4.9 NOISE AND VIBRATION Introduction

Transcription

1 Environmental Impact Evaluation 4.9 Noise and Vibration 4.9 NOISE AND VIBRATION Introduction This section of the EIR addresses the existing acoustic environment on and adjacent to the Project Site and evaluates potential on-site and off-site noise impacts related to implementation of the Proposed Project. The Proposed Project s potential impacts are discussed and mitigation measures are provided for impacts determined to be potentially significant. This section is based on a noise analysis prepared for the Proposed Project entitled Noise Impact Analysis for Azusa Rock Revised CUP Applications, City of Azusa, prepared by Giroux & Associates, December 14, 2009, to specifically address potential impacts related to the Proposed Project. The City of Azusa has reviewed the analysis prepared by Giroux & Associates and believes it to be an accurate and reasonable representation of the existing and proposed conditions of the Proposed Project. The Noise Analysis is included in this EIR as Appendix C Environmental Setting Noise is currently generated at the Project Site from existing quarry operations and the overland conveyor. The primary sources of noise are related to heavy equipment usage and material processing. Noise generating sources include the rock crushing and screening plants, material loading and unloading, drilling and blasting, mobile construction equipment, and haul trucks. Under the Proposed Project, a larger fleet of trucks would move excavated rock from the working face in the West Side to the primary crusher. The noise from any on-going reclamation of the East Side is considered part of the existing ambient or baseline environment. Mining activities under the Proposed Project would extend westerly approximately 1,325 feet further than the current designated mine boundary. There are three general methods used to measure sound over a period of time: the Community Noise Equivalent Level (CNEL), the equivalent energy level (Leq), and the Day/Night Average Sound Level (Ldn). CNEL: The predominant community noise rating scale used in California for land use compatibility assessment is the Community Noise Equivalent Level (CNEL). The CNEL reading represents the average of 24-hourly reading of equivalent levels, known as LEQ's, based on an A-weighted decibel with upward adjustments added to account for increased noise sensitivity in the evening and night periods. These adjustments are +5 db for the evening (7:00 p.m. to 10:00 p.m.), and +10 db for the night (10:00 p.m. to 7:00 a.m.). CNEL may be indicated by "db CNEL" or just "CNEL. Leq: The Leq is the sound level containing the same steady-state total energy over a given sample time period as a continuously varying ambient level. The Leq can be thought of as the steady (average) sound level which, in a stated period of time, would contain the same acoustic energy as the time-varying sound level during the same period. Leq is typically computed over 1-, 8- and 24-hour sample periods

2 4.9 Noise and Vibration Environmental Impact Evaluation Ldn: Another commonly used method is the day/night average level or Ldn. The Ldn is a measure of the 24-hour average noise level at a given location. It was adopted by the United States Environmental Protection Agency (EPA) for developing criteria for the evaluation of community noise exposure. It is based on a measure of the average noise level over a given time period called the Leq. The Ldn is calculated by averaging the Leq's for each hour of the day at a given location after penalizing the "sleeping hours" (defined as 10:00 p.m. to 7:00 a.m.), by 10 db to account for the increased sensitivity of people to noises that occur at night. In most applications, CNEL and Ldn are generally indistinguishable. Lmax: The maximum noise level recorded during a noise event is typically expressed as Lmax. The sound level exceeded over a specified time frame can be expressed as Ln (i.e., L 90, L 50, L 10, etc.). For example, L 50 equals the level exceeded 50 percent of the time. Sound is technically described in terms of the loudness (amplitude) of the sound and frequency (pitch) of the sound. The standard unit of measurement of the loudness of sound is the decibel (db). As the human ear is not equally sensitive to sound at all frequencies, special frequencydependent rating scales have been devised to relate noise to human sensitivity. The A-weighted decibel scale db(a) performs this compensation by discriminating against frequencies in a manner approximating the sensitivity of the human ear. Any further reference to decibels in this report written as db should be understood to be A-weighted. Decibels are based on the logarithmic scale. The logarithmic scale compresses the wide range in sound pressure levels to a more usable range of numbers in a manner similar to the Richter scale used to measure earthquakes. In general, a 1 db change in the sound pressure levels of a given sound is detectable only under laboratory conditions. A 3-dB change in sound pressure level is considered a "just detectable" difference or the threshold of human perception in most situations. The threshold of human perception of noise level differences under ambient conditions is approximately 3 db. A 5-dB change is readily noticeable by most people and a 10-dB change is considered a doubling (or halving) of the subjective loudness. However, a 3-dB increase or decrease in the average traffic noise level is realized by a doubling or halving of the traffic volume. As few projects individually cause a doubling of traffic volumes on already heavily traveled roadways, most traffic noise impacts tend to be cumulative in nature. For non-transportation noise sources affecting noise sensitive land uses, many jurisdictions consider an increase in ambient noise levels of greater than 5 db to be potentially significant. This amount of change in environmental noise levels is considered noticeable by most people. Therefore, for changes in project-related, non-transportation noise sources affecting noise sensitive land uses, the threshold of significance will be changes greater than 5 db CNEL/L dn or 5 db L eq. In terms of human response to noise, a sound 10 db higher than another is judged to be twice as loud; 20 db higher four times as loud; and so forth. Everyday sounds normally range from 30 db (very quiet) to 100 db (very loud). Examples of various sound levels in different environments are shown in Table 4.9-1, Sound Levels and Human Response

