Helena Joyce
Lake Washington, located along the state of Washington's west coastline, was once heavily contaminated by untreated sewage. The lake, which is the second-largest natural lake in the state, received an estimated 20 million gallons of sewage effluent per day from surrounding communities in the 1950s, leading to a decline in water quality. This prompted extensive pollution control efforts by the city of Seattle, including the diversion of sewage and the construction of treatment plants. By the 1970s, Lake Washington's water quality had significantly improved, and it is now known as a successful example of lake restoration.
| Characteristics | Values |
|---|---|
| Lake Washington's pollution | Heavily contaminated by untreated sewage until extensive pollution controls by the city of Seattle |
| Restoration | The Municipality of Metropolitan Seattle, or Metro, was established in 1958 and tasked with diverting sewage from the lake |
| Restoration cost | $140 million |
| Sewage reduction | Effluent entering the lake was reduced to zero in February 1968 |
| Water transparency | Improved from 30 inches in 1964 to 10 feet in 1968 |
| Water transparency in 1971 | More transparent than in 1950 |
| Water transparency in 1975 | Returned to 15 feet |
| Potassium and nitrogen levels in 1975 | Decreased by more than 60% |
| Phosphorus load | The Cedar River contributes 25%. The Sammamish River contributes 41% |
| Water quality | Eutrophication and declined water quality due to increasing amounts of secondary treated sewage |
| Water quality in the 1950s | Declined due to pollution generated by Seattle's growing suburbs |
| Water quality in the 1940s | Impaired due to sewage overflow from the booming growth of the Eastside suburbs after World War II |
| Water quality in 1941-1963 | Declined due to increasing amounts of secondary treated sewage |
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What You'll Learn
Lake Washington's pollution history
Lake Washington, located along Washington state's west coastline, has a long history of pollution and subsequent restoration efforts. In the early 20th century, the lake served as both a drinking water source and a sewage repository for the city of Seattle. While Seattle switched its water source in 1901, it continued to dump untreated sewage into the lake for several decades.
The construction of the Lake Washington Ship Canal in 1916 significantly altered the lake's ecosystem. The canal connected Lake Washington and Lake Union to Puget Sound, lowering the lake's water level by about 9 feet and causing the Black River, which drained the lake, to run dry. The Cedar River, which previously fed the Black River, was diverted into Lake Washington, becoming one of its major influent streams.
During and after World War II, the region experienced rapid population growth, particularly in the suburbs surrounding the lake. This growth overwhelmed the existing sanitation infrastructure, and sewage began to overflow into the lake. The booming development also led to increased runoff, further contributing to the lake's pollution.
By the 1950s, the pollution problem had become critical. UW researchers observed a decline in water quality and tied it to the pollution generated by the growing suburbs. In 1955, oceanographer George Anderson and UW professor W.T. Edmondson played a crucial role in bringing attention to the issue by discovering the presence of cyanobacteria Oscillatoria rubescens, indicating the deterioration of the lake's ecosystem. Their findings spurred public initiatives to clean up the lake.
In 1958, the Municipality of Metropolitan Seattle, or Metro, was established to address the sewage issue. Between 1963 and 1968, Metro installed over 100 miles of sewer trunk lines and interceptors to divert sewage away from the lake and towards treatment plants. This $140 million project successfully reduced the effluent entering the lake to zero by February 1968. The transparency of the lake's waters improved significantly, and the lake's ecosystem began to recover.
The successful restoration of Lake Washington is considered a testament to the ability of humans to reverse the damage caused by pollution. By the 1970s, the lake had returned to its former glory, with improved water clarity and reduced levels of pollutants. Today, Lake Washington stands as a shining example of successful lake restoration through the diversion of sewage and the collaborative efforts of various communities.
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Successful restoration efforts
Lake Washington, the second-largest natural lake in the State of Washington, was heavily contaminated by untreated sewage for decades. In the 1950s, UW researchers observed a decline in water quality and tied it to the pollution generated by Seattle's growing suburbs. The lake was cloudy, dirty, and smelly, with an estimated 20 million gallons of sewage effluent entering it daily. The presence of blue-green algae, a common sign of lake deterioration, was also discovered.
The successful restoration of Lake Washington is a well-known example of how human efforts can improve water quality. The Municipality of Metropolitan Seattle, or Metro, was established in 1958 with the task of diverting sewage from the lake. Between 1963 and 1968, more than 100 miles of large sewer trunk lines and interceptors were installed to carry sewage to treatment plants built at West Point and Renton. The $140 million campaign, considered the most costly pollution control effort in the country at that time, paid off. By February 1968, the effluent entering the lake was reduced to zero discharge, restoring the lake's thriving and healthy ecosystem.
The transparency of Lake Washington's waters improved significantly, from only 30 inches in 1964 to a depth of 10 feet in 1968. The elimination of the phosphorus load from the effluent set off a complex chain reaction of species responses. The decline of Oscillatoria, a type of cyanobacteria, led to improved conditions for the water flea (Daphnia), a filter-feeding crustacean.
The successful restoration of Lake Washington has been extensively studied and researched by natural and social scientists for decades. It is internationally recognized as an example of how the application of scientific information to public action can successfully rescue a lake from deterioration. The findings of Dr. W.T. Edmondson and other scientists were crucial in developing effective strategies to clean up the lake and restore its ecological balance.
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The role of human activities
Lake Washington, the second-largest natural lake in the State of Washington, has been heavily influenced by human activities. The lake, which is 24 miles long and 2–4 miles wide, was once clear and pristine. However, human activities have had a significant impact on its water quality.
