TM 5-852-5/AFR 88-19, Volume 5
ice breakup, and storage is relied on as the water
Frazil ice can be a serious problem for intakes
supply. This approach is suitable for small popula-
during the freeze-up period. Frazil ice occurs as
small crystals in flowing water slightly below 32EF
tions. A temporary intake consists of a pump and a
simple shelter.
in temperature. It will adhere to and accumulate on
(2) Permanent construction. Numerous ar-
any submerged object it contacts. Water intakes,
rangements and configurations have been designed.
trash racks and similar structures can become
Figure 3-2 illustrates the intake in the river at Fort
completely choked by frazil ice in a few hours. It
Norman, Northwest Territories, Canada. Figure 3-3
can be avoided by locating the intake in a long calm
illustrates the water intake at Cambridge Bay,
reach of the river where surface ice will occur
Northwest Territories, Canada. Special features of
before the water becomes supercooled. The surface
this design include the insulation provided, heat
ice cover then prevents rapid heat loss and precludes
tracing in the wet well and in the intake line, and the
frazil ice formation. Heating the intake and bar
recirculating line from the town site. Dual intakes
screens to about 33 degrees F will prevent
are recommended to ensure reliability. Continuous
formation of frazil ice. This can be done electrically
water circulation is then used to prevent freezing.
or by backpumping hot water or steam.
3-3
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