 dba, a tickling sensation occurs in the human ear even with short-term exposure. This level of noise is called the threshold of feeling. 2. Existing Ambient Noise Levels An LSA noise technician conducted short-term ambient noise monitoring on the project site on Tuesday, August 21, 2007 between the hours of 10:30 a.m. and 1:00 p.m. at three separate locations within the vicinity of the project site. The purpose of this noise monitoring was to document the existing noise environment and capture the noise levels associated with operations and activities in the project vicinity. Table lists the noise levels measured during the short-term 20-minute noise measurements. Maximum and minimum noise levels were recorded as well as the equivalent continuous noise level

7 TABLE SHORT-TERM AMBIENT NOISE MONITORING RESULTS, dba Location No. Description Northwest corner of project site, 70 feet 1 south of Branham Ln. Southwest corner of project site, 115 feet 2 north of sound wall by State Route 85 Southeast corner of project site, 136 feet 3 west of Snell Ave., 21 feet north of Chynoweth Ave. Start Time 10:50 a.m. 11:20 a.m. 12:25 p.m. L eq a L max b L min c Primary Noise Sources Traffic on Branham Lane Traffic on State Route Traffic on Snell Avenue and Chynoweth Avenue, yardwork, airplanes approaching San Jose International Airport a Leq represents the average of the sound energy occurring over the 20-minute time period. b Lmax is the highest instantaneous sound level measured during the 20-minute time period. c Lmin is the lowest instantaneous sound level measured during the 20-minute time period. Source: LSA Associates, Inc., August measure Leq. The meteorological conditions at the time of each noise measurement are shown in Table Figure shows the monitoring locations. Vehicular noise is the primary source of ambient noise within the vicinity of the project site. The primary noise sources include traffic on SR-85, Branham Lane, and on Snell Avenue. The County of Santa Clara has identified noise environments with ambient noise levels up to 65 dba Ldn as satisfactory for open space and agricultural land use development. Measured ambient noise levels on the project site range from 57.8 dba to 62.3 dba Leq

8 S TAT E S TAT E LN BRANHAM 1 P A R K O F C A L I F O R N I A / C O U N T Y O F S A N TA C L A R A G E N E R A L P L A N / BRANHAM LN 1 SNELL AVE SNELL AVE 3 COLON Y FIEL 2 COLON D DR Y FIEL 3 HI GH D DR WA Y8 5 HI FIGURE GH WA Y8 5 Project Site 1 Noise Monitoring Locations Martial Cottle Park Noise Monitoring Locations FIGURE Source: LSA Associates, Inc., DC&E, MAPS, res\fig_ ai (5/13/10) Project Site N feet SOURCE: GOOGLE MAPS, Noise Monitoring Locations Martial Cottle Park Noise Monitoring F I G U Locations R E M O N I T O R I N G L O C AT I O N S

9 TABLE METEOROLOGICAL CONDITIONS DURING AMBIENT NOISE MONITORING Location Number Maximum Wind Speed (mph) Average Wind Speed (mph) Temperature (F) Relative Humidity (%) Source: LSA Associates, Inc., August Although the noise descriptors Leq and Ldn are not interchangeable, typically in suburban environments where noise levels drop off significantly at night, the Ldn can be equivalent to or even lower than daytime Leq ambient noise levels. 3. Existing Aircraft Noise Levels Mineta San Jose International Airport is located approximately 7 miles northwest of the project site. Noise exposure information in the community is developed for airport operations by the City of San Jose on a quarterly basis, based on current airport operations data and continuously measured noise levels. According to the most recent available quarterly report on existing noise contours and according to the projected 2010 conditions, the project site would not be located within the 65 dba CNEL contour of the airport. 1 Although aircraft related noise is occasionally audible on the project site, it would not result in a perceptible increase in 24-hour averaged ambient noise levels such as CNEL. 1 Mineta San Jose International Airport, 2007, Fourth Quarter 2006 Noise Monitoring Report, Contour Map and dB Contour Map

