Sidestream Elevated Pool Aeration (SEPA) Stations

Waterfalls with a purpose

The MWRD’s sidestream elevated pool aeration (SEPA) stations provide more than a captivating waterfall and attractive park for picnics and wedding photos. We built the SEPA stations along the Cal-Sag Channel and Calumet River to also aerate the water. This added oxygen improves the water quality and creates new life in the Chicago Area Waterway System (CAWS).Protecting water quality

The SEPA stations are different sizes, but all serve the same purposes. From April through October, the five SEPA stations combine to pump up to 1.3 billion gallons of water per day. This in turn adds 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.

A view of a pool of water with trees and geese flying overhead — SEPA station 4 in Worth is a popular destination for relaxing walks, picnics and group photos.

More oxygen in waterways leads to more aquatic life

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 habitats are emerging.

Creating a natural setting

Because we created many parts of the CAWS as part of the reversal of the Chicago River and Calumet River systems, we also want to create a natural state for these waterways to thrive. The SEPA stations are located along the Cal-Sag Channel but add oxygen to the Calumet-Main channel waterway segment, which stretches for 42 miles from Lake Michigan to Lockport. These waterways rely on a well-maintained dissolved oxygen (DO) concentration to support healthy waterway ecosystems. The bottom and banks of the man-made portions of the CAWS are smooth and the current is slow, so there is not enough turbulence to shake up the water. That is why we came up with the idea of installing SEPA stations.

Award winning waterfalls

The SEPA stations were built in the early 1990s.The stations range in size from two to 20 acres and occupy MWRD land along the waterways. With the exception of SEPA 5, we provide access to all of the stations to the public. Not only have the stations attracted crowds and cleaner waters, but the stations are also award winning. American Society of Civil Engineers (ASCE) honored the MWRD for the stations with the Outstanding Civil Engineering Achievement Award in 1994, the highest honor bestowed on a civil engineering project by the ASCE.

Meeting the goal

The five SEPA stations are designed to achieve DO concentration standards for Illinois waterways. The warmer the weather, the harder the pump stations work to maintain the appropriate dissolved oxygen levels. But during colder months when water temperatures are lower, DO levels are high enough that pumping is not needed. 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 elevate the water as high as 17 feet. The pumping process is so strong that the water resembles a white water rapid and it can generate more oxygen than the waterfalls outside along the channel. 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. 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.

A view of large diameter screw pumps that lift water as they rotate — Interior view of SEPA station 4 showing the screw pumps in action as they lift water up to the pools from the canal.

A closeup view of a screw pump working to lift water as it rotates — Interior view of SEPA station 4 showing the screw pumps in action as they lift water up to the pools from the canal.

A sign describing how SEPA stations work by lifting water up from the canal to pools where it then flows over waterfalls back to the canal — Explanatory sign on the grounds of SEPA 1

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 Cal-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 that attracts many visitors and special events, including weddings and photo shoots. It also 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 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).

A view of pools and waterfalls next to the Cal Sag Channel with a large bridge in the background

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

Aerial view of waterfalls and fall foliage next to a body of water

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.

Aerial view of a semi-circle of waterfalls next to a waterway with golden fall foliage

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.

Aerial view of pools of water and waterfalls next to a waterway and a bridge

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.