Got a surprise call from Matt Johnson the other day. Turns out a local gravel company needed recovery divers to help get one of their gravel dredges back in service. These big monsters are pretty cool. They consist of a float supporting a pivoting grinding head attached with to a massive pump. Gravel removal operations consists of moving the head up and down against a vertical wall of the quarry while the head grinds away. The pump then pulls the water, mud and rock through a floating pipeline to a sorting mechanism which catches the rock and then returns the rest to the quarry.
The head is supported by cables attached to a cross member on the float and the whole thing is balanced. If the cable breaks, the grinding head falls to the quarry floor and the float becomes unbalanced and in danger of sinking.
Our job was to dive down to the grinding head laying on the quarry floor, untangle the cable and attach a temporary cable so the head could be pulled up and a more permanent repair conducted. Check out the pictures: