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Sewer Line

Evaluating CIPP Options for Large-Diameter Sewer Pipe Renewal

Challenge

Severely deteriorated large-diameter sewage pipes present special challenges for maintenance and renewal. Cured-in-place pipe (CIPP) and other emerging technologies offer more cost-effective alternatives to digging up and replacing failing pipelines. However, while CIPP has been used for more than 40 years for some applications, its use in large or technically challenging sites has not been extensively evaluated. At the same time, new materials, curing methods and other innovations for CIPP must be evaluated to determine cost-effectiveness, sustainability, and durability.

A wastewater utility in Irving, TX needed to rehabilitate 17,200 ft (5,243 m) of 96-in (2,400 mm) reinforced concrete pipe (RCP) running alongside a river. Both the diameter of the pipe and the length of sections to be restored presented special challenges as did the above-ground obstructions, which include a golf course. Fiber-reinforced CIPP presented a better alternative than traditional open trench replacement. However, before beginning the full project, they came to Battelle for assistance in evaluating alternatives and developing a plan for testing the installed materials.  Battelle also served as the lead of a full-scale field evaluation of the feasibility, complexity, performance, cost, and environmental impact of the technology selected.

Solution

Battelle has developed a framework for an innovative technology demonstration program to evaluate commercially available technologies to make the technologies’ capabilities better known to the industry. For the Texas large-diameter pipe demonstration, we used one 780 ft section of the pipe to serve as our demonstration segment. The fiber- and glass-reinforced liner was prepared and installed on site using a hot water curing method. During curing, we measured temperature in real time using a fiber optic cable and monitored readings remotely using a cell phone app. After the lining was cured, we completed a visual inspection of the liner and took measurements of the thickness, peak strength and short-term flexural modulus on various samples. Our measurements showed an average thickness of 35.0 mm and average peak strength of 11,848 psi, more than 2.5 times the required strength. Average short-term flexural modulus was 1,000 ksi, 4 times that required. The entire demonstration project was completed in six days, including pre-inspection, installation, curing, cool down, and post-inspection.

Outcome

The results of the project demonstrated that fiber-reinforced, hot water-cured CIPP was an appropriate technology to use for the full restoration project. The completed liner met the utility owner’s requirements, and testing showed that it exceeded the design requirements. As a result of the demonstration project, we were able to document the planning and preparation that would be needed for successful completion of the entire pipeline, and help our client make effective decisions regarding site access, layout, equipment and personnel needs. By completing the technology evaluation, we were able to give our client confidence in the technology chosen and the process of installation and testing. The data that we gained in the field demonstration will also be used to help the industry as a whole better understand how emerging CIPP technologies and methods can be used in a variety of technically challenging circumstances.