10 4. Existing Railroad Noise Levels The closest rail line to the project site is the Santa Clara Valley Transportation Authority (VTA) light rail line located between the east- and west-bound lanes of State Route 85. The Blossom Hill Station is located immediately south of the project site. It was observed during the ambient noise monitoring that, although several light rail trains passed during the monitoring period, noise from train passings were not audible on the project site over the noise levels from traffic on State Route 85. The Southern Pacific railroad line runs parallel to the Monterey Highway (State Route 82) and is located approximately 2100 feet northwest of the Branham Lane and Snell Avenue intersection. Train horn noise from this railroad is occasionally audible on the project site. 5. Existing Traffic Noise Levels Vehicular noise is the primary source of ambient noise in the project vicinity. The primary noise sources include traffic on State Route 85, Branham Lane, and on Snell Avenue. The Federal Highway Administration (FHWA) highway traffic noise prediction model (FHWA RD ) was used to evaluate traffic-related noise conditions on roadway segments in the vicinity of the project site. Traffic data used in the model was obtained from the traffic impact analysis prepared by Hexagon Transportation Consultants for the project. 2 The resultant noise levels were weighted and summed over a 24-hour period in order to determine the Ldn values. Table shows the traffic noise levels for roadway segments in the project site vicinity under existing traffic conditions. The traffic noise model printouts are included in Appendix I. As shown in the table, calculated traffic noise levels at 50 feet from the outermost travel lanes of the modeled roadway segments range up to 67.5 dba Ldn. However, the current alignments of Branham Lane and Snell Avenue 2 Hexagon Transportation Consultants, Inc., 2009, Martial Cottle Park Master Plan Transportation Impact Analysis

11 TABLE EXISTING TRAFFIC NOISE LEVELS Roadway Segment Branham Lane, Vista Park Drive to Safeway entrance Branham Lane, Safeway entrance to Snell Avenue Snell Avenue, Branham Lane to Chynoweth Avenue ADT a Centerline to 70 L dn b (feet) Centerline to 65 L dn (feet) Centerline to 60 L dn (feet) L dn (dba) 50 feet From Centerline of Outermost Lane 17,600 < ,000 < ,900 < a Average Daily Trips. b Day/Night Noise Level. The 24-hour A-weighted average sound level from midnight to midnight, obtained after the addition of 10 decibels to sound levels occurring in the night between 10:00 p.m. and 7:00 a.m. Source: LSA Associates, Inc. May, adjacent to the project site are setback approximately 75 and 80 feet respectively from the edge of the project property line. With the resulting geometric spreading of this noise, these traffic noise levels would attenuate to below 65 dba Ldn at the nearest project property line. 6. Existing Agricultural Operations Noise Levels. The current land use of the project site is agricultural land use, consisting primarily of flat, open fields that are seasonally cultivated for agricultural production. Related operational noise sources primarily consist of daytime diesel equipment crop harvesting operations. The majority of the site is currently dry farmed with hay and other grains. Past agricultural operations on the project site have included a dairy operation, growing grain, pasturage for cattle and horses, a family orchard, row crops, and milling cattle feed, each of which has had its own mix of equipment and, consequently, its own noise

12 characteristics. Typical noise levels from tractors as measured at a distance of 50 feet from the operating equipment range from 78 dba to 106 dba Lmax, with an average of about 84 dba Lmax. 3 In addition to the farming equipment noise sources, the operation of seasonal agricultural-related concessions (including a produce stand, a Christmas tree farm, and pumpkin patch) also contribute to the existing ambient noise environment. Associated noise sources include parking lot activities such as cars starting, car doors slamming, and people conversing which would take place during business hours. 7. Existing Land Uses in the Vicinity of the Project Site The project site is bordered on all sides by medium density, single- and multifamily residential land uses. Residential properties to the west of the project site immediately abut the project property. Other adjacent residential land uses are located across the surrounding streets of Branham Lane, Snell Avenue, Chynoweth Avenue, Colony Field Drive, Velasco Drive, and State Route 85. The Carlton Plaza Senior Assisted Living facility is located adjacent to the northwest corner of the project property and would also be considered a sensitive receptor to noise. A commercial shopping center is located adjacent to the project property at the northwest corner of the Branham Lane and Snell Avenue intersection. Commercial uses include restaurants, a gas station and car service center, a Safeway grocery store, and adjoining retail uses. Sensitive land uses in the project vicinity, other than the residential land uses, include an elementary school on Avenida Almendros, located 375 feet south of Chynoweth Avenue, buffered by several rows of homes. 3 Bolt, Beranek & Newman, Noise Control for Buildings and Manufacturing Plants

