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Metropolitan Water Reclamation District of Greater Chicago

The Metropolitan Water Reclamation District of Greater Chicago (MWRD) has been improving the environment and protecting public health since it was formed as the Sanitary District of Chicago in 1889. While our operations have expanded and mission evolved, many of our goals remain the same. As new challenges emerge, the work of the MWRD continues to evolve to benefit the environment. 

Two images from the 1890s showing workers and various equipment during excavation of a large canal
Excavation for the Chicago Sanitary and Ship Canal in the 1890s required a lot of people and equipment in tough working conditions.

The first assignment

There was a sense of urgency creating a sanitary district due to a booming population, the fear of waterborne illness, the quality of the drinking water supply in Lake Michigan and a contaminated river. The city’s first sewers were designed to flow straight to the Chicago River and local waterways, and when it rained those waterways would pool and flood the surrounding landscape. The Sanitary District’s first assignment was clear: reverse the flow of the river and protect the region’s water resources. To accomplish this major task, they discovered that they could construct a vast network of canals. However, they had to create the agency first. Previous attempts to create the District through legislation in the Illinois General Assembly were stalled over concerns of discharging wastewater downstream.

A deal to create the Sanitary District of Chicago

A special commission consisting of then Chicago Mayor John Roche and two members of the Illinois House and two members of the Illinois Senate were appointed to gather public opinion and then the support  for another round of legislation. The committee proposed constructing a canal wide enough to accommodate steamboat traffic, satisfying downstate interests. The chance to promote economic development linking the Great Lakes to the Gulf of Mexico ultimately persuaded the rest of the state to adopt legislation. On May 29, 1889, the General Assembly approved “the Act to Create Sanitary Districts and to Remove Obstructions in the Des Plaines and Illinois Rivers.”

A demand for District services

The Enabling Act required that residents vote on establishing the boundaries of the District, roughly covering 185 square miles from the lakefront west to Harlem Avenue and from Devon Avenue on the north to 87th Street on the south. The District’s services were in so much demand that the residents living in the proposed area voted in favor of its creation, in an overwhelming vote of 70,958 to 242.

The District would change its name again years later. From 1955 through 1988, the District was called the Metropolitan Sanitary District of Greater Chicago. In order to provide a more accurate perception of the District’s current functions and responsibilities, the name was changed effective January 1, 1989, to Metropolitan Water Reclamation District of Greater Chicago. Despite the name changes, the reliable and innovative record of service remained the same.

The vision: Reversing the flow and creating a network of waterways

Workers and large bucket on a cable system during excavation of a large channel in the 1890s


Proposing a river reversal is one challenge, but delivering it was an altogether different story of determination, and the MWRD followed through on that promise. The MWRD reversed the Chicago River in 1900 by constructing the Chicago Sanitary and Ship Canal to take wastewater away from Lake Michigan to send downstream, thus protecting the source of the region’s drinking water. The water was discharged to the Des Plaines River, where it could be diluted as it flowed into the Illinois River and eventually the Mississippi River. The canal construction was considered one of the world’s largest public works excavations and was named one of the “Seven Wonders of American Engineering” by the American Society of Civil Engineers in 1955. Several of the engineers, including Chief Engineer Isham Randolph, went on from this experience to help build the Panama Canal.

Construction of the Calumet-Sag Channel.

The Sanitary and Ship Canal was so successful that two more canals were built. In 1910, the North Shore Channel was completed to provide drainage to the marshy areas north of the city and to direct lake water into the North Branch of the Chicago River for dilution. The Cal-Sag Channel was ready for operation in 1922, which also was the year the first treatment plant of the Sanitary District of Chicago was finished. The Cal-Sag Channel reversed the Calumet Rivers. In total, the MWRD constructed 61.3 miles of canals and waterway improvements that are today known as the Chicago Area Waterway System (CAWS).


