Polypropylene Pipe Used For Maine Combined Sewer Overflow Project

January 2012, Vol. 67 No. 1

The sanitary manholes (SMH) from ADS were fabricated at the factory using the 60-inch SaniTite HP pipe with a 48-inch riser. Once in place, each was encapsulated in concrete with a field-placed steel reinforcing cage. Each of the 21 structures was individually designed for an H-20 load rating and fill heights. The alternative was to use eight-foot precast concrete structures that would have been heavy and cumbersome to move especially in some areas.

"We had low clearance under an electrical transmission lines and had to maintain the required separation that the local utility required. And that went well. The shorter pipe lengths and the fact that the pipe is easy to move made it possible. We were able to use small machines and worked a little slower," stated Grondin.

"And for this project we used their T-base as well instead of concrete access manholes. This made it possible to maintain the alignment and be in the same trench, rounding the corners, etc.

"For us it was ideal to use T-bases because essentially you plug them in and at the end of every night you can open up the line installed that day and go home, not worry about flows or your bypass pump as opposed to a precast concrete structure," he continued

But there was a greater challenge that awaited the R.J. Grondin crew. The last half of the pipeline would go through a park with a wetland 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 was as much as 22 feet deep," Grondin stated.

Another local company, Everett J. Prescott, Inc. (Gardiner, ME) provided logistics and system design support.

Gorrill-Palmer Consulting Engineers, Inc. (Gray, ME) was selected to perform construction monitoring services and provided continuity between the city and R. J. Grondin and Woodard & Curran.

The project started June 2010 and had to be completed in five months. Bedrock, terrain, low power lines plus an ecologically delicate wetland all presented time barriers.

The Capisic Pond area is an inland wading waterfowl habitat, as identified by the Maine Department of Inland Fisheries and Wildlife and the Department of Environmental Protection, which limited construction to starting no earlier than Aug. 1 and ending no later than Oct. 15.

With the park deadline fast approaching, R. J. Grondin brought in another crew, basically splitting the park segment in half, one crew starting upstream, the other downstream and meeting in the middle.

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