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  • Sidestream elevated pool aeration (SEPA) stations: effects on in-stream dissolved oxygen


  • As a result of increased pollutant loading and low in-stream velocities, dissolved oxygen (DO) levels in the Chicago waterways historically have been low. In 1984, the Metropolitan Water Reclamation District of Greater Chicago (MWRDGC) issued a feasibility report on a new concept of artificial aeration referred to as sidestream elevated pool aeration (SEPA). The SEPA station concept involves pumping a portion of water from a stream into an elevated pool. The water is then aerated by flowing over a series of cascades or waterfalls, returning to the stream. The MWRDGC proceeded with design criteria for SEPA stations as a result of experimental work performed by the Illinois State Water Survey (ISWS). Five SEPA stations were constructed and placed in operation along the Calumet River, Little Calumet River, and the Cal-Sag Channel waterway. In 1995 the ISWS returned to conduct research to evaluate the reaeration efficiencies and their effects on in-stream DO. Continuous monitoring of DO, temperature, pH, and conductivity was performed at 14 locations along the Calumet and Little Calumet Rivers, Cal-Sag Channel, and Chicago Sanitary and Ship Canal to evaluate the effectiveness of the SEPA stations on maintaining in-stream DO concentrations. Also, supplemental cross-sectional measurements were made at the 14 locations and at an additional seven locations. Comparisons of mass balance, completely mixed, in-stream mean DO concentrations at the SEPA station outfalls and those measured at cross-sectional stations immediately downstream of each SEPA station were made. Results showed that each SEPA station has an immediate positive impact on in-stream DO concentrations. At SEPA stations 1 and 2, where the impacts are small, the positive effects can best be demonstrated using completely mixed values. Two important conclusions can be made. One is that the SEPA stations, particularly stations 3, 4, and 5, are fulfilling the intended function of maintaining stream DO standards in the Calumet and Little Calumet Rivers and the Cal-Sag Channel. The second is that DO concentrations less than the DO standard are still observed in the Chicago Sanitary and Ship Canal in the reach beginning above its juncture with the Cal-Sag Channel to the Lockport Lock and Dam. Over the entire study period, DO concentrations were maintained above the standard 98.6 percent of the time from the SEPA station 3 outfall to the intake of SEPA station 4 and 97.5 percent of the time from the outfall of SEPA station 4 to the intake of EPA station 5. Significant improvements in DO concentrations were also achieved for at least 4 miles downstream of SEPA station 5 in the Chicago Sanitary and Ship Canal.

Originally Deposited as: 999999994078

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Language(s): EN-English

Volume or Year: 2000
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Date Created: 9 24 2004
Date Last Modified: 5 13 2003

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1. Sidestream elevated pool aeration (SEPA) stations: effects on in-stream dissolved oxygen (20060929185840_ISWSCR2000-02.pdf).
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