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Dry Falls Dam |
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Power Generation Narration
Geology Dry Falls Dam is located 43 km within the area underlain by the massive basalt flows of the Columbia Plateau lava. The flows dip gently to the north under most of the foundation, but rise to the west in a steep monocline. Jointing is closely spaced but tight in the flows. Fractures are irregular and wide spaced even in the rocks of the monocline. Interflow zones of various widths separate the flows. The site is in a wide, steep-walled valley cut in basalt. On a large scale, the floor appears quite flat, but in detail narrow channels as much as 18m deep are present and numerous rock knobs and closed basins dot the floor. Except in the channels where thick deposits of silt are present overburden is thin and swamp deposits cover many low areas. Except where zone 2 and 3 of the dam overlie deep channels all structures are founded on basalt. Deep layers of silt were left under zones 2 and 3 in the channel areas. At the damsite the rock has exceptional bearing strength and vertical permeability is very low. Horizontal permeability is low within the mass of the flow and ranges from low to high in the interflow zones. High water tables in the reservoir walls limit losses through the interflow zones. Other Dams or Dikes which enclose Banks Lake 1) North Dam Links | Dams Located by State | USBR Washington Dams | Pacific Northwest Region Dams | | Owner: Bureau of Reclamation, Grand Coulee Power Office, | Operator: Bureau of Reclamation, Grand Coulee Power Office, |
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