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Klamath Dams: Sediment studies being formulated

by David Smith, Siskiyou Daily News 7/15/09

Siskiyou County, Calif. - The sediment behind dams along the Klamath River should soon be tested to answer questions from all sides of the issue on whether or not the dams will be taken out as part of an agreement in principle reached by dam owner PacifiCorp and a number of stakeholders and stakeholder groups, according to Dave Gore, project manager for the Klamath with the Bureau of Reclamation.

Gore said in an interview Tuesday that the sediment studies are still in the formative phase, during which he will work with PacifiCorp, the Environmental Protection Agency (EPA) and others to develop a framework, which will determine the substances that will be tested for and the areas that will be tested, along with other details.

Although the studies are not yet finalized, Gore described general protocols for sediment studies. He said that the sampling essentially involves taking a barge over the area being tested and “core”?samples are taken from the sediment. He added that the substance being tested for will dictate how it must be handled; for example, some samples may have to be frozen on site with dry ice before being sent to the lab.

Asked what the number and distribution of samples would be, Gore said that he and his agency will be working with the EPA?and its Corps of Engineers to determine those aspects of the study, but those have not yet been determined.

“We’ll be trying to distribute the sampling so it is representative of where the sediment is,”?Gore said, explaining that while the sampling can show the spatial locations of toxins if they exist, it will not be possible to determine everywhere the toxins may be.

Gore stated that even though the testing can not give a complete picture of where the toxins may be, it can reveal what possible problems exist if the sediment is released. He also said that determining where the toxins are also depends on the type of toxin, as some may latch on to sediment particles, while others disperse naturally.

Asked how accurate the sampling is for showing whether or not toxins are present, Gore said that that number typically depends on the type of toxin tested for because different tests have differing levels of accuracy.

Gore said that toxins will not be the only aim of the study, which will also include an approximation of the volume of sediment behind the dams.

According to Gore, the group will be using bathymetry, the measurement of the depth of large bodies of water, in its attempt to calculate the volume. He explained that in order to get a more accurate estimate, an attempt must be made to differentiate the accumulated sediment from the alluvial material that makes up the original lake bed.

Gore said that once the sediment level and the alluvial level have been determined, a computer model can be used to calculate the volume, and he said that he would like to make three-dimensional models for a visual image of what the sediment buildup might actually look like.

Ultimately, Gore said, the studies are to determine what will happen to the river during dam removal. As the studies become more clearly defined, the Siskiyou Daily News will cover the aspects that have yet to be determined.

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