Harcon Inc., of Spokane, has been awarded a $3.6 million contract by the U.S. Army Corps of Engineers to improve the juvenile fish bypass system at Little Goose Dam on the lower Snake River. The work is scheduled to start this month, with the bulk of it expected to be completed by March.

Gina Baltrusch, a Corps spokeswoman in Walla Walla, says Harcon will install a passive integrated transponder (PIT) tag-detection system that will pick up readings from PIT tags in juvenile fish in a bypass flume that extends through the dam. PIT tags are injected into fish so they can be monitored as they move downriver.

In the past, she says, the number of juvenile fish traveling through the bypass flume was known only when water in the bypass flume was diverted through a fish facility at the dam, although that can put additional stress on the fish as they migrate to the sea.

"When the system is installed, the movement of juvenile fish migrating downstream will be detected year-round, not just during the peak migration season, and can be used to double check the PIT tag detection in the fish facility," Baltrusch says. "It will fill in a data gap at the dam to locate previously undetected fish that were detected downstream of Little Goose, but it was unknown how or when they passed through the Little Goose Dam."

Harcon also will modify a dewatering structure for the bypass flume, including replacing some valves in it, and will install access ladders to improve operator access to the valves, she says.

The dewatering structure is a critical part of the bypass system that reduces a high volume of water flow to a manageable volume for the juvenile fish facility, she says.

Also, Harcon will relocate and extend the river outlet location of the fish bypass flume outfall on the downstream side of the dam, with the intention of reducing the loss of juvenile salmon and steelhead there to predators, she says.

The Corps did the design work for the PIT tag detection system and extension of the bypass flume outfall, Baltrusch says. HDR Engineering Inc., of Omaha, Neb., assisted the Corps with the design work on the dewatering system modifications, she says.

Baltrusch says the Corps saved about $79,000 by hiring one contractor to do all the work, reducing mobilization costs needed if separate contractors were used.

"The work on each of these projects all came together in the same timeframe, and since all of the work affected the bypass flume, it made a lot of sense to use just one contractor to coordinate all of the work," she says.