By Abby Crisostomo
When it comes to water resources in Chicago, most people think immediately of Lake Michigan. But increasingly, the rivers, creeks, canals and channels that weave throughout the region are getting their day in the sun – from investments in the Chicago Riverwalk to community improvements along the Cal-Sag Channel to talks of re-reversing the river system to combat invasive species. A far cry from the natural streams and wetlands that existed before the city, for the past century these waterways have been a highly managed network – the Chicago Area Waterway System (CAWS) – controlled and manipulated by the Metropolitan Water Reclamation District of Greater Chicago (MWRD) with some help from the U.S. Army Corps of Engineers.
As the regional wastewater and stormwater utility for most of Cook County, MWRD operates the waterways with three goals: to maintain water quality, to manage stormwater and to maintain navigation. They have seven wastewater treatment facilities that treat sewage and return it to the CAWS, which eventually makes its way out to the Mississippi River and the Gulf of Mexico.
To manage such a huge engineering marvel, MWRD needs to keep close tabs on everything that is going on with the CAWS, including the Chicago River, Chicago Sanitary and Ship Canal, North Shore Channel, Cal-Sag Channel and Little Calumet River. That task falls to Ed Staudacher, Supervising Civil Engineer for MWRD, and his two-man crew, Tom Fitzgerald and Lawrence Mazzocco. Ed manages what amounts to a waterways command center at MWRD’s downtown headquarters, where MWRD monitors weather conditions and responds to weather events from a centralized hub. Using weather models and radar, a contracted meteorologist issues weather reports to MWRD staff, who then decide what actions to take to ensure the smooth flow of water through the CAWS.
The CAWS is not only a waterway, but also a stormwater storage facility. MWRD and the Army Corps of Engineers actively maintain the depth of the CAWS at two feet below the Chicago City Datum (the base elevation at LaSalle & Adams used for surveying purposes). “This level allows vessels to pass freely under bridges and yet stay afloat. It’s not too high, and it’s not too low,” says Ed. When the meteorologist predicts precipitation, Tom and Lawrence, the MWRD system dispatchers, lower the water level in the CAWS by another foot to provide more space for the stormwater, rather than inundating MWRD’s seven reclamation plants or flooding properties.
The MWRD controls the level of the CAWS remotely from the command center through four control structures, or locks—three of which are connected to Lake Michigan and the fourth in Lockport. Since the level of Lake Michigan typically fluctuates between three feet above and three feet below the Chicago City Datum, water flows by gravity from the lake through the CAWS out to the Des Plaines River. To lower the CAWS levels, the gates at Lockport are opened, and water flows downstream.
Lowering the CAWS allows for some additional storage capacity, but sometimes the amount of precipitation exceeds the amount that the CAWS and MWRD’s treatment facilities can handle, as with the severe rain storms the region experienced in April. Since the 1970s, MWRD has been working on adding more storage through the Tunnel and Reservoir Plan (TARP), a massive system consisting of deep tunnels and three large reservoirs to hold water until water treatment facilities can handle it. Though the tunnels have been completed, the reservoirs will not be finished until 2029. When the full system is complete, it will hold 17 billion gallons of water.
But even completion of TARP won’t be able to handle the more than five inches of rain that fell on already saturated ground in April, which amounted to roughly 70 billion gallons of rain. Older communities, like Chicago, have combined sewer systems, which direct both wastewater and stormwater into the same pipes to be treated by MWRD. Many of these pipes are decades old and not built to handle the current amount of water swept into them due to vast amounts of impervious surfaces and storms of increasing frequency and intensity. When the treatment facilities, the CAWS, TARP and local sewer lines are full, the water has to go somewhere. Generally, the stormwater-wastewater mix either backs up into basements or MWRD must release the water through combined sewer overflows back into the CAWS or Lake Michigan through 36 outfall locations. The outfall pipes have flap gates that are connected to alarms at the command center, which MWRD can monitor and post in real time online.
Unable to rely completely on TARP and other systems, MWRD and many others – including the Metropolitan Planning Council (MPC) – are looking for solutions to flooding, basement backups and combined sewer overflows. Additional grey infrastructure, like the recently announced MWRD and City of Chicago project to build a tunnel between the Albany Park neighborhood and the North Shore Channel to relieve flooding or infrastructure repairs, are an important but expensive step. MPC is looking into more strategic and cost-effective ways to manage stormwater through a combination of both grey infrastructure and more natural green infrastructure solutions.
Storms aren’t the only reason that MWRD must manage the CAWS water levels, however. Water quality for both wildlife and human health is a big part of it. Ensuring that there’s enough dissolved oxygen in the CAWS to support habitats is an important part of what MWRD does. To keep oxygen levels up, the utility maintains certain water levels and water flows by diverting water from Lake Michigan into the CAWS and with the use of Sidestream Elevated Pool Aeration (SEPA) stations.
MWRD also manages the CAWS to maintain navigability of the waterways. This again means keeping the water at the appropriate level to allow boats to travel freely, as well as providing water downstream of the CAWS. During the drought of 2012, water levels were low throughout the state, including the Mississippi River and Lake Michigan. Some worried that if the drought dropped lake levels too low, that the Chicago River would “re-reverse” and flow back into the lake, but because the CAWS is managed so closely by MWRD, it was an unfounded fear. As Ed explained, MWRD manages the system to keep a six-inch difference between the lake level and the CAWS. The real problem would come if the lake were to drop so low that the flow of the CAWS had to be dropped to a level not sufficient for water quality and navigation.
The creation of the CAWS was a monumental feat that made Chicago what it is today. As a managed, rather than a natural system, however, investments in infrastructure, technology, manpower and research are critical to ensuring that this 100-plus-year-old system continues to serve today’s needs—and meet future demands. Threats from extreme weather, invasive species and aging infrastructure, as well as a renewed interest in developing the CAWS as a community and economic asset, highlight the need to coordinate and plan for a resilient system in the future.
Miles of rivers and canals managed by MWRD along with 32 retention reservoirs
Square miles serviced by MWRD
Population served by MWRD’s wastewater treatment
Miles of TARP
Residents can help reduce the risk of flooding by managing rainwater on their own property. For example, residents can store 55 gallons of water in a rain barrel (which can be purchased from the MWRD or at a home improvement store) for later use.
Residents should also minimize water-based activities, like showering, watering the lawn, and washing laundry, up to four hours before, during and after a wet weather event. Any water used during this timeframe flows through the sewer system, which in turn reduces the amount of space available for stormwater.
Contact the agency’s 24 hour hotline (1-800-332-DUMP) (monitored by Staudacher, Fitzgerald and Mazzocco) to report a dump or spill into a sewer or into the CAWS.