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What the dams trapped
Conservancy to weigh Klamath sediment study
Hydropower dams on the Klamath River have been holding back much of the upper river's share of sediment since 1918, when Copco Dam was built.
Some 15.2 million cubic yards of sediment -- almost enough to build a foot bridge 1 cubic yard thick from San Francisco to Tokyo -- sit behind the six dams. The Federal Energy Regulatory Commission is considering relicensing the dams owned by Pacificorp, and a parallel settlement process aims to hash out an agreement.
Many in that process, including tribes, fishing interests and downstream communities, want the dams removed, since they block salmon and other fish from about 300 miles of spawning grounds. For the tribe and others who rely on salmon -- which once numbered between 650,000 to 1 million in the Klamath -- the stakes are high.
Removing some dams would send huge amounts of sediment downstream. But while the amount behind the dams is known, its exact size and composition is not.
Now the California Coastal Conservancy may authorize $350,000 to study whether the sediment is mostly silty, sandy or rocky, and whether pollutants like PCBs are mixed into it. A huge slug of silt could smother spawning beds, while large amounts of pollutants could contribute to the river's already poor water quality.
"It's great to dream about dam decommissioning, but what does that really mean?" said Michael Bowen, a coastal conservancy project manager. "Would you be able to release it, or would you have to truck it out? Is it clean?"
The need for the information is urgent. An understanding of the quality of the sediment behind the dams will likely factor into settlement talks, and a draft environmental impact statement is due on the relicensing alternatives in June of 2006.
Yurok Tribe senior fisheries biologist Dave Hillemeier called the type of study being proposed essential to understand what it will take to decommission the dams.
"When you take out dams there's going to be some ramifications downstream," Hillemeier said. "I see these studies as a step in the process of taking out the dams to improve fish and water quality."
The State Water Resources Control Board has identified the information that would be gleaned by the study as the most significant gap in understanding dam removal on the Klamath. Pacificorp can't get its license renewed -- it expires in March -- without a water quality certification from the board.
Bowen hopes to have the drilling and coring of sediments behind the dams completed this summer. The conservancy is expected to approve the item, and the National Marine Fisheries Service would make a $50,000 in-kind contribution.
The conservancy meeting is Thursday at 10 a.m. in Oakland at the Trudeau Training Center.
The board will also consider:
* Authorizing $433,000 to the Mattole Restoration Council for watershed improvement work in the Mattole River.
* Allotting $270,000 to Trinity County to prepare new fish passage projects for the Five Counties Salmon Restoration Program.
Page Updated: Thursday May 07, 2009 09:14 AM Pacific
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