The Bangor Daily News has reported that there are two proposals for dams to be built in Maine in the greater Cobscook Bay for the purpose of harnessing tidal currents. Both of these proposals are in the process of going through the federal regulatory process.
The first is a project that has been brought forward by Pennamaquan Tidal Power under the name Halcyon Tidal Power. The company would like to build a tidal barrage that will measure 1,616 feet across the Pennamaquan River between Leighton Neck and Hersey Neck south of Pembroke. This project has been estimate as costing $120 million.
The second is a request for approval from Tidewalker Associates who are looking to build a 1,200 foot long dam in Half Moon Cove. This project is being operated under the name Maine Tidal Power and would be located between Eastport and Pleasant Point.
In both cases the initial permits have expired and they are seeking successive preliminary permits to continue.
According to the preliminary permit application, the Pennamaquan Tidal Power project proposal consists of:
- A new tidal barrage extending from Leighton Neck to Hersey Neck consisting of:
(a) Two 5-foot-thick concrete walls, one 545-foot-long and one 135-foot-long, located in the intertidal area at each end of the barrage;
(b) six 82-foot-long, 10-foot-thick concrete modular wall panels extending about 22 feet above mean low tide;
(c) a new 438-foot-long, 91-foot-high concrete powerhouse with 16 reversible bulb generating units with a total capacity of 24.0 megawatts;
(d) a new steel 65-foot-long, 44-foot-wide boat lock integral with the powerhouse;
- a tidal basin (i.e., impoundment) with a surface area of 489 acres at low tide and 862 acres at high tide;
- a new 328-foot-long utility road providing access from Hersey Neck to the powerhouse; and
- a new 35 kilovolt, 2.5-mile-long transmission line to Emera Maine’s substation in Pembroke, Maine.
The following is an artists impression of what the tidal barrage will look like.
Image: Halcyon Tidal Power
The preliminary permit application that was lodged by Tidewalker Associates for the Half-Moon Bay area consisted of the following:
- A new 1,200-foot-long rock-filled barrage with a crest elevation of approximately 27 feet above mean sea level (msl);
- a new 30-foot-wide, 15-foot-high filling and emptying gated section;
- the 850-acre Half-Moon Cove with a surface elevation of 13.0 feet above msl;
- a new powerhouse with four turbine generating units with a total capacity of 9.0 megawatts; and
- a new 34.5 kilovolt, 7.1-mile-long transmission line.
Below is an artists impression of what the Maine Tidal Power barrage will look like when it is in operation.
Image: Maine Tidal Power
The environmental impacts of the proposed projects are determined during this permitting process. The initial preliminary permit was valid for three years which was not long enough for the initial planning phase of the environmental impact study to be completed.
Should both of the projects gain approval to go ahead with their plans the estimates for future renewable energy power production are good.
The Pennamaquan Tidal Power project has estimated that the facility will be capable of generating 80,000 megawatt hours of electricity per year. This would be enough to provide power to 13,000 homes. The Half Moon Cove project would be capable of generating around 40,000 megawatt hours.