Large-Diameter CIPP Used as Part of Major Stormwater Drainage Improvement Project at Georgia Tech

When Georgia Institute of Technology (Georgia Tech) first opened its doors in October 1888, there were only 84 students attending the school. Today, more than 125 years later, the university boasts more 21,000 undergraduate students and is ranked as one of the top 10 public universities in the United States.

Georgia Tech’s campus is nestled on 400 acres in the heart of Atlanta. The landscape is hilly, tree-filled and, over time, has become checkered with campus buildings ranging from administration, departmental, research, and classrooms to dormitories, student activity centers, parking garages and recreational facilities
However, all this growth has taken its toll on the university’s Ecosystem, particularly in the area of storm water run-off. Since the Institute began monitoring stormwater runoff, it has risen from 315 CFS in 1951 to more that twice that, 698 CFS today.

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Recognizing the ecological performance of its campus today is very different from what it was in the past — when there were fewer buildings, streets and sidewalks and more natural vegetation — the university implemented a comprehensive stormwater management and drainage improvement program.

One of the goals was to improve storm water run-off, whereby Georgia Tech’s contribution to the Atlanta storm sewer system would be reduced to 1951 hydrology conditions. IPR SE led on this project and Georgia Tech graduate Fil Borroni said that part of this plan was the development of the Eco-Commons; a natural retreat on campus where shrubs, trees and other native plants pay will enhance and promote the Institute’s historical landscape.

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Eco-Commons is a unique project that leverages the development of a new storm water management system as an opportunity to provide new wooded and open areas for education, research, and passive and active recreation on the Georgia Tech campus. In keeping with Georgia Tech’s focus on sustainability, this project will ultimately improve the quality of life on campus, while at the same time serving as an outdoor lab for storm water management and hydrology studies.

The line in question was approximately 1,385 ft and 72-in. in diameter reinforced concrete pipe (RCP).For Phase I of the Eco-Commons stormwater infrastructure improvement, it was determined a section of an interceptor sewer line, which is actually owned by the City of Atlanta, but was routed below this newly designated section, was contributing too much of the increased stormwater runoff. The line in question, approximately 1,385 ft and 72-in. in diameter reinforced concrete pipe (RCP). Adding to the complexity was an additional 100 ft of 78-in. old rubble wall construction. Since it now lies beneath, buildings, streets and green space, above-ground logistics, cost and student safety were concerns.

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Early discussions and original plans called for the physical relocation of the line. However, because of what was now above it — buildings, streets, sidewalks and a lot of student traffic — it was the City of Atlanta that suggested a trenchless solution be used, specifically cured-in-place pipe (CIPP).

“The City proposed using CIPP as an alternate method and we jumped at that opportunity,” stated Jerry Young, landscape project manager at Georgia Tech. “Since the City had much success with CIPP in the past, its endorsement of this process helped us become more comfortable with a trenchless solution and get this job under way a lot faster.”

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Contractor Selection Criteria Important

Specifying a trenchless technology was also less disruptive and a natural fit for the Eco-Commons goals and objectives of developing a sustainable area using environmentally friendly means of restoration.
However, Georgia Tech’s lead contractor in charge of the Eco-Commons project, Manhattan Construction, had little experience in the area of overseeing trenchless infrastructure repair methods. “We weren’t very familiar with this technology when we started the construction process. Manhattan is traditionally a vertical builder rather than being focused on underground infrastructure. With Tech’s confidence in our abilities, they asked us to take on this role,” said Don Bailey, senior project manager at Manhattan Construction. “Working closely with Jacobs Engineering, we performed a tremendous amount of investigation, to find best way to line this pipe.”

Steve Lindsey, senior pipelines rehabilitation specialist and project engineer for Jacobs Engineering also expressed concern about the ability to restore the old arched pipe sections. “Given some of the unique rehabilitation aspects of this project, we felt that the contractor must also be well-versed in multiple trenchless rehab methods,” said Lindsey. “We knew that portions of this line would require some additional reconstruction.”

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Over the hole, large diameter CIPP rehabilitation, in this case 72 in. in diameter, is much more complex than a typical 8-in. liner job.Ultimately, four contracting firms were interviewed and asked to bid on the project. Based on a combination of experience, cost and a solution-based approach, IPR Southeast was awarded the project. “IPR did a very good job from the get go of really showing us they knew what they were doing,” stated Bailey. “IPR an excellent job of describing the process.”

Once the project was approved to proceed, the IPR team went to work fast. Since both the RCP and arch pipe were well more than 100 years old, the pre-installation inspection revealed quite a bit of prep work; in particular the separate sections of 78-in. brick arch culverts. IPR is nationally known for its solutions-based approach and is equally qualified to perform a variety of trenchless applications. For this unusual condition, IPR brought in its EcoCast crew to fill the annular arch space with a cementitious spray to match the incoming and outgoing 72-in. RCP lines. The filling of the annular space allowed the lining crews to install CIPP straight through the portions of arch pipe to ensure a seamless liner from manhole to manhole. Once this and other standard prep work was completed, the CIPP lining portion of this project was ready to commence.

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Student Safety and Minimal Surface Disruption

“One of the big reasons for choosing the CIPP method is that we had a lot less surface disruption on campus. Safety was also a big issue. The original project would have taken months using open trench, and would have caused major headaches on campus,” said Young. “The whole time we were doing this project, we didn’t really disturb anything. Students were able to safely walk past the construction site and ecologically, other than three entry pits, we didn’t have to dig anything up.”

“Considering the location of the line, it was determined that the CIPP lining would be divided into three segments, or ‘shots,’ to complete the task,” said IPR project manager Eric Simpson. The first shot, which was roughly 400 ft, ran from State Street to Atlantic Drive. In its path were a parking lot, a campus building and a parking garage. The second shot, approximately 390 ft, ran from the front of the garage on Atlantic Drive, beneath the street and ended in student recreational area called Glade Park. The third and final shot ran 555 ft from Glade Park, through a heavily wooded area and ended on Cherry Street.

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Over the hole, large diameter CIPP rehabilitation, in this case 72 in. in diameter, is much more complex than a typical 8-in. liner job. The wetout process alone takes up to eight hours before the first few feet can be inserted and must be conducted onsite right next to the entry pit. “It is also critical for the resin’s pot life be long enough to last through the entire wetout, insertion and curing process,” added IPR vice president of technology Al Jedneak. This is where the experience of the installation crew becomes critical to the installation’s success.

The Georgia Institute of Technology Eco-Commons Infrastructure Sewer Rehabilitation Project in Atlanta.

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As the first few feet of thoroughly saturated liner come off the line, it is immediately lowered into the hole and “turned” into the pipe section. Water is then used to invert the liner into the pipe. For this particular job, it was calculated that a constant 10 ft of head pressure was required to push the liner through. On average, the liner moved through the old pipe at about 18 ft per hour. Once it poked through at the end of each shot, IPR’s boiler truck quickly heated the water up to 185 F to activate the resin and begin the curing process. In each case, the liner cured in place in four to six hours. Once cured, laterals were restored and the line was placed back into service.  To keep the job moving, IPR rotated two crews on 12-hour shifts and worked around the clock to complete the task.

In all, the contractor was able to complete the 1,385-ft, 72-in. diameter relining in just less than three weeks. Other than a few sidewalk and street closures, for safety purposes, faculty and students were not inconvenienced. The surface environment was relatively unscathed and the storm sewer system was rehabilitated to improve stormwater flow rates. All this was done in a matter of weeks as opposed to the many months it would have taken to dig and replace the old system.

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Mike Vellano is vice president of sales and marketing for IPR.

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