No Need to Dig-and-Replace
The steel water line running along Interstate 80 in South Salt Lake City had suffered only one or two leaks in the lead joints in more than 30 years. But as the Utah Department of Transportation (UDOT) began widening the interstate, officials realized that a new shoulder and concrete lane barriers would end up above the 12-in. water line, piling substantial new weight on top of the pipe buried in a soil type that could settle and shift enough under pressure to threaten the integrity of the lead joints.
UDOT and the city’s Public Works Department agreed that remedial action during the road project was clearly preferable to a series of costly and inconvenient water line repair projects later.
The water line, however, ran under 2400 South Street, a residential street adjacent to the Interstate. Digging up more than 1,500 ft of the street to replace the line would be a significant inconvenience to homeowners and drivers alike, and the cost to replace the entire line was a significant concern as well.
“The existing pipe had solid integrity, but we were worried about the lead joints,” said Dennis Pay, public works director for South Salt Lake City. “Any movement in the soil could break those joints. We didn’t want to tear up the street at every single joint. That would be very disruptive to the residents. Insituform Technologies had been doing a lot of sewer rehabilitation work in the area and also had rehabilitated a 30-in. interceptor line for our wastewater treatment plant. We asked them if they could do anything to help us with this water line.”
The result was a combination of a challenge in the field and an innovative technological solution. The work that followed has won the 2008 Project of the Year Award from the Utah Chapter of the American Public Works Association (APWA). The project clearly demonstrated the value of trenchless technology to the potable water industry.
No Open Trenches
Pay said Insituform’s potable water business, Insituform Blue, used its Thermopipe lining system that could be installed without excavating an open trench along 2400 South Street. The thin, polyester-reinforced polyethylene liner pipe could be installed into the existing water line from small access pits dug at hydrants to create a continuous, jointless, impermeable and structural pressure pipe—without digging up the street, blocking traffic or creating potential safety hazards for drivers and workers. Insituform’s trenchless solution clearly was preferable to a dig-and-replace approach.
Pay was not only familiar with low-dig technology from a presentation by Insituform engineers at an APWA conference in Utah, but he also saw an opportunity for the technology to alleviate another concern by officials on the 2400 South Street project. He wanted to avoid digging up every resident’s yard to restore service connections. Pay remembered that Insituform had pioneered a patented robotic technology called iTap that was capable of reinstating service connections from inside the rehabilitated pipe. In his mind, Pay called that technology a “tipping point” on this project.
“Two public works employees, a consultant for the Utah Department of Transportation and I visited their world headquarters in St. Louis for a demonstration,” Pay said. “We saw the display in their R&D center, and we were very impressed. I was a little nervous about whether it would perform in field conditions the way it did in the lab. But it performed perfectly in the field. They installed 28 taps without missing a single one of them.”
Matt Wassam, national sales manager for Insituform Blue, said South Salt Lake City was an excellent example of how the iTap robot travels through the system installing a mechanical fitting at each corporation to ensure a long-term, watertight seal. Wassam said this technology already is revolutionizing the potable water industry and was perfect for the project in South Salt Lake City.
“In concert with our Class 4 structural lining in Thermopipe, iTap completes the solution for pressure-pipe rehabilitation and helps municipalities guarantee delivery of clean, safe drinking water without disruption to traffic, people and the environment,” Wassam said.
Cooperation in the Face of Complications
But complications continued to pile up before the project could get started. Pay said UDOT’s geotechnical engineer determined that work on the water line would have to be completed by the end of March to keep the highway project on schedule. Pay had hoped to wait until April to take advantage of milder weather.
“It’s difficult to do a water job in March,” Pay said. “But Insituform was able to get its crews in there and get the job done in three-and-a-half weeks in March. I thought that was just incredible. They lined more than 1,500 ft of water line and made 28 service connections. The crews were well trained, and they knew what they were doing. Our inspector said he couldn’t say enough good [things] about the crews. There weren’t even any cups or paper left in the pits. He’d never seen that before.”
Chantal Evans, Insituform’s business development manager for the region, said the project was “a perfect example of a cooperative effort to solve this emergency situation for South Salt Lake City and UDOT. Because of the collaboration between all the parties on this project, we were able to come in and do our jobs and get out quickly.”
Evans said the project also served as a valuable demonstration for public works officials from other municipalities in the area, and even some from Idaho, who visited the site to watch the iTap robot install the taps.