Turbidity problem addressed
Spray in place liner from 3M extends life of ductile iron pipe in Dieppe, New Brunswunswick
In Dieppe, New Brunswick, complaints about the quality of drinking water running through a decades-old water main had city engineers scratching their heads for a solution that wouldn’t create too much disruption for residents.
After examining its options the city elected to go with a spray in place liner from 3M. The area with reports of turbid water was in an older neighbourhood containing ductile iron pipe likely installed soon after the end of the Second World War.
Flushing the pipe was unsuccessful in improving water quality, as was a later attempt to swab it; in fact, swabbing only seemed to make the problem worse.
A neighbourhood survey, combined with flow models, indicated that the pipe was in a section with low flows, which explained the high turbidity levels. A CCTV camera inspection did not provide conclusive evidence of the extent of the wear on the pipe, but the results were enough to indicate that there was tuberculation and that the pipe was structurally sound.
Ruling out a cured in place pipe (CIPP) solution due to its higher cost, Dieppe chose 3M’s Scotchkote Pipe Renewal Liner 2400. Applied through a spin cast trenchless process, the Scotchkote Liner 2400 is appropriate for pipes made of steel, ductile iron, cast iron, cement, asbestos cement and PVC, in pipe diameter ranges of 100 to 900 millimetres.
One of the main advantages of 3M’s liner is its quick return to service, often the same day. For Dieppe, that was important because it meant the job could be done without need of a bypass. As a precaution, a two-day boil water advisory was issued, then lifted after positive water quality test results were returned.
No need for external curing sources
The contractor, Trenchless Solutions out of Moncton, NB, dug three access pits in preparation for lining the 150-metre stretch of pipe. The process started by rack feed boring, which uses rotating steel flail arms to dislodge tuberculation along the pipe, and was followed by another CCTV inspection to assess the cleanliness of the pipe. The spray in place liner was then applied with a spinning spray head which coated the inside walls of the water main.
Scotchkote’s two-part polyurea allows for a fast cure time, without need for external sources like heat or ultraviolet light. The material usually hardens in 10 minutes and is fully cured within an hour.
One of the main advantages of the Scotchkote Pipe Renewal Liner 2400 liner is its quick return to service, often the same day. The liner is appropriate for pipes made of steel, ductile iron, cast iron, cement, asbestos cement and PVC.
Chris Vienneau, senior water distribution operator with the City of Dieppe, said a spray in place liner is a good solution for areas of the city that do not require an increase in the size of the pipe and with little disruption to the asphalt or other utilities. With most of Dieppe’s infrastructure under 20 years old, and most of the newer pipes made of plastic materials, there is not a pressing need to replace older concrete or iron pipes.
However, Vienneau suggested for those pipes that are reaching the end of their service life, the 3M solution works well in extending its usefulness, if the results from their water main relining are any indication. The best judge of the job’s success are also the toughest critics: area residents.
“Prior to this project, we installed automatic flushing apparatus on the hydrants just to make sure that we were getting water through that dead zone. The water we wasted and the time it took to go and check on those things was incredible,” said Vienneau.
“After [the pipe relining], we tested a couple of samples. We said, ‘We’ll wait until they call,’ and they never did. No news from the residents is actually good news for us. So I think they were satisfied.” CUI