The arch was still standing, but it looked liked it might not stand for another 100 years.
This tunnel was one of the failed attempts, built by the Georgian Bay Power Company in 1906/07. It was just under 900 feet long, and would have carried water through the hill beside the falls, then down into the valley to a generating plant. It would also have required construction of a dam right above the falls, and most of the water flow would have been diverted through the tunnel. There was widespread debate in the town over losing the beauty of the waterfalls.
But they too went bankrupt, and though the tunnel remained a tourist attraction for years, it was eventually filled in for safety reasons. The only evidence remaining is these two gates. The power rights were sold to the Hydro Electric Power Commission, now Ontario Hydro. A decade later, in 1914, the dam upstream creating Lake Eugenia was built, with pipes carrying water to a hydro plant further north in the valley. That plant celebrated its 100th anniversary in 2014. It has the highest head (water drop) of any power plant in Canada east of the Rockies - small but mighty! And Eugenia Falls has almost never looked the same since!