Proponents Environmental Assessment 4.12-1 Valley-Ivyglen Subtransmission Project
4.12 Noise and Vibration
4.12.1 ENVIRONMENTAL SETTING
General Noise Information Noise is generally defined as unwanted or objectionable sound, and airborne sound can be described as a rapid fluctuation of air pressure above and below the atmospheric pressure. Most sounds that humans hear in the environment consist of a broad band of frequencies, with each frequency differing in sound level. The intensities of each frequency add together to generate a sound. The method commonly used to quantify environmental sounds consists of evaluating all of the frequencies of a sound in accordance with a filter that reflects the fact that human hearing is less sensitive at low and extreme high frequencies compared to mid-range frequencies. This is called A weighting, and the decibel level measured is called the A-weighted sound level (dBA).
Expressed on a logarithmic (power of 10) scale the units are depicted as dBA using a frequency-weighted pattern that duplicates the sensitivity of the human ear. A noise of 70 dBA is approximately twice as loud as a noise of 60 dBA and four times as loud as a noise of 50 dBA. Table 4-12-1 defines acoustical terms used in this PEA.
Since noise levels from various sources vary over time, they are frequently expressed as an equivalent noise level (Leq), which is a computed steady noise level that represents the same energy transmission over a specified time. Leq values are commonly expressed for one-hour periods, but different averaging times may be specified.
For the evaluation of environmental or community noise effects, it is customary to define a 24-hour-long noise level based on hourly Led values, and to apply an excess or penalty noise during the nighttime hours to account for the added nuisance during those periods and to adjust for lower average ambient levels during that period. Depending on the exact penalty scheme, the resulting noise descriptor is either a Community Noise Equivalent Level (CNEL) or a Day-Night Average Noise Level (Ldn). The two ways of expressing such noise levels are nearly equivalent, and are often used interchangeably.
Figure 4.12-1 identifies typical noise levels in the environment.
Ground-borne Vibration Vibrating objects in contact with the ground radiate energy through the ground. Large and/or powerful vibrating objects can be perceptible by humans and animals. The rumbling sound caused by the vibration of room surfaces is called ground-borne noise. The ground motion caused by vibration is measured as particle velocity in inches per second and in the United States is referenced as vibration decibels (VdB) (Caltrans 1998).
The background vibration velocity level in residential and educational areas is usually approximately 50 VdB. The vibration velocity level threshold of perception for humans is approximately 65 VdB. A vibration velocity level of 75 VdB is the approximate dividing line between barely perceptible and distinctly perceptible levels for many people. Most perceptible indoor vibration is caused by sources within buildings such as the operation of mechanical equipment, movement of people, or the slamming of doors. Typical outdoor sources of perceptible ground-borne vibration are construction equipment, steel-wheeled trains, and traffic on rough roads. If a roadway is smooth, the ground-borne vibration from traffic is rarely perceptible. The range of interest is from approximately 50 VdB, which is the typical background vibration velocity level, and 100 VdB, which is the general threshold where minor damage can occur in fragile buildings (Caltrans 1998).
