Hydrokinetic Energy Project Phases and Activities

Impacts from a hydrokinetic energy project can result from activities that occur during each phase of the project: site evaluation, construction, operation, and decommissioning and reclamation.

What Activities Occur During the Site Evaluation Phase?

The purpose of site evaluation is to determine whether a given site is suitable for a hydrokinetic energy facility. The technical and financial viability of projects are site-specific. Activities would include:

• Conducting ocean or river bottom studies;
• Collecting bathymetry and surficial geology data for anchoring and cable installation;
• Identifying underwater obstructions and archaeological sites;
• Conducting ecological studies to characterize the aquatic biota; and
• Gathering seasonal sea state data (e.g., wave height, period, direction), tidal data, or seasonal river flow data.

Information would be required relating to competing use of space (e.g., shipping lanes, fishing grounds, protected marine or river areas, military operations areas).

A topographic survey would be performed in order to establish onshore site design, placement, and access roads for an interconnection substation, and the location of existing transmission lines.

What Activities Occur During the Construction Phase?

Wave Energy Farm

The assembly of the components of wave energy devices, including the anchoring devices, would be done onshore near the project site. The component parts would be transported to the on-shore assembly location via truck or ship. Existing ports may require expansion to accommodate shipment and assembly of components. Construction could include dredging and dock expansion or construction. Large cranes would be required for moving heavy components.

For some technologies, the entire device may be built onshore and transported as a unit to the site; others would require additional assembly offshore. This would likely be done from a barge or special-purpose vessel with the capacity to handle large equipment. Normally, trenching would be required to bury the electrical cable, but in some instances directional drilling or blasting could be required. Cable-laying vessels would be used for both transport and installation of the cables.

Onshore construction would include staging areas, access roads, connection to an existing electrical substation or construction of a new substation, and construction of new electrical transmission lines to connect to the existing power grid.

Tidal Turbine Farm

Construction activities would be similar to those for a wave energy farm, although construction would likely be occurring in an area with strong tidal currents. The assembly of turbine components would be done onshore near the site. The component parts would be transported to the onshore assembly location via truck or ship. For some technologies, the entire device may be built onshore and transported as a unit to the site; others would require additional assembly offshore. This would likely be done from a barge or special-purpose vessel with the capacity to handle large equipment.

Depending on the type of device used, drilling for placement of the support piling(s) or foundations or placement of anchoring systems would be required. Normally, trenching would be required to bury the electrical cable connecting units to the shore-based substation, but, in some instances, directional drilling or blasting could be required. Cable-laying vessels would be used for both transport and installation of the cables.

Onshore construction would include staging areas, access roads, connection to an existing electrical substation or construction of a new substation, and construction of new electrical transmission lines to connect to the existing power grid.

River In-Stream Facility

The assembly of the components of river in-stream devices would be done onshore near the site. The component parts would be transported to the onshore assembly location via truck or ship. For some technologies, the entire device may be built onshore and transported as a unit to the site; others would require additional assembly offshore. This would likely be done from a barge or special-purpose vessel with the capacity to handle large equipment.

Depending on the type of device used, drilling for placement of the support piling(s) or foundations or placement of anchoring systems would be required. Normally, trenching would be required to bury the electrical cable connecting units to the shore-based substation, but, in some instances, directional drilling or blasting could be required. Cable-laying vessels would be used for both transport and installation of the cables.

Onshore construction would include staging areas, access roads, connection to an existing electrical substation or construction of a new substation, and construction of new electrical transmission lines to connect to the existing power grid.

Tidal Barrage

Construction of a tidal barrage would be similar to construction of a dam or causeway, but much of the construction would be in an area that is normally underwater. The project area would be impacted by site preparation activities such as clearing and grading; construction of the dam to hold water in the basin; construction of the intake system; construction of access roads; construction of the powerhouse and installation of the turbines and generators; construction of an electrical substation and transmission line; and preparation and use of material and equipment laydown areas. Rock, earth, concrete and other materials for construction would need to be extracted and hauled to the site. A refueling station (with diesel and gas storage tanks) would likely be used during construction.

What Activities Occur During the Operation and Maintenance Phase?

Routine monitoring of ocean- or river-based hydrokinetic energy facilities would most likely be automated and not require full-time on-site personnel. Regular monitoring activities would be conducted largely from shore, but offshore systems would need to be visited by boat or helicopter for regular maintenance activities and would need to be returned periodically to shore for major maintenance and refit.

Operation and maintenance of a tidal barrage would be similar to that required for a low-head hydroelectric dam. Depending on the design of the installation, many monitoring activities may be done remotely, but resident on-site staff would be required to provide normal generator and structural maintenance activities and perhaps visitor services.

What Activities Occur During the Decommissioning and Reclamation Phase?

Decommissioning of a hydrokinetic energy facility would consist of removal of the hydrokinetic energy devices and most components. All onshore facilities would be removed. Any underwater foundations, support piers, and electrical cables would either be abandoned in place or be removed to a suitable depth below the seabed or riverbed to minimize obstructions to other uses. Following removal of onshore components, site reclamation and revegetation would be implemented to stabilize the area.