2007 CBC Tidal Power Costs & Benefits Discussion
Will Hopkins started a discussion on the tidal power presentations by asking, “What will be the impact of each project on fisheries, aquaculture, boat traffic, and marine mammals? How will each project benefit people in the area? Will it create new jobs, lower our electric rates, or attract new businesses? Is it a viable project or just another grand scheme?”He said that he did not expect that any of us would go home at the end of the day with instant answers about tidal power; for now it would be enough to ask the questions.
Question to Chris Sauer: You stated that the ORPC turbines would be kept at a depth of 40’ from the surface of the water. Ships currently transiting to Bayside draft 45’. If you figure a 10% safety factor over the draft, you should be planning to have your units 60’ below the surface for low water. This would mean they’d be about 80’ below the surface at high tide. We already know that LNG ships only have a 35-39’ draft so this depth would accommodate them as well.
Questions to Normand Laberge: You should really be talking to clammers as they will be greatly affected by your project. Have you contacted any neighbors along the Toll Bridge Road or any fishermen about your project?
Answer: No.
Will Hopkins, summarizing a general discussion about impacts on fisheries:
So, fisheries that would be affected by the proposed tidal power projects include scallop draggers, urchin draggers, cucumber draggers, mussel draggers, and clammers.
Question to Normand Laberge: How many acres will be lost to fishermen?
Answer: About 1000 acres will go from being intertidal to subtidal in Half Moon Cove.
Questions to Normand Laberge: The dam project will have traumatic consequences to the ecology of Half Moon Cove. Flushing time will change, temperature will rise in the summer, and the amount of nutrients will change. How much will water temperature change in the impoundment and how will this affect things? What about ice in the impoundment?
Answer: Estimate a temperature change of 3-5 degrees Celsius. There would be more ice in the winter than currently forms in Half Moon Cove.
Question to Chris Sauer: How many acres of bottom do you need for a profitable project?
Answer: Off the top of my head… each module produces 750kw. We need to produce at least 10 megawatts for a commercial venture, so estimate 15 modules. This will take up roughly 1600’ x 500’ of bottom for the full-scale commercial project.
Question to Chris Sauer: What is the deepest water you can put the modules in?
The deepest water in this area is 300’. We can deploy the modules at this depth. The modules are almost neutrally buoyant. Chris then noted that it is important to determine how many modules you can put in one area before the current flow in the whole region is affected. Dr. Huijie Xue at the University of Maine is working on modeling this.
Summary of discussion on deploying modules in Cobscook Bay: Inside Cobscook Bay the deepest parts are around 65’. The most boat draft you would see would be if someone was towing a fish pen with fish in it, with a draft about 30’. It was noted that the Hailey and Matthew has a draft of 15’ and draggers have about a 10’ draft.
Question to Chris Sauer and Steve Crawford: These tidal power units in the Western Passage could affect herring running up the Perry shore. Also, how deep do whales swim? Will these modules affect the whales?
The session ended with a discussion of where the fishing grounds are in Cobscook Bay and marking those areas on navigational charts. Will Hopkins invited people to send their questions, ideas or concerns to the Cobscook Bay Resource Center, where they will be forwarded to the appropriate person. Question and answers will then be posted on the website at www.cobscook.org .