Mossyrock Dam
Encyclopedia
Mossyrock Dam is a concrete
arch-gravity dam
on the Cowlitz River
near Mossyrock
in Lewis County
, Washington. The reservoir created by the dam is called Riffe Lake
and the primary purpose of the dam is hydroelectric production while flood control
is secondary. The dam is the tallest in Washington State and its hydroelectric
power station supplies 40% of Tacoma Power
's electricity.
, the city of Tacoma purchased its electricity from the Bonneville Power Administration
and Seattle which would cost as much as $1 million a year. To generate its own electricity, Tacoma City Light, now known as Tacoma Power would build several dams including the Mossyrock Dam. Plans for the Mossyrock Dam were announced in 1948 but met stiff opposition. The Washington State Legislature
enacted a fish sanctuary on the Cowlitz River that initially blocked the project. The City of Tacoma then went to court and after the case was before the U.S. Supreme Court three times, 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.
hydroelectric generators
totaling a 300 MW capacity. The generators are fed by three penstock
s ranging from 248 – 285 ft. feet long. One of the three penstocks is unused as the plant has an additional space for one more generator.
was selected to upgrade both of the power plant's generators. The $50 million dollar project includes replacing the turbine
s, stator
s, wicket gate
s and transformer
s among other improvements. Installation of the first generator began in 2008 and was completed and commissioned in 2009. The second generator was completed in later 2010. The power plant upgrade will increase the total capacity by 70 MW and it should operate around 95% efficiency.
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...
arch-gravity dam
Arch-gravity dam
An arch-gravity dam, curved-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 against the canyon rock walls, providing the force to compress the dam...
on the Cowlitz River
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....
near Mossyrock
Mossyrock, Washington
Mossyrock is a city in Lewis County, Washington, United States. The population was 759 at the 2010 census.-History:The city began as a trading post named Mossy Rock in 1852, after a high moss-covered rock at the east end of Klickitat Prairie...
in Lewis County
Lewis County, Washington
Lewis County is a county located in the U.S. state of Washington. As of 2010, the population was 75,455. The county seat is at Chehalis, and its largest city is Centralia....
, Washington. The reservoir created by the dam is called Riffe Lake
Riffe Lake
Riffe Lake is a long reservoir on the Cowlitz River in the U.S. state of Washington. Originally named Davisson Lake, it was created in 1968 with the construction of Mossyrock Dam. The lake was renamed in 1976 after the community of Riffe, which was inundated by the lake....
and the primary purpose of the dam is hydroelectric production while flood control
Flood control
In communications, flood control is a feature of many communication protocols designed to prevent overwhelming of a destination receiver. Such controls can be implemented either in software or in hardware, and will often request that the message be resent after the receiver has finished...
is secondary. The dam is the tallest in Washington State and its hydroelectric
Hydroelectricity
Hydroelectricity is the term referring to electricity generated by hydropower; the production of electrical power through the use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy...
power station supplies 40% of Tacoma Power
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, Fircrest, University Place, and Fife, and also provides service to parts of Steilacoom, Lakewood and unincorporated Pierce County...
's electricity.
History
The Mossy Rock Dam was originally planned in the 1940s but opposition from local fishers and Washington State's Game Department delayed construction. During World War IIWorld War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
, the city of Tacoma purchased its electricity from the Bonneville Power Administration
Bonneville Power Administration
The Bonneville Power Administration is an American federal agency based 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 construct facilities necessary to transmit that power...
and Seattle which would cost as much as $1 million a year. To generate its own electricity, Tacoma City Light, now known as Tacoma Power would build several dams including the Mossyrock Dam. Plans for the Mossyrock Dam were announced in 1948 but met stiff opposition. The Washington State Legislature
Washington State Legislature
The Washington State Legislature is the state legislature of the U.S. state of Washington. It is a bipartisan, bicameral body, composed of the lower Washington House of Representatives, composed of 98 Representatives, and the upper Washington State Senate, with 49 Senators.The State Legislature...
enacted a fish sanctuary on the Cowlitz River that initially blocked the project. The City of Tacoma then went to court and after the case was before the U.S. Supreme Court three times, 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.
Power plant
The Mossyrock Dam's power plant contains 2 x 150 MW Francis turbineFrancis turbine
The Francis turbine is a type of water turbine that was developed by James B. Francis in Lowell, Massachusetts. It is an inward-flow reaction turbine that combines radial and axial flow concepts....
hydroelectric generators
Electrical generator
In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric charge to flow through an external electrical circuit. It is analogous to a water pump, which causes water to flow...
totaling a 300 MW capacity. The generators are fed by three penstock
Penstock
A penstock is a sluice or gate or intake structure that controls water flow, or an enclosed pipe that delivers water to hydraulic turbines and sewerage systems. It is a term that has been inherited from the technology of wooden watermills....
s ranging from 248 – 285 ft. feet long. One of the three penstocks is unused as the plant has an additional space for one more generator.
Power plant upgrade
In 2006, GE EnergyGê
Gê are the people who spoke Ge languages of the northern South American Caribbean coast and Brazil. In Brazil the Gê were found in Rio de Janeiro, Minas Gerais, Bahia, Piaui, Mato Grosso, Goias, Tocantins, Maranhão, and as far south as Paraguay....
was selected to upgrade both of the power plant's generators. The $50 million dollar project includes replacing the turbine
Turbine
A turbine is a rotary engine that extracts energy from a fluid flow and converts it into useful work.The simplest turbines have one moving part, a rotor assembly, which is a shaft or drum with blades attached. Moving fluid acts on the blades, or the blades react to the flow, so that they move and...
s, stator
Stator
The stator is the stationary part of a rotor system, found in an electric generator, electric motor and biological rotors.Depending on the configuration of a spinning electromotive device the stator may act as the field magnet, interacting with the armature to create motion, or it may act as the...
s, wicket gate
Wicket gate
A wicket gate is a small gate or door, particularly one built into a larger one. The cricket term "wicket" comes from this usage. The term wicket gate is also used in English to refer to automatic ticket barriers or older staffed ticket gates on Japan's railway network...
s and transformer
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field...
s among other improvements. Installation of the first generator began in 2008 and was completed and commissioned in 2009. The second generator was completed in later 2010. The power plant upgrade will increase the total capacity by 70 MW and it should operate around 95% efficiency.