Coordinated Effort: Sliplining to Improve Water Quality in Saint John

Port City Water Partners – the consortium of consultants, contractors and financiers formed to design, construct and manage the public-private partnership (P3) project — slated 10 km of the project be sliplined using high density polyethylene (HDPE) piping. According to Nicholas Miller, who served as a project coordinator for ACCIONA Infrastructure, EPCM and one of the Port City Water Partners member companies, approximately 4 km of pipeline on the west side and 6 km on the east side were sliplined.

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Handling the sliplining portion of the project was U.S.-based Murphy Pipeline Contractors. “The work was spread over three years based on the segment area that they were working at that time, which meant we had to mobilize and demobilize on three different occasions,” says David Kinsella, director of operations at Murphy Pipeline Contractors.

For the trenchless component, the logistics were some of the more complex aspects of the job. Part of Miller’s duties included sequencing all of the moving parts of the transmission main work for the project.

“Some of the lines we were sliplining were in service during the project and we could only shut them off when other new trenched piping was installed,” Miller says. “We sliplined sections because there was access to the old piping and there were some rock cuts if the project went open cut. We used what we could to keep costs low and reduce disruption.”

Because of this sequencing, Murphy Pipeline Contractors completed portions of the project in 2016, 2017 and 2018. This project required the use of both local workers and Murphy’s own employees. All told, Murphy Pipeline Contractors had 10 people on the project and transported its specialized equipment to New Brunswick with all other equipment rented locally.

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Murphy Pipeline Contractors mobilized all of its specialized sliplining equipment to Saint John for its project and opted to source all other equipment locally.

“The spec that the city’s engineer developed was fairly stringent. We had to send a gauge pig through before we pulled in the new line to make sure there weren’t any flaws. They also required a lot of camera work,” says Miller. “When we opened a pit, we had to send a camera down to look for obstructions or protrusions.” Miller adds that the engineer specified that gouging had to be limited to less than 7 per cent of wall thickness. Normally this spec would be around 10 per cent.

In some sections the thickness of the pipe could be off as much as 2 cm. Based on the vintage of the pipe following an initial CCTV run, it was discovered that there were several areas where unknown services protruded into the pipe. Those were removed before sliplining could commence.

“This is something we deal with on a lot of projects,” Kinsella says. “Especially when working on pipelines that were installed in the 19th century and the records were not up to scratch.”

Sliplining in Saint John involved the structural lining of 10 km of 24-in. cast iron transmission main with 22-in. HDPE pipe. Because of the higher C Factor of HDPE pipe, the designers were confident a 22-in. pipe would not result in a loss of capacity to customers. Port City Water Partners sourced the Uponor HDPE pipe from Engineered Pipe Group in Dartmouth, Nova Scotia.

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Though 90 per cent of its work is in the southern United States, Kinsella notes that Murphy Pipeline Contractors is always on the lookout for interesting and challenging projects. “This project opened the doors to our Powell River project in British Columbia,” he says.

At this time the Safe, Clean Drinking Water Project is wrapping up. All of the west side work was in service in late summer 2017 and the east side system was placed into service in January 2019.