13 On-site land uses that would be sensitive to noise impacts include the historic residential property located within the 30.9-acre Life Estate adjacent to the project site. The construction and operation of the proposed project could affect these surrounding land uses. The on-site residential property located on the Life Estate would be the closest receptor to construction and operational noise impacts. The closest off-site noise sensitive receptors would be the residences bordering the park to the west on Barron Park Drive, Birmingham Drive, and Vistapark Drive. Other close off-site receptors are the residential land uses located along the south side of Chynoweth Avenue, along the east side of Snell Avenue, and along the north side of Branham Lane. B. Regulatory Framework The following section summarizes the regulatory framework related to noise, including federal, State, County of Santa Clara, and local plans, policies, and standards. 1. United States Environmental Protection Agency (EPA) In 1972 Congress enacted the Noise Control Act. This act authorized the EPA to publish descriptive data on the effects of noise and establish levels of sound requisite to protect the public welfare with an adequate margin of safety. These levels are separated into health (hearing loss) and welfare (annoyance) levels, as shown in Table The EPA cautions that these identified levels are not standards because they do not take into account the cost or feasibility of the levels. For protection against hearing loss, 96 percent of the population would be protected if sound levels are less than or equal to an Leq(24) of 70 dba. The (24) signifies an Leq duration of 24 hours. The EPA activity and interference guidelines are designed to ensure reliable speech communication at about

14 TABLE SUMMARY OF EPA NOISE LEVELS Effect Level Area Hearing loss Leq(24) < 70 db All areas. Outdoor activity interference and annoyance Indoor activity interference and annoyance Ldn < 55 db Leq(24) < 55 db Leq < 45 db Leq(24) < 45 db Outdoors in residential areas and farms and other outdoor areas where people spend widely varying amounts of time and other places in which quiet is a basis for use. Outdoor areas where people spend limited amounts of time, such as school yards, playgrounds, etc. Indoor residential areas. Other indoor areas with human activities such as schools, etc. Source: 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. 5 feet in the outdoor environment. For outdoor and indoor environments, interference with activity and annoyance should not occur if levels are below 55 dba and 45 dba, respectively. The noise effects associated with an outdoor Ldn of 55 dba are summarized in Table At 55 dba Ldn, 95 percent sentence clarity (intelligibility) may be expected at 3.5 meters, and no community reaction. However, one (1) percent of the population may complain about noise at this level and 17 percent may indicate annoyance. 2. State of California The State of California has established regulations that help prevent adverse impacts to occupants of buildings located near noise sources. Referred to as the State Noise Insulation Standard, it requires buildings to meet performance standards through design and/or building materials that would offset

15 TABLE SUMMARY OF HUMAN EFFECTS IN AREAS EXPOSED TO 55 DBA L DN Type of Effects Magnitude of Effect 100 percent sentence intelligibility (average) with a 5 db Speech Indoors margin of safety. 100 percent sentence intelligibility (average) at 0.35 meters. Speech Outdoors 99 percent sentence intelligibility (average) at 1.0 meters. 95 percent sentence intelligibility (average) at 3.5 meters. None evident; 7 db below level of significant complaints Average Community and threats of legal action and at least 16 db below vigorous action. Reaction 1 percent dependent on attitude and other non-level related Complaints factors. 17 percent dependent on attitude and other non-level related factors. Annoyance Attitude Towards Noise essentially the least important of various factors. Area Source: 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. any noise source in the vicinity of the receptor. These requirements are found in the California Code of Regulations, Title 24 (known as the Building Standards Administrative Code), Part 2 (known as the California Building Code), Appendix Chapters 12 and 12A. The State has also adopted the California Environmental Quality Act (CEQA). The main objectives of CEQA are to disclose to decision makers and the public the significant environmental effects of proposed activities and to identify ways to avoid or reduce those effects by requiring implementation of feasible alternatives or mitigation measures. Under CEQA, a substantial noise increase may result in a significant adverse environmental effect; if so, the noise increase must be mitigated or identified as a noise impact for which it is likely that only partial (or no) mitigation measures are available. Specific economic, social, environmental, legal, and technological conditions may make noise mitigation measures infeasible. The State has also established land use compatibility guidelines for determining acceptable noise levels for specified land uses. The

