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:
|
Maximum Permissible Environmental Noise Levels (dBA)
|
|
Statistical Descriptor
|
Daytime(7 a.m. to 10 p.m.)
|
Nighttime(10 p.m. to 7 a.m.)
|
|
L50
|
55 or Ambient + 10 dBA
|
50 or Ambient + 10 dBA
|
|
L10
|
60 or Ambient + 10 dBA
|
55 or Ambient + 10 dBA
|
|
L1
|
75
|
60
|
| Based on Table 8 of OAR 340-035: New Industrial and Commercial Noise Source Standards and OAR 340-035-0035(1)(b)(B)(i). |
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.