jams. Mechanical control These methods include stabilizing freeze without restricting water flow, such as implementing weirs and ice booms, installing water jets to break up any accumulation that might occur, and using manual labour to rake away the accumulation. This final method is often not preferred because of high labour costs, cold, wet and late night working conditions. Back flushing is another technology that uses the idea of cancelling out the differential pressure caused by the frazil ice accumulation. This technology creates a high pressure on the downstream side of objects to reverse the differential pressure. Thermal control These methods either heat the structures in the water to prevent frazil ice adhesion or heat the water to prevent frazil ice from forming in the first place. When heating the structure, it must be heated to a temperature above freezing. Electrical resistance heaters have been found to work well, but these have potential safety problems. Installing hollow tubes in the structures through which steam or warm water is pumped also works, but this method has been seen to cause operational problems. Other active methods are also available. Sometimes warm water byproducts are released from nearby water facilities, and the warm water is wasted. Redirecting this water to potential frazil ice accumulation regions could raise the water temperature by , often enough to prevent supercooled water from developing. Vibration Although still in the experimental stages, blasting with dynamite is one form of vibrational control that will break loose any frazil ice accumulation. The charge must be precise such that the ice breaks, but surrounding structures and environment are not harmed. Safety of the blasting also is important and nearby residents might complain about sound pollution. For all these reasons, this method is not often used, except as an emergency last resort. Materials selection Man-made structures are often the objects to which frazil ice adheres. As such, the choice of materials for these structures should include consideration of ice adhesion. Steel structures, for example will rust, and rust-to-ice adhesion is very strong. Choosing a material with lower adhesion such as plastic, fiberglass, graphite or even an epoxy paint coating on the steel will reduce the adhesion probability. Although adhesion will still occur, using such materials makes other methods, such as raking, easier. Damage mitigation Damage could be reduced by protecting designated flood regions with mechanical structures. See also Grease ice References Daly, Steven