3 Environmental Impact Evaluation 4.9 Noise and Vibration Table Sound Levels and Human Response Noise Level Noise Source db(a) Carrier Jet Operation 140 Harmfully Loud 130 Pain Threshold Jet Takeoff (200ft.), Discotheque Unmuffled Motorcycle, Auto Horn (3 ft.), Rock'n Roll Band, Riveting Machine 110 Loud Power Mower, Jet Takeoff (2,000 ft) Garbage Truck Heavy Truck (50 ft.) Pneumatic Drill (50 90 ft.) Alarm Clock, Freight Train (50 ft.) Vacuum Cleaner (10 ft.) Response Maximum Vocal Effort Physical Discomfort 100 Very Annoying, Hearing Damage (Steady 8-Hour Exposure) 80 Annoying Freeway Traffic (50 ft.) 70 Telephone Use Difficult Dishwashers, Air Conditioning Units (20 ft.) 60 Intrusive Light Auto Traffic (100 ft.) 50 Quiet Living Room 40 Bedroom Library, Soft Whisper (15 ft.) 30 Very Quiet Broadcasting Studio 20 Just Audible 10 Threshold of Hearing Source: Melville C. Branch and R. Dale Beland, Outdoor Noise in the Metropolitan Environment, 1970 (p.2). Noise Impact Analysis, Giroux & Associates, September Applicable Plans, Policies and Regulations CNEL or Ldn-based standards are designed to insure land use compatibility with the acoustic environment for those noise sources pre-empted from local control. Such sources are mainly mobile sources such as cars, trucks, airplanes, trains, etc. Local jurisdictions cannot regulate the noise strength of the source, they control the pattern of land use exposed to such sources. Stationary sources such as mining operations are amenable to control of the source itself rather than through general plan siting considerations. State The State of California has established guidelines for acceptable community noise levels that are based on the CNEL rating scale. The guidelines rank noise land use compatibility in terms of "normally acceptable", "conditionally acceptable", and "clearly unacceptable" noise levels 4.9-3

4 4.9 Noise and Vibration Environmental Impact Evaluation for various land use types. As shown in Table 4.9-2, Land Use Compatibility for Community Noise Exposure, single-family homes are "normally acceptable" in exterior noise environments up to 60 CNEL and "conditionally acceptable" up to 70 CNEL based on this scale. Multiple family residential uses are "normally acceptable" up to 65 CNEL and "conditionally acceptable" up to 70 CNEL. Schools, libraries and churches are "normally acceptable" up to 70 CNEL, as are office buildings and business, commercial and professional uses. Industrial, manufacturing, and utilities are normally acceptable up to 75 CNEL. City of Azusa General Plan The City of Azusa General Plan (April 2004) includes the following goals and policies pertaining to noise (refer to pages 5-62 through 5-73 of the General Plan): Goal 1: Maintain Community Noise Levels that Meet Health Guidelines and Allow for a High Quality of Life. Policies 1.1 Integrate noise considerations in the City s land use planning and project approval process (N1, N2, N3, N5, N6, N10, N11, and N12. These relate to specific Noise Implementation Programs in the General Plan). 1.2 Protect those areas of the City where the existing noise environments are considered unacceptable or noise sensitive (Figure N-2) (N4 through N9, N12, N14, N16, N17, and N18). 1.3 Maintain or reduce noise levels within acceptable levels adjacent to existing or planned major transportation facilities such as freeways, major highways, railroads, and light rail transit (N5 through N8, N10, N13, N14, and N15). 1.4 Maintain or reduce noise levels within acceptable levels adjacent to industrial processing and mining activities and the San Gabriel Valley Gun Club. (N9 through N12, N16, N17). 1.5 Establish policy for outdoor activities including but not limited to sports, music, and festivals. (N19) 1.6 To the extent feasible, minimize the noise levels generated by trains throughout the city. (N20) 4.9-4

