Union Gap

The Union Gap canal diversion (approximately 50 cfs) is located on the left bank of the Yakima River about 1.5 miles downstream of the Naches River confluence near Yakima, Washington. The fish screens are located on the canal, about 1/2 mile downstream from the diversion. The current Union Gap fishscreen facility (improved during the 1995 and 1996) replaces a drum screen that did not meet design criteria for the protection of juvenile anadromous fish during canal diversions.

The facility now consists of four vertical flat plate screen panels, each 5 feet high by 11 feet long. The screens are constructed of 0.069-inch (1.75-mm) wedge wire fabric placed with slots oriented vertically. Control baffles installed immediately downstream of these panels allow flows to be regulated to maintain uniform approach velocities.

A mechanical cleaning brush moves back and forth over the length of the screen to keep the screen free of debris.

The bypass entrance channel is a full-depth, 18-inch wide rectangular channel that is 10 feet long. An adjustable weir gate at the end of this channel controls flows that then drop into an angled downwell with sections that are 3 feet wide by 4.5 feet long and 3 feet wide by 5 feet long. Bypass flows are then conveyed through a 15-inch diameter PVC pipe for 153 feet to the Roza Wasteway.