Horizontal directional drilling (HDD) has been used to install an electricity transmission line under the East River in New York.
The Champlain Hudson Power Express (CHPE) is a buried transmission line to deliver hydroelectric power from Canada to the New York metropolitan area.
The 545km-long project starts at the US-Canada border, travels south through Lake Champlain, under the Hudson River and crosses the East River to end at a new converter station in Astoria, Queens.
Installed in two parallel 1,585m drives under the East River, the HDD pipeline will house fusible PVC carrier pipe for the project’s fibre optic cables, connecting Randall’s Island and the Astoria converter station. Kiewit is the contractor on the project and Michels Trenchless the subcontractor for this trenchless segment.
HDD was chosen because of the depth of the East River, and the project was originally designed to have a pipe string out on Randall’s Island. However, space constraints, including rail crossings, highway overpasses, and a sports complex and recreational facilities in the area, meant pipe string out was not feasible, and an approach with a smaller footprint was needed.
For the crossing, Northwest Pipe Company supplied 3,170m of 508mm steel casing pipe with Permalok HDD joints. Permalok is a weld-free solution that allows for the casing pipe to be cartridge-fed from the launch rig side, eliminating the need for string out on the exit side.
The 345 sections of pipe were manufactured in 9m sections at Northwest Pipe’s Permalok plant in Missouri.
To prepare for the HDD pipe installation, Michels drilled two pilot bores, starting at 309mm diameter and upsizing to 864mm. The bores extend from the onshore launch rig at the Astoria converter station, 45m below the East River, to an exit rig on Randall’s Island. The first Permalok HDD joint was welded to a 36.5m section of uncoated steel casing, designed to absorb the vibration created by the spinning pull head. The pull head is used to guide the HDD pipe along the pilot bore path as it advances. Built by the Michels team, the drill rig uses a hydraulic press to push the pipe into the pilot bore and the interlocking design means no field welding is required.
Michels assistant operations manager Jeremiah Yliniemi said it was a simple process for a complex project.
“The Permalok HDD joint is very easy to work with and installs much faster and more efficiently than welding traditional HDD pipe strings,” he said. “The biggest cost savings are on welding crews and other equipment needed for pipe string layout and pullback assistance, plus it can all be done on the space you are already using.”
The installation was completed in a tight timeframe. The first 1,585m drive was completed in less than 2.5 days, averaging a rate of 30.5m per hour, and the second drive even more quickly.