5 Environmental Impact Evaluation 4.9 Noise and Vibration Land Use Single Family, Multi-Family Homes, Duplex Table Azusa Land Use Compatibility Guidelines for Exterior Community Noise Community Noise Equivalent Level (CNEL) in db 1 Normally Acceptable* Conditionally Acceptable* Normally Unacceptable* Clearly Unacceptable* Above 75 Mobile Homes Above 75 Schools, Libraries, Churches, Hospitals, Nursing Homes Above 75 Transient Lodging: Motels, Hotels Above 80 Auditoriums, Concert Halls, Amphitheaters, Meeting Halls Sports Arena, Outdoor Spectator Sports, Amusement Parks Above Above 75 Playgrounds, Neighborhood Parks Above 70 Golf Courses, Riding Stables, Water Recreation, Cemeteries Office Buildings, Business and Professional Commercial Retail, Banks, Restaurants, Theaters Above Above Industrial, Manufacturing, Utilities Source: Azusa General Plan Noise Element 1 db = decibel *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. Conventional construction, but with closed windows and fresh air supply systems or air conditioning will normally suffice. Normally Unacceptable: New construction or development should generally 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 should generally not be undertaken. Noise Standards for Cities of Azusa and Duarte The City of Azusa Noise Control regulation, Section of the Municipal Code, sets a daytime standard of 65 db at any residential property line for single impulsive sources such as a blasting boom. Section states that the exterior noise standard for new continuous events is an hourly average of 50 db Leq from 7 a.m. to 10 p.m. The nocturnal standard is 4.9-5

6 4.9 Noise and Vibration Environmental Impact Evaluation 5 db more stringent or 45 db Leq. These standards have been reduced by 5 db per Section (b) in the event the offensive noise consists entirely of impact noise. Section states the following: It shall be unlawful for any person at any location within the incorporated area of the city to create any noise, or to allow the creation of any noise on property owned, leased, occupied, or otherwise controlled by such person, which causes the noise level when measured on any residential, public institutional, professional, commercial or industrial property, either within or without the city, to exceed the applicable noise standards: (1) For a cumulative period of more than 30 minutes in any hour; (2) Plus five db(a) for a cumulative period of more than 15 minutes in any hour; (3) Plus ten db(a) for a cumulative period of more than five minutes in any hour; (4) Plus 15 db(a) for a cumulative period of more than one minute in any hour; or (5) Plus 20 db(a) for any period of time. The City of Duarte Noise Regulation, Section 9.68 of the Municipal Code, lists the policy of the City to prohibit unnecessary, excessive and annoying noises from all sources. Per Section , the City of Duarte noise standard is 70 db for any noise event lasting less than one minute in duration. The Duarte Noise Regulations state that: It is unlawful for any person within the city of Duarte to make, cause or allow to be produced noise which is received on property occupied by another person within the designated zone, in excess of the following levels which are: 55 db Leq for the hourly average standard from 7 a.m. to 9 p.m. for low to medium residential zones (R1 or R2) and 45 db Leq from 9 p.m. to 7 a.m. The Noise Regulations correct the standards by reducing it by 5 db (to 50 db daytime and 40 db nighttime) if noise is repetitive impulsive, pure tones and sound with cyclically varying amplitude [Source: City of Duarte Municipal Code, Chapter (Ambient base noise levels)]. Vibration Standards Vibration may be described in terms of the physical motion of a vibrating object (displacement), the speed of motion (velocity), or the rate of change from negative to positive motion (acceleration). Velocity can be described in terms of the average amount of sway (the root mean squared or r.m.s. velocity), or the maximum velocity during a single oscillation. The peak particle velocity (PPV) in inches per second (ips) is the descriptor used in this discussion because it is most closely related to any possibility of structural damage. Table shows some typical PPV's associated with earth disturbance activities and the human reaction to such vibration. Human perception is seen to be relatively pronounced before any structural damage is observed. The Cities of Azusa and Duarte have no vibration performance standards in their municipal codes. The U.S. Department of the Interior, Office of Surface Mining (OSM) is the federal agency that regulates the blasting effects of mining operations. The OSM has developed vibration limits recognizing frequency dependence for vibration associated with distance. For mining operations, the OSM has adopted a PPV standard of 1.0 ips for any home, school, church, etc. within a range of 300 to 5,000 feet from the blast site. Although such a level of vibration generally creates no perceptible structural damage, it is unsettling to people when in direct contact with the ground (carpet and building framework effectively attenuates ground vibration). Therefore, 4.9-6

