May 2025 Vol. 80 No. 5
Features
Fort Wayne, Ind., tunnel project uses Vortex inserts to protect sewer system
(UI) — Fort Wayne City Utilities is constructing a large tunnel located in the bedrock below the city. Along with the tunnel, there will be an associated network of pipes nearer to the surface.
The system, known as Tunnel Works, will collect and transport sewage from locations where Fort Wayne’s combined sewer system might overflow during wet weather events, to the sewage treatment plant. This is part of the city’s long- term control plan to reduce CSOs into its rivers. The tunnel has a life expectancy of 100 years.
The 16-foot-diameter tunnel will be five miles long and constructed 150 to 200 feet below ground using a tunnel boring machine. The project includes consolidation sewers and nine drop shafts, four – 8 feet in diameter, to convey combined sewer overflows (CSOs) from 22 outfalls along the St Mary’s and Maumee Rivers. The drop shafts will direct the combined sewage into the tunnel. The combined sewage will travel through the tunnel to the sewage treatment plant where it will be stored temporarily and treated after the wet weather event is over and when the plant has sufficient capacity.
Five of these drop shafts include IPEX’s Vortex Flow Inserts to reduce odors and dissipate the energy that would normally cause corrosion issues in such deep drops.
At the bottom of the Vortex Flow Insert, the flow enters an energy dissipation pool where the air and gases drawn down the air core are forced back into the wastewater. This process aerates wastewater with a higher dissolved oxygen concentration, intensifying the chemical oxidation process that neutralizes corrosive agents in the flow. The flow exit of the Vortex is submerged in the dissipation pool so there is no splashing or release of gaseous hydrogen sulfide. The aerated flow continues the process of oxidation down the line.
Black and Veatch engineers knew they needed something to help with the energy dissipation at these drop structures. Having worked with IPEX Vortex Inserts in the past, they knew they were the best product for the job.
With no moving parts and requiring virtually no maintenance, the Vortex Flow Insert is a revolutionary technology for eliminating odors and minimizing corrosion in sewer drops. Its patented spiral flow design creates a downdraft that traps odorous gases and sucks them downward toward the bottom where they are entrained back into the sewage flow. Wastewater flows into the top of the Vortex Flow Insert where it is directed around a channel of decreasing radius that accelerates the wastewater flow at a higher velocity.
As the accelerated flow is channeled downward, that velocity causes the wastewater to hug the inside walls, creating a negative air core that draws airborne gases downward. Accordingly, there is no need for the city to treat the air surrounding the drop structure with costly odor treatment like chemical injections and biofilters.
By oxidizing the hydrogen sulfide, the Vortex Flow Insert reduces concrete and metal corrosion to extend the life of the sewer for overall lower total cost of ownership. Through the process of aeration and oxidation, the overall quality of the wastewater is improved prior to treatment, which can further save on chemical and aerations used in the treatment process. With no moving parts and no corrosion, municipal sewer maintenance costs are dramatically reduced.
IPEX USA, LLC custom designs and builds every Vortex Flow Insert depending on each unique application and project. The Vortex drop height can be as little as 6 feet or more than 100 feet tall, and they are sized based on the peak flow that the unit is required to manage. The five Vortex Flow Inserts on the Fort Wayne project range in size from 23 to 91 MGD and all have a 175-foot drop.
FOR MORE INFORMATION: ipexna.com, (800) 463-9572
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