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Cascade Dam |
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Statistics |
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Power Generation Narration
Geology Cascade Dam is sited on igneous rock of granitic type, which generally is of fair quality, but there are numerous localized areas of poor quality. The rock `is light gray coarse-crystalline porphyritic granite and locally is gneissic. It is extremely sheared, conspicuously sheeted and jointed and zones of crushed rock are numerous. Much of the rock is hard, competent and relatively fresh. The dam embankment cutoff trench extends to bedrock and includes a concrete cutoff wall with footings in bedrock. A pressure grout curtain was placed to depth not exceeding 100 feet under the cutoff wall footings. An area of badly broken rock (by blasting) was consolidated with grout. Soils remaining in the embankment foundation upstream and downstream of the cutoff trench are mostly coarse-grained and bouldery, not types considered subject to liquefaction. The gated spillway structure and chute are in a rock cut on the right abutment. The outlet works intake structure and tunnel are on the right side. Foundation rock conditions for the spillway and outlet works are similar to rock described above. An inferred east-west trending fault has been mapped a short distance north on the left abutment. The dam is located within a notch in a bedrock ridge which is interpreted to be a tilted fault block nor an uplift block (horst) related to regional block faulting. The abutments upstream and downstream are natural bedrock slopes, which are stable. The excavated slope of rock adjacent to the spillway and outlet works is stable. None appear to be subject to landslides or rock falls. Basement igneous rocks enclose the basin, which makes the water holding capability of the reservoir satisfactory. Links | Recreation | Cascade Reservoir - Boat Ramp Elevations | | Dams Located by State | USBR Idaho Dams | Pacific Northwest Region Dams | | Owner: Bureau of Reclamation, Snake River Area Office - West, | Operator: Bureau of Reclamation, Snake River Area Office - West, | Top |
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