7 Environmental Impact Evaluation 4.9 Noise and Vibration a more conservative threshold of significance of 0.20 ips for any single event was used in this analysis. A 0.20 ips PPV is approximately equivalent to a magnitude 2.7 quake on the Richter Scale and is five times more stringent than the USDI standard. Such an event may be noticeable when standing on a slab or other hard surface, but would not be noticeable on carpet or other cushioned floor covering. Peak Ground Velocity (inches/second) Table Vibration Comparisons Construction Sources Structural Damage Human Perception feet None Barely Noticeable 0.03 Truck or 50 feet None Easily Noticeable Strongly Normally None Noticeable 0.50 Pile 50 feet Loose Items Shift Unpleasant Limited Damage Very Unpleasant feet Limited Damage Extremely Unpleasant Minor Damage Intolerable Structural Damage Intolerable Source: Cowan, James, Architectural Design Guide, Mc Graw-Hill: New York (2000); Noise Impact Analysis, Giroux & Associates for VMC, September Impacts and Mitigation Measures Thresholds of Significance The City of Azusa Initial Study Checklist is utilized to identify the primary thresholds of significance relating to CEQA issues. Therefore, the Proposed Project would have a significant effect on Noise and Vibration if it would result in the following: N-1: N-2: N-3: 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? Exposure of persons to or generation of excessive groundborne vibration or groundborne noise levels? A substantial permanent increase in ambient noise levels in the project vicinity above levels existing without the project? 4.9-7

8 4.9 Noise and Vibration Environmental Impact Evaluation N-4: N-5: N-6: A substantial temporary or periodic increase in ambient noise levels in the project vicinity above levels existing without the project? For a project located within an airport land use plan or, where such a plan has not been adopted, within two miles of a public airport or public use airport, would the project expose people residing or working in the project area to excessive noise levels? For a project within the vicinity of a private airstrip, would the project expose people residing or working in the project area to excessive noise levels? For non-transportation noise sources affecting noise sensitive land uses, an increase in ambient noise levels of greater than 5 db is also considered to be potentially significant. Project Design Features The Proposed Project will include the implementation and compliance with all applicable federal, State, County, and City rules and regulations related to noise and vibration impacts as discussed in this section. In addition, previous Project Site improvements, specifically those related to the construction and utilization of the overland conveyor linking the quarry to the Reliance facility were developed to reduce or eliminate potential noise impacts from off-site truck traffic through residential areas. The conveyor transfer of material eliminated the daily haul truck traffic on Encanto Parkway and its associated traffic, air, and noise impacts to the affected communities. The Proposed Project will continue to utilize the overland conveyor to transport material from the site to the Reliance Processing Plant, therefore there will be no change in transportation noise Noise Issues Identified to Have No Impacts Based upon the City s Initial Study, the following noise issues were found to have no impact: N-5: For a project located within an airport land use plan or, where such a plan has not been adopted, within two miles of a public airport or public use airport, would the project expose people residing or working in the project area to excessive noise levels? The Project Site is not located within an airport land use plan or within two miles of a public airport or public use airport. The nearest airport is the El Monte Airport located at 4233 Santa Anita Avenue in El Monte approximately eight miles to the southwest. The Proposed Project would not introduce new sensitive receptors to the area that would be affected by airport noise. Therefore, no impacts would occur. N-6: For a project within the vicinity of a private airstrip, would the project expose people residing or working in the project area to excessive noise levels? 4.9-8

9 Environmental Impact Evaluation 4.9 Noise and Vibration The Project Site is not located in the vicinity of a private airstrip. The nearest public or private airport is the El Monte Airport located at 4233 Santa Anita Avenue in El Monte approximately eight miles to the southwest. The Proposed Project would not introduce people to the area that would be affected by airport noise. Therefore, no impacts would occur Noise Impact Analysis The City of Azusa Initial Study Checklist is utilized to identify the primary thresholds of significance relating to CEQA issues. Therefore, the Proposed Project would have a significant effect on Noise if it would result in: N-1: 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? Impact: Potentially Significant Impact Since the Azusa Rock Quarry is an existing, permitted use, the focus of the noise analysis is on the net difference between the existing noise conditions that presently occur at the Project Site, and those that would occur under the Proposed Project. This includes the potential noise and vibration impacts that would derive from a westward shift of mining and blasting in the West Side area proposed for mining. The primary sources of noise related to quarry mining and rock processing are heavy equipment usage and material processing plants. Noise generating sources would include the primary and secondary crushing and screening plants, material loading and unloading, drilling and blasting, mobile construction equipment, and on-site haul trucks. Mining activities and associated equipment operations would also change location. A larger fleet of trucks would move excavated rock from the proposed working face in the West Side to the primary crusher as compared to existing operations. The noise from any ongoing reclamation of the East Side is considered part of the existing baseline or ambient noise environment. The mining equipment is mobile and is most heavily concentrated around the primary crusher, which is considered the acoustic noise center of noise generation and used to evaluate the maximum noise impacts. Although the primary crusher and most future operations will continue to remain shielded by an intervening ridge from the nearest homes on Brookridge Road in adjacent Duarte, the closest point of possible mining will decrease from a present 2,225 feet to a point 1,800 feet from the nearest Duarte homes (see Figure 4.9-1). Therefore, the assessment includes a smaller mix of equipment used exclusively at the active mining site nearest to the southwestern boundary adjacent to Duarte for the existing and proposed mine areas. In addition, noise from Phases I-W and II-W (refer to Figure 3-16) in the northwest portion of the West Side along the ridge would have a direct line of sight and would not have the benefit of an intervening ridge to block potential noise levels. The average distances from the acoustic noise center (existing and proposed processing operations associated with maximum noise levels) and from the nearest mining area are as follows: 4.9-9

