C O Y N E R ANCH S P E C I F I C P L A N C O U N T Y O F I M P E R I A L, CA

Transcription

1 N O I S E & G R O U N D B O R N E V I B R A T I O N I M P A C T A S S E S S M E N T F OR C O Y N E R ANCH S P E C I F I C P L A N C O U N T Y O F I M P E R I A L, CA JUNE 2016 PREPARED FOR: MR. MARTIN COYNE PREPARED BY: TH STREET, SUITE 201 PASO ROBLES, CA 93446

2 TABLE OF CONTENTS Introduction... 1 Project Description Summary... 1 Existing Setting... 1 Acoustic Fundamentals... 1 Noise Descriptors... 4 Sound Propagation & Attenuation... 5 Atmospheric Effects... 5 Human Response to Noise... 6 Effects of Noise on Human Activities... 6 Regulatory Framework... 8 Noise... 8 Groundborne Vibration Affected Environment Noise-Sensitive Receptors Ambient Noise Environment Impacts and Mitigation Measures Significance Criteria Methodology Impacts and Mitigation Measures Cumulative Setting Cumulative Impacts & Mitigation measures References LIST OF TABLES Table 1 Common Acoustical Descriptors... 4 Table 2 County of Imperial Land Use Compatibility Noise Criteria Table 3 County of Imperial Noise Compatibility Criteria Table 4 County of Imperial Property Line Noise Standards Table 5 County of Imperial Construction Noise Limitations Table 6 Damage Potential to Buildings at Various Groundborne Vibration Levels Table 7 Annoyance Potential to People at Various Groundborne Vibration Levels Table 8 Summary of Measured Ambient Noise Levels Table 9 Existing Traffic Noise Levels Table 10 Typical Construction Equipment Noise Levels Table 11 Predicted Future Traffic Noise Levels & Distances to Traffic Noise Contours Table 12 Predicted Future Traffic Noise Levels at Nearest On-Site Residential Land Uses Table 13 Predicted Increases in Traffic Noise Levels Table 14 Representative Construction Equipment Vibration Levels LIST OF FIGURES Figure 1 Proposed Coyne Ranch Specific Plan... 2 Figure 2 Common Noise Levels... 3 Figure 3 NAF El Centro Prospective Noise Contours Figure 4 Proposed Project Site & NAF El Centro Prospective Noise Contours Figure 5 Predicted Future 60 CNEL On-site Traffic Noise Contours & Recommended Traffic Noise Barrier Locations Figure 6 Recommended Off-Site Barrier Location 1704 W. Ross Road i

3 LIST OF APPENDICES Appendix A: Ambient Noise Monitoring Surveys Appendix B: Traffic Noise Modeling Appendix C: Sample Building Noise-Reduction Techniques Appendix D: Example Noise Barrier Construction Detail LIST OF COMMON TERMS AND ACRONYMS AICUZ ALUCP Caltrans CALVENO CEQA CNEL db dba DOD FHWA in/sec Ldn Leq Lmax NAF NAFEC NAFEC JLUS OPR ppv SCP Air Installations Compatible Use Zones Airport Land Use Compatibility Plan California Department of Transportation California Vehicle Reference Noise Emission Levels California Environmental Quality Act Community Noise Equivalent Level Decibels A-Weighted Decibels Department of Defense Federal Highway Administration Inches per Second Day-Night Level Equivalent Sound Level Maximum Sound Level Naval Air Facility Naval Air Facility El Centro Naval Air Facility El Centro Joint Land Use Study California Office of Planning & Research Peak Particle Velocity Seeley Community Plan ii

4 INTRODUCTION This report discusses the existing noise setting and identifies potential noise impacts associated with implementation of the proposed project. Noise mitigation measures are recommended where the predicted noise levels would exceed applicable noise standards. PROJECT DESCRIPTION SUMMARY The proposed Coyne Ranch Specific Plan (project) encompasses approximately 129 acres located within the northwestern quadrant of the Bennett Road and Ross Road intersection, within the unincorporated portion of Imperial County. The project includes development of approximately 444 single-family residential units and 219 multi-family residential units. Primary access to the site will be provided via Bennett Road, directly east of the project site. The project location and proposed site plan is depicted in Figure 1. EXISTING SETTING ACOUSTIC FUNDAMENTALS Noise is generally defined as sound that is loud, disagreeable, or unexpected. Sound is mechanical energy transmitted in the form of a wave because of a disturbance or vibration. Sound levels are described in terms of both amplitude and frequency. Amplitude is defined as the difference between ambient air pressure and the peak pressure of the sound wave. Amplitude is measured in decibels (db) on a logarithmic scale. For example, a 65 db source of sound, such as a truck, when joined by another 65 db source results in a sound amplitude of 68 db, not 130 db (i.e., doubling the source strength increases the sound pressure by 3 db). Amplitude is interpreted by the ear as corresponding to different degrees of loudness. Laboratory measurements correlate a 10 db increase in amplitude with a perceived doubling of loudness and establish a 3 db change in amplitude as the minimum audible difference perceptible to the average person. The frequency of a sound is defined as the number of fluctuations of the pressure wave per second (defined in Hertz). The human ear is not equally sensitive to sound of different frequencies. For instance, the human ear is more sensitive to sound in the higher portion of this range than in the lower and sound waves below 16 Hz or above 20,000 Hz cannot be heard at all. To approximate the sensitivity of the human ear to changes in frequency, environmental sound is usually measured in what is referred to as A-weighted decibels (dba). On this scale, the normal range of human hearing extends from about 10 dba to about 140 dba. Common community noise sources and associated noise levels, in dba, are depicted in Figure 2. Noise can be generated by a number of sources, including mobile sources, such as automobiles, trucks and airplanes, and stationary sources, such as construction sites, machinery, and industrial operations. Noise generated by mobile sources typically attenuates at a rate between 3.0 to 4.5 dba per doubling of distance. The rate depends on the ground surface and the number or type of objects between the noise source and the receiver. For mobile transportation sources, such as highways, hard and flat surfaces, such as concrete or asphalt, have an attenuation rate of 3.0 dba per doubling of distance. Soft surfaces, such as uneven or vegetated terrain, have an attenuation rate of about 4.5 dba per doubling of distance from the source. Noise generated by stationary sources typically attenuates at a rate of approximately 6.0 to 7.5 dba per doubling of distance from the source. 1

5 Figure 1 Proposed Coyne Ranch Specific Plan 2

6 Figure 2 Common Noise Levels Source: Caltrans

7 Sound levels can be reduced by placing barriers between the noise source and the receiver. In general, barriers contribute to decreasing noise levels only when the structure breaks the "line of sight" between the source and the receiver. Buildings, concrete walls, and berms can all act as effective noise barriers. Wooden fences or broad areas of dense foliage can also reduce noise, but are less effective than solid barriers. Noise Descriptors The intensity of environmental noise fluctuates over time, and several descriptors of timeaveraged noise levels are used. The three most commonly used descriptors are Leq, Ldn, and CNEL. The energy-equivalent noise level, Leq, is a measure of the average energy content (intensity) of noise over any given period. Many communities use 24-hour descriptors of noise levels to regulate noise. The day-night average noise level, Ldn, is the 24-hour average of the noise intensity, with a 10-dBA penalty added for nighttime noise (10 p.m. to 7 a.m.) to account for the greater sensitivity to noise during this period. CNEL, the community equivalent noise level, is similar to Ldn but adds an additional 5-dBA penalty for evening noise (7 p.m. to 10 p.m.). Another descriptor that is commonly discussed is the single-event noise exposure level (SENEL), also referred to as the sound exposure level (SEL). The SENEL/SEL describes a receiver s cumulative noise exposure from a single noise event, which is defined as an acoustical event of short duration, such as a backup beeper, the sound of an airplane traveling overhead, or a train whistle. Noise analyses may also depend on measurements of Lmax, the maximum instantaneous noise level during a specific period of time, and Lmin, the minimum instantaneous noise level during a specific period. Common noise level descriptors are summarized in Table 1. Descriptor Energy Equivalent Noise Level (Leq) Table 1 Common Acoustical Descriptors Definition The energy mean (average) noise level. The instantaneous noise levels during a specific period of time in dba are converted to relative energy values. From the sum of the relative energy values, an average energy value (in dba) is calculated. Minimum Noise Level (Lmin) Maximum Noise Level (Lmax) Day-Night Average Noise Level (DNL or Ldn) Community Noise Equivalent Level (CNEL) Single Event Level (SEL) The minimum instantaneous noise level during a specific period of time. The maximum instantaneous noise level during a specific period of time. The 24-hour Leq with a 10 dba penalty for noise events that occur during the noise-sensitive hours between 10:00 p.m. and 7:00 a.m. In other words, 10 dba is added to noise events that occur in the nighttime hours to account for increases sensitivity to noise during these hours. The CNEL is similar to the Ldn described above, but with an additional 5 dba penalty added to noise events that occur between the hours of 7:00 p.m. to 10:00 p.m. The calculated CNEL is typically approximately 0.5 dba higher than the calculated Ldn. The level of sound accumulated over a given time interval or event. Technically, the sound exposure level is the level of the time-integrated mean square A-weighted sound for a stated time interval or event, with a reference time of one second. 4

