Noise and New Project Development
By David E. Filippi, Greg D. Corbin
10/1/2002

Editor’s Note: This article is the first in a four-part series by attorneys with Stoel Rives LLP to address what some consider to be non-traditional environmental permitting issues arising in new project development. The series will address noise, odor, and view issues associated with the construction and operation of new development projects in Oregon, and is intended to provide readers with a broad overview of relevant terms, applicable regulations, and unique issues likely to be encountered by project developers.

Introduction

Since 1973, the Oregon Department of Environmental Quality (“DEQ”) has had in place administrative rules that set a limit on the amount of ambient noise that a new industrial or commercial development may produce (see OAR 340, Division 35). While DEQ’s rules establish the applicable limits, DEQ dissolved its noise control program in 1991. As a result, DEQ no longer maintains noise staff or enforces its noise regulations directly. However, the rules oftentimes are applied and enforced by other state agencies or local jurisdictions overseeing the approval of a given project. For example, the Oregon Energy Facility Siting Council requires adherence to DEQ’s noise regulations as part of its facility siting process. Similarly, many local governments mandate compliance with DEQ’s noise regulations as a condition of the local land use approval for new projects. While local governments may go beyond the limits and restrictions imposed by the DEQ rules, understanding the general application of the DEQ rules for new project development is a good starting point. This article reviews the type and extent of evidence that is often required to support findings of compliance with DEQ’s noise regulations.

Definitions and Measurements

To understand how the significance of noise impacts is determined, it is useful to understand how noise is defined and measured. Airborne sound is a rapid fluctuation of air pressure above and below atmospheric pressure. There are several ways to measure noise, depending on the source of the noise, the receiver, and the reason for the noise measurement.

There are several, basic acoustical terms that merit definition. As a basic starting point, ambient noise level is defined as the normal or existing level of environmental noise at a given location. Ambient noise is the composite of noise from all sources near and far. Noise itself is measured in decibels (dB). A decibel is a unit that describes the amplitude or loudness of sound, equal to 20 times the logarithm to the base 10 of the ratio of the reference pressure to the sound pressure, which is 20 micropascals (20 micronewtons per square meter). Based on the concepts of ambient noise and decibel measurement, the A-weighted sound level (dBA) refers to the sound pressure level in decibels as measured on a sound level meter using the A-weighted filter network. The A-weighted filter deemphasizes 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. Thus, noise levels stated in terms of dBA reflect the response of the human ear by filtering out some of the noise in the low- and high-frequency ranges that the ear does not detect well. The A-weighted scale commonly is used in local ordinances and standards.

Another key concept is that of the equivalent sound pressure level (L_eq), which is the energy average A-weighted noise level during the measurement period (such as hourly). From this concept follows the concept of measurements that relate to the noise-level distribution during the measurement period. Thus, L₉₀ is a measurement that represents the noise level exceeded during 90 percent of the measurement period. Similarly, L₁₀ represents the noise level exceeded for 10 percent of the measurement period. These measurements play a key role in DEQ’s noise regulations, as discussed below.

The effects of noise on people fall into three general categories: (i) subjective effects of annoyance, nuisance, and dissatisfaction; (ii) interference with such activities as speech, sleep, and learning; and (iii) physiological effects such as startling and hearing loss. In most cases, environmental noise produces effects in the first two categories only. However, workers in industrial plants may experience noise effects in the third category. No completely satisfactory way exists to measure the subjective effects of noise or to measure the corresponding reactions of annoyance and dissatisfaction. This lack of a common standard is primarily a result of the wide variation in individual thresholds of annoyance and habituation to noise. Thus, an important way of determining a person's subjective reaction to a new noise is by comparing it with the existing or “ambient” environment to which that person has adapted. In general, the more the level or the tonal (frequency) variations of a noise exceed the previously existing ambient noise level or tonal quality, the less acceptable the new noise will be, as judged by the exposed individual.

To provide a sense of scale, typical sound levels measured in the environment range from a civil defense siren at 100 feet with an A-weighted sound level of 130 dB, which surpasses the pain threshold on a scale of subjective impressions; to a freeway at 100 feet with an A-weighted sound level of 80 dB, which is considered moderately loud; to a soft whisper at 5 feet with an A-weighted sound level of 30 dB, which is considered quiet.

Noise Assessment

The starting point for any noise impact assessment for a new project development is the determination of the appropriate analysis area for noise impacts, which likely will include those areas that have the potential to be affected by construction or operational noise resulting from the proposed facility. With an analysis area established, the next step is to conduct noise-level measurements to establish an existing noise baseline. From here, the final step is to predict noise levels resulting from the construction and operation of the proposed facility.