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11 Environmental Impact Evaluation 4.9 Noise and Vibration Location Source Existing Proposed (West Side) Nearest Azusa Homes From Acoustic Noise Center 3,900 feet 5,600 feet Nearest Duarte Homes From Acoustic Noise Center From Nearest Mining on Southwest From Mining Along West Side with Line of Sight 3,500 feet 3,100 feet 2,225 feet 1,800 feet Not Applicable 5,200 feet Single Blasting Event Noise Level Impact Blasting events at the Project Site will not exceed one per day or one hundred per year. Noise data was obtained at a distance of approximately 2,000 feet between a heavy charge blast site and the noise meter for a direct line of sight condition (no intervening terrain). The reading was adjusted for distance and with terrain obstruction to simulate the maximum plausible noise for the existing Project Site configuration and for the Proposed Project West Side mining activities. Two noise meters operating in the Lmax mode were used to measure the A-weighted noise boom during a heavy charge rock production blast. Both meters recorded 66 dba at 2,000 feet under direct line of sight conditions. Had that event occurred as close as possible to the nearest homes in the City of Duarte (approximately 1,800 feet), the following estimated noise levels would have been observed: Existing mining plan = 66 db - 2 db distance adjustment - 5 db terrain screen = 59 db Lmax Proposed mining plan = 66 db + 1 db distance adjustment - 6 db terrain screen = 61 db Lmax The resulting maximum noise levels will be 4 db below the City of Azusa s standard of 65 db, and 9 db below the City of Duarte s standard of 70 db for peak single events. The net difference between the existing and proposed noise levels at the nearest receptors was approximately + 2 db. The threshold of human perception of noise level differences under ambient conditions is approximately 3 db and an increase in ambient noise levels of greater than 5 db is considered to be potentially significant. Therefore, maximum single event noise levels associated with the Proposed Project s blasting events will not be perceptibly different for either scenario. The change in mining operations to create micro-benches that will require smaller charges off-set the small increase in noise associated with the proposed West Side mining activities. Therefore,

12 4.9 Noise and Vibration Environmental Impact Evaluation impacts from the generation of new single event (blasting) noise are anticipated to be less than significant. Continuous Sources Noise Level Impact Heavy equipment noise levels were derived from EPA data for construction operations. Average hourly noise levels were estimated by assuming that equipment operates under heavy load for approximately 30 minutes during any hour. Equipment noise levels for the existing operation were compared to those from the Proposed Project. Noise levels from published inventories were presumed to decay due to distance spreading, atmospheric absorption and the blocking action of intervening terrain. The reference noise levels at 50 feet from the source for the existing and future equipment fleet were calculated as listed in Table To determine noise from active mining along the western Project Site boundary nearest to Duarte, a loader, dozer, water truck, and two haul trucks were assumed to be operating at any one time. The active mine would produce less noise than at the acoustic noise center (i.e., crusher plus mobile equipment) but would be closer or have direct line of sight to the off-site residences. A comparison of the maximum plausible noise change at the closest residence in Duarte was made by comparing noise levels from equipment operations at the points of minimum possible distance. Under the current permit, the minimum possible separation to homes on Brookridge Road is 2,225 feet. With the Proposed Project, the minimum set-back is 1,800 feet. Both locations are screened by a massive intervening ridge. In addition, noise from Phases I-W and II- W along the northwest and west portion of the West Side mining area (proposed approximate 80- acre area) along the ridge would not have the benefit of an intervening natural ridge. Potential noise levels are presented in Table Table Equipment Noise Levels At 50 Feet from Source (in db) Source Existing Conditions Proposed Project Equipment Number of Units Acoustic Noise Center Mining Noise Level Number of Units Acoustic Noise Center Mining Noise Level Excavator * * --- Dozer * * --- Loader Water Truck Haul Trucks Grader Drill Rig Composite 95 db 92 db 97 db 92 db Note: Acoustic Noise Center Level is composite of all equipment near primary crusher for maximum noise levels. Mining Noise Level is maximum noise from only equipment conducting mining activities nearest to Project Site boundary adjacent to Duarte residences. * Remains on East Side for reclamation work, unchanged from existing. Source: Noise Impact Analysis, Giroux & Associates for VMC,