8 Sound Propagation & Attenuation Geometric Spreading Sound from a localized source (i.e., a point source) propagates uniformly outward in a spherical pattern. The sound level decreases (attenuates) at a rate of approximately 6 decibels (db) for each doubling of distance from a point source. Highways consist of several localized noise sources on a defined path, and hence can be treated as a line source, which approximates the effect of several point sources. Noise from a line source propagates outward in a cylindrical pattern, often referred to as cylindrical spreading. Sound levels attenuate at a rate of approximately 3 db for each doubling of distance from a line source (i.e., roadways, rail lines, etc.), depending on ground surface characteristics. For acoustically hard sites (i.e., sites with a reflective surface between the source and the receiver, such as a parking lot or body of water,), no excess ground attenuation is assumed. For acoustically absorptive or soft sites (i.e., those sites with an absorptive ground surface between the source and the receiver, such as soft dirt, grass, or scattered bushes and trees), an excess ground-attenuation value of 1.5 db per doubling of distance is normally assumed. When added to the cylindrical spreading, the excess ground attenuation for soft surfaces results in an overall attenuation rate of 4.5 db per doubling of distance from the source. Atmospheric Effects Receptors located downwind from a source can be exposed to increased noise levels relative to calm conditions, whereas locations upwind can have lowered noise levels. Sound levels can be increased at large distances (e.g., more than 500 feet) from the highway due to atmospheric temperature inversion (i.e., increasing temperature with elevation). Other factors such as air temperature, humidity, and turbulence can also have significant effects. Shielding by Natural or Human-Made Features A large object or barrier in the path between a noise source and a receiver can substantially attenuate noise levels at the receiver. The amount of attenuation provided by shielding depends on the size of the object and the frequency content of the noise source. Natural terrain features (e.g., hills and dense woods) and human-made features (e.g., buildings and walls) can substantially reduce noise levels. Walls are often constructed between a source and a receiver specifically to reduce noise. A barrier that breaks the line of sight between a source and a receiver will typically result in minimum 5 db of noise reduction. Taller barriers provide increased noise reduction. Noise reductions afforded by building construction can vary depending on construction materials and techniques. Standard construction practices typically provide approximately 15 db exterior-to-interior noise reductions for building facades, with windows open. With windows closed, older homes in good repair typically provide exterior-to-interior noise reductions of approximately 20 db. With compliance with current Title 24 energy efficiency standards, which require increased building insulation and inclusion of an interior air ventilation system to allow windows on noise-impacted façades to remain closed, exterior-to-interior noise reductions typically average approximately 25 to 30 db. The absorptive characteristics of interior rooms, such as carpeted floors, draperies and furniture, can result in further reductions in interior noise. 5

9 Human Response to Noise The human response to environmental noise is subjective and varies considerably from individual to individual. Noise in the community has often been cited as a health problem, not in terms of actual physiological damage, such as hearing impairment, but in terms of inhibiting general well-being and contributing to undue stress and annoyance. The health effects of noise in the community arise from interference with human activities, including sleep, speech, recreation, and tasks that demand concentration or coordination. Hearing loss can occur at the highest noise intensity levels. When community noise interferes with human activities or contributes to stress, public annoyance with the noise source increases. The acceptability of noise and the threat to public well-being are the basis for land use planning policies preventing exposure to excessive community noise levels. Unfortunately, there is no completely satisfactory way to measure the subjective effects of noise or of the corresponding reactions of annoyance and dissatisfaction. This is primarily because of the wide variation in individual thresholds of annoyance and habituation to noise over differing individual experiences with noise. Thus, an important way of determining a person s subjective reaction to a new noise is the comparison of it to the existing environment to which one has adapted: the so-called ambient environment. In general, the more a new noise exceeds the previously existing ambient noise level, the less acceptable the new noise will be judged. Regarding increases in A-weighted noise levels, knowledge of the following relationships will be helpful in understanding this analysis: Except in carefully controlled laboratory experiments, a change of 1 db cannot be perceived by humans; Outside of the laboratory, a 3-dB change is considered a just-perceivable difference; A change in level of at least 5 db is required before any noticeable change in community response would be expected. An increase of 5 db is typically considered substantial; A 10-dB change is subjectively heard as an approximate doubling in loudness and would almost certainly cause an adverse change in community response. Effects of Noise on Human Activities The extent to which environmental noise is deemed to result in increased levels of annoyance, activity interference, and sleep disruption varies greatly from individual to individual depending on various factors, including the loudness or suddenness of the noise, the information value of the noise (e.g., aircraft overflights, child crying, fire alarm), and an individual s sleep state and sleep habits. Over time, adaptation to noise events and increased levels of noise may also occur. In terms of land use compatibility, environmental noise is often evaluated in terms of the potential for noise events to result in increased levels of annoyance, sleep disruption, or interference with speech communication, activities, and learning. Noise-related effects on human activities are discussed in more detail, as follows: Speech Communication For most noise-sensitive land uses, an interior noise level of 45 db Leq is typically identified for the protection of speech communication in order to provide for 100-percent intelligibility of speech sounds. Assuming an average 20-dB reduction in sound level between outdoors and indoors 6

10 (which is an average amount of sound attenuation that assumes windows are closed), this interior noise level would equates to an exterior noise level of 65 dba Leq. For outdoor voice communication, an exterior noise level of 60 dba Leq allows normal conversation at distances up to 2 meters with 95 percent sentence intelligibility (U.S. EPA 1974.) Based on this information, speech interference begins to become a problem when steady noise levels reach approximately 60 to 65 dba. Within more noise-sensitive interior environments, such as educational facilities and places of worship, an average-hourly background noise level of 45 dba Leq is typically recommended. Annoyance & Sleep Disruption With regard to potential increases in annoyance, activity interference, and sleep disruption, land use compatibility determinations are typically based on the use of the cumulative noise exposure metrics (i.e., CNEL or Ldn). Perhaps the most comprehensive and widely accepted evaluation of the relationship between noise exposure and the extent of annoyance was one originally developed by Theodore J. Schultz in In 1978 the research findings of Theodore J. Schultz provided support for Ldn as the descriptor for environmental noise. Research conducted by Schultz identified a correlation between the cumulative noise exposure metric and individuals who were highly annoyed by transportation noise. The Schultz curve, expressing this correlation, became a basis for noise standards. When expressed graphically, this relationship is typically referred to as the Schultz curve. The Schultz curve indicates that approximately 13 percent of the population is highly annoyed at a noise level of 65 dba Ldn. It also indicates that the percent of people describing themselves as being highly annoyed accelerates smoothly between 55 and 70 dba Ldn. A noise level of 65 dba Ldn is a commonly referenced dividing point between lower and higher rates of people describing themselves as being highly annoyed. The Schultz curve and associated research became the basis for many of the noise criteria subsequently established for federal, state, and local entities. Most federal and state of California regulations and policies related to transportation noise sources establish a noise level of 65 dba CNEL/Ldn as the basic limit of acceptable noise exposure for residential and other noise-sensitive land uses. For instance, with respect to aircraft noise, both the Federal Aviation Administration (FAA) and the State of California have identified a noise level of 65 dba Ldn as the dividing point between normally compatible and normally incompatible residential land use generally applied for determination of land use compatibility. For noise-sensitive land uses exposed to aircraft noise, noise levels in excess of 65 dba CNEL/Ldn are typically considered to result in a potentially significant increase in levels of annoyance. Allowing for an average exterior-to-interior noise reduction of 20 db, an exterior noise level of 65 dba CNEL/Ldn would equate to an interior noise level of 45 dba CNEL/Ldn. An interior noise level of 45 db CNEL/Ldn is generally considered sufficient to protect against long-term sleep interference (U.S. EPA, 1974.) Within California, the California Building Code establishes a noise level of 45 dba CNEL as the maximum acceptable interior noise level for residential uses (other than detached single-family dwellings). Use of the 45 dba CNEL threshold is further supported by recommendations provided in the State of California Office of Planning and Research s General Plan Guidelines, which recommend an interior noise level of 45 db CNEL/Ldn as the maximum allowable interior noise level sufficient to permit normal residential activity (OPR 2003.) The cumulative noise exposure metric is currently the only noise metric for which there is a substantial body of research data and regulatory guidance defining the relationship between noise exposure, people s reactions, and land use compatibility. However, when evaluating environmental noise impacts involving intermittent noise events, such as aircraft overflights and train passbys, the use of cumulative noise metrics may not provide a thorough understanding of 7

