Garco Construction Inc., of Spokane, has won a $48.3 million contract through the U.S. Army Corps of Engineers to construct improvements on a Snake River dam to increase survival rates of juvenile salmon in their migration toward the Pacific Ocean, says Tim Loucks, the project manager for Garco.

The project will take place at Lower Granite Dam, which is about 40 miles west of Lewiston on the Snake River, 107 miles from the Snake’s confluence with the Columbia River, and a total of 460 river miles from the ocean.

Loucks says the project will have two main components. One component will include widening the fish-collection channel inside the dam, he says, and the other will include modifying the system that routes fish to a holding area called the juvenile fish facility.

Seagoing smolts, which include young chinook and sockeye salmon and steelhead, currently are diverted away from the dam turbines into a nearly vertical shaft which carries them via a pressurized system through a 1,700-foot underground channel that upwells into the juvenile fish facility below the dam.

The construction project will eliminate the underground system and replace it with an elevated flume that will carry smolts at a more gradual incline to the juvenile fish facility on the south bank of the river, Loucks says.

The construction project is a product of a biological opinion issued by the National Marine Fisheries Service that calls for fishery improvements at Snake and Columbia river dams to enhance survival rates and aid in the recovery of endangered salmonid species.

The National Marine Fisheries Service estimated in 2010 that the combined survival rate of transported and in-river fish through the eight dams and reservoirs on the lower Snake and Columbia rivers was 69 percent for chinook salmon and 74 percent for steelhead.

Loucks says construction will begin Dec. 15, and the deadline to complete the project is Feb. 28, 2017.

Garco will have about 35 employees on the site, and subcontractors likely will have another 35 to 40 workers there.

The Army Corps of Engineers describes the Lower Granite juvenile fish bypass system as the first and most critical facility smolts face in their journey toward the ocean. The Army Corps also operates juvenile fish collection facilities downstream from Lower Granite at Little Goose and Lower Monumental dams on the Snake River and McNary Dam on the Columbia River.

From the juvenile fish facility, smolts will be discharged into the river downstream from the dam or will be barged 400 miles downstream and released below Bonneville Dam, about 46 miles from the Pacific Ocean in the Columbia River.

Loucks says the contract is one of the largest Garco has landed in recent years.

“This is a market we’re paying a bit more attention to now,” he says. “A lot of features are similar to a water treatment plant work, which we’ve done a fair amount of.”