SWEET HOME — A new fish weir the Army Corps of Engineers is installing at the Foster Dam spillway is designed to enhance the passage of young Chinook salmon and winter steelhead into the South Santiam River, according to biologist Fenton Khan.
The weir is scheduled to be put into place Tuesday and will replace one constructed in 1984 that is inefficient by today’s standards.
“The old weir was used from 1984 until 2012,” Khan said. “In 2008, we received the NOAA (National Oceanic and Atmospheric Administration) biological opinion that put a priority on improving fish passage.”
Khan said the Corps of Engineers initiated fish passage research in 2012. Balloons and radio transmitters were attached to young fish that traveled through the generator turbines at Foster Dam to determine their likelihood of survival.
“We found that there was extensive damage,” he said. “We studied both low- and high-level reservoir pools and the data showed we needed a new weir.”
Khan said the old weir was designed to work with water flows less than 250 cubic feet per second. At that rate, young fish often choose a route with faster water, which was through the turbines. If they did go through the weir, their cushion of water over the dam face itself was only a few inches.
The new weir will operate at up to 800 cubic feet per second, attracting fish away from the turbines and provide at least two feet of water cushion for the young fish as they make their way over the dam and into the South Santiam River.
Khan said the project would not be possible without the cooperation of Linn County Parks Director Brian Carroll, as well as the cities of Albany and Lebanon.
“We have had to keep the water level down about two feet lower than normal for the last five years,” he said. “We know recreation is a big thing, and Brian had to extend boat docks to deal with the lower water levels.”
Khan said the cities of Albany and Lebanon allowed the Corps of Engineers to install research equipment in the river.
The new weir project cost about $400,000, according to structural engineer Tyler Magill. The weir is 47 feet wide, 10 feet tall and 3 feet, 7 inches deep.
Unlike Detroit Dam, no mixing tower is planned at Foster or Green Peter dams, Khan said. A mixing tower mixes water from various depths and temperatures in the reservoir, providing a more stable water temperature for fish survival.
“The water in Foster is already cooler than at Detroit, because Foster is a regulating dam for Green Peter,” Khan said.
Once the weir is operational, he added, the Corps of Engineers will continue to collect data to determine the project's effectiveness.
“The number of returning winter steelhead was extremely low last year,” Khan said.
Khan said that in the past, there were an estimated 700 or more returning adult winter steelhead at the dam, but last year, the number was estimated in the dozens.
In 2014, a new $14 million adult fish passage system became operational at the dam. The new facility reduced the amount of manual labor needed to move the adult fish above the dam and greatly reduced the need to touch the fish, which can harm them.
Khan pointed out that adult salmon travel back to their birth place to lay eggs and then die. But steelhead will travel back to the ocean after laying their eggs.
“They are tired and haven’t eaten in months,” Khan said. “We need to get them back to the ocean as quickly as possible.”
Bagikan Berita Ini
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