16 County has adopted and modified the State s land use compatibility guidelines, as discussed below. 3. County of Santa Clara The County s land use compatibility standards are contained within the Noise Element 4 of the General Plan and in Chapter VIII of the Environmental Health Division of the County s Ordinance Code. 5 The following sections of the County s Noise Element outline the standards that are applicable to the proposed project. Two tables, the Noise Compatibility Standards for Land Use in Santa Clara County and the Satisfactory Interior Noise Levels, were developed to set the levels of noise which are compatible with the performance and enjoyment of different classes of land use. The standards include both exterior and interior levels of sound. Standards such as these should be used in the review of subdivisions, building sites, architectural and site approval permits, use permits, and zone changes in areas subject to noise impacts. Each of these standards is intended to protect the people on-site from noise coming from outside sources, and to prevent new projects from generating adverse noise levels on adjacent properties. The Noise Compatibility Standards for exterior noise specify three classifications of compatibility between ambient noise levels at the site and various land uses: satisfactory, cautionary, and critical (see Table ). These standards serve as a preliminary analysis of potential noise incompatibility and serve to protect the proposed development from existing noise sources. 4 County of Santa Clara, 1994, Santa Clara County General Plan, Health and Safety Chapter, Noise. 5 County of Santa Clara, 2009, Ordinance Code, County of Santa Clara, California

17 TABLE NOISE COMPATIBILITY STANDARDS FOR LAND USE IN SANTA CLARA COUNTY Source: Santa Clara County, 1994, Santa Clara County General Plan. Noise studies and possible attenuation procedures will also be imposed on the project if the project itself is considered a source of incompatible noise for a nearby land use. The noise compatibility levels are defined as follows: Satisfactory noise levels are those which pose no serious threat to the proposed land use. The ambient noise level at the site is compatible with the

18 land use category of the proposed project and will not create annoyance and/or activity interference. Standard construction techniques will be adequate. Cautionary noise levels are those which could potentially pose a threat to the proposed land use. The ambient noise level is great enough to require study on the compatibility of the proposed project. Normal building methods may not be adequate to protect the use. Critical noise levels are those which probably pose a threat to the proposed land use. The ambient noise level is severe. The situation requires rigorous analysis of the compatibility of the proposed project with the ambient noise level at the site. This analysis should include both exterior and interior impacts. Simple solutions to noise attenuation may not be adequate and uses should be allowed only if they have been designed for noise reduction by a professional who is competent in sound reduction. The County s land use compatibility guidelines, shown in Table , indicate the following standards for new development within the county: Noise environments with ambient noise levels less than or equal to 55 dba Ldn are considered satisfactory for all land uses. Noise environments with ambient noise levels up to 60 dba Ldn are satisfactory for development of new public or semi-public facilities. Noise environments with ambient noise levels up to 65 dba Ldn are satisfactory for open space and agricultural land areas development. The County s Ordinance Code also addresses noise in Chapter VIII of the Environmental Health Division, including restricting noise producing construction activities to between the hours of 7:00 a.m. to 7:00 p.m., Monday through Saturday, and prohibits noise producing construction activities on Sundays and holidays. In addition, where technically and economically feasible, construction activities will be conducted in a manner that the maximum noise levels at affected properties will not exceed those listed in the Table