11 the resultant impact. The general public often finds it difficult to understand the relationship between intermittent noise events and cumulative noise exposure metrics. In such instances, supplemental use of other noise metrics, such as the Leq or Lmax descriptor, are sometimes used as a means of increasing public understanding regarding the relationship between these metrics and the extent of the resultant noise impact. REGULATORY FRAMEWORK Noise Federal Noise Control Act of 1972 The Noise Control Act of 1972 establishes a national policy to promote an environment for all Americans free from noise that jeopardizes their health and welfare. The Act also serves to (1) establish a means for effective coordination of Federal research and activities in noise control; (2) authorize the establishment of Federal noise emission standards for products distributed in commerce; and (3) provide information to the public respecting the noise emission and noise reduction characteristics of such products. Aviation Safety and Noise Abatement Act of 1979 (ASNA) Among the stated purposes of this act is to provide assistance to airport operators to prepare and carry out noise compatibility programs. The law establishes funding for noise compatibility planning and sets the requirements by which airport operators can apply for funding. The law does not require any airport to develop a noise compatibility program. The decision to do so is the choice of each individual airport proprietor. Regulations implementing the act are set forth in Federal Aviation Regulations Part 150. Federal Aviation Regulations Part 150, Airport Noise Compatibility Planning As a means of implementing the Aviation Safety and Noise Abatement Act of 1979, the Federal Aviation Administration adopted these regulations establishing a voluntary program which airports can utilize to conduct airport noise compatibility planning. Part 150 prescribes the procedures, standards, and methodologies that govern the development, submission, and review of airport noise exposure maps and airport noise compatibility programs. Part 150 also prescribes a system for measuring airport noise impacts and presents guidelines for identifying incompatible land uses. The noise exposure maps prepared under Part 150 are depicted in terms of annual average-daily noise contours. For the purposes of federal regulations, all land uses are considered compatible with noise levels of less than 65 dba CNEL/Ldn. At higher noise exposures, selected land uses are also deemed acceptable, depending upon the nature of the use and the degree of structural noise attenuation provided. However, local jurisdiction have final responsibility for determining land use compatibility. Federal Interagency Committee on Urban Noise (FICUN) The product of this committee was a 1980 report entitled Guidelines for Considering Noise in Land Use Planning and Control. These guidelines were not intended to substitute for those of individual federal agencies, but rather serve to establish a common basis upon which agency standards can be developed. The report features a table indicating the compatibility or incompatibility of various land uses. Consistent with Part 150 guidelines, all land uses are 8

12 considered compatible within noise exposure zones less than 65 dba CNEL/Ldn. Beginning at that level, residential and certain other land uses are judged compatible only if adequate noise level reduction is provided by the structure. Department of Housing and Urban Development (HUD) HUD guidelines for the acceptability of residential land use are set forth in the Code of Federal Regulations Title 24, Part 51, Environmental Criteria and Standards. These guidelines parallel those suggested in the FICUN report: noise exposure of 65 dba CNEL/Ldn, or less, is acceptable and between 65 and 75 dba CNEL/Ldn noise exposure is considered normally acceptable provided appropriate sound-reduction measures are provided. Above 75 dba CNEL/Ldn noise exposure is generally considered unacceptable. The guidelines also identify a recommended interior noise levels of 45 dba CNEL/Ldn. These guidelines apply only to new construction supported by HUD grants and are not binding upon local communities. Department of Defense Air Installations Compatible Use Zones (AICUZ) Program The AICUZ Program was established by the Department of Defense in 1973 as an effort to protect the federal government s investment in military airfields. The current noise compatibility criteria (as set forth in the Code of Federal Regulations Title 32, Part 256) are basically the same as those indicated in the FICUN report and the FAA s Part 150 program. AICUZ plans prepared for individual airfields are primarily intended as recommendations to local communities regarding the importance of maintaining land uses which are compatible with the noise and safety impacts of military aircraft operations. State of California California Code of Regulations, Title 24 Title 24 of the California Code of Regulations contains standards for allowable interior noise levels associated with exterior noise sources (California Building Code, 1998 edition, Volume 1, Appendix Chapter 12, Section 1208A). The standards apply to new hotels, motels, dormitories, apartment houses, and dwellings other than detached single-family residences. The standards state that the interior noise level attributable to exterior sources shall not exceed 45 dba CNEL in any habitable room. Proposed residential structures to be located where the CNEL exceeds 60 dba are required to prepare an acoustical analysis showing that the proposed building design would achieve the prescribed allowable interior noise standard. Worst-case noise levels, either existing or future, shall be used as the basis for determining compliance with these standards. California General Plan Guidelines The State of California regulates vehicular and freeway noise affecting classrooms, sets standards for sound transmission and occupational noise control, and identifies noise insulation standards and airport noise/land-use compatibility criteria. The State of California General Plan Guidelines (State of California 2003), published by the Governor s Office of Planning and Research, also provides guidance for the acceptability of projects within specific CNEL/Ldn contours. The guidelines also present adjustment factors that may be used in order to arrive at noise acceptability standards that reflect the noise control goals of the community, the particular community s sensitivity to noise, and the community s assessment of the relative importance of noise pollution. 9

13 Imperial County Imperial County General Plan Land Use Compatibility Noise Criteria The Noise Element of the County s General Plan identifies goals, objectives, and policies to reduce noise-related impacts and land use compatibility conflicts. For determination of land use compatibility the Noise Element identifies noise criteria for various land-use designations, based on the average-daily noise descriptor (i.e., CNEL). Land use compatibility noise standards are summarized in Table 2 and Table 3. Table 2 County of Imperial Land Use Compatibility Noise Criteria Land Use Category Normally Acceptable Average-Daily Noise Level (dba CNEL) Conditionally Normally Acceptable Unacceptable Clearly Unacceptable Residential < >75 Transient Lodging-Motels, Hotels < >80 Schools, Libraries, Churches, Hospitals, Nursing Homes Auditoriums, Concert Halls, Amphitheaters < >80 -- <70 -- >70 Sports Arena, Outdoor Spectator Sports -- < >75 Playgrounds, Neighborhood Parks < >75 Golf Courses, Riding Stables, Water Recreation, Cemeteries < >80 Office Buildings, Business Commercial and Professional < >80 Industrial, Manufacturing, Utilities, Agriculture < >80 Notes: Normally Acceptable: Specified land use is satisfactory, based upon the assumption that any buildings involved are of normal conventional construction, without any special noise insulation requirements. Conditionally Acceptable: New construction or development should be undertaken only after a detailed analysis of the noise reduction requirements is made and needed noise insulation features included in the design. Normally Unacceptable: New construction or development should be discouraged. If new construction or development does proceed, a detailed analysis of the noise reduction requirements must be made and needed noise insulation features included in the design. Clearly Unacceptable: New construction or development clearly should not be undertaken. Source: County of Imperial, General Plan, Noise Element 1997 For residential land uses, exterior noise levels up to 60 dba CNEL are generally considered normally acceptable. Between 60 and 70 dba CNEL such land uses are considered conditionally acceptable provided necessary noise-reduction measures have been incorporated. Residential land uses are considered normally unacceptable between 70 and 75 db CNEL and clearly unacceptable where exterior noise levels exceed 75 dba CNEL. The County has also established and average-daily interior noise standard of 45 dba CNEL for residential uses and an average-hourly noise standard of 50 dba Leq for schools, libraries, offices, and other noise-sensitive uses where occupancy is typically limited to the daytime hours. 10

