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4.2 CHAPTER FOUR

~creells
or Shore
--~ Sludge ~--!~ Sludge Well
FIGURE 4.1 Component block diagram.

Intake Design Objectives
Specific components that make up an intake facility are influenced by many factors, in-
cluding characteristics of the water source, required present and future capacity, water
quality variations, climatic conditions, existing and potential pollution sources, protection
of aquatic life, water level variations, navigation hazards, foundation conditions, sediment
and bed loads, required reliability, and economic considerations. In general, an intake fa-
cility consists of some combination of the components shown in Figure 4.1.
Each intake system presents unique challenges. Once the specific components are de-
fined, the facility design must achieve the following:
• Reliability during water level fluctuations or channel instability
• Flexibility for water withdrawal at various depths, where desirable and feasible
• Protection against hydraulic surges, ice, floods, floating debris, boats, and barges
• Location to provide the best available water quality
• Prevention of entry of objects that might damage pumps and treatment facilities
• Adequate space for routine equipment cleaning and maintenance
• Facilities for removing pumps and other equipment for inspection and maintenance
• Location and design to minimize damage to aquatic life
• Adequate space and facilities for receiving, storing, containing, and feeding treatment
chemicals

Intake Capacity
Unlike water system components such as pumping stations, basins, and filters, intake fa-
cilities are difficult to expand to provide additional future capacity. For this reason, long-
range water supply needs must be carefully considered during the intake design. In gen-
eral, intake requirements to meet water needs 20 to 40 years in the future (minimum)
should be investigated. Although intake facility construction is generally costly, the in-
cremental cost of incorporating provisions for expansion of capacity to meet future re-
quirements into the original intake facility design and construction is relatively small.

Intake Reliability and Redundancy

Reliability is essential, especially for waterworks that depend on a single intake facility.
For larger systems, construction of duplicate intake structures is becoming increasingly
common, including multiple inlet ports and screens, screen chambers, pump wetwells, and