19 C. Standards of Significance Noise impacts associated with the project would be considered significant if the project would: 1. Result in exposure of persons to or generation of noise levels in excess of standards established in the local general plan or noise ordinance, or applicable standards of other agencies. 2. Result in exposure of persons to or generation of excessive groundborne vibration or groundborne noise levels. 3. Result in a substantial permanent increase in ambient noise levels in the project vicinity above levels existing without the project. 4. Increase substantially the ambient noise levels for adjoining areas during and/or after construction. D. Impact Discussion All potential impacts described below would be the same for Phase I and subsequent project phases. As such, project-level and program-level components are not distinguished below. 1. Exposure of Persons to or Generation of Noise Levels in Excess of Standards i. Traffic Noise Impacts The project site is located in a developed area and is, therefore, influenced by several surrounding noise sources. Vehicular noise is the primary source of ambient noise in the project site vicinity. The primary noise sources include traffic on State Route 85, Branham Lane, and Snell Avenue. Railroad and aircraft noise sources do not significantly impact the project site. The FHWA highway traffic noise prediction model (FHWA RD ) was used to evaluate traffic-related noise conditions on roadway segments in the vicinity of the project site. The resultant noise levels were weighted and

20 TABLE MAXIMUM NOISE LEVELS FOR OPERATION OF MOBILE EQUIPMENT Daily, except Sundays and legal holidays 7:00 a.m. to 7:00 p.m. (daytime hours) Single- and Two-Family Dwelling Residential Area Multi-Family Dwelling Residential Area Commercial Area 75 dba 80 dba 85 dba Daily, 7:00 p.m. to 7:00 a.m. (nighttime hours) and all day Sunday and legal holidays 50 dba 55 dba 60 dba Source: Santa Clara County, 2009, Ordinance Code, County of Santa Clara, California. summed over a 24-hour period in order to determine the Ldn values. The traffic noise model printouts are included in Appendix I. Tables and show the traffic noise levels for roadway segments in the project site vicinity under background and background plus project traffic conditions respectively. Traffic data used in the model was obtained from the traffic impact analysis prepared by Hexagon Transportation Consultants for this project. Background traffic volumes were estimated by adding to existing peak-hour volumes the projected volumes from approved but not yet completed developments. Background plus project volumes were obtained by adding to background volumes the additional traffic generated by the project. On-site traffic noise levels along roadway segments adjacent to the project site would range up to 69.0 dba Ldn under background plus project conditions at 50 feet from the centerline of the outermost travel lane. With the resulting geometric spreading of this noise, these traffic noise levels would attenuate to

21 TABLE BACKGROUND TRAFFIC NOISE LEVELS Roadway Segment Branham Ln., Vista Park Dr. to Safeway entrance Branham Ln., Safeway entrance to Snell Ave. Snell Ave., Branham Ln. to Chynoweth Ave. ADT a Centerline to 70 L dn b (Feet) Centerline to 65 L dn (Feet) Centerline to 60 L dn (Feet) L dn (dba) 50 feet from Centerline of Outermost Lane 17,600 < ,000 < ,900 < a Average Daily Trips. b Day/Night Noise Level (dba). The 24-hour A-weighted average sound level from midnight to midnight, obtained after the addition of 10 decibels to sound levels occurring in the night between 10:00 p.m. and 7:00 a.m. Source: LSA Associates, Inc. May, below 67 dba Ldn at the nearest project property line adjacent to Branham Lane. This assumes that the current alignment of Branham Lane adjacent to the project site would remain the same, with the current edge of roadway remaining at approximately 75 feet from the project property line. Under background conditions it is assumed that the segment of Snell Avenue adjacent to the project site will be widened to six lanes. Thus the predicted traffic noise levels at the nearest proposed trail areas along adjacent to Snell Avenue would be exposed to traffic noise levels up to 66.6 dba Ldn under background plus project conditions. Noise from traffic along State Route 85 was also calculated using the latest traffic volume data from Caltrans Traffic Data Branch. 6 The modeling 6 Caltrans, 2008, Traffic Volumes (Annual Average Daily Traffic),

