In Beverly Harbor and Collins Cove, workers will drill from both sides at the same time, with the two sides meeting somewhere underneath the middle.
“This method is preferred, as it is less time-consuming, and the exact entry and exit locations can be predetermined,” wrote Algonquin.
At its deepest, the line will run roughly 80 feet below the Collins Cove seafloor. Once the reaming process is complete, sections of pipe will then be pushed into the hole, each welded to the next. Later, the pipe will flushed for dirt and debris.
It will be a similar process for Beverly Harbor, except that the beginning point for one side of the HDD hole will be underwater, 85 feet from where it will tie in with the HubLine.
To access to that site, workers will set up an at least 85-feet-by-55-feet cofferdam, an enclosure that will be constructed with steel support beams and sheet piles driven into the seabed. Suction pumps eventually will be used to excavate materials around the connecting points, and the resulting water and soil slurry will be pumped into barges.
Work to link the pipelines is expected to take between four and five months and is scheduled for next summer. Numerous support vessels and material barges will likely be employed throughout the process.
As for the horizontal directional drilling, the Beverly Harbor portion is expected to take 45 days, and the Collins Cove portion about 75 days.
On land, the pipe will generally be laid about 5 feet underground, though deeper burial might be necessary in certain areas. The pipe will be coated with an epoxy to protect it from corrosion, and certain pieces might have to be bent on site to fit curves in the route. Algonquin will install a 2-feet-wide yellow warning tape above the pipe and below the grade of the land to warn anybody digging that the pipe is below.