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Mossyrock, located in Toledo, Washington, is a public utility owned hydroelectric dam on the Cowlitz River.
Completed in 1968, this arch dam stands at 606 feet tall and has a storage capacity of 1.9 million acre-feet. With a primary purpose of generating hydroelectric power, the dam also serves flood risk reduction and recreation purposes.
Managed by the Federal Energy Regulatory Commission, Mossyrock is considered a high hazard potential dam with a very high risk assessment rating. The dam features a controlled spillway with a width of 170 feet and is equipped with four Tainter radial gates for regulating water flow. Despite its age, the condition assessment of Mossyrock is not available, highlighting the need for further inspection and maintenance to ensure its safety and functionality.
As a key structure in the region, Mossyrock plays a vital role in water resource management and climate resilience efforts. With its strategic location and impressive engineering, the dam stands as a testament to the importance of sustainable water infrastructure in the face of changing environmental conditions.
Year Completed |
1968 |
Dam Length |
1750 |
Dam Height |
366 |
River Or Stream |
Cowlitz River |
Primary Dam Type |
Arch |
Hydraulic Height |
528.5 |
Drainage Area |
1042 |
Nid Storage |
1900000 |
Structural Height |
606 |
Outlet Gates |
Tainter (radial) - 4 |
Hazard Potential |
High |
Foundations |
Rock |
Nid Height |
606 |
| Location | Reservations | Toilets |
|---|---|---|
Main Campground
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Mossyrock Park - Tacoma Power
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S'mores Loop
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Riffe Lake Campground
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Ike Kinswa State Park
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Mayfield Lake - Tacoma Power
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Mount St. Helens National Volcanic Monument Boundary To Mount St. Helens National Volcanic Boundary In Sw 1/4 Of Sec 32, T11N, R5E
Headwaters In Sw1/4 Sec 28, T9N, R5E To Mount St. Helens National Volcanic Monument Boundary
Goat Rocks Wilderness Bounday To Cowlitz Falls Ferc Project Boundary In Ne1/4 Of Nw1/4 Of Sec 4, T11N, R6E
Mount St. Helens National Volcanic Monument Boundary To To Point River Reenters Mshnvm In Se 1/4 Of Sec 11, T10N, R5E
Headwaters In Se1/4 Of Sec 31, T10N, R6E To Mount St. Helens National Volcanic Monument Boundary
Nw1/4 Of Sec 21, T11N, R8E To Confluence With Cispus River