22 TABLE BACKGROUND PLUS PROJECT TRAFFIC NOISE LEVELS Centerline to 70 Ldn b (feet) Centerline to 65 Ldn (feet) Centerline to 60 Ldn (feet) Ldn (dba) 50 feet from Centerline of Outermost Lane Increase Over Background Conditions Roadway Segment ADT a Branham Lane, Vista Park Drive to Safeway entrance 27, Branham Lane, Safeway entrance to Snell Avenue 16,800 < Snell Avenue, Branham Lane to Chynoweth Avenue 23,400 < a Average Daily Trips. b Day/Night Noise Level (dba). The 24-hour A-weighted average sound level from midnight to midnight, obtained after the addition of 10 decibels to sound levels occurring in the night between 10:00 p.m. and 7:00 a.m. Source: LSA Associates, Inc. May,

23 showed that traffic noise levels along the portion of State Route 85 west of Blossom Hill Road ranges up to 78.0 dba Ldn at 50 feet from the outermost travel lane. With the resulting geometric spreading of this noise, these traffic noise levels would attenuate to below 71 dba Ldn at the nearest proposed trail area adjacent to State Route 85. This predicted noise level assumes implementation of the proposed 60 foot setback landscaped buffer and berm shown in Figure 3-4 of the Chapter 3, Project Description. Impacts to on-site uses are compared to the County s land use compatibility standards. The County of Santa Clara has identified noise environments with ambient noise levels up to 65 dba Ldn are satisfactory for open space and agricultural land use development. However, as shown in Table , the County notes that for open space uses, there are no critical levels listed and homes in agricultural areas, such as the existing residence located in the Life Estate portion of the project site, are not subject to the Residential standards. Public buildings in parks and open space areas shall meet noise standards as listed under Public or Semi-Public Facilities (i.e., environments with noise levels up to 60 dba Ldn are considered satisfactory, those with noise levels greater than 60 dba and up to 65 dba Ldn are considered cautionary, and those with noise levels greater than 65 dba Ldn are considered critical for new development). Traffic noise levels on the project site under background plus project conditions would range from 66.6 dba to 71 dba Ldn; these levels are within the County s cautionary range for new open space development. All proposed public buildings would be located more than 350 feet from adjacent roadways, well beyond the 60 dba Ldn traffic noise contours shown in Table , and would meet the County s satisfactory land use compatibility criteria. Therefore, all traffic noise impacts to proposed on-site uses would be less than significant

24 Project-related traffic noise impacts to off-site sensitive receptors are discussed under Standard of Significance #3 (Substantial Permanent Increase in Ambient Noise Levels in the Project Vicinity above Levels Existing without the Project). ii. Construction Noise Impacts Implementation of the proposed project would result in construction activities, including site preparation activities using heavy earthmoving equipment. The project site is bordered on all sides by medium density, single- and multifamily residential land uses, including the Carlton Plaza Senior Assisted Living facility located adjacent to the northwest corner of the project property. Project construction would result in short-term noise impacts on these adjacent land uses. The level and types of noise impacts that would occur during construction are described below. Two types of short-term noise impacts could occur during the construction of the proposed project. First, construction crew commutes and the transport of construction equipment and materials to the site for the proposed project would incrementally increase noise levels on access roads leading to the site. Although there would be a relatively high single event noise exposure potential causing intermittent noise nuisance, the effect on longer term (hourly or daily) ambient noise levels would be small. Therefore, short-term construction related impacts associated with worker commute and equipment transport to the project site would be less than significant. The second type of short-term noise impact is related to noise generated during site preparation, and the construction on the project site. Construction is completed in discrete steps, each of which has its own mix of equipment and, consequently, its own noise characteristics. These various sequential phases would change the character of the noise generated on the site and, therefore, the noise levels surrounding the site as construction progresses. Despite the variety in the type and size of construction equipment, similarities in the dominant noise sources and patterns of operation allow construction related noise ranges to be categorized by work phase. Table lists typical

