Mossyrock Dam is a

concrete Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wi ...

arch-gravity dam An arch-gravity dam or arched dam is a dam with the characteristics of both an arch dam and a gravity dam. It is a dam that curves upstream in a narrowing curve that directs most of the water pressure against the canyon rock walls, providing the ...

on the

Cowlitz River The Cowlitz River is a river in the state of Washington in the United States, a tributary of the Columbia River. Its tributaries drain a large region including the slopes of Mount Rainier, Mount Adams, and Mount St. Helens. The Cowlitz has a ...

near Mossyrock in Lewis County,

Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered o ...

. The reservoir created by the dam is called Riffe Lake and the primary purpose of the dam is hydroelectric production while

flood control Flood control methods are used to reduce or prevent the detrimental effects of flood waters."Flood Control", MSN Encarta, 2008 (see below: Further reading). Flood relief methods are used to reduce the effects of flood waters or high water level ...

is secondary.Mossyrock Dam
, NPDP Dam Directory The dam is the tallest in Washington State and its

hydroelectric Hydroelectricity, or hydroelectric power, is electricity generated from hydropower (water power). Hydropower supplies one sixth of the world's electricity, almost 4500 TWh in 2020, which is more than all other renewable sources combined and ...

power station supplies 40% of

Tacoma Power Tacoma Power is a public utility providing electrical power to Tacoma, Washington and the surrounding areas. Tacoma Power serves the cities of Tacoma, University Place, Fircrest, and Fife, and also provides service to parts of Steilacoom, L ...

's electricity.

History

Planning for the Mossyrock Dam began in the 1940s but opposition from local fishers and Washington State's Fish and Wildlife Department delayed construction. During

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

, the city of

Tacoma, Washington Tacoma ( ) is the county seat of Pierce County, Washington, United States. A port city, it is situated along Washington's Puget Sound, southwest of Seattle, northeast of the state capital, Olympia, Washington, Olympia, and northwest of Mount ...

purchased its electricity from the

Bonneville Power Administration The Bonneville Power Administration (BPA) is an American federal agency operating in the Pacific Northwest. BPA was created by an act of Congress in 1937 to market electric power from the Bonneville Dam located on the Columbia River and to cons ...

and from

Seattle Seattle ( ) is a seaport city on the West Coast of the United States. It is the seat of King County, Washington. With a 2020 population of 737,015, it is the largest city in both the state of Washington and the Pacific Northwest regio ...

, with costs of up to $1 million/year. To generate its own electricity, Tacoma City Light (now Tacoma Power) built several dams, including the Mossyrock Dam. Plans for the Mossyrock Dam were announced in 1948 but met stiff opposition. The

Washington State Legislature The Washington State Legislature is the state legislature of the U.S. state of Washington. It is a bicameral body, composed of the lower Washington House of Representatives, composed of 98 Representatives, and the upper Washington State Senat ...

enacted a fish sanctuary on the Cowlitz River that initially blocked the project. Tacoma City sued, with its suit being raised to the

US Supreme Court The Supreme Court of the United States (SCOTUS) is the highest court in the federal judiciary of the United States. It has ultimate appellate jurisdiction over all U.S. federal court cases, and over state court cases that involve a point of ...

a total of three times. After that, construction of the dam was approved. Construction began in 1965 and ended in 1968. On October 13, 1968, the dam's power plant generated its first electricity. Several towns were forced to evacuate ahead of the rising dam waters including Riffe, Nesika, and Kosmos. Tacoma City Light originally proposed naming the facility the "Homer T. Bone Dam", in honor of Senator

Homer Bone Homer Truett Bone (January 25, 1883 – March 11, 1970) was an American attorney and politician in Washington state, where he settled in Tacoma, Washington, Tacoma as a youth with his family from Indiana. He ran as a candidate for a variety of par ...

of Tacoma.

Power plant

The Mossyrock Dam's power plant contains two

Francis turbine The Francis turbine is a type of water turbine. It is an inward-flow reaction turbine that combines radial and axial flow concepts. Francis turbines are the most common water turbine in use today, and can achieve over 95% efficiency. The proces ...

generators, each rated at 150 MW, or 300 MW total capacity. They are fed by three

penstock A penstock is a sluice or gate or intake structure that controls water flow, or an enclosed pipe that delivers water to hydro turbines and sewerage systems. The term is inherited from the earlier technology of mill ponds and watermills. H ...

s ranging from 248 – 285 feet in overall length. One of the three penstocks is presently unused, awaiting possible future installation of a third turbine.

Power plant upgrade

In 2006,

GE Energy GE Power (formerly known as GE Energy) is an American energy industry, energy technology company, owned by General Electric. Structure As of July 2019, GE Power is divided into the following divisions: * GE Gas Power (formerly Alstom Power, Als ...

was selected to upgrade the two turbines. The $50 million project included replacing the

turbine A turbine ( or ) (from the Greek , ''tyrbē'', or Latin ''turbo'', meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced by a turbine can be used for generating ...

s, stators,

wicket gate A wicket gate, or simply a wicket, is a pedestrian door or gate, particularly one built into a larger door or into a wall or fence. Use in fortifications Wickets are typically small, narrow doors either alongside or within a larger castle or ...

s and

transformer A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits. A varying current in any coil of the transformer produces a varying magnetic flux in the transformer' ...

s. Installation of the first generator began in 2008; it began operation in 2009. Replacement of the second generator was completed in late 2010. The power plant upgrade increased the total capacity by 70 MW, with an expected overall

energy conversion efficiency Energy conversion efficiency (''η'') is the ratio between the useful output of an energy conversion machine and the input, in energy terms. The input, as well as the useful output may be chemical, electric power, mechanical work, light (radia ...

of near 95 percent.

References

External links

''Tacoma News Tribune'' video of the Mossyrock Dam's power plant rebuild
{{Use mdy dates, date=December 2018 Dams in Washington (state) United States power company dams Hydroelectric power plants in Washington (state) Buildings and structures in Lewis County, Washington Arch-gravity dams Dams completed in 1968 Energy infrastructure completed in 1968 Tacoma Public Utilities

History

Power plant

Power plant upgrade

See also

References

External links