3 August 1998
ice. Inlet velocities in the range of 75 mm to 150 mm (0.25 to 0.5 ft) per second are desirable
for avoiding ice clogging of intakes. Where ice is a problem, river intakes must have the
structural stability to resist the thrust of ice jams and the openings must be deep enough to
avoid slush ice which has been reported as deep as 2 to 2.5 m (6 to 8 ft). Frazil and anchor
ice can also cause difficulties, but on rivers, floating ice is usually the greater hazard. Steam
heating has been employed to cope with ice problems at some northern lake intakes.
Nonferrous materials are preferred for cold-climate inlet construction because their lower heat
7-4. INTAKE LOCATION. Meandering streams in deep alluviums pose especially difficult
intake problems. Here, expensive dikes, jetties and channel protection may be required to
prevent the river channel from moving away from the intake or cutting behind it. On such
streams, careful consideration must be given to intake location. Generally, the intake site
should be on the outside bank of a well established bend where the flow is usually swiftest and
deepest. If the outside bend site includes a rock bank, a reliable intake probably can be
placed there. Inside bends are to be avoided because of shallow water and sand bars.
Sufficient depth at extreme low stage must also be a consideration. In addition to structural
and hydraulic considerations, water quality is of major importance in connection with intake
design and location, and the water quality aspects of a proposed location should be carefully
examined. The location study should include a sanitary survey whose objective is evaluation
of the effects of existing and potential sources of pollution on water quality at the intake site.
The survey should include a summary of historical water quality data at the site plus an
assessment of the probable impact of all wastewater discharges likely to influence present or