A little ingenuity saved Cottage Grove taxpayers nearly $90,000 in repairs to a cracked underground pipe, and city workers say they'll use the same method again.
Late last year, Cottage Grove workers had spotted a crack in a concrete drainage pipe. The 66-inch-diameter pipe is 50 years old and deteriorating on the bottom.
Instead of digging up the pipe, installing a new one, and reconstructing the ground surface, as they'd usually done, employees slipped a 60-inch diameter fiberglass-reinforced polymer pipe inside the existing concrete pipe.
With no dirt and no excavating, workers quickly fixed the pipe, which runs beneath railroad tracks and a local walkway, said Brian Bellemare of Stantec, an engineering consulting firm known previously as Bonestroo.
"If this type of slip lining would not have been used, we would have had to excavate or tunnel under the railroad tracks and that would not have been easy," said city spokesman Ken Smith. "It would have increased the project cost by three times for that portion."
In addition to saving nearly $90,000 with the "slip-in" remedy, other types of repairs avoided the need to excavate West Point Douglas Road and parts of Hwy. 61, which would have inconvenienced drivers and lengthened repair time, Smith said. With the new process, it takes only minutes to move, connect and install each 4,000-pound section, he said.
Other cities have used the slip-lining method, Smith said, but this was its debut in Cottage Grove.
To see photos and a video of the process, go to vimeo.com/34617754.
