I'm having fun looking up the concept of tunneling in karst. Here is a perfect picture of the Bruce site.
The Bruce site is below the collapse cliff. The windmills are on the top. You just have to look at the old air photos to see this. Since the lake is just at this level, all the caves are filled up. The karst topography is caused by deep dissolution of soft rocks, such as salt and gypsum. The weakness allowing the water ingress, is caused by the Grenville Front, one of the many megathrusts of southern Ontario.
Now, you must remember kiddies, that all I'm telling you is not acknowledged by anybody, since there is no money in discovering bad geology. All the money is in confirming good geology for the rich guys. They tried really hard, and actually found a layer in the rock that wasn't beaten up as badly as the other layers. They confined all their studies to this layer, and the boreholes were lucky enough to go through some solid chunks. Yeah!
But getting to this amazing layer is going to be tough, far worse than the Niagara Tunnel. They will have to inject large amounts of grout, and here is what someone says about that:
Grouting is a procedure in which grout is injected into different kinds of spaces. This procedure has had broad applications in modern civil engineering, especially in karst terrains, for nearly 200 years. Ingredients for the preparation of mortars and grouting suspensions include cement, clay and fillers, bentonite, asphalt, additives for stability and water. During their construction, thousands of tons of materials are injected into the karst underground. Some ingredients and chemicals used in the preparation of mortars and grouting suspensions may be toxic, neurotoxic or carcinogenic, and may be irritants or corrosives. Their use is dangerous to both humans and the environment.
Ooooh! Sounds nasty! Do they mention this in their environmental impact statement? No. That's the Big Lie!
Legal Statement - The above was presented for the public interest. It is protected by the recent Supreme Court ruling.