25 TABLE TYPICAL CONSTRUCTION MAXIMUM NOISE LEVELS, L MAX Type of Equipment Range of Maximum Sound Levels (dba at 50 feet) Suggested Maximum Sound Levels for Analysis (dba at 50 feet) Pile Drivers 81 to Rock Drills 83 to Jackhammers 75 to Pneumatic Tools 78 to Pumps 74 to Scrapers 83 to Haul Trucks 83 to Cranes 79 to Portable Generators 71 to Rollers 75 to Dozers 77 to Tractors 77 to Front-End Loaders 77 to Hydraulic Backhoe 81 to Hydraulic Excavators 81 to Graders 79 to Air Compressors 76 to Trucks 81 to Source: Bolt, Beranek & Newman, 1987, Noise Control for Buildings and Manufacturing Plants

26 construction equipment noise levels recommended for noise impact assessments, based on a distance of 50 feet between the equipment and a noise receptor. Typical noise levels range up to 91 dba Lmax at 50 feet during the noisiest construction phases. The site preparation phase, which includes excavation and grading of the site, tends to generate the highest noise levels, because the noisiest construction equipment is earthmoving equipment. Earthmoving equipment includes excavating machinery such as backhoes, bulldozers, draglines, and front loaders. Earthmoving and compacting equipment includes compactors, scrapers, and graders. Typical operating cycles for these types of construction equipment may involve one or two minutes of full-power operation followed by three or four minutes at lower power settings. Construction of the proposed project is expected to require the use of earthmovers such as bulldozers and scrapers, loaders and graders, water trucks, and other trucks. Pile drivers and rock drills are not expected to be used during construction of this project. As shown in Table , the typical maximum noise level generated by backhoes is assumed to be 86 dba Lmax at 50 feet from the operating equipment. The maximum noise level generated by bulldozers is approximately 85 dba Lmax at 50 feet. The maximum noise level generated by water and other trucks is approximately 86 dba Lmax at 50 feet from these vehicles. Each doubling of the sound sources with equal strength would increase the noise level by 3 dba. Assuming each piece of construction equipment operates at some distance apart from the other equipment, the worst-case combined noise level could be 91 dba Lmax at a distance of 50 feet from an active construction area with three or more pieces of operating earthmoving equipment. Therefore, construction of the project would generate noise in excess of County Standards, and expose people to unacceptable noise levels. This would be a significant impact. Implementation of the following multi-part mitigation measure would reduce construction noise impacts on off-site sensitive receptors to a less-thansignificant level

27 Impact NOISE-1: Construction activities could result in exposure of persons to or generation of noise levels in excess of County standards. This would be a significant impact. Mitigation Measure NOISE-1: The construction contractor shall implement the following measures: In accordance with Chapter VIII of the County of Santa Clara Ordinance Code, the operating of tools and equipment for construction activities (including earthmoving and grading) within the project site shall be conducted only between the hours of 7:00 a.m. and 7:00 p.m. Monday through Saturday. Noise producing construction activities shall not occur on Sundays or holidays. A notice of these construction hour restrictions shall be conspicuously posted at the entrance to the work site prior to commencement of the work informing all contractors and subcontractors, their employees, agents, materialmen and all other persons at the property of the basic limitations upon noise and construction activities provided in the County s Ordinance Code. The applicant shall designate a Noise Disturbance Coordinator who shall be responsible for responding to any complaints about construction noise. The Noise Disturbance Coordinator shall determine the cause of the noise complaint and shall require that reasonable measures warranted to correct the problem be implemented. The applicant shall conspicuously post a telephone number for the Noise Disturbance Coordinator at the construction site. The construction contractor shall minimize the number of earthmoving equipment pieces operated simultaneously within 60 feet of any single adjoining noise sensitive land use. During construction, all construction equipment powered by internal combustion engines shall be properly muffled and maintained. Unnecessary idling of internal combustion engines shall be prohibited