13 Environmental Impact Evaluation 4.9 Noise and Vibration Off-site noise levels were adjusted for various correction factors to determine residual equipment noise relative to City of Azusa or Duarte standards. Noise levels will be reduced from their 50-foot measured reference levels by the following factors: Load Adjustment - Equipment does not operate at 100 percent load (max power) for an entire hour. An average of 50% load factor per hour was assumed based on the range of load factors and the number of haul and water trucks (up to seven at 41%), loaders (two at 46.5%), graders (one at 57.5%), and drill rig (one at 75%). Distance Adjustment - Sound levels reduce by geometrical spherical spreading losses at a rate of 6 db for each doubling of the source-receiver distance. The location of the maximum sound source would be the center of operations adjacent to the primary crusher (acoustic noise center) since the standard is an hourly average. Absorption Adjustment - Molecular absorption acts like a viscous substance that reduces wave amplitude, particularly for shorter wavelengths. The rate of absorption attenuation is typically 1-2 db for each doubling of distance beyond the initial 1,000 feet of travel. Terrain Obstruction - Sound wave propagation is strongly line-of-sight. Receivers within the sound shadow behind an obstruction experience measurably reduced noise levels. The degree of attenuation depends upon the size of the barrier. Attenuation levels range from minimal (-5 db), limited (-10 db), substantial (-15 db), and massive (-20 db) to maximum theoretical (-23 db). Application of these attenuation factors yields the predicted equipment noise levels (db Leq) as listed in Table for the acoustic noise center and the mining maximum at the active working area in the West Side. Equipment operations noise will continue to be shielded by a very substantial topographic barrier during most operations and is generally reduced by distance. When the acoustic noise center is closest to Duarte (3,100 feet), the combination of an increased operations fleet and a decrease of set-back distance may cause noise levels at the closest Duarte residences to increase by +4 db. An increase of +4 db is below the net change threshold level of 5 db. Hourly average noise will remain at 10 db below the allowable Duarte nocturnal noise ordinance level, and 20 db below the daytime standard. Levels at the nearest Azusa residences will decrease slightly because of increased distance set-back associated with the relocation of mining activities from the East Side to the West Side. The proposed change at the closest point of mining (1,800 feet) would increase maximum noise levels by +2.5 db for residences in Duarte. The change in the maximum is almost identical to the calculated change in average levels based upon using the acoustic noise center. Changes of 2.5 db are only marginally perceptible under ambient conditions and less than the significance threshold of +5 db

14 4.9 Noise and Vibration Environmental Impact Evaluation Distance to Nearest Home Reference Noise Level of Equipment Load Adjustment Distance Adjustment Absorption Adjustment Terrain Obstruction Resulting Noise Levels City Noise Standard (day) Exceeds Significance Daytime Standard City Noise Standard (night) Exceeds Significance Night Time Standard Azusa R6 Acoustic Center 3,900 ft Table Existing and Proposed Noise Levels (in db) Existing Proposed Duarte Duarte Azusa Duarte Duarte R3 R2 R6 R2 R2 Mining Acoustic Mining Acoustic Acoustic Location Center Location Center Center 1,800 ft 3,500 ft 2,225 ft 5,600 feet 3,100 ft Duarte R(LOS) LOS Mining Location 5,200 ft (-5) 35 (+4) 36 (+2.5) 0 40 (+6.5) No No No No No No No No No No No No No No Source: Noise Impact Analysis, Giroux & Associates for VMC, Potential noise levels from mining with no natural barrier in Phases I-W and II-W in the northwest portion of the West Side along the ridge, would not have the benefit of an intervening ridge during the initial excavations. These areas are approximately 5,200 feet from the nearest Duarte residences with direct line of sight. The potential noise levels are estimated at 40 db. The potential increase of +6.5 db as compared to existing noise levels as R2 is greater than the net

