Thanks for the pics from above BVic - very very loud on the next level down.
Building a cage - note the diameter
Keeping up the pressure
Catching Pokemon ?
The place where the pressure meets the T-Bar this rotating collar is on the top of the long shaft that has the drill at the other end.
The crains have 2 or more winches, here one is being attached to the collar. The compressed air after driving the hammers causes a convection current which deposits the tailings (sp ?) on the top of the bit.
And out it comes - the crane operator shook the bit back and forth first which settled out the gravel (de-watered ?). After the deluge he then lowered the collar and used it to scrape off most of the remaining gravel.