The screening facility houses ten rotary drum screens with axes parallel to the length of the structure. Each screen is about 3.7 m (12 ft) long and 1.7 m (5.5 ft) in diameter. Screen mesh openings are 3.2 mm (1/8 in.). Water depth in the forebay is maintained at about 1.3 m (4.2 ft). The fish bypass is located in the flow control structure at the downstream end of the screening facility. Water and fish diverted past the front of the screens pass through the fish bypass and out the fish return pipe. Flow through the fish bypass is 0.6 m3/sec (20 cfs).
The drum screens are installed at a 26-degree angle to canal flow. This angle provides a sweeping-velocity-to-approach-velocity ratio equal to or exceeding 2:1. The maximum allowable approach velocity is 0.15 m/sec (0.5 fps). Screen orientation and flow velocity differential help direct fish to the fish return pipe and back to the river.
Figure 1. Flow Control Structure and Fish Bypass System in the Town Canal Fish Screening Facility