If you’ve ever ridden a bike trail along a creek, you’ve probably rolled past a utility pipe crossing the water on piers without giving it a second look.<\/p>\n
Omaha had one of those right by the Keystone Trail, except it wasn’t a gas line. It was a 90-inch steel sewer pipe, with about 50 feet of it hanging in the open air over Copper Creek, and every time the creek flooded, the pipe went underwater and took hits from whatever debris the current dragged past. Hanging a sewer main over a creek was normal practice decades ago, and frankly it aged about as well as you’d expect.<\/p>\n
The City of Omaha’s filing with FEMA<\/a> lays out the shape it was in: damage from debris strikes on the exposed steel, and a buried section behind it, 90-inch reinforced concrete pipe from the early 1970s, running inside a levee and under the trail, and getting close to the end of its design life.<\/p>\n Benesch<\/a>, the engineering firm the city brought in back in early 2020 to sort this out, puts the flow through that interceptor at 35 million gallons a day, all of it headed to the Papillion Creek treatment plant. The crossing itself sits in Bellevue, on Omaha’s southern edge.<\/p>\n So how do you replace a sewer main moving 35 million gallons a day without ever shutting it off?<\/p>\n You build the replacement next door and swap the flow over. The new crossing went in about 200 feet upstream of the old one, and instead of another pipe on stilts, it dives under the creek.<\/p>\n Doing nothing wasn’t on the table, and the other options the city weighed had problems of their own. Relining the old pipe would’ve left the crossing exposed to the same floods and the same debris. A new elevated crossing was on the list too, but by the city’s filing, the slopes and pipe elevations it had to match meant it’d still sit below the 50-year flood level. So under the creek it went.<\/p>\n The new crossing’s an inverted siphon, which is a fancy term for a simple move. The sewage drops down a structure on one bank, runs through pipes buried below the creek bed, and rises back up on the far side, driven by the weight of the water behind it. Copper Creek got three barrels: a 42-inch, a 48-inch and a 66-inch, all of them fiber-reinforced plastic.<\/p>\n Why three? The standard logic with siphons, and I’d bet it holds here, is that one huge barrel moves sewage too slowly on a dry day, and slow sewage drops its solids and clogs. Smaller barrels keep the flow brisk when there isn’t much of it, the big one wakes up in a storm, and if a barrel ever needs work, the other two carry the load while it’s down. Sewage doesn’t take days off.<\/p>\n The contractor, Super Excavators out of Menomonee Falls, Wisconsin, used slurry microtunneling for all three. We covered the method when a machine ground through more than 2,000 boulders under Winnipeg<\/a>, but the basics are quick. A microtunneling machine is a cutting head sealed against the ground. Nobody rides inside it. Hydraulic jacks in the launch shaft shove it forward, and the new pipe follows it into the earth, section by section. A driver runs it all from a cabin up top, watching screens instead of soil. That’s the whole trick.<\/p>\n The “slurry” part is what makes a creek crossing workable. The machine pumps pressurized fluid against the ground it’s cutting, and that pressure props up the tunnel face so it can’t slump in on itself. Akkerman<\/a>, the Minnesota outfit that built the machines, says the ground here was wet silty clay, which is pretty much the definition of soil that quits on you the second you stop holding it up.<\/p>\n Super Excavators ran three Akkerman machines, an SL36C, an SL51C and an SL60C, one sized for each pipe diameter, with guidance systems keeping line and grade honest under an active waterway. The three drives added up to 525 feet of tunneling. Akkerman only publishes the combined figure, so I can’t tell you how the footage splits between the barrels.<\/p>\n By tunneling standards, 525 feet isn’t exactly a heroic distance, and that Winnipeg bore ran more than a mile. What made this one finicky, going by Akkerman’s write-up, was doing it three times in a row with three different machine setups, all squeezed into a tight work area between a levee, a trail and the creek. It’s the same reason a boring machine pushing steel pipes in California<\/a> made this section: with jobs like these, the draw’s rarely the distance.<\/p>\n It’s gone. Benesch reported in November 2025 that the aerial pipe had been removed and the abandoned interceptor filled with flowable fill concrete, a soupy, low-strength mix you pour into a dead pipe so it can never collapse and drop the ground above it. Getting the steel section down meant working around people too, because the city’s filing called for temporarily removing the pedestrian bridge that crossed directly over the pipe.<\/p>\n The new alignment sits outside the levee and away from the spot where Copper Creek meets the Big Papillion, and that placement’s most of the point. A pipe that fails inside a levee can undermine the levee itself, and the city told FEMA a failure here risked sending sewage into the creek. That risk is why federal money came in through the Hazard Mitigation Grant Program, alongside Nebraska disaster recovery block grant funds.<\/p>\n I’ll be straight with you on the timeline: this isn’t a fresh dig. The tunneling and the removal wrapped a while back, and the finished project has since picked up a project-of-the-year nod from the state APWA chapter, in the environmental category. What’s new is the machine side of the story. Akkerman published its full case study of the Copper Creek tunneling on August 20, 2026, and that’s where the machine models, the wet silty clay and the 525-foot figure come from.<\/p>\n","protected":false},"excerpt":{"rendered":" If you’ve ever ridden a bike trail along a creek, you’ve probably rolled past a utility pipe crossing the water … <\/p>\nSo why three pipes instead of one big one?<\/h2>\n
How do you get three pipes under a live creek?<\/h2>\n
What happened to the old pipe?<\/h2>\n