Returning fall salmon and steelhead now have freshly laid spawning beds awaiting them near the base of Lewiston Dam on the Trinity River.

The Trinity River Coarse Sediment Injection Project, funded by the Trinity River Restoration Program in cooperation with the U.S. Forest Service and the Bureau of Reclamation, was completed Friday, according to a news release.

The project placed coarse sediment a quarter- to 5-inch-diameter gravel downstream of Lewiston Dam near the Trinity River Hatchery.

More than 2,500 tons of rock were spread over 1,000 feet of the Trinity River during the three-week period beginning July 27.

“Gravel is a key requirement for sustainable fish habitat,” said Shasta-Trinity National Forest Fisheries Biologist Bill Brock. “Gravel beds within a stream provide important spawning areas for salmon and steelhead.”

This project goal was to increase useable spawning habitat and spawning and egg incubation success for juvenile steelhead and salmon, in addition to improving the river’s hydrodynamics.

The downstream dam area is just one of several gravel sites identified in the Trinity River Flow Evaluation Report where the river channel will receive additional coarse sediment input, according to the release.

Since the completion of the Trinity Division of the Central Valley Project in the early 1960s, water released from Lewiston Dam has gradually removed coarse sediment up to 5 inches in width from the river downstream.

Without the injection of coarse sediment, soil particles in the Trinity River can cover spawning areas, smothering fish eggs, aquatic insects and oxygen-producing plants, according to the release.

Additionally, suspended soil in a stream will increase water temperatures, reduce light penetration and plant growth and affect the ability of fish to locate and capture prey by greatly reducing visibility. Salmon and steelhead can die from the abrasive, gill-clogging effects of suspended soil, which interferes with their breathing.