Whychus Creek fish screen now under construction

Last week, Three Sisters Irrigation District began pouring concrete for the new fish screen that will play a key role role in salmon and steelhead restoration on upper Whychus Creek. Marc Thalacker, TSID Manager, said that the pouring of the 140-foot slab is complete, and construction of the vertical walls should be finished this week.

"A company called Specialty Metal Fabricators will be coming from Portland the first week in March to start installing the metal screen," said Thalacker. "They have been fabricating it over the last couple of months."

The elaborate fish screen is an important part of a TSID project that is projected to save more than a billion gallons of Whychus Creek water every year. Over half the saved water will be returned to the creek to help mitigate the effects of irrigation use, and the remainder will augment irrigation demand.

The loss of fish into the irrigation system has long been a concern, and the new fish screening system is the best exclusion device ever attempted on the creek. The screen, to be installed in the new concrete structure, is fine enough to exclude even the smallest fish fry from the irrigation water.

When fish are drawn into the irrigation diversion, the device will separate them from the water flow before it enters the new four-and-a-half-foot irrigation system pipelines. The screen is positioned horizontally, so the fish will swim above it. The fish are then funneled into a separate pipe that will safely return them to the creek downstream of the diversion.

The water savings will be realized when the water passes through the new high-density polyethylene pipes instead of through the former open - and porous - canal. The fully enclosed pipelines replacing the old canal have already reached Highway 20, and Thalacker says the remaining pipes to reach the reservoir will be delivered and installed by the end of March.

Thalacker hopes to have the screen and associated structures completed by the first of April.

"We will continue to pour concrete through the month of March for the approach bays and the headwall for the new weir gate," he said.

The 140 feet that comprise the fish screen structure make up less than half the length of the entire diversion reconfiguration. With the head gate, approach bays, the weir and its gate, the entire complex will be longer than a football field.

He described the final design for the covering of the screening device as "still kind of a work in progress." An aesthetically suitable design is the goal, and TSID is working with the Forest Service to create the final look that will be a part of the forest and stream picture for many years to come.

Most of the major construction work is expected to be completed a full two weeks before irrigation season begins on April 15, but Thalacker said there will be plenty of finishing details to work on during that two-week period.

The fish screen project is at the upstream edge of a reach of Whychus Creek that underwent a major stream channel redesign last fall. More than 1,500 feet of the creek was reengineered and is now undergoing stream bank and riparian habitat regeneration. The final phase of the irrigation diversion and fish screen project will include further habitat restoration when construction is complete.