15 Environmental Impact Evaluation 4.9 Noise and Vibration change threshold level of 5 db. Therefore, noise impacts during mining operations in Phases I-W and II-W when there is a direct LOS are considered potentially significant and mitigation measures N-1 through N-3 are required. The proposed mining activity noise levels are superimposed upon background noise from localized sources and the hum from distant traffic in Table The noise ordinances for Azusa and Duarte are focused on the noise signature of a specific activity unless background levels already exceed standards. Background noise levels at residential areas closest to the Project Site are low and therefore this possible exception to the standards is not applicable. Nevertheless, it is instructive to compare project-related noise impacts to background conditions as a frame of reference. Baseline (ambient) noise levels were measured on December 9 and 10, 2009 at residences in Azusa and Duarte closest to the Proposed Project mining areas. Measurements were also made at the nearest Duarte residences that may have a limited future line-of-sight (LOS) when mining activities daylight at the far northwest corner of the West Side. Addition of the Proposed Project noise to the baseline (ambient noise level) produces the following results as shown in Table Project activities from the acoustic noise center and the nearest mining location to Duarte are not expected to measurably increase the baseline (ambient) noise conditions at nearby receptors. Proposed Project noise levels will meet the City of Azusa s and Duarte s noise standards of not creating noise in excess of the established noise levels and will not increase noise by more than 5 db due mainly to the distances to the receptors and to the intervening ridges that will remain in-place. A typical condition of approval that will be applied to the Proposed Project will provide that the Applicant mitigate noise levels that cause valid complaints from residential land uses. Upon receipt and validation of any noise complaints pertaining to the operation of the facility, the Applicant will be required to conduct further noise analysis, which shall be conducted by a qualified acoustical consultant with experience in evaluating community noise levels and standards. The acoustical analysis shall address complaints received and shall be submitted to the City of Azusa Planning Department for review and approval. The City may require that additional noise attenuating measures be implemented to ensure compliance with the City of Azusa and the City of Duarte noise standards. As mining activities daylight in the far northwest corner of the West Side during Phases I-W and II-W and prior to excavating behind the existing terrain, noise attenuation from the intervening topography is lost towards the residential area approximately one mile to the south-southwest in Duarte. Daytime noise standards would be met in Duarte, however, baseline nighttime noise levels already exceed nighttime standards. The Proposed Project noise levels would not increase existing nighttime noise levels or exceed the incremental change threshold of 5 db. In order to avoid any substantial noise impact, the following mitigation measures are required

16 4.9 Noise and Vibration Environmental Impact Evaluation Azusa (R6 Mirador) Table Baseline Plus Proposed Project Noise Levels (in db) Day Evening Night From Acoustic Noise Center Baseline Project Combined Standard Significant Increase No (> 5 db) No No Duarte (R3 Brookridge) Duarte (R2 Van Tassel Creek) Duarte (Direct LOS) From Acoustic Noise Center Baseline Project Combined Standard Significant Increase (> 5 db) No No No From Nearest Mining Baseline Project Combined Standard Significant Increase No No No (> 5 db) From Direct LOS Mining Baseline Project Combined Standard Significant Increase No No No (> 5 db) Source: Noise Impact Analysis, Giroux & Associates for VMC, Mitigation Measures Mitigation Measure N-1 Mining activities shall only be permitted within Phases I-W and II W along the western and southern boundary of the Project Site during the defined construction hours of 7 a.m. to 6 p.m. At such time as the excavations result in the creation of a line of sight (LOS) barrier of

17 Environmental Impact Evaluation 4.9 Noise and Vibration 20-feet or greater in height between the operational face and the sensitive receptors, nighttime operations may then commence. Mitigation Measure N-2 During all excavation, hauling, and processing of materials, the operator shall equip equipment with properly operating and maintained mufflers, stationary engine enclosures, or other noise suppression devices consistent with manufacturers standards. Mitigation Measure N-3 Blasting shall only be conducted between the hours of 10 a.m. and 6 p.m. Monday through Saturday with no blasting allowed on Sundays or holidays. Level of Significance After Mitigation Implementation of Mitigation Measures N-1 through N-3 would reduce potentially significant impacts during nighttime hours to less than significant and reduce noise impacts to residences in Duarte to less than significant. N-2: Exposure of persons to or generation of excessive groundborne vibration or groundborne noise levels? Impact: Potentially Significant Impact Blasting vibrations were measured in terms of the peak particle velocity (PPV) for existing blasting events by an independent contractor at two locations on the Project Site. One monitoring station was located approximately 2,700 feet from the blast to reasonably simulate the maximum plausible vibration exposure at the closest residence for the current mining plan and one monitoring station was located approximately 2,200 feet from the blast site representing potential vibration impacts from future blasting near the southwestern corner of the proposed West Side mining area. A threshold of 0.20 ips is used as the standard of significance in this analysis. Eleven blast events were monitored to establish vibration levels as a function of ground-borne propagation distance. The measured peak particle velocities for these events at two locations that best simulate possible residential exposure are shown in Table By way of a reference, a PPV of inch/sec is a magnitude 0.0 on the Richter Scale. A level of inch/sec is approximately a magnitude 0.2. The maximum of ips is below a magnitude 1.0. The measured vibration levels were extrapolated to the closest plausible residential separation distance for the proposed westward operation (1,800 feet) using a standard power law spreading equation. The vibration level for a blast at 1,800 feet is calculated as ips average, ips worst-case. These levels are at least 10 times less than the adopted significance threshold of 0.20 ips. They correspond to a Richter Scale magnitude of 0.5 average and 0.9 worst-case. Such levels are barely perceptible to people and would not cause damage to

