Illinois Utility Finds New Fix for Failing Sewer

Savvy trenchless team uses powered sliplining technique to renovate failing sanitary line over icy river

Illinois Utility Finds New Fix for Failing Sewer

Sliplining began by pulling gently with a HammerHead HG1200AT cable winch. When the pipe’s progress stopped, the crew powered up the bursting tool. From that point, the winch’s job was solely to supply just enough tension to keep the pipe from backing up.

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Sometimes a failing sewer line presents a simple fix. Sometimes not so much.

The city of Aurora, Illinois, needed to restore sanitary flow through a badly compromised 10-inch vitrified clay sewer line under the northwest side of East Benton Street. The 180-foot section ran from a brick manhole at the intersection of Benton Street and Stolp Avenue to its exit into a sewer along the bank of the Fox River. At a depth of 16 feet, the sewer passed through a bridge abutment and beneath a massive covered concrete pavilion near a water feature between the river and the manhole. Major communication and electrical utility ducts over the sewer line further complicated a traditional opencut replacement.

“The cost of excavation would have been astronomical,” says Jason Bauer, Aurora’s assistant city engineer and assistant director of Public Works. The city decided to investigate trenchless solutions for rehabilitating the line.

Sections of the pipe had been identified as on the brink of collapse during an annual contracted inspection. The city was fearful that pipe bursting would be detrimental to the 3-foot-thick concrete bridge abutment and doubted that CIP lining was even feasible. They shared the video with several CIPP installers in July 2018 to determine if it might be worth an attempt, but the consensus was that it was unlikely to work in this situation.   


One of the CIPP installers recommended Bauer consult with Nate Hrabosky of HammerHead Trenchless, a company specializing in trenchless pipe installation, repair and replacement techniques. The company provides consultation in each application covered by its product lines, which span a broad range of noninvasive techniques.

Hrabosky has over 20 years’ experience in trenchless pipe solutions, including as a field technician and application consultant. “If it could have been lined, I would have lined it in a second,” Hrabosky says. But when he saw inside the pipe, he agreed with the CIPP installers. “It looked like squashed eggshells in there — far too risky to try lining it.”

Conventional pipe bursting was also too risky. Since the time the century-old sewer had been installed, other service lines had been laid along the same route, including conduits to a communication hub. Ducts and conduits crowded the pipe path. Some ran parallel to the existing pipe. Others crossed over and under the sewer at odd angles all along the route. The potential for damage to the bridge abutment was another major concern.

Another option

Hrabosky offered an alternate trenchless solution he referred to as powered sliplining. The method utilizes pipe bursting tools, but the object is not to burst the pipe, only to slip a similar-diameter replacement pipe through it. Most sliplined pipe can be pulled in place using just a winch alone, but in this case, the pipe was too badly compromised to trust a winch to go the distance. A pneumatic hammer ensured it would.

A constant tension winch is still used in a powered sliplining operation to counter “swim.” Swim is the tendency of a percussive hammer and its attached pipe or casing to rock back and forth rather than advance when ground conditions do not provide sufficient friction to maintain forward progress. The pipe moves forward with each forward strike of the hammer but then backs up during its backstroke. Steady tension provided by the cable winch counters the force of the backstroke, maximizing operational efficiency and, in this case, ensuring continual advancement of the pipe through a cavity filled with loose debris.

Slipping a pipe of similar diameter through the existing pipe path eliminated the risk of interference with shared utilities and allowed the new pipe to be connected without excessive reconstruction of the brick manholes.

As for capacity, an 8-inch-diameter pipe was more than adequate for this run. Although the legacy pipe had originally been a combination storm and wastewater system, stormwater and sanitary services for this line had been separated years ago. The new pipe would be used exclusively as a sanitary line.

Choosing a contractor

The project was publicly bid, but due to its delicate requirements, only two qualified contractors sent in bids. The contract went to Benchmark Construction, headquartered in Bartlett.

“We’ve been using the pipe bursting method for over 10 years and are well acquainted with powered sliplining, though we don’t normally do it from a bridge,” says Benchmark Construction’s George Coleman.

In addition to Benchmark Construction’s own personnel, the construction team included Hrabosky from HammerHead and Drew Yandel from MG Underground, a sister company to Benchmark Construction. Yandel provided on-site support and fused the 8-inch HDPE.

Initial discussions of how to perform the operation included placement of a raft in the river to support the pipe. Ice flows on the river at that time of year ruled out the use of watercraft, so the team went with Benchmark Construction’s suggestion to suspend the pipe from the bridge. It was just a matter of waiting for the right time.

Waiting for weather

Plans were to begin in November, but all parties agreed the operation should be postponed until the weather gave them a work window free from snow, preferring to avoid the additional complication if they could. Yet operations couldn’t be delayed beyond the cold of winter, as melting snow and ice would raise river levels. The manhole could be accessed by the cable winch’s self-deploying boom at the street any time of year, but the entry point for the pipe beneath the bridge had to be accessed before the spring thaw brought higher water. 

By February 2019, Benchmark Construction had staged three cranes rented from Atlas Crane out of Aurora and fused the 8-inch HDPE in Benton Street’s parking lane on the northside of the east-west bridge. The city had removed ornamental streetlights to give the cranes unobstructed access over the side of the bridge. Benchmark Construction owns its own pipe bursting equipment, but for this job, it rented a HammerHead 8-inch, pneumatic burst system, including the HammerHead HG1200AT cable winch.

No excavation was required for this project. The manhole in the riverbank was modified to permit entry of the pipe prior to the arrival of the cranes. The pipe’s invert lies above river level, and the manhole protrudes out of the water by approximately 4 feet. Therefore, only slight modifications to the manhole were required to accommodate insertion of the pipe.

The weather finally gave the crew the opening they had been waiting for during the first week of March. It took just a day to fuse the pipe and prepare the machinery and equipment to begin the next morning.

Powering up

The crew placed the hammer inside the leading end of the new pipe and bolted on the burst head, with its air hose running through it to the compressor on the bridge. As the operation was about to begin, however, the crew had trouble aligning the 8-inch HDPE with the host pipe. The angle was too great from the side of the bridge where it was suspended to the entry point. Quickly brainstorming a suitable solution, the team widened the entry point in the side of the manhole and used a strap-and-pulley system to adjust and maintain the angle of entry for the new pipe. They encountered no further complications.

Sliplining began by pulling gently with the winch. When the pipe’s progress stopped, the crew powered up the bursting tool with air at 110 psi from a 185 cfm compressor. Once the hammer went to work, the winch’s job was solely to supply just enough tension to keep the pipe from backing up.

“Tension was so low that I’m not sure the pressure even registered on the gauge,” Coleman says.

When the pipe reached the manhole, the crew reversed the hammer, backing it out and removing it from the newly installed pipe. They cut the burst head from the front of the pipe and extracted it from the manhole. Finally, they grouted in the new HDPE pipe, giving it a sealed finish in both manholes.

Successful outcome

Coleman says it was a smooth operation. “The insertion itself took about 90 minutes to do. Setting up took about 2 1/2 hours and tearing down a little less. I’d say less than six hours of on-site activity that day, total.”

The short time frame meant that anyone working a day shift downtown missed the chance to see a powered sliplining operation — unless, of course, they made a lunchtime run across the bridge, which was open to traffic throughout the operation.

“The only other option was excavation, which would have cost the city at least five times as much when you take the cost of restoring the pavilion and water feature into account,” Bauer says. “This work was done without any pavement removal and with minimal impact to traffic or downtown activities.”


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