Construction noise is usually considered short-term noise, and noise levels often vary depending on the construction phase. Construction of new industrial facilities can be divided into five phases, when different types of construction equipment are used: site preparation and excavation, concrete pouring, steel erection, mechanical, and cleanup. Predictions are oftentimes based on individual pieces of construction equipment as well as empirical evidence generated from construction sites of similarly sized industrial projects. Such predictions may also factor in site-specific attenuating factors, such as topography and the divergence of multiple sound waves in open air. Finally, as explained below, the predictions will want to estimate average construction noise levels projected to the nearest noise receptors from the project site.

Operational noise is viewed as long-term noise, and may vary depending on whether the facility is in the testing and commissioning phase or is operating during normal, full-load operations. Operational noise should also be examined for potential cumulative noise effects, in the event that the new project is being built and brought online at the same time as other new projects. Again, the predictions will want to estimate average operational noise levels projected to the nearest noise receptors from the project site.

Applicable Noise Regulations

OAR chapter 340, division 35, establishes statewide maximum permissible environmental noise levels for both existing and new commercial and industrial uses. The noise regulations apply at “appropriate measurement points” on “noise-sensitive property.” The “appropriate measurement point” is defined as whichever of the following is farther from the noise source: twenty-five feet toward the noise source from that point on the noise-sensitive building nearest the noise source; or that point on the noise-sensitive property line nearest the noise source.

“Noise-sensitive property” is defined as “real property normally used for sleeping, or normally used as schools, churches, hospitals or public libraries. Property used in industrial or agricultural activities is not Noise-Sensitive Property unless it meets the above criteria in more than an incidental manner.” Private residences often-times turn out to be the relevant noise-sensitive property identified.

In setting maximum permissible environmental noise levels, the DEQ rules distinguish between new sources located on previously used sites and new sources located on previously unused sites. A key limit that many developers face is the limit set for new sources located on previously unused sites. In such circumstances, the rules provide that the developer cannot operate a noise source if the noise levels generated by that source increase the ambient statistical noise levels, L₁₀ or L₅₀, by more than 10 dBA in any one hour, or other maximum limits. Such limits may be difficult to achieve, especially in previously undeveloped, rural settings.

The following table summarizes applicable state regulations, assuming a new noise source located on a previously unused site:

A hypothetical proposed facility subject to the above maximum permissible noise levels might play out as follows: Assuming that the proposed facility will operate 24 hours per day and emit a relatively constant level of noise, the nighttime limits will be the controlling regulatory threshold. Further assuming that the monitoring results show the Ambient L₁₀ to be 25 dBA and the Ambient L₅₀ to be 21 dBA, the proposed facility would be subject to the following limits:

• The L₁ would be limited to 60 dBA.
• The L₁₀ would be limited to 35 dBA (25 dBA + 10 dBA).
• The L₅₀ would be limited to 31 dBA (21 dBA +10 dBA).

In addition to the above limits, the DEQ noise rules also regulate “impulse sounds,” meaning a single pressure peak or a single burst of sound for a duration of less than a second (such as blasting). Finally, the DEQ rules establish standards to regulate octave band sound pressure levels and audible discrete tones. Such standards can be applied by DEQ when it does not believe that the basic limits for existing or new sources (such as those described above) adequately protect the health, safety, or welfare of the public.

DEQ noise regulations do exempt several categories of noise sources from the industrial noise limits. The rules exempt sounds created by: tires or motor used to propel any road vehicle complying with the noise standards for road vehicles; sounds that originate on construction sites; and sounds created in the construction or maintenance of capital equipment. Variances may be requested - perhaps difficult given that DEQ does not maintain any noise staff.

Noise Mitigation Measures

Local governments, in particular, will often incorporate requirements into their local codes that call on project developers to take measures to reduce predicted noise levels where possible. In such circumstances, common noise mitigation measures associated with construction activities include limiting noisy construction activities between 10 p.m. and 7 a.m.; ensuring that all construction equipment is properly muffled; and using low-pressure steam blows or temporary blowout silencers when appropriate. With respect to operational noise, common mitigation features include the use of acoustically insulated buildings, the use of silencers, and other appropriate noise control (e.g., duct silencers, acoustical louvers, and acoustical caulking). Some form of monitoring during facility construction and/or operation may also be required. Finally, it may be possible to address certain noise receptors on noise-sensitive properties through noise or non-occupancy easements.

In sum, noise is one of several environmental issues that deserves attention during the planning and permitting stages of new project development. While regulations may vary depending on the local jurisdiction and the nature of the project, a good starting point for those considering new projects is a noise analysis aimed at showing compliance with applicable DEQ noise regulations. Careful, predictive noise analysis, taking into account the steps and regulations described above, may be the key to building a solid administrative record for addressing potential noise impacts.

For Additional Information, Contact: Stoel Rives LLP attorneys David Filippi (503) 294-9529, Greg Corbin (503) 294-9632, or Thomas Wood (503) 294-9396.