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Acoustics (Noise) Mitigation Measures

Mitigation measures to avoid or reduce acoustical impacts (noise) from low-head hydropower development.

The following are examples of mitigation measures that could be applied to reduce the noise impacts of a project that are dependent upon site- and project-specific conditions. Noise impacts are related to the source of the noise (e.g., vehicles, construction equipment, workers, blasting, and project facility components), the proximity to the noise receptor (e.g., humans and wildlife), and the time of day at which noise-producing activities occur. Many impacts can be reduced or avoided when taken into account during the siting and design phase.

Develop a final set of mitigation measures for the project in consultation with the appropriate federal resource management agencies and with stakeholders. Conduct these consultations as part of the project development process, preferably prior to final project siting and design.

Siting and Design Mitigation Measures

Siting and design considerations that mitigate impacts include:

  • Proponents of a low-head hydropower facility should take measurements to assess the existing background noise levels at a given site and compare them with the anticipated noise levels associated with the proposed project. Nearby residences and likely sensitive receptors should be identified at this time.
  • Locate all stationary equipment (i.e., compressors and generators) as far as practicable from nearby residences and other sensitive receptors.
  • Locate permanent sound-generating facilities away from residences and other sensitive receptors. In areas of known conflicts, consider installing acoustic screening.
  • Where feasible, incorporate low-noise systems, such as ventilation systems, pumps, generators, compressors, and fans.
  • To the extent practicable, site the transmission line right-of-way (ROW) to avoid residential areas and important wildlife habitat areas (e.g., rookeries, raptor nesting areas, calving areas).

General Mitigation Measures

General mitigation practices and principles that could apply to any or all phases of a low-head hydropower project include:

  • Limit noisy activities (including blasting) to the least noise-sensitive times of day (weekdays between 7 a.m. and 10 p.m.).
  • All equipment should have sound-control devices no less effective than those provided on the original equipment. Motorized equipment should be adequately muffled and maintained.
  • Enclose the noise source, if feasible.
  • Notify nearby residents in advance if blasting or other noisy activities are required during the construction period.
  • Whenever feasible, schedule different noisy activities (e.g., blasting and earthmoving) to occur at the same time, since additional sources of noise generally do not increase the total noise level significantly, i.e., less-frequent noisy activities would be less annoying than frequent less-noisy activities.
  • To the extent feasible, route heavy truck traffic away from residences and other sensitive receptors.

Project Phase-Specific Mitigation Measures

Mitigation measures specific to a particular phase of a low-head hydropower project include: