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Keechelus Dam |
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Statistics |
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Power Generation Narration
Geology Bedrock in the vicinity of the dam is rhyolite of the Naches Formation, which crops out on the left side of the spillway and provides the foundation for the spillway structure and the left abutment of the dam. Forming most of the foundation for the dam embankment are two Quaternary-age glacial units that extend across the Yakima River valley floor. The older and more extensive unit is Quaternary Glacial Drift, deposited in a terminal moraine to unknown depths. Quaternary Outwash Sediments overly a portion of the glacial drift and form the shallow foundation of the dam to the right of station 44+00, to a maximum known thickness of 42 feet. Both units are generally dense, as indicated by the majority of standard penetration test (SPT) blowcounts and crosshole shear wave velocities. Differentiation between the two units is principally based on percentage of gravel and oversize materials (which is higher in the glacial drift), and on density (indicated by field hand test, blowcounts, and shear wave velocities). The glacial drift seems to have a very low permeability, leading to the assumption the extensive seepage see downstream of the dam either passes through the outwash sediments, or along the contacts with either the embankment or the glacial drift. Miscellaneous Links | Current Reservoir Storage, plus other storage Units within the Yakima River Basin | Links | Recreation | | Dams Located by State | USBR Washington Dams | Pacific Northwest Region Dams | | Owner: Bureau of Reclamation, Upper Columbia Area Office, | Operator: Bureau of Reclamation, Upper Columbia Area Office, |
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