2024 Trenchless Technology Rehabilitation Project of the Year – The Front Street Interceptor
Due to the project’s complexity, challenging logistics and intricate engineering and installation efforts, the Front Street Interceptor rehabilitation project in Harrisburg, Pennsylvania, has been awarded the 2024 Trenchless Technology Project of the Year for Rehabilitation.
Many water and wastewater structures built centuries ago were both functional and architecturally stunning, blending beauty with utility. However, in today’s world of rehabilitation, these once-picturesque structures present significant challenges for those responsible for upgrading and improving their functionality.
Such was the case in the Pennsylvania capital city of Harrisburg, when the 113-year-old Front Street Interceptor was in dire need of rehabilitation before it deteriorated to the point of a possible catastrophic end.
The Front Street Interceptor, situated in the heart of the historic and popular Susquehanna Riverfront Park, is a critical concrete box arch pipe that conveys a significant portion of the region’s combined sewage, handling over 20 million gallons per day during wet weather events. Spanning nearly three miles, the interceptor’s condition has long been a concern for its owner, Capital Region Water, with efforts to address its deterioration reaching a point of urgency.
This project demanded innovative thinking, specialized expertise, and a great deal of patience and precision to rehabilitate this critical infrastructure for long-term durability into the next century. Its distinctive, hard-cornered rectangular shape required the application of a recently adopted ASCE standard for non-circular pipe design to ensure both efficiency and success — the first major U.S. project designed using this standard.
A considerable amount of engineering was utilized in the planning, implementation and verification phases. With the use of cured-in-place pipe (CIPP), wetout liner for all 28 installs — some that were more than 1,000 ft in length — were able to be trucked in. In all, approximately 725,000 lbs of resin was used in the project. This combination of install method, diameter, shape, location, depth and alignment are rare and unique and were the central focus of this $18 million project.
“We were extremely excited to hear that this project was being considered and actually awarded this honor, knowing the complexity, scope and scale of the other projects nominated,” says Capital Region Water vice president of engineering Jeff Bowra, P.E., PMP, who oversaw this project for the public utility.
“The industry is booming. With infrastructure funding the way it is and the need where it is, there are some great projects being designed and planned,” says Insituform vice president of sales Andrew Costa. “So, to stick out in a crowd of great projects with exceptional execution from a team that works their butts off is an honor. The amount of blood, sweat and tears that went into this cannot be measured. To be recognized is very special for us.”
Project Description
Capital Region Water (CRW) is a publicly funded authority, entirely supported by ratepayer fees, that assumed control of Harrisburg’s water, sewer, and stormwater assets in 2014. The utility provides wastewater services for the City of Harrisburg and portions of surrounding municipalities.
The Front Street Interceptor conveys flows from roughly half of the City, as well as the entirety of Susquehanna Township. Built in 1911, the Front Street Interceptor had never undergone rehabilitation or upgrades since its original construction. “When we took over in 2014, we started a CCTV inspection program, which prioritized inspection of all of our interceptor sewers,” says Bowra.
The inspection data revealed such significant deterioration in the Front Street Interceptor that CRW immediately made it a top priority. Bowra noted the severe state of the structure, which included exposed rebar, concrete loss, cracks and voids along its 14,000-ft alignment, all indicating severe compromise.
“We were definitely concerned with the loss of wall thickness and preserving what was there with some type of rehabilitation or liner system,” Bowra says. “Our primary concern was to address the pipe before something catastrophic happened.”
The interceptor’s unique shape added many layers of complexity to the design and execution of this project. Its shape consists of several sizes of rectangular cast-in-place concrete box pipe with straight side walls and curved top and invert sections in four discrete cross sections:
- 5 segments of 32-in. x 30-in
- 7 segments of 36-in. x 30-in.
- 11 segments of 39-in. x 36-in.
- 10 segments of 42-in. x 42-in.
Onsite work for the rehabilitation project took place from October 2022 to August 2023. While the massive and critical bypass was constructed by United Rentals, work began by two cleaning crews (Utility Services Group and Duke’s), removing more than 300 tons of debris.
Front Street Interceptor Project Challenges
This project presented numerous engineering and construction challenges, demanding the full expertise, patience, and innovation of the design and contractor teams to successfully rehabilitate the interceptor. The site itself offered numerous issues, including its limited and narrow access to the pipe, making for a careful, precise and precarious route for equipment delivery.
“Our access was a 14-ft wide concrete trail next to the river. There was not a lot of room for error,” says Insituform project manager Nick Rosengarten. “Every tractor-trailer had to be reversed up the trail from the access point — a very narrow trail — for 28 installs.”