14 Table 3 County of Imperial Noise Compatibility Criteria Source: County of Imperial, General Plan, Noise Element

15 Property Line Noise Standards The County s General Plan also establishes maximum allowable average-hourly noise limits for various land use designations (refer to Table 4). These noise standards are to be applied at the property line of the noise-generating land use for non-transportation noise sources. In instances where the adjoining land use designations differ from that of the noise-generating land use, the more restrictive noise standard shall apply. Where the ambient noise level is equal to or exceeds the property line noise standard, the increase of the existing or proposed noise shall not exceed 3 dba Leq. It is important to note that these standards imply the existence of a sensitive receptor on the adjacent, or receiving, property. In the absence of a sensitive receptor, an exception or variance to the standards may be appropriate. These standards do not apply to construction noise. Land Use Zone Residential Multi-Family Residential Commercial Table 4 County of Imperial Property Line Noise Standards Time Period 7 am-7 pm 7 pm-7 am 7 am-7 pm 7 pm-7 am 7 am-7 pm 7 pm-7 am Average-Hourly Noise Level (dba L eq) Light Industrial/Industrial Park Any time 70 General Industrial Any time 75 Notes: When the noise-generating property and the receiving property have different uses, the more restrictive standard shall apply. When the ambient noise level is equal to or exceeds the Property Line noise standard, the increase of the existing or proposed noise shall not exceed 3 dba Leq. Source: County of Imperial, General Plan, Noise Element 1997 Construction Noise Standards The County General Plan Noise Element also establishes noise limitations pertaining to construction-related activities. For short-term activities, construction equipment noise levels are limited to 75 db Leq, averaged over an eight-hour period. In instances where construction activities would occur for an extended duration (more than a few weeks) a more restrictive noise standard of 75 db Leq averaged over a one-hour period, is applied. These standards are applied at the nearest noise-sensitive receptor. To minimize potential nuisance impacts to nearby receptors, the General Plan also establishes hourly restrictions for noise-generating construction activities. The County s General Plan noise limitations for construction activities are summarized in Table 5. Duration Table 5 County of Imperial Construction Noise Limitations Noise Level (dba Leq) Averaging Period Short-term (days or weeks) 75 8 hours Extended Duration 75 1 hour Source: County of Imperial, General Plan, Noise Element 1997 Hourly Restrictions 7:00 a.m. 7:00 p.m., Monday Friday 9:00 a.m. 5:00 p.m., Saturdays No commercial construction allowed on Sundays or holidays 12

16 Significant Increase of Ambient Noise Levels The County General Plan Noise Element also establishes guidelines for the evaluation of projectgenerated increases in ambient noise levels. Projects resulting in increases in ambient noise levels, as identified below, would typically be considered to have a potentially significant noise impact (County of Imperial 1997): a. If the future noise level after the project is completed will be within the "normally acceptable" noise levels shown in the Noise/Land Use Compatibility Guidelines, but will result in an increase of 5 dba CNEL or greater, the project will have a potentially significant noise impact and mitigation measures must be considered. b. If the future noise level after the project is completed will be greater than the "normally acceptable" noise levels shown in the Noise/Land Use Compatibility Guidelines, a noise increase of 3 dba CNEL or greater shall be considered a potentially significant noise impact and mitigation measures must be considered. Imperial County Noise Abatement and Control Ordinance The County of Imperial Noise Abatement and Control Ordinance (Title 9, Division 7) identifies property line noise limitations for non-transportation noise sources that are consistent with those identified in the County s General Plan Noise Element (refer to Table 4). As noted above, the noise limits are applied at the property line of the noise-generating land use. In instances where the adjoining land use designations differ from that of the noise-generating land use, the more restrictive noise standard shall apply (County of Imperial 1998). Seeley Community Plan The Seeley Community Plan (SCP) was approved in The Seeley community is located approximately two miles south of Naval Air Facility El Centro (NAFEC) and encompasses approximately 1,520 acres. The SCP includes noise goals and objectives intended to provide an acceptable noise environment for existing and future residents located within the urbanized area. The SCP includes objectives to adopt standards which protect sensitive noise receptors from adverse impacts, identification of receptors within less than acceptable environments, and development of evaluation measures to improve the noise environment. The SCP does not include identification of noise exposure standards for land use compatibility. Within Seeley, the County noise standards would be applicable. Naval Air Facility El Centro Joint Land Use Study The NAFEC Joint Land Use Study (JLUS) was prepared jointly by the NAFEC, the cities of El Centro and Imperial, and Imperial County. The purpose of a JLUS is to guide planning and development of areas located in the vicinity of NAFEC through the identification of compatible land uses and growth management guidelines. The NAFEC JLUS included evaluation of 24 compatibility factors, including those related to noise and vibration, as well as, identification of recommended goals, objectives, policies and strategies to aid in future planning and land use development activities and decision-making processes. It is important to note that the inclusion of military airports in compatibility plans is optional under the State Aeronautics Act (PUC Section 21675(b)). Nevertheless, many airport land use commissions (ALUCs) have included these facilities in their plans or have developed supplemental plans, such as the NAFEC JLUS to help ensure the compatibility of surrounding land uses. Several factors make compatibility planning for military facilities distinct from that for civilian 13

17 airports. For military airports, aircraft activity and compatibility factors are typically based on the maximum mission activity levels of the base, rather than projected growth. The best source of data for development of compatibility plans for military airports are the Air Installation Compatible Use Zone (AICUZ) studies, which the Department of Defense (DOD) requires for each base. The AICUZ studies contain analyses of noise, accident potential, and height restrictions impacts of aircraft operations. To assist the communities in land use decisions, the DOD uses decibel noise contours to illustrate the exposure to noise associated with aviation activities and to guide land use decision processes. In general, projected noise exposure levels of 65 dba CNEL, or less, are considered have minimal noise exposure but may be a noise nuisance to certain types of land uses and activities. Noise exposure levels of between 65 and 75 CNEL are generally considered unacceptable for noise-sensitive land uses, unless noisereduction measures are included. Noise exposure levels of 75 dba CNEL and higher are considered to have potentially severe noise impacts and typically deemed unacceptable for noise sensitive activates and land uses. The noise contours contained in the NAFEC JLUS were derived from the recently updated 2010 NAFEC AICUZ Study. These recently updated AICUZ noise contours reflect new training missions postulated to occur at the NAFEC. The 2010 NAFEC AICUZ report illustrates two different airfield noise contour footprints for NAFEC, an existing baseline footprint and a prospective footprint. The prospective noise footprint includes the projected noise contours associated with the F-35C Lightning II aircraft. Although the F-35C are not based at NAFEC, the F-35 are expected to train at NAFEC. NAFEC s prospective 60 CNEL noise contour is depicted in Figure 3. As depicted, the proposed project site is located within NAFEC s 65 CNEL prospective noise contour. Nearby existing land uses, including Sunbeam Lake and the RV resort are also located within NAFEC s 65 CNEL prospective noise contour. Imperial County Airport Land Use Compatibility Plan The Imperial County Airport Land Use Compatibility Plan (ALUCP) was approved in 1982 and last amended in The ALUCP identifies criteria and policies to be used by the Imperial County Airport Land Use Commission for assessing the compatibility between the principal airports in Imperial County and proposed land use development located in nearby areas. The emphasis of the ALUCP is predominantly on the review of local general and specific plans, zoning ordinances, and certain development projects to ensure compatibility with airport operations. The plan also provides individual airport policies, aircraft accident characteristics, safety compatibility policies, noise characteristics, and compatibility policies and implementation strategies for local jurisdictions. The ALUCP includes identification of projected airport noise exposure contours and noise criteria for various land use designations to help ensure continued compatibility with nearby airport operations. In accordance with the ALUCP noise compatibility criteria, residential uses are generally considered acceptable at levels up to 60 dba CNEL. Noise exposure levels in excess of 60 CNEL may result in substantial interference with both outdoor and indoor activities, particularly if windows are open. Noise-reduction measures and increased building insulation may be necessary for residential land uses located in areas exceeding 65 CNEL to achieve acceptable interior noise levels, however, interference with outdoor activities may still occur. In such instances, real-estate disclosure statements are advisable. It should be noted that the ALUCP has not yet been updated to incorporate the 2010 NAFEC AICUZ noise contours. 14

