From Wikipedia:Frazil ice is a collection of loose, randomly oriented, plate or discoid ice crystals formed in super-cooled turbulent water. Frazil ice is notorious for blocking water intakes as crystals accumulate and build up on the intake trash rack. Such blockages negatively impact water supply facilities, hydro-power plants, nuclear power facilities, and vessels navigating in cold waters, and can lead to unexpected shut downs of the facility or even collapse of the trash rack.
Though somewhat rare considering the plethora of dams in the northern latitudes of Canada, Frazil ice can impact a dam's water intake systems and build up tons of ice in just a few hours.
The folks at Yukon Energy know this situation well and have a well developed attack plan for when resources must be quickly deployed else the dam will be shut down for a lengthy period of time.
Cranes, Steam trucks and experienced divers are marshaled to arrive at the dam quickly which for this project, was contacting us Sunday morning. By Sunday afternoon, we had a full team of divers, supervisor and support personnel with their gear, on a flight from Vancouver. CANPAC maintains an inventory of emergency equipment on standby in the Yukon for just these sorts of events.
Upon arrival, equipment checks and safety meetings, the divers dove down the front of the dam in the super-cooled water to see how bad the Frazil ice buildup was.
It was bad! From the divers helmet camera's, we could see a buildup on the intake racks of close to 45 inches of ice.
The divers started cutting into the ice with high pressure steam wands. Cutting the ice into manageable blocks with each block weighing approximately 1000 lbs or half a ton.
Like all ice cubes, once the block was cut away, it would float to the surface ready for other teams to have the cranes lift the blocks out of the dam flow area.
Next image, beginning to see the racks! The divers are successfully cutting away the ice for the middle trash racks
Ice removal in progress, approximately 40 inches thick.
This is a hazardous job completed safely and efficiently by highly trained diving, steam truck and crane crews guided by the experienced Yukon Energy management team.
Job well done, all the ice has been removed from all the trash racks!