4.12 NOISE AND VIBRATION
4.12-2 Proponents Environmental Assessment Valley-Ivyglen Subtransmission Project
Table 4.12-1: Definition of Acoustical Terms Used in this PEA
Decibel, dB A unit describing the amplitude of sound, equal to 20 times the logarithm to the base 10 of the ratio of the pressure of the sound measured to the reference pressure; the reference pressure for air is 20
A-Weighted Sound Level, dBA
The sound pressure level in decibels as measured on a sound level meter using the A-weighting filter network; the A-weighting filter de-emphasizes the very low and very high frequency components of the sound in a manner similar to the frequency response of the human ear and correlates well with subjective reactions to noise
Equivalent Noise Level, Leq
The average A-weighted noise level during the measurement period. The hourly Leq used for this report is denoted as dBA Leq [h]
Community Noise Equivalent Level, CNEL
The average A-weighted noise level during a 24-hour day, obtained after addition of 5 decibels in the evening from 7:00 PM to 10:00 PM and after addition of 10 decibels to sound levels in the night between 10:00 PM and 7:00 AM
Day/Night Noise Level, Ldn
The average A-weighted noise level during a 24-hour day, obtained after addition of 10 decibels to levels measured in the night between 10:00 PM and 7:00 AM
L01, L10, L50, L90 The A-weighted noise levels that are exceeded 1%, 10%, 50%, and 90% of the time during the measurement period
Ambient Noise Level The composite of noise from all sources near and far. The normal or existing level of environmental noise at a given location
SOURCE: Caltrans 1998
Project Study Area The cities of Lake Elsinore and Perris are relatively small communities with a rural character. Much of the Proposed Subtransmission Line, in addition to traveling through these communities, travels through rural and rural residential areas in unincorporated Riverside County. Ambient noise levels throughout most of the Project Study Area are low as a result of the existing environment. The predominant noise sources in the Lake Elsinore, Perris, Newcomb, and Sun City areas are mobile sources, particularly motor vehicles, and occasionally aircraft. Interstates 15 and 215, Highway 74, and several other arterial roadways would be located in or adjacent to the Proposed Transmission Line Route. General aviation aircraft operations originating from the Perris Airport and Skylark Airport (a private airport in the southeast portion of the City of Lake Elsinore) also contribute to the noise environment. Other sources of noise in the Project Study Area are from non-transportation sources including industrial and commercial operations. The noise environment in the Project Study Area is generally typical of a rural setting, except at locations affected by transportation, recreation, and commercial noise sources.
Subtransmission Line The proximity of the Proposed Subtransmission Line Route to sensitive receptors is described in Table 4.12-2.
4.12 NOISE AND VIBRATION
Proponents Environmental Assessment 4.12-3 Valley-Ivyglen Subtransmission Project
Figure 4.12-1: Typical Noise Levels in the Environment
SOURCE: Caltrans 1998
4.12 NOISE AND VIBRATION
4.12-4 Proponents Environmental Assessment Valley-Ivyglen Subtransmission Project
Table 4.12-2: Proximity to Sensitive Receptors
Segment Sensitive Receptor Location
Segment E-1 Less than 300 feet from residences in portions of unincorporated Riverside County east of I-15
Within 300 feet of residences in portions of the City of Perris just west of Murrieta Road and east of Goetz Road before crossing State Highway 74
Segment C-1 Within 300 feet of residential areas within the City of Lake Elsinore near SR-74
Segment C-3 Within 100 feet of residences in unincorporated Riverside County
Segment C-4 Within 200 feet of residences in unincorporated Riverside County
Segment C-6 Crosses I-15, and no sensitive receptors within 1,000 feet
Segment W-1 Within 300 feet of residences at the western end of the segment
Segment W-4 Within 300 feet of residences at Horsethief Canyon Road, approximately 0.25 miles south of I-15
Segment W-8 Would cross I-15, and there are no sensitive receptors within the area of potential impact (1,000 feet)
Segment W-10 Western end of the segment, where it terminates at the Ivyglen Substation, within 300 feet of several residences across Temescal Canyon to the north; a large wall separates the residential area from the roadway, and the area is raised substantially in comparison to the roadway and the substation
Substations The Valley Substation is located within an area of undeveloped land surrounded by light and heavy industrial development. No sensitive receptors are within 1,000 feet of the substation. The area is designated Light Industrial Use by the County of Riverside (County of Riverside 1990).
The Ivyglen Substation is located just south of Temescal Canyon Road, roughly 800 feet west of I-15 and about 300 feet from several residences. The area is designated Open-Space/Mineral by the County of Riverside (County of Riverside 1990).
Telecommunications Line The telecommunications line would follow the path of the Proposed Subtransmission Line Route along its entire length and would be located near the same sensitive receptors.
4.12.2 REGULATIONS, PLANS AND STANDARDS
Federal In 1974, the US EPA published Information on Levels of Environmental Noise Requisite to Protect Public Health and Welfare with an Adequate Margin of Safety. This document provides information for state and local governments to use in developing their own ambient noise standards. The US EPA, the Federal Aviation Administration, the Federal Highway Administration, and the US Department of Transportation (DOT) have developed guidelines for noise. Under the authority of the Noise Control Act of 1972, the US EPA established noise emission criteria and testing methods, publi