Ever wonder how they remove really big dams? Admit it, you have. I know I have. At 47 feet high, the Sandy River's Marmot Dam will be the largest dam ever removed in Oregon and the tallest removed in the Northwest in 40 years.
The process began in July 2007 with the construction of a shallow earthen "coffer" dam upstream from Marmot Dam. This step creates a dry work area and exposes the concrete dam for demolition crews.
The tunnel that takes water from Marmot Dam to the Little Sandy River will also be removed in 2007.
Actual dam deconstruction will be performed with large, pneumatic hammers connected to front-end loaders, equipment similar to that seen working on concrete roads.Demolition will continue throughout the summer, one piece at a time.
Once the concrete dam is removed, the coffer dam will be extended across the river, blocking the bypass channel. It will disappear when high water flows in the fall gradually wash it downstream, eventually restoring the river to its natural state.
Great care will be taken during demolition. PGE is working with the State Historic Preservation Office to protect any archaeological resources, while impact on riverbanks and vegetation will also be remedied to preserve the scenic beauty of one of Oregon's most beloved areas.
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