Holding Water

A trenchless lining system saves a small municipality in southwest Minnesota from digging up the bottom of its new swimming pool
Holding Water

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The municipal swimming pool in Tracy, Minn., was losing hundreds of gallons of water per day. When a local contractor televised the pool’s 6-inch drain line, he found multiple, severe cracks in the two-year-old Schedule 40 PVC pipe.

Looking at the damage, Paul Desmith, a Public Works technician, remembered questioning the rationale when told by the pool builder that it didn’t need winterizing. What he saw on the video was clearly the work of ice.

Two contractors tried to repair the 90-foot drain line using pulled-in-place liner systems, but the material hung up on seven tight 90-degree bends. Both repairs were aborted for fear the resin would cure with the liner halfway through the pipe.

Desmith contacted other area contractors to install a liner, but most told him flat out, “No way.” He then searched the Internet, found Perma-Liner Industries Inc., and was directed to Troy Ouverson of Ouverson Sewer and Water Inc. in Buffalo, Minn.

“One of my first calls was to Doug McCullough at Perma-Liner to ask if we were getting in over our heads,” says Ouverson. “We had never shot a liner with that many tight bends spaced so closely together, and neither had the majority of Perma-Liner installers. We also would be using a product that was new to us.”

With technical support from McCullough and his confidence that a special liner could be shot, Ouverson’s crew repaired the drain line without digging up the bottom of the city’s multi-million-dollar pool.

Slow and steady

Officials wanted the repair done in April, giving them enough time before summer to dig up the pipe and repair the bottom of the pool if Ouverson failed.

Preparation was critical, and Ouverson talked often with Desmith and McCullough.

“I studied the video and drawing Paul sent until I felt confident about working on the line,” says Ouverson. He learned that when the pool was emptied over the past two winters, no one plugged the two drains afterward. Enough residual water trickled down, froze, and cracked the drain line.

Ouverson, whose shop is a four-hour drive from Tracy, scheduled three days to complete the job. “I wanted one day just to assess the situation and talk about different approaches on how to shoot the liner,” he says. “We didn’t want to rush into anything.”

City workers cut a 4- by 4- by 5-foot-deep hole in the bottom of the concrete pool to expose the drain line, then removed a 4-foot-long section for access. Ouverson planned to use part of the first day as a training session. “Everybody had to know what to do at exactly the right time, and we had to block out our emergency response should something go wrong,” he says. The schedule was to shoot one liner on each of the next two days.

McCullough had recommended a 2-mil 6-inch flex liner instead of the standard 3-mil Perma-Lateral system, which uses a needled felt material that is stretchy and could be pulled too thin during installation. Ouverson discussed the risk factor with McCullough, who advised keeping the air pressure low.

Lucky charm

A security fence surrounds the pool, but Ouverson was allowed to back the lining trailer up to a gate. After evaluating the situation and walking through the motions, the team felt confident enough to go live.

The crew impregnated and wet out 40 feet of the liner using a warm epoxy resin to give them ample working time. “The process was challenging because the felt kept wiggling away and wouldn’t readily soak up the resin,” says Ouverson. “When completely wet out, the liner was similar to handling a cooked noodle.”

The men rolled up the liner, then quickly transported it from the trailer to the air inversion tank in the pool. “Our first shot was upstream and had five tight 90s, three to four feet apart,” says Ouverson. “We crossed our fingers, put 2 psi on the liner, and watched it take off like a Slinky toy down the stairs. We couldn’t believe it.”

The last 90-degree bend went straight up to a pool drain. As the nose of the liner rose over the lip, the men sighed with relief. They then shot in the calibration tube and inflated it to 8 psi to force the liner against the walls of the host pipe.

“The tube went around the bends effortlessly, then climbed right out of the drain to protrude two feet past the liner,” says Ouverson. After waiting into the evening hours for the first liner to cure, the men decided to shoot the 50-foot liner. The downstream pipe had two tight 90-degree bends, the last going straight up to a second pool drain.

“The shoot was a repeat performance of the first and absolutely flawless,” says Ouverson. The men left the pressure at 8 psi on both liners overnight. “By giving ourselves a lot of working time, we also extended the curing time,” he says.

Morning after

Early the next morning, the men removed the calibration tubes. “That became the hardest part of the job, because they didn’t want to come back around those bends,” says Ouverson. “I had three people pulling on the tube line, working it back and forth, trying to rock the tube past the 90s. I was afraid we’d rip the reinforced rubber bladder because it has no stretch.

“Mentally, this was one of my harder jobs for 2009. It was very stressful because of the multiple tight bends and the unknowns working with a new product. If we failed, breaking up the bottom of the pool would be a nightmare for the city, and cost the taxpayers tons of money. Moreover, the pool would never look the same. The patch on the bottom would always be visible.”

With the calibration tubes removed, Ouverson inspected the liner using a mainline push camera from MyTana Mfg. Co. Inc. There was no stretching. Before heading home at 8 a.m., the men connected the new pipe sections with two Fernco couplings.

City officials were thrilled to hear that their pool was repaired and unmarred. Ouverson credits McCullough’s technical support as playing an integral role in the success and completion of this job.


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