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I.9.0 NOISE

Noise as defined by Washington State constitutes the intensity, duration, and character of sounds from any and all sources (WAC 173-60). Sound is produced when a noise source induces vibrations into the surrounding air causing fluctuations in atmospheric pressure. Decibels (dB) are units of sound pressure used to measure changes in atmospheric pressure caused by the vibrations. Primary factors that influence the measurement of noise in ambient air are frequency and duration. The normal human auditory system cannot clearly discern sounds below 100 Hz (hertz or Hz is a measure of frequency or pitch) or substantially above 10,000 Hz. Sound occurring outside this range is not generally perceived as noise. Researchers have developed an A-weighted noise scale (dBA) to describe sounds emanating in those frequencies that are most readily detected by normal human hearing. Table I.9.0.1 lists some common levels of sound and their corresponding dBA levels. Sound duration is another important factor in determining cumulative noise impacts. Noise levels often are reported as the equivalent sound level (L_eq) and expressed as a weighted average (dBA) over a specified period of time; the L_eqintegrates noise levels over time and expresses them as steady-state continuous sound levels.

I.9.1 REGULATORY CONTEXT AND PREVIOUS NOISE STUDIES

The Hanford Site (including its unoccupied areas) is classified as a Class C Environmental Designation for Noise Abatement by Washington State on the basis of industrial activities (Table I.9.1.1). Because they are neither Class A (residential) nor Class B (commercial), unoccupied Hanford Site areas are also classified as Class C areas.

Because of the remoteness of the Hanford Site, only a limited number of studies have been conducted that document environmental noise levels. Two sources of measured environmental noise at Hanford Site are 1) measurements made in 1981 during Hanford Site characterization of the Skagit/Hanford Nuclear Power Plant Site; and 2) noise measurements at five Hanford Site locations performed in 1987 as part of the Basalt Waste Isolation Project.

I.9.1.1 Skagit/Hanford Studies

During preconstruction measurements of environmental noise associated with the Skagit/Hanford Nuclear Power Plant Site, 15 sites were monitored and noise levels ranged from 30 to 65 dBA (L_eq). The values for isolated areas ranged from 30 to 38.8 dBA (L_eq). Measurements taken at the proposed reactor sites ranged from 50.6 to 64 dBA. Measurements taken along the Columbia River near the proposed intake structures were 47.7 and 52.1 dBA, as compared to noise levels of 45.9 dBA measured at a more remote location about 5 km (3 mi) upstream from the intake structures. By comparison, community noise levels in North Richland (at Horn Rapids Road and the Bypass Highway) were 60.5 dBA (NRC 1982).

Table I.9.0.1 Common Sounds and Corresponding Noise Levels

Table I.9.1.1 Applicable State Noise Limitations for the Hanford Site ¹

I.9.1.2 Basalt Waste Isolation Project Studies

As part of the investigation for proposed Basalt Waste Isolation Project at the Hanford Site, background noise levels were determined at five locations. Noise levels can be expressed as L_eq for 24 hours (L_eq-24). Based on information provided in Cushing (Cushing 1994), wind was identified as the primary contributor to background noise levels with winds exceeding 19 km/hr (12 mi/hr), substantially impacting noise levels. As a result, it was concluded that background noise levels in undeveloped areas at the Hanford Site can best be described as having a mean L_eq-24 of 24 to 36 dBA. Periods of high wind, which normally occur in the spring, would elevate background noise levels.

I.9.1.3 Noise Levels of Hanford Field Activities

To protect Hanford Site workers and to comply with Occupational Safety and Health Administration standards for noise in the workplace, the Hanford Environmental Health Foundation monitors noise levels resulting from routine operations performed at the Hanford Site (DOE 1991 and Cushing 1992). Occupational sources of noise propagated in the field are summarized in Table I.9.1.2. These levels are reported because operations such as well sampling are conducted in the field away from established industrial areas and have the potential for contributing to environmental noise and disturbing sensitive wildlife.

Table I.9.1.2 Monitored Levels of Noise Propagated from Outdoor Activities at the Hanford Site ¹

I.9.2 HANFORD SITE NOISE CONDITIONS

Existing noise conditions produced by current, routine operations at the Hanford Site do not violate any Federal or State standards. Measurements show that even near the current operating structures along the Columbia River noise levels are less than experienced in part of the community of Richland (less than 52.1 dBA versus 60.5 dBA). Noise levels measured near intake structures at the Columbia River are well within the 60 dBA tolerance levels for daytime residential use. Five km (3 mi) upstream of the intake structures noise levels fell well within levels suited for daytime and nighttime residential use.

Moreover, the remoteness of the main areas of Hanford Site industrial activities from population centers means that there are no offsite populations within auditory range of Site industrial activities. However, Affected Tribal Nations use Site locations such as Gable Mountain for religious purposes.