The 17,000 ft bypass ran continuously, allowing the Insituform crews to safely work inside the pipes during the process, which included restoring the lateral connections. “We had personnel crawling through these pipes all the time and their safety was critical,” says Rosengarten.
Due to the project’s location in the heart of Harrisburg’s largest and busiest park, the standard approach of starting at one end and progressing through to the other wasn’t possible. Instead, the rehabilitation of the interceptor began in the most heavily trafficked section: the middle. This area, which attracts thousands of visitors in the spring and summer for concerts, art festivals, marathons and bicyclists, needed to be addressed first.
“The project was also unique because it had to be sequenced and staged with a very tight timeline in order facilitate all the social activities in the area,” Costa says. “Strict deadlines were non-negotiable and execution needed to be flawless to meet the outlined schedule — exactly how the owner needed it and how the engineering team designed it.”
Logistics also included ensuring there was a consistent delivery of liners to the site so that work was not disrupted or delayed. Due to the small footprint needed and tight access, a crane was positioned to pick up and lower the wetout liner into the liner’s tower for water inversion installations.
“Logistics for this were a feat in and of itself,” Rosengarten says. “The liners were made in Mississippi and shipped to Indiana to a wetout facility, where we coordinated the wetouts of the liner to be impregnated with resins. We were getting six to seven liners a week. [Because of the liner’s size and weight], installation included tubes with up to 62,350 lbs of resin, special permits and police escorts were needed in trucking them to the site to keep the liners coming to us consistently to keep the job moving.”
Project Design
The design of this project was a challenge like no other, due to the interceptor’s unique non-circular shape. AECOM engineer and trenchless icon Chris Macey was the lead on this endeavor, tasked with designing and quality assurance/quality control.
“I’ve worked on a lot of vintage pipes in my life so I have much more faith in them when you test them than most people,” Macey says. “CIPP in this case was most unique. I have great respect for engineers of different [eras] but sometimes they put shapes together that just blow me away. To call this interceptor a ‘box’ was grossly oversimplifying it.”
Macey followed the relatively new North American standard for non-circular pipe design — ASCE MOP145 — marking its first use on a project of this size, scale and complexity.
“MOP145 is new to North America [as a standard] but it is based on the French national standard so it’s not ‘new’ necessarily,” Macey explains. “I’ve been borrowing [the French standard] for oddball pipe shapes for the last 10 to 15 years because it has been a proven standard and we understood it.”
But, as Macey notes, using the new North American standard for this project required CRW to trust the AECOM and Insituform teams — as well as the process.
“It was a leap of faith for the owner, and, in some cases, for the contractor, as thickness design was not only using a ‘new’ standard, structural design responsibility shifted back to the engineer of record as opposed to conventional CIPP project delivery” he says. “We showed them this was the proper way to use it and that it was the only the way to look at a shape like this one and be comfortable with close-fit lining technology.”
The Front Street Interceptor required Macey to run more than 2,000 design cases to understand and confirm the CIPP dimensions and mechanical properties, as well as forcing the Insituform team to obtained many large size liner samples in the installation phase to make sure the design requirements could be verified, he said.
According to Costa, use of MOP145 enabled Insituform to truck-in all installs vs. installing over-the hole, which drastically reduced cost, increased the quality of the installation, reduced risk and quelled potential environmental concerns of onsite wetout, along with the smaller footprint and reduced social impact. The use of reinforced tubes, combined with the optimized design approach, reduced the required resin volume from well over 1.8 million lbs to the 725,000 lbs used. In some sections, an unreinforced product would simply not have been technically feasible to build, Macey explains.
All involved attribute the project’s success to the collaborative partnership between CRW, AECOM and Insituform. “We worked well together and understood the complexity of this project,” Rosengarten says. “We were all on the same page throughout to get this done.”
Costa further notes this about the project site, “Pulling off a successful large diameter CIPP rehabilitation project on the historic waterfront location with all of the challenging components makes it a very special job. The pipeline’s riverfront alignment also traverses under a large railroad bridge, which provided additional access, installation and sequencing challenges on an already difficult work plan.”
He adds that this project tops Insituform’s list of non-circular pipe projects in terms of complexity and size. “We’ve done odd rectangular and non-circular shapes before. I don’t think we have done one to this magnitude,” he says.
“It’s exciting that something can get recognized for all of the innovative things that people contributed,” Macey says. “Projects that achieve success as a result of a collaborative effort are something to be truly celebrated.”
Sharon M. Bueno is editor of Trenchless Technology.
