With the pipe buried below a busy highway and a need to keep it in service, Warwick Sewer Authority officials had to look beyond the dig-and-replace method
The sole pipe delivering wastewater to the headworks of the Warwick Sewer Authority’s (Rhode Island) treatment plant lies beneath Interstate 95. So the fact that the 48-inch cement pipe was corroding and needed repair created a dilemma for the utility.
With an average of 4.7 million gallons of wastewater from 21,700 customers flowing through the pipe daily, service needs to be maintained. And a temporary bypass across I-95 was out of the question unless Warwick Sewer was interested in receiving backlash from drivers.
According to a recent article in the Warwick Beacon, the utility decided to use a sliplining method to solve the problem. The utility awarded the $753,902 contract to R. Zoppo Corp. of Stoughton, Massachusetts to run 42-inch fiberglass composite pipe through the deteriorating pipeline.
In the article, Warwick Sewer’s collections system manager, Matthew Solitro, says pits were to be dug on both ends of the pipe and the top half of the pipe will be cut off to allow the new pipe sections to be placed within.
The sections are grooved so that they fit within each other and they were rammed into place through 650 feet of the old pipe. A grout was also injected in between the old and new pipe so that a solid connection is formed.
During this process, wastewater was to remain flowing.
According to the article, Warwick Sewer was taking on this repair just in time. Last year, a camera inspection of the pipe revealed corrosion due to hydrogen sulfide gases. Oftentimes, that can also mean the pipe taking on an oblong shape, which would have made a method like sliplining difficult, the utility’s executive director, Janine Burke, says in the article. Fortunately for Warwick Sewer, the pipe hadn’t deteriorated to that extent.
Though the pipe diameter was being reduced by 6 inches, the sliplining project actually will improve flow in the line and increase its capacity by 5 percent. In the article Solitro says that’s because of the smooth lining of the new fiberglass composite pipe compared to the rough interior of the old cement pipe. Regardless, the treatment plant is still well below capacity at 4.7 mgd. It was designed for 7 mgd.
The project was completed in early November. According to the article, it won’t impact ratepayers. Burke says funding is coming from fees assessed to commercial users who don’t meet pretreatment requirements.
Source: Warwick Online