This project shines a light on a not-too-often considered use of the cured-in-place pipe (CIPP) relining method.
As an international air hub for the Baltimore-Washington Metropolitan area, Washington Dulles International Airport is a 24-hour, seven-day a week, hub of activity. Clearly, this is not a place people want to see without power or taxi and runway areas shutdown for repairs.
The airport recently undertook a project to improve its electric infrastructure, much of which is buried deep below the tarmac. Prime contractor on the project was Cynergy Electric Inc., which contacted Aiken, South Carolina-based Pipe Lining Co. to handle the rehabilitation of the conduit.
“The rehab was needed due to failing electrical lines throughout the airport. The owner chose the trenchless method because the location of these electrical lines since they were encased in concrete banks and ran underneath the airport’s working terminals,” says Robert Giancroce, owner of Pipe Lining Co. “Trenchless rehabilitation was the only way to prepare the conduits for new wiring without interrupting the day-to-day operations at one of the nation’s busiest airports.”
Made of Orangeburg pipe and set in the 1960s, the conduit ran approximately 4,000 ft below Terminals C and D at the airport. The lines are encased in concrete banks and connected via manhole at different lengths and heights. The length of these conduits ranged from 125 to 480 ft. The manholes ranged from 8 to 18 ft deep. These manholes also varied in location; some were in mechanical rooms while others were in the middle of the taxiways.
Assembling the Team
“In the lining industry Orangeburg has become a ‘no fly zone’ per se — no airport pun intended — since it can be unpredictable and become incredibly unsound structurally over time. It was certainly challenging at the start,” Giancroce says. “Once we began preparing for this particular project, we did extensive research and testing on Orangeburg pipe and looked into how it would react to the products we currently use.”
Planning for the project took almost a full year with Giancroce signing the contract in October 2021 and mobilizing to site in June 2022. He notes that part of this was due to clearing the required security checks to work at the airport. The rest, he says was planning, including coordinating with Cameron Manners at Internal Pipe Technologies (IPT) on getting the proper liner and working with trenchless industry veteran Rick Fast to utilize his NuConduit system developed specially for lining electrical conduit.
“It’s not the first [electrical conduit] project that Rick [Fast] has done. It’s the first large project that we’ve done. We did a small piece at Charleston Southern University, but this is the first Orangeburg,” says Giancroce. “Cynergy Electric reached out to us because we are a lining contractor, they contacted several other contractors that weren’t interested.”
The original plan, Giancroce says was to only handle the lining portion of the project; cleaning was added after the original cleaning contractor ran into some problems.
Preparation Is Key
What Giancroce’s team found out was that the Orangeburg conduit was plagued with what he refers to as internal blistering and external blistering. The former, like a paint blister, was caused by the heat of the electric lines running through the pipe and water. The latter were likely caused when the pipes were installed – over compressing the concrete, people standing on the pipe, etc. – because behind those blisters was solid concrete. One 450-ft section was so bad it took 10 days to clean.
Giancroce and Fast developed tools specific for the project that helped clean and prepare the pipe. The crews used a combination of methods including steaming the conduit by inserting a calibration tube and inflating it, to millers and more standard cleaning practices. This preparation work resulted in what Giancroce terms, “a rifle barrel finish.”
Unlike a sewer, which has grade to it, these conduits are flat, meaning the team had to use manual methods to make sure the line was completely dry before pulling the liner in place. After cleaning a sewer, some internal anomalies might be present, but still be okay to line and put into service. Electrical conduit is a different ball game. There are more precise requirements for maintaining the circular shape of the pipe and calculations for running a certain level of voltage through the conduit.
“We had to revive Orangeburg that had been blistered, torn and battered over the years so that we could seamlessly line the pipe with only ¼-in. margin of error and meet the roundness required,” Giancroce says. “Two different sizes of electrical mandrels had to be pulled through prior to lining and after lining. All conduits had to be videoed and preapproved prior to lining by the airport authority’s personnel.”
Custom Lining Solution
The custom-made 4⅞-in. diameter, 2-mil thick, liner was made of a geotextile felt that made it stronger and seems were overlap welded so it could withstand being pulled into place without tearing. Giancroce and Fast sourced a custom-made flame-retardant resin for the project. When complete the new liner had to be able to withstand the high heat produced by the electric line running through the conduit. Because of access, the crew could not invert the liner, so a pull-in-place product was required. Wet-out took place onsite as each run was pulled into place.
Work began in June 2022 and as of December 2022, The Pipelining Co. completed the work of cleaning and lining two 4,000-ft runs of conduit. Giancroce notes that the lining itself was relatively straightforward – similar to what his crews would see relining sanitary lines – it was more the location of the lines that posed the most challenges and required constant communication.
“It was imperative that there was transparent and frequent communication between The Pipelining Co., Cynergy Electric, the airport’s operations team and the employees at United Airlines,” he says. “Luggage carts, firetrucks, operations vehicles, and of course airplanes themselves were always a factor in determining how to navigate our working areas and timeline in addition to the customs area and TSA agents.”
When all was said and done, Giancroce was impressed with the finished product, as was Cynergy Electric. Cynergy Electric handled pulling the new lines in place and used a cable puller capable of 7,500 lbs of pulling force. Typically pulling through PVC conduit Cynergy Electric typically sees pulling forces in the 2,500- to 3,500-lb range. They reported to Giancroce that they never had to go beyond 800 lbs when pulling through the NuConduit product.
“We can’t have wrinkles in the liner. This is artwork. It’s a rifle finish. And that’s because of our preparation work, the way IPT made the liner, the resin we acquired, and the processes developed by Rick,” says Giancroce. “It’s smoother than PVC pipe. I can’t be prouder of the finished product. What we were able to accomplish at Dulles International Airport was incredible. Instrumental in getting the project done was Sam Finnerty, our operations manager, and his team. Overall, our team did a fantastic job.”