The 1994 Outstanding Civil Engineering Achievement Award goes to successful implementation of an elegantly simple idea: aerate sluggish water by letting it fall through man-made waterfalls. The Metropolitan Water Reclamation District of Greater Chicago calls its project SEPA--Sidestream Elevated Pool Aeration. The project placed the waterfalls off-stream in small parks that serve the people in five south side neighborhoods, leaving the Cal-Sag waterway open to shipping and pleasure craft. Each day, the SEPA waterfall project pumps up to 1.3 billion gallons through five stations, adding up to 25 tons of oxygen to the sluggish waterway. Built for $40 million, the system eliminated the need for some $300 million worth of advanced secondary and tertiary treatment installations at two plants, saving taxpayers at least $260 million. The project also eliminated the navigation hazards and high maintenance and operations costs of instream aeration that had been tried in the 1970s. The water is lifted by screw pumps into pools where reinforced concrete weirs with hydraulically sharp crests and 5 ft wide teeth break the falls at intervals. The 2 ft/sec flow reduces sedimentation in the pools, which remain filled during non-pumping warm weather periods but must be drained to prevent ice damage during the winter. The exception to this is the wetland pool at station 1.
Available upon request at the American Society of Civil Engineer