Abstract
Energy harnessed from wave motion is a promising candidate as a clean renewable energy source. The Oregon coast is a key location for Wave Energy Converter (WEC) technology in North America due to the state’s abundant access to ocean wave resources and its coastline transmission capacity. Additionally, the research facilities at Oregon State University (OSU) are ideal to act as a WEC test bed for research and development. A summary of the wave energy potential and the work that has been carried out to date at OSU has been published (Brekken et al, 2009).
The potential for creating underwater noise disturbance is one environmental impact that must be accounted for by wave energy developers to meet the needs of regulatory agencies. This review study has been conducted to provide a concise knowledge base of the expected underwater noise conditions in the near shore environment in regions of the Oregon coast where wave energy projects could be developed and to present an overview of noise measurement methodologies that would be suitable for the effective regulatory assessment of potential acoustic impacts. This report is intended as a reference to be used by wave energy developers in the specification and selection of approaches to underwater noise measurement that would be acceptable to regulatory bodies, consistent with the state of the industry and cost effective to implement.
In an attempt to address some of the uncertainties surrounding these types of environmental noise assessment studies, this report provides information on the expected existing ambient noise conditions, the sound propagation characteristics of the environment, and the expected sources of noise associated with various types of wave energy devices. Guidelines detailing specific noise measurement studies are provided, along with a listing of several commercially available devices that are suitable for performing these measurements.
Section 2 of this report provides an overview of the factors that contribute to ambient noise in near-shore environments. As part of this study a literature review was conducted to identify any available measurements of ambient noise along the Oregon coast, but no relevant data were found in published research. To address at least partially this knowledge gap, the latter part of Section 2 provides an overview of the characteristics of the Oregon coast that influence the ambient noise environment and thus helps define a basis for future studies.
Section 3 provides on overview of the various types of currently available WEC devices suitable for use in the Oregon coastal environment and lists the potential sources of noise associated with the construction, operation and decommissioning phases for these devices.
A framework for a comprehensive noise assessment program is detailed in Section 4 of this report with a description of specific measurement programs that are recommended to meet regulatory needs. The types of equipment suitable for performing these noise assessment measurement programs are detailed in Section 5.
As a complement to the above, an indicative sound propagation modeling study was conducted to provide an introduction to an estimation tool that is becoming the standard in noise impact assessments for regulatory approval. Section 6 of this report presents transmission loss estimates at three sample sites along the Oregon coast that are suitable for wave energy installations and are representative of a range of propagation conditions that can be found along the coast. These results provide an indication of the rate at which sound levels can be expected to decay as a function of distance from potential WEC development sites in the Oregon coastal environment.