28 All stationary noise-generating equipment, such as air compressors, shall be located as far as practical from residences in the vicinity of the project site. Whenever feasible, quiet construction equipment, particularly air compressors, shall be utilized. Significance after Mitigation: Less than significant. iii. Operational Noise Impacts Operational noise sources associated with implementation of the proposed project would include agricultural and farming equipment noise sources. These noise sources would be similar to those currently produced on the project site during the seasonal agricultural operating periods. Typical noise levels from tractors as measured at a distance of 50 feet from the operating equipment range from 78 dba to 106 dba Lmax, with an average of about 84 dba Lmax. The closest off-site sensitive land uses would be located over 140 feet from proposed cultivation areas where large farming equipment would operate. At this distance, due to geometric spreading, these operational noise levels would be reduced to below 70 dba Lmax, which is below the County s daytime maximum noise level standard for operation of mobile equipment of 75 dba Lmax, shown in Table Operation of farming equipment associated with implementation of the project is not expected during nighttime periods. Operational noise impacts to the existing residential property located in the Life Estate adjacent to the project site must be compared to the County s land use compatibility standards for open space and agricultural land use development since, as noted in Table , homes in agricultural areas are not subject to the Residential standards. Therefore, operational noise sources would not result in exposure of persons to or generation of noise levels in excess of adopted standards, and any associated impacts would be less than significant

29 2. Exposure of Persons to or Generation of Excessive Groundborne Vibration or Groundborne Noise Levels No permanent noise sources that would expose persons to excessive ground borne vibration or noise levels would be located within the project site. Therefore, implementation of the proposed project would not permanently expose persons within or around the project site to excessive groundborne vibration or noise. Construction activities associated with implementation of the proposed project could temporarily expose persons in the vicinity of the project site to excessive ground borne noise levels. This would be a significant impact. Construction activities would not be expected to result in significant impacts associated with ground borne vibration levels, due to the distance between construction areas and the nearest sensitive receptors. 3. Substantial Permanent Increase in Ambient Noise Levels in the Project Vicinity above Levels Existing Without the Project The proposed long-term use of the project site is open space and agricultural land use. Operational noise sources associated with implementation of the proposed project would include agricultural and farming equipment noise sources. These noise sources would be similar to those currently produced on the project site during the seasonal agricultural operating periods, and would therefore not result in a substantial permanent increase in ambient noise levels at sensitive receptors in the vicinity of the project site. Also, as shown in Table , the project would not generate enough traffic to create a perceptible change (at least 3 dba) in traffic noise in the vicinity of the project site. A substantial long-term increase in ambient noise levels is not expected as a result of project implementation. Therefore, project-related traffic noise impacts to off-site sensitive receptors would be less than significant. 4. Substantial Increase in Ambient Noise Levels for Adjoining Areas During or After Construction As discussed above under Standard of Significance #2, construction activities associated with implementation of the proposed project could temporarily

30 increase ambient noise levels. Increased ambient noise levels would be intermittent and short term, and would be considered less than significant. E. Cumulative Impacts The project site is located in a built out portion of the county, bordered on all sides by medium density, single- and multi-family residential land uses, and commercial land uses. There are no known planned future development projects in the immediate project vicinity. The number of daily project trips, as outlined in the transportation impact analysis report prepared for this project, is anticipated to remain steady over time. As shown in Table , the project would not generate enough traffic to create a perceptible change (at least 3 dba) in traffic noise in the vicinity of the project site, and a substantial long-term increase in ambient noise levels is not expected as a result of project implementation. Therefore, project-related cumulative traffic noise impacts to off-site sensitive receptors would be less than significant. The current land use of the project site is agricultural land use, consisting primarily of flat, open fields that are seasonally cultivated for agricultural production. The majority of the site is currently dry farmed with hay and other grains. Implementation of the project would include agricultural production, habitat enhancement, parks and recreation, and agricultural education land uses. These uses would result in similar noise levels in the project site vicinity as currently exist with the seasonal agricultural operations. These cumulative operational noise levels would not result in a significant increase in ambient noise levels at sensitive receptors in the project vicinity. Therefore, project-related cumulative operational noise impacts would be less than significant