Mossyrock Dam facts for kids
Quick facts for kids Mossyrock Dam |
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Mossyrock Dam
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| Location | Lewis County, Washington, USA |
| Coordinates | 46°32′4″N 122°25′43″W / 46.53444°N 122.42861°W |
| Construction began | 1965 |
| Opening date | 1968 |
| Construction cost | $117,769,400 |
| Operator(s) | City of Tacoma |
| Dam and spillways | |
| Type of dam | Concrete, arch-gravity |
| Impounds | Cowlitz River |
| Height | 606 feet (185 m) |
| Length | 1,648 feet (502 m) |
| Spillway type | Service, gate-controlled |
| Reservoir | |
| Creates | Riffe Lake |
| Total capacity | 1,685,000 acre-feet (2.08 km3) |
| Catchment area | 1,042 square miles (2,700 km2) |
| Surface area | 11,830 acres (4,790 ha) |
The Mossyrock Dam is a huge concrete dam on the Cowlitz River in Washington state. It's located near the town of Mossyrock in Lewis County. This dam creates a large body of water called Riffe Lake.
The main job of Mossyrock Dam is to make electricity using the power of water. It also helps to control floods in the area. This dam is the tallest in Washington State. Its power station creates about 40% of the electricity used by Tacoma Power, which is a big energy provider.
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Building the Mossyrock Dam
Planning for the Mossyrock Dam started way back in the 1940s. However, there was some disagreement about building it. Local fishers and the Washington State's Fish and Wildlife Department were concerned about its impact.
During World War II, the city of Tacoma, Washington had to buy electricity from other places. This was very expensive. To make its own power, Tacoma City Light (now called Tacoma Power) decided to build several dams.
Early Challenges and Approval
Plans for the Mossyrock Dam were announced in 1948. But many people were against it. The Washington State Legislature even made the Cowlitz River a special "fish sanctuary." This rule initially stopped the dam project.
Tacoma City Light took the issue to court. The case even went to the US Supreme Court three times! After these legal battles, the dam's construction was finally approved.
Construction and First Power
Building the Mossyrock Dam began in 1965. It took three years to complete, finishing in 1968. On October 13, 1968, the dam's power plant started making electricity for the very first time.
Before the dam's waters rose to form Riffe Lake, several towns had to be moved. These towns included Riffe, Nesika, and Kosmos.
How the Power Plant Works
The Mossyrock Dam's power plant has two large Francis turbine generators. These generators use the flowing water to create electricity. Each generator can produce 150 megawatts (MW) of power. This means the plant can make a total of 300 MW.
The water that spins these turbines comes through three large pipes called penstocks. These pipes are between 248 and 285 feet long. One of the three penstocks is not used right now. It's ready for a third turbine to be added in the future.
Power Plant Upgrades
In 2006, a company called GE Energy was chosen to make the two turbines even better. This project cost $50 million. It involved replacing important parts like the turbines themselves, the stators, wicket gates, and transformers.
The first upgraded generator started working in 2009. The second one was finished in late 2010. These upgrades increased the total power capacity by 70 MW. This means the plant can now turn nearly 95% of the water's energy into electricity.
