From Niagara This Week:

Visitors to Niagara Falls may have noticed a crane dangling workers over the ledge above the lower observation deck of Journey Behind the Falls on Monday.

The workers were chipping away at loose rock in a process called ice-jacking on the Canadian side of the Horseshoe Falls, 13 storeys above the falls basin.

Throughout the winter, water can creep into the crevices of the rock and through the freezing process slowly loosen pieces of rock as the frozen water expands, which then poses a danger to people standing on the observation deck below.