18 Figure 3 NAF El Centro Prospective Noise Contours Source: NAFEC JLUS

19 Groundborne Vibration There are no federal, state, or local regulatory standards for ground-borne vibration. However, various criteria have been established to assist in the evaluation of vibration impacts. For instance, the California Department of Transportation (Caltrans) has developed vibration criteria based on potential structural damage risks and human annoyance. Caltrans-recommended criteria for the evaluation of groundborne vibration levels, with regard to structural damage and human annoyance, are summarized in Table 6 and Table 7, respectively. The criteria differentiate between transient and continuous/frequent sources. Transient sources of groundborne vibration include intermittent events, such as blasting; whereas, continuous and frequent events would include the operations of equipment, including construction equipment, and vehicle traffic on roadways (Caltrans 2002, 2004). The ground-borne vibration criteria recommended by Caltrans for evaluation of potential structural damage is based on building classifications, which take into account the age and condition of the building. For residential structures and newer buildings, Caltrans considers a minimum peak-particle velocity (ppv) threshold of 0.5 inches per second (in/sec) for transient sources and 0.3 in/sec for continuous/frequent sources to be sufficient to protect against building damage. With the exception of fragile buildings, ruins, and ancient monuments, continuous ground-borne vibration levels below approximately 0.2 in/sec ppv are unlikely to cause structural damage. In terms of human annoyance, continuous vibrations in excess of 0.04 in/sec ppv and transient sources in excess of 0.25 in/sec ppv are identified by Caltrans as being distinctly perceptible. Within buildings, short periods of ground vibration in excess of 0.2 in/sec ppv are generally considered to result in increased levels of annoyance (Caltrans 2002, 2004). Table 6 Damage Potential to Buildings at Various Groundborne Vibration Levels Vibration Level (in/sec ppv) Structure and Condition Transient Continuous/Frequent Sources Intermittent Sources Extremely Fragile Historic Buildings, Ruins, Ancient Monuments Fragile Buildings Historic and Some Old Buildings Older Residential Structures New Residential Structures Modern Industrial/Commercial Buildings Note: Transient sources create a single isolated vibration event, such as blasting or drop balls. Continuous/frequent intermittent sources include impact pile drivers, pogo-stick compactors, crack-and-seat equipment, vibratory pile drivers, and vibratory compaction equipment. Source: Caltrans 2002,

20 Table 7 Annoyance Potential to People at Various Groundborne Vibration Levels Human Response Transient Sources Vibration Level (in/sec ppv) Continuous/Frequent Intermittent Sources Barely Perceptible Distinctly Perceptible Strongly Perceptible Severe Note: Transient sources create a single isolated vibration event, such as blasting or drop balls. Continuous/frequent intermittent sources include impact pile drivers, pogo-stick compactors, crack-and-seat equipment, vibratory pile drivers, and vibratory compaction equipment. Source: Caltrans 2002, 2004 AFFECTED ENVIRONMENT Noise-Sensitive Receptors Noise-sensitive land uses are generally considered to include those uses where noise exposure could result in health-related risks to individuals, as well as places where quiet is an essential element of their intended purpose. Residential dwellings are of primary concern because of the potential for increased and prolonged exposure of individuals to both interior and exterior noise levels. Additional land uses such as parks, historic sites, cemeteries, and recreation areas are also considered sensitive to increases in exterior noise levels. Schools, churches, hotels, libraries, and other places where low interior noise levels are essential are also considered noise-sensitive land uses. Surrounding land uses consist predominantly of agricultural uses. An existing rural residence is located adjacent to and north of the project site, adjacent to Bennett Road. The County Park and Sunbeam Lake RV Resort are located southwest of the project site, across Ross Road. Ambient Noise Environment The noise environment in the proposed project area is defined primarily by aircraft overflights originating from NAFEC. As depicted in Figure 3, the project site is located within the 65 CNEL noise contour for NAFEC. To a less extent, vehicular traffic on nearby roadways also contribute to the existing noise environment. To document existing ambient noise levels at the project site, short-term ambient noise measurements were conducted on April 7, Noise measurements were conducted using a Larson Davis Laboratories, Type I, Model 820 integrating sound-level meter positioned at a height of approximately 5 feet above ground level. Measured ambient noise levels are summarized in Table 8. As depicted, measured ambient noise levels in the project area, excluding aircraft overflights, range from roughly 39 dba Leq near the northwestern site boundary to 54 dba Leq near the southeastern site boundary. With the inclusion of aircraft overflights, ambient noise levels near the northern site boundary measured approximately 59 dba Leq with instantaneously levels reaching approximately 78 dba Lmax. 17

21 Measurement Location Table 8 Summary of Measured Ambient Noise Levels Monitoring Period Calculated existing traffic noise levels and distances to existing average-daily noise contours (in CNEL/Ldn) for nearby roadways are summarized in Table 9. As depicted, existing traffic noise levels at 75 feet from the near-travel-lane centerline of nearby roadways range from approximately 54 to 58 dba CNEL along Ross Road and approximately 52 dba CNEL along the adjacent segment of Bennett Road. Table 9 Existing Traffic Noise Levels CNEL/Ldn at 75 Feet from Near- Roadway Segment Travel-Lane Centerline 1 Noise Levels (dba) Duration Noise Sources Leq Lmax 1: Ross Road, Approximately 50 feet from Road Centerline 20 Minutes Roadway Traffic : Bennett Road, Approximately 48 feet from Road Centerline 10 Minutes Roadway Traffic Minutes Roadway Traffic/ Aircraft Overflight : Northwestern Site Boundary, South of Seeley Drain One 15 Minutes Distant Roadway Traffic Ambient noise measurements were conducted on April 7, 2016 using a Larson Davis Laboratories, Type I, Model 820 integrating sound-level meter placed at a height of approximately 5 feet above ground level. Predicted Distance From Road Centerline to CNEL Contour (feet) Ross Road, Drew Road to Bennett Road 54 WR WR WR Ross Road, Bennett Road to Forrester Road 58 WR WR 64 Bennett Road, Ross Road to Evan Hewes Highway 52 WR WR WR Traffic noise levels were calculated using the FHWA roadway noise prediction model. Refer to Appendix B for noise modeling assumptions and results. WR=Within Roadway Right-of-Way IMPACTS AND MITIGATION MEASURES SIGNIFICANCE CRITERIA Criteria for determining the significance of noise impacts were developed based on information contained in the California Environmental Quality Act Guidelines (CEQA Guidelines, Appendix G). According to the guidelines, a project may have a significant effect on the environment if it would result in the following conditions: a) Exposure of persons to, or generation of, noise levels in excess of standards established in the local general plan or noise ordinance, or of applicable standards of other agencies; b) Exposure of persons to or generation of excessive groundborne vibration or groundborne noise levels; c) A substantial permanent increase in ambient noise levels in the project vicinity above levels existing without the project; 18

22 d) A substantial temporary or periodic increase in ambient noise levels in the project vicinity above levels existing without the project; e) For a project located within an airport land use plan area or, where such a plan has not been adopted, within two miles of a public airport or a public use airport, would the project expose people residing or working in the project area to excessive noise levels; f) For a project within the vicinity of a private airstrip, would the project expose people residing or working in the project area to excessive noise levels? Short-term Construction Noise Short-term construction noise impacts would be considered significant if the proposed project would exceed applicable County noise standards (Table 5). Construction activities would also be considered to have a significant impact if construction would result in substantial increases in ambient noise levels at the nearest noise-sensitive land uses during the more noise-sensitive evening and nighttime hours (i.e., 7 a.m. to 7 p.m.). For purposes of this analysis, a substantial increase is defined as an increase of 3 dba, or greater. Long-term Operational Noise Impacts Long-term operational noise impacts would be considered significant if occupants of proposed land uses would be exposed to transportation noise levels that would exceed the County s noise exposure standards (refer to Table 2 and Table 3). For residential uses, exposure to transportation noise levels in excess of 60 dba CNEL within outdoor activity areas or 45 dba CNEL within interior areas would be considered a potentially significant impact. Exposure to non-transportation noise sources would be considered potentially significant if noise levels would exceed the County s noise exposure standards (refer to Table 4). A substantial increase in noise levels would be defined as an increase of 5.0, or greater, where the noise levels, without project implementation, are less than the County s normally acceptable noise standard. Where the noise level, without project implementation, equals or exceeds applicable noise standards, an increase of 3.0 dba, or greater, would be considered a substantial increase. Exposure to Ground-borne Vibration Ground-borne vibration levels would be considered significant if predicted short-term construction or long-term operational groundborne vibration levels attributable to the proposed project would exceed normally applied groundborne vibration criteria at nearby structures (refer to Table 6 and Table 7). METHODOLOGY A combination of existing literature, noise level measurements, and application of accepted noise prediction and sound propagation algorithms were used for the prediction of short-term construction and long-term non-transportation and transportation source noise levels, as well as, for the evaluation of groundborne vibration impacts. Short-Term Noise Exposure Predicted noise levels at nearby noise-sensitive land uses were calculated utilizing typical noise levels and usage rates associated with construction equipment, derived from the U.S. Department of Transportation, Federal Highway Administration s Roadway Construction Noise 19

