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Frequent Challenges For Winter Ocean Drilling In Maine
Water crossings -- installing utilities under streams, rivers, lakes and other bodies of water -- are among the most significant benefits offered by horizontal directional drilling technology.
Perhaps the most challenging water-related installations are those with the pilot hole launched from the shore and extending beneath the water of a bay or ocean, exiting through the floor of the body of water.
The past winter, drilling contractor ETTI, Lisbon Falls, ME, completed a project to take a 12-inch diameter HDPE sanitary sewer outflow line from a pump station into the Atlantic Ocean at Northport, ME. The project owner was the Town of Northport. The Town operates under a Maine DEP permit to discharge treated effluent into ocean. This project extends the outfall line an additional 300 feet to allow better mixing and dispersion of the treated discharge, said Tim Folster, vice president of operations, Sargent Corp., primary contractor for the project.
The project was designed to be constructed in the winter because the area has many high-end seasonal homes used from spring through fall, and the outfall was located adjacent to the municipal pier which is a gathering spot for tourists.
The design length of the outfall, from the pump house on land to the underwater exit point of the outflow line, was approximately 300 feet with an additional 300 feet laid upon the ocean bottom.
The original plan called for burying the pipe by open-cut construction using 100,000-pound excavators with extended booms working off barges, to excavate a trench underwater and allow the pipe to be installed and then backfilled.
“Without question, the plan was risky and would be very time consuming to execute,” said Kelly.
The Sargent Corp. approached ETTI seeking the HDD specialist’s input about whether directional drilling could be utilized.
“Actually,” said Kelly, “the first site visit raised major concerns. Drilling in Maine in January itself poses many issues with cold temperatures and short workdays. Structures are necessary to keep the mud systems warm and lines must be broken down quickly to keep them from freezing. Add to that the drill unit would have to be set up in a spot where tides average 11 feet. And moving 600 feet of 12-inch diameter pipe across the water in those rising tides and high winds seemed almost impossible.”
However, Kelly said Sargent is a bold and progressive company, always ready to think outside the box.