Seattle Municipal Light and Power Plant facts for kids

Quick facts for kids
Seattle Municipal Light and Power Plant
U.S. National Register of Historic Places
Cedar Falls crib dam, 1903
Location in Washington (state)
Location	20030 Cedar Falls Rd. SE, North Bend, Washington
Area	88 acres (36 ha)
Built	1904 (1904)
Built by	City of Seattle Engineering Dept.
Architectural style	industrial vernacular
NRHP reference No.	97001077
Added to NRHP	September 11, 1997

The Seattle Municipal Light and Power Plant, also known as the Cedar Falls Historic District, is a special place near North Bend, Washington. It's a hydroelectric plant that uses water power to make electricity. This plant was the very first power station owned by the public in Seattle. It was also one of the first of its kind for a city Seattle's size in the whole country! Because of its importance, it was added to the National Register of Historic Places in 1997.

Seattle grew super fast between 1880 and 1910, from 3,500 people to 237,000! The city needed a lot more power for everyone. At first, electricity was used for streetlights and electric trains. Later, homes and businesses also got electricity for lights and appliances. The Cedar Falls plant started by making 3,500 kilowatts of power. By 1910, it could make 13,500 kilowatts, and later even 40,000 kilowatts! This meant Seattle residents paid some of the lowest electricity prices in the country. It was much cheaper than what private companies charged.

What Makes Up the Cedar Falls Plant?

This historic area is inside the Cedar River Watershed. This watershed provides two-thirds of all the drinking water for Seattle! A long power line, about 37 miles, connects the power station to Seattle. The main parts of this historic district are the big masonry dam, built in 1914, and the power-generating station, added in the 1920s. There was also a company town where workers lived. Some newer buildings are there now, but they aren't part of the original historic site.

How Was the Dam Built?

The very first part of the hydroelectric system was a timber crib dam built in 1902. A crib dam is like a big wooden box filled with rocks. This one was 250 feet long. Later, in the 1980s, this old crib dam was used to help build a much bigger masonry dam. It took four years to build the new masonry dam. This dam was 215 feet tall and almost 1,000 feet wide! After the new dam was finished, the old crib dam was taken apart.

City engineer Reginald H. Thomson even built a sawmill near the lake. This mill cut about 2 million board feet of lumber. This wood was used to build the dam and other parts of the plant. In 1903, the natural level of Cedar Lake was raised 18 feet, creating a reservoir (a big storage area for water). A second reservoir, Masonry Pool, was made when the big masonry dam was built in 1914. Cedar Lake was later renamed Chester Morse Lake to honor a long-time water department superintendent.

The Power Plant Buildings

The area for the power plant was cleared in 1902. The first plant had a powerhouse made of wood with seven sections. Behind it was the transformer house, built from concrete and stone. This building held nine transformers, which change the voltage of electricity. A switch house, also made of concrete and stone, was behind the transformer house. There was also a wooden workshop. An oil house on a hill above the plant sent oil to the transformers using gravity.

By 1908, the plant grew even bigger. They added a second pipeline for water, two larger generators, and two more turbines (machines that spin to make power). A second power line to Seattle was also added. The powerhouse was made larger, about 50 by 200 feet, to hold all the new equipment. A second switch house was also built.

Employee cottages

The Company Town at Cedar Falls

In 1908, the early construction camp had a kitchen, a dining hall, bunkhouses, small cottages, and a foreman's house. Camp Two was set up in 1911 and housed about 200 workers when construction was busiest. It continued to house employees and loggers until the 1930s, even after a big forest fire in 1922 burned many buildings. In 1912, two bungalow-style dorms and a boarding house replaced the old bunkhouse and dining areas. The streets of the City Light company town had special streetlights with five globes. In the 1910s, a gym with a pool was built near the community gardens.

Over time, machines took over many jobs, so fewer employees were needed on-site. Houses and other buildings were removed in the 1960s as the number of workers decreased. By 1996, only three homes and two large garages were left. The Cedar River Watershed Education Center started construction in 2000. Today, the City of Seattle owns and runs the power plant. The Seattle Water Department owns and runs the townsite.

Important Historic Parts of the Plant

Many parts of the hydroelectric plant are considered important to its history:

• The big masonry dam, built between 1912 and 1914.
• The controlling gate house, built in 1914.
• The power tunnel, built between 1912 and 1914.
• The penstock valve house (also called the lower gate house), built in 1914.
• An open concrete arch bridge, built in 1914.
• The penstocks (large pipes that carry water to the turbines) and their supports, built in the 1920s.
• Early penstock piers (supports) from 1904-1908.
• The foundations of the powerhouse, built in 1904.
• The concrete powerhouse itself, built between 1921 and 1928.
• The concrete transformer house, built in 1904.
• The stone switch house, built in 1908.
• The City Light building, built in 1932.
• Foundations for the transformer and switch yards, from around 1920.
• Three early penstocks, built in 1908.

History of the Cedar Falls Plant

In 1902, city engineer Thomson suggested building a hydroelectric plant below Cedar Falls. He thought it could make 25,000 horsepower of electricity for Seattle. Seattle voters agreed and approved spending $590,000 for the project. James Delmage Ross created the plans for the plant. In 1903, Ross became the chief electrical engineer for Seattle. He helped develop both the Cedar Falls plant and the Skagit River Hydroelectric Project.

The first timber dam on the Cedar River raised the water level by 18 feet. The dam sent water into a 49-inch wide pipeline that was over 15,000 feet long. This pipeline connected to a steel penstock. The water then flowed from the penstock to two Pelton impulse waterwheels. These wheels spun two 1,200-kilowatt generators. The generators first made power for the lights in the powerhouse on October 7, 1904. By January 31, 1905, electricity was flowing to the city of Seattle through the new Seattle City Light company.

People needed more and more power. By 1908, the Cedar Falls plant was making four times the amount of electricity it was first designed to produce!

1915 flood

In 1912, voters approved spending $1.4 million more. This money was for building a new masonry dam. This dam would collect more water and help keep the water flow steady throughout the year. The dam was approved even though some geologists worried about the ground on the north side of the lake. In 1915, the new dam caused the water level in Rattlesnake Lake to rise, which destroyed the town of Moncton. Another problem happened in December 1918. Heavy rain caused a flood in Boxley Creek, destroying the town of Edgewick.

In 1921, a new 15,000-kilowatt unit was added, making the plant even more powerful. Another 15,000-kilowatt unit was added in 1929. By 1930, the original generators were removed. Some were sent to Ketchikan, Alaska, and others to Brazil.

The first construction camp eventually became the town of Cedar Falls. It was a shared company town for workers from Seattle City Light, the Seattle Water Department, and the Chicago, Milwaukee, St. Paul and Pacific Railroad. Each company provided homes and services for its employees and their families.

Seattle eventually bought 91,000 acres of the upper Cedar River watershed. This was done to protect the water supply by keeping public access limited.

Images for kids

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  Employee cottages

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  1915 flood