23 Model (version 1.1) and representative data obtained from similar construction projects. Construction noise levels were predicted assuming an average noise attenuation rate of 6 db per doubling of distance from the source and an excess noise-attenuation rate of 1.5 db per 1,000 feet. Long-term Noise Exposure Predicted noise levels associated with onsite stationary noise sources and activities were calculated based on representative data obtained from existing literature and noise assessments prepared for similar projects. The compatibility of proposed land uses was evaluated based on projected onsite roadway traffic and aircraft noise levels. Roadway traffic noise levels were calculated using the FHWA roadway noise prediction model (FHWA-RD ) based on California vehicle reference noise emission factors and traffic data obtained from the traffic analysis prepared for this project. Predicted onsite noise contours for NAFEC operations were based on the recently updated 2010 NAFEC AICUZ prospective noise contours obtained from the NAFEC JLUS. These prospective noise contours reflect new training missions postulated to occur at the NAFEC. Modeling assumptions and results are included in Appendix B. Ground-borne Vibration No major existing sources of groundborne vibration have been identified in the proposed project area. Groundborne vibration levels associated with construction-related activities were evaluated based on typical vibration levels associated with construction equipment, obtained from the U.S. Department of Transportation, Federal Transit Administration s Transit Noise and Vibration Impact Assessment Guidelines (2006). Groundborne vibration impacts related to structural damage and human annoyance were evaluated taking into account the distance from construction activities to nearby land uses and typically applied criteria for structural damage and human annoyance. IMPACTS AND MITIGATION MEASURES IMPACT 1: Short-term Exposure to Construction-Generated Noise. Construction noise typically occurs intermittently and varies depending upon the nature or phase of construction (e.g., land clearing, grading, excavation, and paving). Noise generated by construction equipment, including earth movers, material handlers, and portable generators, can reach high levels. Although noise ranges are generally similar for all construction phases, the initial site preparation phase tends to involve the most heavy-duty equipment having a higher noise-generation potential. Noise levels associated with individual construction equipment is summarized in Table 10. As depicted, noise levels generated by individual pieces of construction equipment typically range from approximately 74 dba to 89 dba Lmax at 50 feet (FTA 2006). Combined average-hourly noise levels associated with construction projects can vary, depending on the activities performed, reaching levels of up to approximately 83 dba Leq at 50 feet. Based on this noise level, predicted construction noise levels at the existing residential dwelling located adjacent to and north of the project site would be approximately 65 dba Leq, or less. Predicted construction-generated noise levels at Sunbeam Lake RV Resort would be approximately 58 dba Leq, or less. 20

24 During the daytime hours, construction-generated noise levels would not be anticipated to reach levels that would result in activity interference within the outdoor activity areas of nearby noise-sensitive land uses. In addition, construction-generated noise levels at Sunbeam Lake RV Resort would be partially masked by vehicle traffic noise levels along Ross Road. Predicted construction noise levels at the nearest existing noise-sensitive land uses would not exceed the County s noise standard of 75 dba Leq. However, construction activities occurring during the more noise-sensitive nighttime hours, if required, could result in substantial increases in ambient noise levels, which may result in increased levels of annoyance and potential sleep disruption to nearby building occupants. As a result, noise-generating construction activities occurring during the nighttime hours would be considered to have a potentially significant short-term noise impact. Sources: FTA 2006 Table 10 Typical Construction Equipment Noise Levels Equipment Typical Noise Level (dba Lmax) 50 feet from Source Air Compressor 81 Backhoe 80 Compactor 82 Concrete Mixer 85 Concrete Vibrator 76 Crane, Mobile 83 Dozer 85 Generator 81 Grader 85 Impact Wrench 85 Jack Hammer 88 Loader 85 Truck 88 Paver 89 Pneumatic Tool 85 Roller 74 Saw 76 Mitigation Measures MM-1: The following mitigation measures shall be implemented: a. Noise-generating construction activities (excluding activities that would result in a safety concern to the public or construction workers) shall be limited to between the hours of 7:00 a.m. and 7:00 p.m., Monday through Friday, and between 9:00 a.m. and 5:00 p.m. on Saturdays. Construction activities shall be prohibited on Sundays and holidays. 21

25 b. Construction equipment shall be properly maintained and equipped with noisereduction intake and exhaust mufflers and shrouds, in accordance with manufacturers recommendations. c. All motorized construction equipment and vehicles shall be turned off when not in use. Timing/Implementation: Enforcement/Monitoring: Significance After Mitigation Implement prior to construction Imperial County Community Development Department Implementation of Mitigation Measure 1 would limit construction activities to the less noisesensitive periods of the day. Use of manufacturer-recommended noise control devices, such as exhaust mufflers and engine shrouds, would further reduce individual equipment noise levels and potential increases in ambient noise levels. With implementation of the above mitigation measures, noise-generating construction activities would be considered less than significant. IMPACT 2: Exposure to Non-Transportation Source Noise Levels. The proposed project includes development of residential land uses, open space/recreational uses, and utility infrastructure facilities (e.g., pump stations). These land uses would result in new non-transportation noise sources that could potentially exceed the County s applicable noise standards at nearby noise-sensitive land uses. Noise levels typically associated with these land uses and associated noise impacts are discussed separately below. Residential Land Uses Noise associated with proposed residential dwellings would expose other nearby residences (both existing and project related) to minor increases in ambient noise levels. Noise typically associated with such development includes lawn and garden equipment, voices, air conditioning equipment, and amplified music. Noise generated by these land uses would result in only minor increases in ambient noise levels, primarily during the day and evening hours and less frequently at night. As a result, increased noise levels associated with proposed residential land uses would be less than significant. Neighborhood Parks, Trails & Open Space Land Uses Noise typically associated with neighborhood parks, trails and open space areas are typically limited to the voices of adults and children and the occasional opening and closing of vehicle doors. Noise levels associated with these uses typically average less than 50 dba Leq at approximately 25 feet. Noise events are typically sporadic and limited primarily to the daytime hours of operation. Parks, trails and open space areas/corridors are typically considered to be an accepted land use within residential developments and generally do not result in noise events that are uncharacteristic of typical residential noise environments. For these reasons, noise-generated by planned park, trails, and open space land uses would be considered to have a less-than-significant impact. 22

26 Utility Infrastructure Facilities The proposed project would require the installation of pump stations generally located within the northwestern and southwestern areas of the project site on Lots L and M. However, the specific equipment to be installed, facility design requirements, and location of equipment to be installed have not yet been identified. Depending on the type and size of the equipment to be installed, operational noise levels can range from approximately 65 to 90 dba Leq at 10 feet. Operational noise levels associated with these facilities can vary substantially depending on the equipment installed, site design, and noise-reduction features included (e.g., equipment enclosures and sound walls). Depending on the specific infrastructure required, facility design, and hours of operation, operational noise levels at nearby proposed residential land uses could exceed applicable County noise standards (refer to Table 4). As a result, noise generated by utility infrastructure facilities would be considered to have a potentially significant impact. Mitigation Measures MM-2: The County shall require an acoustical assessment to be prepared prior to construction of onsite utility infrastructure facilities that include the use of stationary noise-generating equipment (e.g., pump stations). Where acoustical analysis determines that stationarysource noise levels would exceed applicable daytime and nighttime Imperial County property line noise standards of 50 dba Leq and 45 dba Leq, respectively, the County shall require the implementation of noise attenuation measures sufficient to achieve compliance with applicable noise standards. Such measure may include, but are not limited to, the incorporation of setbacks, sound barriers, or equipment enclosures. Timing/Implementation: Implement prior to construction Enforcement/Monitoring: Imperial County Community Development Department Significance after Mitigation With implementation of Mitigation Measure 2, additional acoustical analyses of proposed onsite utility infrastructure improvements would be required. Noise-reduction measures would be required sufficient to achieve compliance with the applicable County exterior daytime and nighttime noise standards of 50 dba Leq and 45 dba Leq. With mitigation, this impact would be considered less than significant. IMPACT 3: Compatibility of Proposed Land Uses with Projected On-Site Noise Levels. As noted earlier in this report, noise levels within the project area are predominantly influenced by aircraft overflights originating from NAFEC. To a lesser extent, vehicle traffic on area roadways also contributes to the existing noise environment. The compatibility of proposed land uses are evaluated based on a comparison of projected onsite noise levels to applicable City s noise standards and discussed, as follows: NAF El Centro Aircraft Noise The Naval Air Facility El Centro (NAFEC) is located approximately 1.5 miles north of the project site. As noted earlier in this report, the proposed project site is located within NAFEC s 65 CNEL prospective noise contour. Projected NAFEC noise contours in relation to the proposed project site are depicted in Figure 4. 23

27 Figure 4 Proposed Project Site & NAF El Centro Prospective Noise Contours All locations are approximate. Source: NAFED JLUS

