Polypropylene Pipe Used For Maine Combined Sewer Overflow Project

January 2012, Vol. 67 No. 1

The West Side Interceptor sewer replacement project in Portland, ME, utilized a 60-inch diameter, high performance polypropylene pipe to increase conveyance capacity, replacing a smaller 100-year old vitrified clay line and separating a parallel 10-foot diameter combined sewer, which now solely conveys storm water.

Completed in October 2010 after just five months of construction, the combined sewer overflow (CSO) abatement project used some 5,600 feet of 60-inch SaniTite HP pipe from Advanced Drainage Systems Inc. (ADS). The $4 million project replaced runs of 24-inch and 30-inch diameter pipe from Congress Street to Lucas Street with a single larger diameter pipeline to eliminate combined sewer overflows at Capisic Pond Dam and stop untreated wastewater from flowing into the Fore River Estuary.

Last summer, the city of Portland was awarded first place for this project in the Public Works Excellence Competition from the Maine Chamber of the American Public Works Association (APWA) in recognition for efforts performed demonstrating excellence, quality, innovation, value and community satisfaction.

The design, by engineering consulting firm Woodard & Curran Inc. (Portland, ME) specified several pipe options such as epoxy coated, reinforced concrete (RCP) and centrifugally-cast glass fiber reinforced polymer pipe. The critical requirements were that the pipe provide a watertight joint and meet the city's standard for pipe stiffness of 46 PII.

"Aside from being rugged, one of the reasons we went with the ADS pipe was because we could set it in place simply with our backhoes and wouldn't need cranes," explained Ken Grondin of R. J. Grondin & Sons, Inc. (Gorham, ME). "Plus there were logistic issues. If we used concrete pipe that comes just in eight-foot lengths, we'd have nearly 200 truckloads that we'd have to coordinate to the holding site and then move again piece by piece to the trench. That's a lot of extra handling and traffic control. So with the 20-foot lengths of the ADS pipe, instead of the eight footers, there are essentially three times fewer trucks required, and it worked out pretty well."

Grondin and his crew buried the line at depths ranging from eight to more than 20 feet. "We basically followed the line of the old pipe, but we did have some challenges. The last half of the project was through a park with a wetlands complex and ecological features that required close attention. In that area, we were limited to a 30-foot wide travel corridor to install the line where it could be as much as 22-feet deep."