The construction of the Lake Washington Bridge in 1940 and the subsequent population boom along the lake's shores led to an increase in sewage pollution. By the 1950s, an estimated 20 million gallons of sewage effluent were being dumped into the lake daily, with communities disposing of their raw sewage directly into the lake with little to no treatment. This had a devastating effect on the lake's water quality, reducing water clarity and decreasing oxygen levels to the point where some fish species disappeared.
The discovery of cyanobacteria in the lake in 1955 and the realisation that sewage was acting as a fertiliser for its production sparked calls for public action. In 1958, the Municipality of Metropolitan Seattle, or Metro, was established to address the sewage issue. Between 1963 and 1968, Metro installed over 100 miles of sewer trunk lines and interceptors to divert sewage away from the lake and into treatment plants. This $140 million project successfully reduced the amount of sewage entering the lake to zero by February 1968, marking a significant step in the restoration of the lake's water quality.
In addition to sewage pollution, human activities have also contributed to phosphorus pollution in the lake. The lake's two major influent streams, the Cedar River and the Sammamish River, contribute a significant portion of the annual phosphorus load. The highly urbanised nature of the immediate watershed, with 63% of it being fully developed, likely contributes to this phosphorus pollution.
While human activities have negatively impacted Lake Washington, they have also played a crucial role in its restoration. The successful diversion of sewage and the resulting improvement in water quality showcase how effective pollution control measures can be. Continuous monitoring of the lake's water quality and environmental conditions by King County and other organisations aims to ensure the maintenance of the lake's health and prevent future degradation.
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Impact on water quality
Lake Washington was heavily contaminated by untreated sewage until extensive pollution controls were implemented by the city of Seattle. The lake changed dramatically in 1916 when the Lake Washington Ship Canal and Hiram M. Chittenden Locks opened, connecting it to Lake Union and Puget Sound. The lake's level dropped about 9 feet, causing the Black River to dry up and the Cedar River to be diverted into the lake.
In the 1950s, an estimated 20 million gallons per day of sewage effluent entered Lake Washington from Seattle and other communities surrounding the lake. The discovery of the cyanobacteria Oscillatoria rubescens in the lake in 1955 and the implication that phosphorus from sewage effluent was acting as fertilizer for its production, led to predictions by UW Zoology professor W.T. Edmondson and other scientists that nuisance algal conditions and water quality deterioration would worsen in the future. Although the lake was already visibly impaired, it had not yet deteriorated seriously, and the call for public action led to the creation of Metro in 1958.
Metro's approach to the Lake Washington problem was to construct a network of sewer lines and sewage treatment plants that directed all sewage away from the lake and delivered it instead to Puget Sound. The lake's pollution problems were solved within a few years. By 1971, Lake Washington's water was more transparent than it had been in 1950, and by 1975, the lake was back to normal, with water clarity returned to 15 feet and levels of potassium and nitrogen in the lake decreased by more than 60%.
The Municipality of Metropolitan Seattle, or Metro, was established in 1958 and tasked with diverting sewage from the lake. Between 1963 and 1968, more than 100 miles of large trunk lines and interceptors were installed to carry sewage to treatment plants built at West Point and Renton. Treated effluent ended up in Puget Sound, where currents and tidal actions diluted it. The $140 million campaign was considered the most costly pollution control effort in the country at the time. The investment paid off: completing these major facilities brought dramatic results. Effluent, which was at one time entering Lake Washington at the rate of 20 million gallons per day, was reduced to zero discharge in February 1968.
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Future conservation measures
Lake Washington, located along the state of Washington's west coastline, was heavily contaminated by untreated sewage until extensive pollution controls were implemented. The lake's restoration has been studied and researched extensively. The following sections outline future conservation measures that can be taken to maintain and improve the water quality of Lake Washington.
Continued Water Quality Monitoring
Regular water quality monitoring is essential to track the lake's health and identify any potential issues. While most lake water quality monitoring is currently conducted by local entities, continued collaboration with the Environmental Protection Agency (EPA) on projects like the National Lakes Assessment can provide valuable data and resources for conservation.
Invasive Species Management
Invasive species, such as cyanobacteria and algae, have been a significant issue in the past. Continued monitoring and management of these species are necessary to prevent their negative impact on the lake's ecosystem. The Washington State Department of Ecology provides resources and guidance on identifying and managing invasive aquatic plants and algae.
Sewage Treatment and Diversion
The successful diversion of sewage from the lake in the 1960s significantly improved water quality. Maintaining and upgrading the network of sewer lines and treatment plants is crucial to ensure that sewage does not re-enter the lake. Any future development or population growth in the region should be carefully planned to minimise the risk of overwhelming the existing sewage infrastructure.
Public Education and Engagement
Public awareness and engagement played a crucial role in the past in advocating for lake conservation. Continuing to educate the public about the importance of lake conservation, the impacts of human activities on water quality, and promoting sustainable practices can help ensure a collective sense of responsibility for the lake's health.
Research and Collaboration
The complex interplay between human activities and biological processes affecting water quality requires ongoing research and collaboration between scientists and local communities. By studying the lake's ecology and the effectiveness of past conservation measures, scientists and policymakers can make informed decisions about future conservation strategies.
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Frequently asked questions
Lake Washington was heavily polluted by untreated sewage until extensive pollution controls were put in place by the city of Seattle. By 1975, the lake was back to normal, with water clarity returning to 15 feet and levels of potassium and nitrogen decreasing by more than 60%.
The pollution in Lake Washington was caused by the dumping of raw sewage by the growing communities surrounding the lake. The sewage caused eutrophication and the growth of cyanobacteria Oscillatoria rubescens, also known as blue-green algae, a common sign of lake deterioration.
In 1958, an agency called Metro was established to address the pollution in Lake Washington. Between 1963 and 1968, Metro installed more than 100 miles of large trunk lines and interceptors to divert sewage away from the lake and into treatment plants. This $140 million project was considered the most costly pollution control effort in the country at the time.