28 In accordance with the ALUCP noise compatibility criteria, residential uses are generally considered acceptable at levels up to 60 dba CNEL Assuming an average exterior-to-interior noise reduction of 15 db with windows open, a maximum allowable exterior noise level of 60 dba CNEL would allow for an acceptable interior noise environment of 45 dba CNEL, or less. With windows closed, a minimum exterior-to-interior noise reduction of 20 db can be achieved, which would equate to an exterior noise levels of up to 65 dba CNEL. With the incorporation of building mechanical air heating and cooling systems that would allow windows to remain closed, and exterior noise level of up to 65 dba CNEL would be considered generally acceptable for typical building construction. Noise-reduction measures and increased building insulation may be necessary for residential land uses located in areas exceeding 65 CNEL to achieve acceptable interior noise levels, however, interference with outdoor activities may still occur. Proposed onsite parks would not be located within NAFEC s 70 CNEL prospective noise contour. As a result, proposed onsite parks would not be considered incompatible. However, as noted earlier in this report and depicted in Figure 4, the project site is located within NAFEC s 65 CNEL prospective noise contour. Residential land uses located within this zone would be exposed to increased aircraft noise levels, including intermittent noise and airborne vibration events associated with NAFEC operations, which could result in increased levels of annoyance and nuisance to building occupants. For these reasons, exposure of residential building occupants to aircraft noise levels would be considered a potentially significant impact. Roadway Traffic Noise Predicted future noise levels for roadways located within the Specific Plan Area, with implementation of the proposed project, were calculated using the FHWA roadway noise prediction model (FHWA-RD ) based on California vehicle reference noise levels and traffic data obtained from the traffic analysis prepared for this project. Predicted distance to future cumulative traffic noise contours and predicted noise levels at the project site are summarized in Table 11. Predicted future cumulative traffic noise levels at proposed residential land uses located adjacent to nearby roadways are summarized in Table 12. Projected on-site future cumulative traffic noise contours are depicted in Figure 5. Table 11 Predicted Future Traffic Noise Levels & Distances to Traffic Noise Contours Predicted CNEL/Ldn at 75 feet from Near-Travel-Lane Distance (feet) to CNEL/Ldn Contours from Roadway Centerline Roadway Segment Centerline Ross Rd., Drew Rd. to Bennett Rd WR Bennett Rd., Ross Rd. to Evan Hewes Hwy WR WR WR = Within Roadway Right-of-Way *Based on distance to the nearest property line. Refer to Appendix B for modeling assumptions and results. 25

29 Table 12 Predicted Future Traffic Noise Levels at Nearest On-Site Residential Land Uses Predicted CNEL/Ldn at Predicted CNEL/Ldn at Roadway Segment Project Site Boundary Nearest Residential Pad Ross Rd., Drew Rd. to Bennett Rd Bennett Rd., Ross Rd. to Evan Hewes Hwy WR = Within Roadway Right-of-Way *Based on distance to the nearest property line. Refer to Appendix B for modeling assumptions and results. Figure 5 Predicted Future 60 CNEL On-site Traffic Noise Contours & Recommended Traffic Noise Barrier Locations 26

30 Under future cumulative conditions, the predicted 60 dba CNEL/Ldn noise contour for the adjacent segments would extend to approximately 126 feet from the centerline of Ross Road and approximately 43 feet from the centerline of Bennett Road. Predicted noise levels at the nearest proposed residential land uses would range from approximately 63 dba CNEL along Ross Road to approximately 61 dba CNEL along Bennett Road. Predicted exterior noise levels within the outdoor activity areas of adjacent residential lots would exceed the County s normally acceptable exterior noise standard of 60 dba CNEL. Predicted future cumulative traffic noise levels at the nearest residential pads would be approximately 60 dba CNEL, or less. Assuming an average exterior-to-interior noise reduction of 25 dba, which is typical for newer building construction, predicted interior noise levels at the nearest residential dwelling units would be approximately 35 dba CNEL, or less. Predicted interior noise levels at proposed residential dwelling units would not exceed the County s interior noise standard of 45 dba CNEL. Because predicted exterior noise levels at residential dwellings located along Ross Road and Bennett Road would exceed the County s normally acceptable exterior noise standard of 60 dba CNEL, exposure to roadway traffic noise levels would be considered potentially significant. Offsite Agricultural Uses Agricultural activities on parcels located adjacent to and near the project site may include the use of various types of heavy equipment. Operation of heavy agricultural equipment typically generates noise levels of up to approximately 75 dba Leq at 50 feet (FHWA 2006). However, agricultural activities (e.g., disking, plowing) are typically sporadic or seasonal and occur over a large area, which results in varying levels of exposure at nearby receptors. In addition, given that agricultural activities typically occur during the daytime hours, noise generated by nearby agricultural activities would likely be somewhat masked by noise generated by nearby roadway traffic noise and aircraft overflights. For these reasons, nearby agricultural activities are not expected to contribute significantly to projected onsite noise levels. As a result, exposure to agricultural noise would be considered to have a less-than-significant impact. Mitigation Measures MM-3: The following mitigation measures shall be implemented: a. Proposed new residential dwellings shall be designed to reduce interior noise levels below 45 dba CNEL. Based on prospective NAFEC noise contours at the project site, an exterior-to-interior noise-level reduction of 25 dba would be required to achieve an interior noise-level below 45 dba CNEL. Actual exterior-to-interior noise-reduction requirements would be dependent on final site/building design. (Sample noise reduction/insulation methods commonly applied to reduce interior noise levels are provided in Appendix C of this report.) b. Mechanical ventilation systems shall be provided for all residential dwellings so that windows can remain closed to maintain an acceptable interior noise environment. c. Real-estate disclosure statements shall be provided for all real-estate transactions that provide notification that the property is located within the projected 60 dba CNEL noise contour zone of NAF El Centro and that the property is and/or may be subject to prolonged or intermittent noise and airborne vibration events associated with NAF El Centro operations. d. A sound barrier shall be constructed sufficient to shield the rear-yard areas of proposed residential dwelling lots located within the projected 60 dba Ldn traffic noise contour (Refer to Figure 5, Lots 4-33, 441, 450). The barrier should be constructed to a minimum height of 6 feet above the proposed residential lot elevation. The barrier 27

31 shall be constructed of masonry block, wood or material of similar density and usage, with no air gaps between construction materials or at the base of the barrier. Joints between construction materials shall be sealed. Materials selected shall meet a minimum combined surface weight of 2.5 pounds per square foot. If wood barriers are used, construction techniques shall be employed to prevent future air gaps from occurring due to weathering and material shrinkage. Such methods may include the use of overlapping panels, board and batten, or tongue-and-grove techniques. An example wood barrier construction detail is included in Appendix D. Timing/Implementation: Significance after Mitigation Implement prior to construction Enforcement/Monitoring: Imperial County Community Development Department The proposed sound barriers would reduce predicted onsite traffic noise levels by a minimum of approximately 5 dba CNEL. The incorporation of mechanical heating and cooling systems and compliance with current building standards, including Title 24 insulation requirements for residential dwellings, would reduce exterior noise intrusion by approximately 25 dba. Additional building insulation and noise-reduction measures may be required depending on final building design. With implementation of recommended mitigation measures, interior noise levels would be reduced to below 45 dba CNEL. Real-estate disclosure statement would be required to ensure that information regarding airport noise impacts will be disclosed as a normal part of real estate transactions. With mitigation, this impact is considered less than significant. IMPACT 4: Contribution to Increased Traffic Noise Levels. Implementation of the proposed project would result in increased traffic volumes on some area roadways. The increase in traffic volumes resulting from implementation of the proposed project would, therefore, contribute to predicted increases in traffic noise levels. The FHWA roadway noise prediction model was used to predict traffic noise levels along primarily affected roadway segments, with and without implementation of the proposed project. The project s contribution to traffic noise levels along area roadways was determined by comparing the predicted noise levels with and without project-generated traffic. Predicted traffic noise levels, with and without development of the proposed plan, are summarized in Table 13. As depicted in Table 13, increases in traffic noise levels along area roadways attributable to the proposed project would range from approximately 1 to 8 dba. The proposed specific plan would result in a substantial increase (i.e., 5 dba, or greater) in traffic noise levels along Ross Road, between Drew Road and Bennett Road. Existing noise-sensitive receptors located along Ross Road, between Drew Road and Bennett Road include the Sunbeam Lake RV Resort, which is located south of Ross Road, and a rural residential dwelling located adjacent to and north of Ross Road, west of the project site (1704 W. Ross Road). With project implementation, predicted traffic noise levels at Sunbeam Lake and RV resort would be approximately 60 dba CNEL at the nearest recreational-use areas and 51 dba CNEL, or less, at the RV parking areas. Predicted traffic noise levels at Sunbeam Lake and the RV resort would not exceed applicable County noise standards. Predicted exterior traffic noise at the existing residential dwelling located at 1704 W. Ross Road would be approximately 62 dba CNEL, which would exceed the County s normally acceptable exterior noise standard of 60 dba CNEL. As a result this impact is considered potentially significant. 28