18 4.9 Noise and Vibration Environmental Impact Evaluation structures as the adopted OSM PPV standard is 1.0 ips for any home, school, church, etc. within a range of 300 to 5,000 feet from the blast site. Table Measured Peak Particle Velocities Peak Particle Velocity 2,700 ft to Blast Site 2,200 ft to Blast Site Measured Readings Non-detectable inches/second inches/second inches/second test average inch/sec inch/second PPV adjusted for 1, inch/sec inch/sec Exceeds Significance Threshold of 0.20 inches/second No No Source: Noise Impact Analysis, Giroux & Associates for VMC, For ground vibrations, neither the peak measured event (0.015 ips), the 11-blast average (0.009 ips), or the PPV at 1,800 feet (0.012 ips) would exceed the adopted significance threshold of 0.20 ips at the closest homes. In addition, the reduction in charge size for the Proposed Project s micro-benching procedures compared to current reclamation methods may more than compensate for any possible vibration increase associated with distance encroachment. Impacts are anticipated to be less than significant. Mitigation: No mitigation is required N-3: A substantial permanent increase in ambient noise levels in the project vicinity above levels existing without the project? Impact: Potentially Significant Impact The ambient noise assessment discussed above in Impact N-1 determined that the net difference between existing approved operational noise conditions and the Proposed Project for single event and continuous noise sources will not create noise effects that would exceed adopted noise standards. Although the Proposed Project will move the closest operations approximately 700 feet closer to the nearest receptors in Duarte, the maximum airborne noise levels for a single event (blasting) will be 4 db below the City of Azusa s standard of 65 db, and 9 db below the City of Duarte s standard of 70 db for peak single events. In addition, the net difference between the existing and proposed noise levels at the nearest receptors will be approximately +2 db. Therefore, noise impacts from single event (blasting) are anticipated to be less than significant

19 Environmental Impact Evaluation 4.9 Noise and Vibration Equipment operations noise will continue to be shielded by a very substantial topographic barrier except during portions of Phases I-W and II-W. The combination of an increased operations fleet and a decrease of set-back distance may cause operational noise levels at the closest Duarte residences to increase by +4 db from the acoustic noise center and +2.5dB from the nearest mining location. An increase of +4 db is below the net change threshold level of 5 db. Hourly average noise will remain at 10 db below the allowable Duarte nocturnal noise ordinance level, and 20 db below the daytime standard. Noise levels at the nearest Azusa residences will decrease slightly because of increased distance set-back associated with the relocation of mining activities from the East Side to the West Side. For the Proposed Project s mining in the northwest area with direct line of sight to Duarte residences, the potential increase of +6.5 db is greater than the net change threshold level of 5 db. However, baseline nighttime noise levels already exceed nighttime standards and the Proposed Project s noise levels would not increase nighttime noise levels. In order to avoid any substantial nighttime noise impacts, mitigation is required. Mitigation Measures Implementation of Mitigation Measures N-1 through N-3 would reduce impacts associated with the Proposed Project s ambient noise level increases. Level of Significance After Mitigation Implementation of Mitigation Measures N-1 through N-3 would reduce potentially significant impacts to less than significant. N-4: A substantial temporary or periodic increase in ambient noise levels in the project vicinity above levels existing without the project? Impact: Potentially Significant Impact The Proposed Project will continue to utilize the overland conveyor to transport material from the Project Site to the Reliance facility. Therefore there will be no change in periodic transportation noise. As discussed under Impacts N-1 and N-4 above, operational noise impacts are anticipated to be less than significant. Mitigation: No mitigation is required

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