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University of Iowa researchers develop model storm sewer system for St. Louis

Dropshaft to be built to handle 4.4 billion gallons of water per day

Water flows through a model of a deep sewer tunnel at the Hydraulics Model Annex in Iowa City on Wednesday, Nov. 16, 2016. The model was designed to support and validate the design of vortex dropshafts for the Metropolitan St. Louis Sewer District. This is a 1:16 scale model of the very large Forest Park Intake Facility. The full-scale facility is designed to handle up to 4,420 billion gallons/day during peak flow. (Stephen Mally/The Gazette)
Water flows through a model of a deep sewer tunnel at the Hydraulics Model Annex in Iowa City on Wednesday, Nov. 16, 2016. The model was designed to support and validate the design of vortex dropshafts for the Metropolitan St. Louis Sewer District. This is a 1:16 scale model of the very large Forest Park Intake Facility. The full-scale facility is designed to handle up to 4,420 billion gallons/day during peak flow. (Stephen Mally/The Gazette)
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IOWA CITY — University of Iowa researchers have designed and built a model of a city sewer system that is planned to be the largest of its kind in the world.

The university’s IIHR-Hydroscience and Engineering, a research and education center within the UI’s College of Engineering, on Wednesday unveiled the model of a deep sewer tunnel it constructed for the city of St. Louis.

The model was constructed to hold storm and sewer water during heavy rains. The design, which includes a section called a vortex dropshaft, reduces the air in sewer systems by swirling the water around a vertical tube before dropping it into another chamber.

The model is just one-16th the size of the sewer system planned for St. Louis, which will be part of the Project Clear sewer district improvement plan — that region’s initiative to improve water quality and wastewater issues.

When finished, the system should be able to handle about 4.4 billion gallons of water per day if needed. The dropshaft will be 20 feet in diameter.

“Our component is a very small piece in the overall project,” IIHR Director of Engineering Services Troy Lyons said. “It’s an incredible experience to be involved in that.”

The large size also is intended to help accommodate for any large areas of concrete in St. Louis, as concrete is less absorbent to rainwater than open ground and pushes more water into the storm sewer system. The system therefore should prevent backups that can pollute the city’s waterways.

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“This is a real measurable environmental improvement,” said Andy Craig, an IIHR hydraulic engineer.

The dropshaft solves a problem with air buildup, which can act like a geyser and blow off manhole covers. While that isn’t a common phenomenon, Lyons and Craig said it can be very dangerous.

To develop the model, Kory Miller, a UI undergrad civil engineering student, took plans from the city of St. Louis and entered them into a computer design program. From there, IIHR staffers constructed the model with the computer designs and then tweaked it to ensure proper water flow and tested it with debris buildup.

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