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INTAKE FACILITIES 4.27

Fish Protection Considerations
Design of intake systems may affect aquatic organisms present in the river, lake, or reser-
voir. An evaluation for endangered species should be conducted. If endangered fish species
are present, the National Oceanic and Atmospheric Administration (NOAA) fisheries
guidelines should be consulted. Fish protection is a significant design element in some
areas such as California and the Pacific Northwest. Three basic types of devices used to
prevent juvenile fish from entering flow diversions are (1) physical barrier screens, (2)
behavioral guidance systems, and (3) capture and release systems. The most widely ac-
cepted and successful method of protecting juvenile salmonid passage is to use physical
barriers. When one is designing a juvenile fish screen, the swimming ability of the species
and the life stage targeted for protection should be considered. In the Pacific Northwest,
the juvenile fish screen criteria developed by the fisheries agencies are designed to pro-
tect the weakest swimming species at its most vulnerable life stage. An effective approach
for fish protection, which also minimizes the introduction of other contaminants, is to use
low entrance velocities. The flow should approach the screen in a laminar mode. A screen
can be placed on the end of the pump intake in a pressurized system. Cleaning of pump
intake screens can be accomplished using fixed spray bar with rotating screen, fixed screen
with rotating bar, or internal air-burst systems.
A positive method to reduce fish entry into submerged intake facilities is the velocity
cap. Figure 4.16 illustrates a horizontal cap on the top of the intake structure, which forces
all water to enter horizontally. Fish tend to swim against horizontal currents and avoid
the intake.
The Clackamas River Waste District (CRW) in Oregon operates a filtration water treat-
ment plant rated at 30 mgd (114 ML per day). Raw water is supplied to the plant via two
concrete caisson intake structures in the Clackamas River connected to a raw water pump
station inland. Original screening consisted of mesh traveling screens located at the pump
station wet well. CRW modified the intake structures to meet NOAA fisheries guidelines
set to protect salmonid fish listed under the Endangered Species Act. The modifications
entailed the installation of 42-in.-diameter (1.07-m) stainless steel T screens on each of
the intake caissons (Figure 4.17). The intake T screens are over 10 ft (3.0 m) long and
sized to meet 0.4 ft/s (12.2 cm/s) approach velocity requirements for salmonid fish pro-
tection, for a flow of 18 mgd (68 ML per day) each. Screen openings are 0.069 in. (1.75

~-- Velocity cap
I " " " ' I
111[12 ......... _ , I Horizontal
Ill r- \ ..... ,S, ,I ~111 inflow
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FIGURE 4.16 Velocity cap. (Courtesy of USFilter, Envirex Products.)