Sidestream Elevated Pool Aeration (SEPA) stations function not only as an attraction for scenic views, photo opportunities, park activities and picnics. The Metropolitan Water Reclamation District of Greater Chicago (MWRD) built these waterfalls to also improve the water quality and create new life in the Chicago Area Waterway System (CAWS).

The five stations located along the Calumet-Sag Channel and the Calumet River pump up to 1.3 billion gallons of water per day and add up to 25 tons of oxygen to the waterways each day. At the stations, up to half of the river's flow is pumped up as high as 17 feet to an elevated, shallow pool, from which the water then cascades over a number of drops back into the waterway. The waterfalls aerate the river water and enhance the aquatic environment by improving and protecting fish populations and eliminating odors. The SEPA stations are thus not only attracting spectators to the park areas, but also creating new schools of fish, and as a result, new birds of prey and other natural habitat are started to arrive.





The SEPA stations were built in the early 1990s and received the Outstanding Civil Engineering Achievement Award in 1994, the highest honor bestowed on a civil engineering project by the American Society of Civil Engineers. The purpose of constructing the stations was to increase and maintain the dissolved oxygen concentration of the water carried in the 42-mile, Calumet-Main channel waterway system, which stretches from Lake Michigan to Lockport. Aeration is necessary due to the unnatural form of the waterway. The bottom and banks of the man-made portions of the CAWS are smooth and the current is slow lacking enough turbulence to aerate the water.

The stations range in size from two to 20 acres and occupy MWRD land along the waterways. With the exception of SEPA 5, all of the stations are open to the public. The five SEPA stations are located along the Calumet-Sag Channel. Depending on weather conditions, the SEPA stations typically run from April 1 through the end of October. The warmer the weather the harder the pump stations work to maintain the appropriate dissolved oxygen levels.

Meeting the goal

The five SEPA stations are designed to achieve dissolved oxygen (DO) concentration standards for Illinois waterways. During colder months when water temperatures are lower, DO levels are high enough that pumping is not needed, but during warmer months the aeration process can establish higher DO levels and enhance aquatic life. The MWRD exceeds state standards by pumping water at stronger outputs that result in DO concentrations at or above 4.0 milligrams per liter at all five stations. These DO levels are monitored around the clock to ensure the MWRD is in keeping with the Environmental Protection Agency's National Pollutant Discharge Elimination System (NPDES) permit program. 

How it works

When the upstream water meets the station, it passes through coarse bar screens inclined on 20-degree angles before drifting into the pumping process. All stations rely on large spiral screw pumps, except for the SEPA 1, which uses vertical propeller pumps. The screw pumps, several feet in diameter, spiral the water up a 30-degree incline, elevating the water as high as 17 feet. All stations, except for the smaller SEPA 2, will pump water at least 400 cubic feet per second (CFS) with SEPA 5 pumping as high as 576 CFS. The aeration during the pumping process is so strong that it in fact generates more oxygen than the waterfalls. The circular screw pumps upward rotation turns the water into something more resembling white water ascending from a rapid. Each of the screw pumps at SEPA stations 3,4 and 5 can pump more than 50,000 gallons of water per minute, while the smaller SEPA 2 will pump 19,300 gallons per minute. There are four at SEPA stations 3 and 4, while SEPA 5 has five pumps. The water then passes through a lengthy discharge channel before cascading down a series of waterfalls and returning to the waterway. During the winter, MWRD workers maintain the stations by inspecting gears, rotating pumps, replacing seals and changing oil to ensure that the pumps are ready to go come April and that the water can flow.




The end result: urban waterfalls 

The grounds of the stations are used by local municipalities as parks to be enjoyed by the public. SEPA stations 1 and 2 are located in Chicago at the intersections of the Calumet River and Torrence Avenue and at Indiana Avenue on the north side of the Little Calumet River. Along the banks of the Calumet-Sag Channel in Blue Island is SEPA 3, where park visitors can enjoy the grounds for recreation or lounge on limestone benches overlooking the various waterfalls and Western Avenue Bridge. SEPA 4 is stationed in Worth within a 12.5 acre park and attracts many visitors and special events, including weddings and photo shoots and provides a scenic background for the Water's Edge Golf Club. In addition to the adjacent golf course, this area includes a pavilion, benches, walking paths and bridges. The MWRD, in coordination with the local municipalities, actively maintains the landscaping and grounds. SEPA 5, which is not accessible to the public, is situated at the meeting point of the Cal-Sag Channel and the Chicago Sanitary and Ship Canal. 




Where to find SEPA stations 

SEPA 1, located near Torrence Avenue, is the closest station to Lake Michigan and is situated near a wildlife habitat, bird sanctuary and prairie wetland. Each waterfall drops three feet and the station passes up to 260 million gallons per day (mgd).

SEPA 2 is the smallest station and is located at 127th Street. The four three-foot cascades pass 56 mgd.

SEPA 3 is located in Blue Island and is a central fixture of 8.5 acres of shady trees and park space. The circular design is divided in half with terraced planters on one side opposing waterfalls on the other side. This station features 5-foot waterfalls and a capacity of 310 mgd. 

SEPA 4 in Worth is within a park and attracts many visitors for photo opportunities for weddings, proms, family reunions and other gatherings. Three 5-foot waterfalls handle 310 mgd.

SEPA 5 is part of the Illinois and Michigan Canal National Heritage Corridor and marks the confluence of the Cal-Sag and Main channels and features a lighthouse near 3-foot waterfalls and a capacity of 372 mgd.