intake below the ice level and by placing lake intakes beyond the ice line of the lake.
The intake structure, however, must be designed to withstand the pressure of the ice.
If ice around an intake cannot be removed by scraping or other manual means, remove
it by pumping water out of the intake (reverse flushing). If necessary, steam can be
piped into the water to raise the temperature.
Maintenance. Maintenance operations on intakes in rivers, lakes, and
impounded reservoirs involve the structures and their appurtenances.
Inspect all structures periodically for cracks or structural defects.
Measure the depth of the suction well to determine the
accumulation of silt and sand. Dredge these accumulations as necessary.
When ice conditions endanger the structure or clog the intake
opening, take protective measures. Install log booms or bubble compressed air into
the water at critical points to prevent freezing. Frazil ice can form in supercooled water
and may cause complete blockage of intakes. Additional information on frazil ice can
be found in pars. 2.1.3 and 2.3.13.
Remove any material on screens that is not removable by ordinary
operations. Lubricate and repair any accessory equipment to movable screens.
Low-Lift Pumps. The term "low-lift" describes pumps that are capable of
pumping large quantities of water against a very low head, usually less than 50 feet
(15 meters [m]). A typical application for such pumps is transferring surface water to
treatment where gravity flow is not practical. Detailed guidance on pump O&M is found
in Section 6 of this handbook.
Water Quality. Most materials are water soluble to some degree. Water
supplies come in contact with many materials, both natural and man-made. As a
contaminants are harmful to humans. Most contaminants cause no significant
problems. Some are a nuisance or impart undesirable esthetic qualities to water, while
others like calcium and fluoride are beneficial in moderate concentrations. However,
certain chemicals, both inorganic and organic, pose a threat to humans. This section
focuses on contaminants found in raw water supplies. Information on treatment
techniques for removal of contaminants can be found in Section 5 of this handbook.
Regulations governing finished water quality are addressed in pars. 2.1.2 and 3.7.