Tinley Park, Illinois, had a huge problem on its hands.
A section of its force main pipe experienced “numerous” breakages over time, according to Joe Fitzpatrick, sewer and water superintendent for the Village of Tinley Park. The pipe, 14-in. ductile iron installed approximately 45 years ago, became particularly troublesome in 2018 and 2019. Portions of the pipe runs under a road. Repairs there were particularly costly.
The Village of Tinley Park is a growing community of 56,200 less than 30 minutes southwest of Chicago. This particular force main, on the town’s north side, runs for 5,700 ft from Post 7 lift station to a gravity flow pipe.
The lift station and all its equipment was replaced about six years ago, Fitzpatrick says, but the pipe remained. The lift station, which serves a residential area as well various businesses, pumps an average of 383,000 gallons per day.
The costly repairs were adding up. “It got to the point where we just needed to look at the whole picture,” Fitzpatrick says. The pipe was rotting from the inside out. Hydrogen sulfide gas, a common byproduct of sewage, had taken its toll on the pipes. Repairing the breaks, especially those under the road, was “quite an undertaking.” The Village decided to tackle the force main once and for all. “No more band-aids,” he adds. “Full repair.”
After a formal bidding process, the Village of Tinley Park selected Visu-Sewer Inc. of Pewaukee, Wisconsin. Experts in sewer line rehabilitation, Visu-Sewer has performed previous rehabilitation projects in the Village.
According to Alex Rossebo, P.E., Visu-Sewer lined a total of 5,700 ft of force main in two stages. Phase one, encompassing approximately 2,200 ft, ran through a mostly residential area. That was completed in 2019. In spring 2020, crews returned to complete the second phase. The second section, 3,500 ft long, ran under a city street and through intersections. “We came back in spring and did the road portion, because they preferred we not shut down one lane of their busy roads during winter conditions,” Rossebo explains.
The Rehabilitation Begins
CIPP work typically involves creating a bypass for the section of pipe being lined. That wasn’t necessary here, Fitzpatrick says. Crews took advantage of an existing overflow pipe at the lift station.
They first needed to locate the force main. Working with as-built drawings provided by the Village, crews had a pretty good idea where to look. “You have to find a spot where you can access the pipe so you can line it from Point A to Point B,” Rossebo explains. Lacking manholes, access pits were needed.
For that process, the Village turned to Tinley Park-based Airy’s Infrastructure. Airy’s had worked on parts of the sewer lines before and is familiar with the system.
Visu-Sewer was most interested in finding bends in the pipe. At 90 degrees, they were too sharp of an angle for Visu-Sewer’s camera equipment to traverse. Opening those sections would provide a straight path down the section of pipe.
A pipe locator was brought in for the search. One component was attached to the camera. As the camera traverses a section of pipe, the supervisor above registers the locator’s signal on his receiver. When the camera got to a bend, the supervisor noted the location for an exploratory dig. “A couple times [the bend] wasn’t where we expected, so we had to move down and dig again,” Rossebo says. All told, Airy’s dug 13 pits for the entire project: eight in the residential area and five in the roadway.
Upon reaching the pipe, a portion would be cut out. Working one section at a time, Visu-Sewer staff cleaned, televised and dewatered the section. “The biggest step was to dewater,” Rossebo explains, adding that dips in the pipe would hold water. Crews pulled a pipe pig – a 14 in. wide Styrofoam cylinder – through the pipe after water jetting. That water was discharged to the closest Village sanitary sewer.
Where they once had 90 degree bends, Visu-Sewer suggested those be replaced with two 45 degree bends. The gentler curve allows for a smoother transition of flow in the pipeline, Rossebo says.
After lining, the open gap in the pipe was closed up by Airy’s Infrastructure. A section of spool pipe (new, replacement pipe) was attached using mechanical joint fittings to the ends of the lined pipe.
In the residential area, lining lengths averaged 500 ft, Rossebo says, and 850 ft each under the roadway.
Each access pit was then closed up and restored: grass seed or sod in the residential area and concrete in the roadway.
Force Main Requires Special Liner, Resin
A National Liner partner, Visu-Sewer installed Applied Felts AquaCure RP Liner. Made of fiberglass, it was designed to handle the operating pressure of 18 psi. Their product is uniquely designed for each project and can be designed for higher pressures, as well.
The resin selected was different, too. Vinyl ester is a less viscous product which correlates well with fiberglass liner resin saturation (“wetout”). Additionally, the resin offers better corrosion resistance and it withstands water absorption.
Per specification, each section of newly lined pipe was pressure tested by Airy’s. All tests passed successfully, Rossebo says.
In addition to capping off the access pits, Visu-Sewer reinstalled the three air relief holes in the system. As the name suggests, the relief holes allow air to vent in case too much pressure builds in the line.
The advantages of CIPP lining for gravity flow pipes apply to force mains, as well. “It saves them digging and replacing the whole [pipe] and the restoration that goes along with it,” Rossebo explains. “We can actually line from Point A to Point B and save all the restoration costs. Even though there is some disruption at times, it’s not throughout the whole sewer pipe. That’s really the big benefit.”
Fitzpatrick echoes that sentiment, pointing out the cost savings of lining versus trenching and replacing pipe.
An immediate benefit, he says, is that the Village no longer encounters the costly emergency repairs. They’ve also noticed an improvement in the flow to the gravity pipe. “The liner offers a very smooth surface versus the old ductile iron pipe,” he adds.
With part of this project running through residential neighborhoods, community support was paramount. The Village helped through an information campaign aimed at affected residents. “All the residents were very cooperative,” Rossebo says. “It went really well.”
He also credits Airy’s Infrastructure for their assistance. “It was to our advantage to have them as part of our team. They did a really nice job.”
Fitzpatrick praises the efforts of everyone involved. “[There was] very good communication between us – the Village of Tinley Park – and Visu Sewer and the engineering firm as well.”