A large waterway lock structure and hydro electric powerhouse at the intersection of the Chicago Sanitary and Ship Canal and the Des Plaines River
Lockport Powerhouse

Powering navigation and canal flow

As part of the river reversal, the District also constructed the Lockport Controlling Works and Lockport Powerhouse and Lock. The powerhouse is located right before the Chicago Sanitary and Ship Canal connects with the Des Plaines River. It allows the MWRD to control the levels of the waterways by controlling the outflow from the Chicago Sanitary and Ship Canal, while also managing the overall flow of water from Lake Michigan to the Des Plaines River. The powerhouse also generates hydroelectric energy using two turbines use the power of the water flowing through the facility, as the water elevation drops 38 feet between the canal and the river. Today, this power generation provides financial benefits to taxpayers, and the red-roofed classically designed powerhouse is listed on the National Register of Historic Places.  
View: How Chicago Reversed Its River: An Animated History

Read: A River Reversed - How 19th Century Engineering Saved Chicago

Protecting and improving: The MWRD constructs intercepting sewers and water reclamation plants to collect, manage and transform wastewater into clean water

In the early 20th century, the MWRD built pilot plants to develop wastewater treatment technology. At the same time, the MWRD began building 560 miles of intercepting sewers and force mains ranging in size from 6 inches to 27 feet in diameter. The intercepting sewers are fed by approximately 10,000 local sewer system connections. They serve as the superhighway of sewers, taking what is in municipal sewers and transferring it to the MWRD for treatment.


The MWRD built the Calumet Sewage Treatment Plant in 1922 and added six additional water reclamation plants (WRPs) soon after. The Stickney Water Reclamation Plant is one of the largest in the world, with the capacity to treat 1 million gallons of wastewater per minute. The MWRD also constructed 23 pumping stations.      


Construction of the MWRD's first three water reclamation plants: Calumet, O'Brien and Stickney. 



Regulating what enters the drains to ensure cleaner water for all

The MWRD was acting well ahead of the environmental movement as new initiatives came into place. Ahead of the federal government’s Clean Water Act in 1972, which launched pollution control programs and wastewater standards for industry, the MWRD Board of Trustees adopted the Sewage and Waste Control Ordinance on Sept. 18, 1969. The ordinance, which has since been amended, sought to protect the public health and safety by preventing pollution. MWRD staff accomplished this by regulating and controlling the quantity and quality of sewage, industrial wastes and other wastes that were discharged into the sewage systems, MWRD water reclamation plants and waters under the jurisdiction of the MWRD.

Establishing a user charge system

On Oct. 4, 1979, the MWRD Board of Commissioners adopted the User Charge Ordinance. The ordinance established an orderly and fair system so that each user disposing industrial wastes and significant sewage could help the MWRD cover the additional operations, maintenance, and replacement costs required. This user charge system helps keep the MWRD in compliance with federal regulations and protects the region’s water resources. Administering the Pretreatment and User Charge Programs, the MWRD’s Monitoring and Research Department works diligently to protect the quality of the water environment. These ordinances also generate an important revenue stream from large commercial/industrial users and tax exempt users of the sewage system and the costs of administering the MWRD’s Pretreatment and User Charge Programs. Projected user charge revenue is about $40 million per year.

No small plans, for a large undertaking

Depending on the amount of stormwater, the MWRD treats about 450 billion gallons of water each year for an average of 1.3 billion gallons of water each day, and the MWRD’s total water treatment capacity is over 2 billion gallons per day. The MWRD also controls 76.1 miles of navigable waterways, which are part of the inland waterway system connecting the Great Lakes with the Gulf of Mexico. It also owns and operates 33 stormwater  reservoirs to provide regional stormwater flood damage reduction.

Another layer of protection: The Deep Tunnel

In 1972, the MWRD adopted the MWRD’s Tunnel and Reservoir Plan (TARP), one of the country’s largest public works projects for pollution and flood control. Three reservoirs today are in operation, in addition to 110 miles of tunnels that hold rainwater mixed with wastewater during storms. It covers a 375-mile combined sewer area, which includes Chicago and 51 suburbs, and once complete, the system will provide 17.5 billion gallons of combined sewage and stormwater storage capacity, allowing the WRPs a chance to keep up during heavy rain events.


TARP and the river resurgence

In its 50 years of service, TARP has made a lasting impact on the environment and reduced flooding and basement backups. In fact, over that time, the tunnels and reservoirs have captured more than 1 trillion gallons of sewage and stormwater. Since it came into service in 2015, Thornton Composite Reservoir has nearly eliminated sewer overflows in the Calumet River system. When complete, the McCook Reservoir is estimated to provide more than $143 million per year in benefits to 3.1 million people in 37 communities. The success of TARP is also evident in the improved ecology and water quality of the CAWS. Game fish have returned, marinas and riverside restaurants abound, river recreation and tourism are booming, and waterfront real estate values have skyrocketed as Chicago area residents see the river system as a major asset. Because of TARP and the partnerships created between the MWRD and U.S. Army Corps of Engineers, the CAWS has rebounded to a quality not once imagined.

