Under The Pond

By Jeff Griffin, Senior Editor | March 2013, Vol. 68 No. 3

“We use a guide rope stretched across the water to keep the boat on course above the path of the bore,” Kelly explained. “If another boat crossing under the causeway hit the rope, it would delay the project and potentially do damage to our boat.” ETTI’s solution was to put a team member on top of the newly-constructed bridge with a two-way radio to keep watch for boat traffic. When a boat approached, the guide rope was detached and lifted out of the boat’s path.

Another challenge was fusing 500 feet of HDPE pipe along busy Route 302 while keeping traffic flowing and businesses accessible to customers.

To avoid interference with normal activities, ETTI used two fusing crews on the side of Route 302 opposite the businesses. Two McElroy TrackStar 412 fusing machines fused the pipe.

Moving pipe
After the string of pipe was assembled, it weighed approximately 10,000 pounds, Kelly said. Personnel of Wyman & Simpson and excavating contractor R.J. Grondin & Sons helped move the pipe string across the street in front of businesses and positioned for the pullback.

“The challenge here,” Kelly said, “was to move the pipe without damaging it and to delay traffic as little as possible. To prevent disturbing a bank and newly-completed landscaping, the crews used their equipment to lift the pipe off the ground and support it during the install, leaving room for vehicles to use both the entrance and exit to businesses.”

Fusing required four hours with another hour to position and lift the pipe.

The pilot bore was completed in about five hours through sandy clay using an 11-inch Railhead bit. Bore depth under the floor of Brandy Pond was approximately 31 feet. The exit point was in a parking area on the west side of the causeway in front of a residence so access was not difficult but still tight with all of the necessary machinery.

Two backreaming passes were made with an 11-inch rock wing reamer with pipe pulled in behind the reamer on the second pass. Backreaming and pipe pull in took about 12 hours.

Once the pipe was in place, ETTI personnel installed MJ adapter kits on both ends of the HDPE pipe so that the crews from Wyman & Simpson could make their final connections with mechanical joint ductile iron pipe.

Ahead of schedule
Start to finish, the HDD installation took two and a half days.