Tighter underground utility corridors packed with more pipelines, electrical cables and fiber optic conduit have made replacing some corroding city water mains increasingly tricky.
City Water Distribution Superintendent David J. Beyersdorf said crews can typically install new, realigned replacement mains after boring through the street.
Occasionally, though, the space available or conditions underground have demanded the city go another route.
"You call them your problem children projects," he said.
The city recently completed its latest "problem child" water main project in a $2.7 million job using a technology new to this otherwise routine city work: cast-in-place — or cured-in-place — pipe lining.
Since 2017, the city has done five projects with Aqua Pipe after hearing of its effectiveness from the Metropolitan Utilities District in Omaha, he said.
Using this method, the existing pipe serves as its own replacement, as a crew uses a machine to spray a plastic material all along the inside of the main, creating a new pipe within, Beyersdorf said.
The Mohawk project, replacing mains on and around Mohawk Street between 37th and 44th streets, marked the first residential project the city has used this method on, he said.
This residential neighborhood work addressed 11,000 feet of water main.
Narrow lots, old and deep-rooted trees and tight right-of-way spaces made it a prime candidate for the method, he said.
This method didn't require the city to tear up as many yards as it would have otherwise needed to if it installed a replacement pipe, he said.
And it serves as a promising way for repairs needed on cul-de-sacs, where the city would otherwise need to dig up the whole area, including driveways and yards.
Minimizing disruption to a neighborhood provides an incalculable benefit to these projects, which otherwise cost about 10% more per foot of 6-inch water main, he said.
The method requires contractors to receive certification to do it, and to date, local contractors haven't received that, he said.
But the city benefits from MUD's use of cast-in-place pipe jobs because the out-of-state contractor can leverage its work in Omaha to pick up jobs in Lincoln, Beyersdorf said.
The new pipe lasts 50 years on its own.
The city has replaced 7 miles of water main this year and plans to tackle an equal amount next fiscal year, too.
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