The MWRD proves an effective stormwater authority

In 2004, the Illinois General Assembly granted authority to the MWRD to manage stormwater for Cook County. While stormwater management did indeed bring the MWRD above ground and into people’s homes and businesses unlike wastewater treatment from pipes below, it became an effort to mitigate flooding and an opportunity to improve area water quality. The MWRD further put its skills in practice in 2013 when the MWRD Board of Commissioners approved the Cook County Watershed Management Ordinance (WMO). The WMO provides uniform stormwater management regulations for Cook County in order to prevent future commercial, municipal, and residential development and redevelopment projects from increasing the chances of flooding.

Empower the people: The MWRD emboldens the public with green infrastructure solutions. 

In addition to TARP, the MWRD currently has more than 220 stormwater management projects in design or construction protecting more than 17,000 homes and facilities. MWRD’s stormwater proj­ects incorporate elements of both gray and green infrastructure, ranging in size between massive res­ervoirs to green alleys and permeable parking lots that soak up stormwater. Green infrastructure mimics the natural environ­ment by handling precipitation where it falls through rain gardens, permeable pavement, rain barrels and other practices. By letting water slowly filter into the ground, this relieves some of the stress on old combined sew­er systems. Other projects include improving Chi­cago schoolyards to better manage water through a partnership known as Space to Grow, acquiring flood prone properties to take homes out of the flood plain and relieve struggling homeowners, and distributing more than 150,000 rain barrels and more than 100,000 free oak tree saplings to soak up stormwater, while also offset­ting the regional loss of ash trees.

Why it matters

Improving stormwater management and develop­ing new technology at water reclamation plants has led to cleaner area waterways. The MWRD not only creat­ed a pre-treatment program to control water en­tering the plant for treatment, but it now controls what is leaving the plant through new disinfection technologies that include chlorination/dechlorina­tion at Calumet WRP and UV disinfection at the O’Brien WRP, using the ultraviolet rays from 896 lamps to kill any remaining pathogens in the water. 

Improvements in water quality: fish species

A testament to the improvements in water quality in the CAWS is swimming below the surface. The number of fish species has shown a steady increase following the implementation of the TARP and Sidestream Elevated Pool Aeration stations. The number of fish species found in the CAWS has drastically increased since the 1970s when monitoring of the fish population first began. From 10 known species in 1974, that number has increased to 77, including 60 that have been found in the CAWS since 2000. The MWRD’s commitment to improving water quality has proven to be essential in supporting aquatic life.

Recovering Resources, Transforming Water

Since its inception, the MWRD has worked to improve the environment and protect public health, but the way it views its work has evolved since 1889. Sewage is no longer a waste product, but instead a collection of resources to be recovered and reused. The MWRD is implementing several innovations in renewable energy, while also recovering and developing reuse opportunities for water, biosolids, algae, phosphorus and other nutrients collected during the water treatment process. 


Each of the seven plants has made strides in helping the MWRD meet its goal of developing a resource recovery model that provides a sustainable return to both taxpayers and the environment. Through these opportunities, the MWRD will add value in traditional and non-traditional ways, while protecting the region’s water quality. The MWRD has also become a proactive agency that prides itself on many partnerships and collaborative efforts to improve the quality of life throughout Cook County. Through its culture of excellence, collaboration, innovation and work that extends beyond traditional water management, the MWRD was honored as a “Utility of the Future.” In 2021, the MWRD adopted a new five-year Strategic Plan to outline its goals and initiatives, and two years later the MWRD formally adopted a Climate Action Plan that highlights its commitment to lowering its carbon footprint.

The next generation of water stewards

What began as an attempt to solve water quality issues and protect the source of drinking water, has led to a transfor­mation in area water quality. Local water quality has improved through the hard work of many MWRD staff to a point never before imagined, and the nation’s environment is also benefiting as a result of many MWRD initiatives. As the MWRD enters its 135th year, there will be new chapters to write, more water to protect and more hard work to come, but thanks to the precedent laid by past MWRD workers, there is great pride and a sense of commitment for today’s staff to carry on that legacy for future generations relying on a quality water environment.