32 Table 13 Predicted Increases in Traffic Noise Levels CNEL/Ldn at 75 Feet from Near-Travel-Lane Centerline 1 Roadway Segment Existing Without Project Existing With Project Predicted Increase (dba) Substantial Increase? 2 Ross Road, Drew Road to Bennett Road Yes Ross Road, Bennett Road to Forrester Road No Bennett Road, Ross Road to Evan Hewes Highway No Drew Road, Evan Hewes Highway to Ross Road No Drew Road, Ross Road to I No Evan Hewes Highway, Drew Road to Bennett Road No Evan Hewes Highway, Bennett Road to Forrester Road No 1. Traffic noise levels were calculated using the FHWA roadway noise prediction model. 2. Substantial increase is defined as an increase of 5.0, or greater. Access to this existing residential dwelling is provided via Ross Road. The current driveway configuration consists of a semi-circular drive with two points of ingress/egress to Ross Road. Assuming that this driveway configuration were to be maintained, the construction of a noise barrier at this location would not provide sufficient mitigation. To be effective, barriers typically need to be constructed with limited breaks or openings in the barrier and of sufficient length to provide substantial reductions in line-of-sight between the noise source and the receiver. However, if the driveway were to be reconfigured to eliminate the semi-circular configuration and provide a single ingress/egress to Ross Road, a noise barrier could be constructed along the southern-most property lines that would provide sufficient reductions in traffic noise levels. The general location for the recommended barrier is depicted in Figure 6. Mitigation Measure MM-4: A noise barrier is recommended for construction at the existing residence located at 1704 W. Ross Road to reduce exterior traffic noise levels. The barrier should be constructed to a minimum height of 6 feet above ground level. The barrier shall be constructed of masonry block, wood or material of similar density and usage, with no air gaps between construction materials or at the base of the barrier. Joints between construction materials shall be sealed. Materials selected shall meet a minimum combined surface weight of 2.5 pounds per square foot. If wood barriers are used, construction techniques shall be employed to prevent future air gaps from occurring due to weathering and material shrinkage. Such methods may include the use of overlapping panels, board and batten, or tongue-and-grove techniques. An example wood barrier construction detail is included in Appendix D. Significance after Mitigation With implementation of Mitigation Measure 4, predicted exterior traffic noise levels at the existing residence would be reduced to 60 dba CNEL, or less, and would not be projected to exceed the County s normally acceptable exterior noise standard of 60 dba CNEL. With mitigation, this impact would be considered less than significant. 29

33 Figure 6 Recommended Off-Site Barrier Location 1704 W. Ross Road Recommended barrier locations are approximate. County code requirements for building and safety shall prevail. Image Source: Imperial County Assessor GIS 2016 IMPACT 5: Exposure to Ground-borne Vibration. Ground-borne vibration spreads through the ground and diminishes in strength with distance. The effects of ground vibration can vary from no perceptible effects at the lowest levels, low rumbling sounds and detectable vibrations at moderate levels, and slight damage to nearby structures at the highest levels. At the highest levels of vibration, damage to structures is primarily architectural (e.g., loosening and cracking of plaster or stucco coatings) and rarely result in structural damage. For most structures, a peak particle velocity (ppv) threshold of 0.5 inches per second (in/sec) is sufficient to avoid structure damage, with the exception of fragile historic structures or ruins. For the protection of fragile, historic, and residential structures, the California Department of Transportation recommends a more conservative threshold of 0.2 in/sec ppv. This same threshold would represent the level at which vibrations would be potentially annoying to people in buildings (FTA 2006, Caltrans 2002). Long-term Exposure to Ground-borne Vibration Long-term operational activities associated with the proposed project would not involve the use of any equipment or processes that would result in potentially significant levels of ground 30

34 vibration. In addition, no major sources of ground vibration were identified in the Specific Plan area. For these reasons, long-term exposure of sensitive receptors to groundborne vibration within the Specific Plan area would be considered to have a less-than-significant impact. Short-term Exposure to Ground-borne Vibration Increases in groundborne vibration levels attributable to the proposed project would be primarily associated with short-term construction-related activities. Groundborne vibration levels associated with construction equipment are summarized in Table 14. Construction activities associated with the proposed improvements would likely require the use of various tractors, trucks, and jackhammers. Based on the vibration levels presented in Table 14, ground vibration generated by off-road construction equipment would be approximately 0.2 in/sec ppv, or less, at the project site boundaries. Predicted ground-borne vibration levels at nearby structures, which are located in excess of 25 feet from the project site, would not exceed 0.2 in/sec ppv. Ground-borne vibration levels generated during project construction would be considered to have a less-than-significant impact. Table 14 Representative Construction Equipment Vibration Levels Peak Particle Velocity Equipment at 25 Feet (in/sec ppv) Vibratory Roller 0.21 Large Tractors Caisson Drilling Loaded Trucks Jackhammer Small Tractors Source: Caltrans 2004, FTA 2006 CUMULATIVE SETTING The geographic extent of the cumulative setting for noise consists of the project area and the surrounding areas within the County. No major stationary sources of noise have been identified in the project area. The primary factor for cumulative noise impact analysis is, therefore, the consideration of the proposed project to future traffic noise levels along area roadways. CUMULATIVE IMPACTS & MITIGATION MEASURES IMPACT 6: Contribution to Cumulative Noise Levels. Predicted future traffic noise levels, with implementation of the proposed project, are summarized in Table 11. As discussed in Impact 4, increases in existing traffic noise levels along area roadways attributable to the proposed project would range from approximately 1 to 8 dba. The proposed project would result in a substantial increase (i.e., 5 dba, or greater) in traffic noise levels along Ross Road, between Drew Road and Bennett Road. Under future cumulative conditions, predicted traffic noise levels along nearby roadway segments would be similar to predicted existing-plus-project noise levels. As a result, the proposed project would still be 31

35 anticipated to result in a substantial contribution to future cumulative traffic noise levels along Ross Road, between Drew Road and Bennett Road. As discussed in Impact 4, existing noise-sensitive receptors located along Ross Road, between Drew Road and Bennett Road include the Sunbeam Lake RV Resort, located south of Ross Road, and a rural residential dwelling located adjacent to and north of Ross Road. Predicted future cumulative traffic noise levels at Sunbeam Lake and the RV resort would not exceed applicable County noise standards. However, predicted traffic noise at the existing residential dwelling located at 1704 W. Ross Road would be approximately 62 dba CNEL, which would exceed the County s normally acceptable noise standard of 60 dba CNEL. With implementation of MM-3 and MM-4, predicted increases in traffic noise levels at existing and proposed sensitive land uses would be reduced to acceptable levels. With mitigation, this impact would be considered less than significant. 32

36 REFERENCES Imperial County. Accessed: November 1, Assessor s GIS. Website url: Imperial County County of Imperial General Plan. Noise Element. Available at Website url: Imperial County. November 24, County of Imperial Land Use Ordinance. Title 9, Divisions 7, Noise Abatement and Control. Available at Website url: Imperial County. March 1, Imperial County Land Use Map. Available at Website url: Imperial County Airport Land Use Commission. June Imperial County Airport Land Use Compatibility Plan. Naval Air Facility El Centro (NAFEC). June Joint Land Use Study. Naval Air Facility El Centro (NAFEC). June Joint Land Use Study. Background Report. State of California. Office of Planning and Research (OPR) State of California General Plan Guidelines. Available at Website url: State of California Department of Transportation (Caltrans) Transportation Related Earthborne Vibrations. Available at Website url: TRANSPORTATION_RELATED_EARTHBORNE_VIBRATIONS.pdf State of California Department of Transportation (Caltrans) Transportation- and Construction-Induced Vibration Guidance Manual. Available at Website url: hq/env/noise/pub/vibrationmanfinal.pdf State of California Department of Transportation (Caltrans). Accessed: February 8, IS/EA Annotated Outline. Available at Website: United States Department of Transportation, Federal Transit Administration (FTA). April Transit Noise and Vibration Impact Assessment Guidelines. Available at Website url: United States Environmental Protection Agency (U.S. EPA) Levels of Environmental Noise Requisite to Protect Public Health and Welfare with an Adequate Margin of Safety. Available at Website url: 33

37 APPENDIX A AMBIENT NOISE MONITORING SURVEYS 34

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39 APPENDIX B TRAFFIC NOISE MODELING 36

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41 APPENDIX C SAMPLE BUILDING NOISE-REDUCTION TECHNIQUES 38

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