Mears Group, Inc. recently completed a record setting bore as part of the Hampton Roads Crossing being constructed by Virginia Natural Gas (VGN).
The drill consisted of installing 7,357 linear feet of 24-inch steel pipeline under the Elizabeth River. This record setting drill was the second in a series of large directional drills that will be required to construct the pipeline system linking Norfolk to Newport News, VA.
Utilizing complimentary services made available by being part of the Quanta Services network, Mears was able to take on the entire first segment of the project as a turnkey operation, subcontracting sister company Bradford Brothers Inc. (BBI) to handle pipe related activities. BBI not only fabricated the steel pipe for the Elizabeth River bore they also handled the pipe during pullback, performed hydro tests, ran gauging/sizing pigs, and connected the crossing to the first drill installed by Mears on the project; a 1,000-foot installation under the Old Dominion University golf course.
To complete the initial pilot hole under the Elizabeth River, Mears utilized a 660,000 pound drilling rig which was set up in a parking lot on the Old Dominion University campus. In accordance with the design, Mears entered the drill at a 12 degree angle, and ultimately achieved a maximum depth of 110 feet over the length of the crossing. Because local conditions presented many challenges to utilizing traditional land based steering methods, Mears teamed with the general contractor, Weeks Marine Inc., to equip a barge with a mobile coil set-up. This innovative approach allowed Mears to track the drill bit at incremental points along the designed installation route verifying position and accuracy while greatly reducing the impacts of river currents, marine traffic etc., during pilot hole installation activities.
After completing the pilot hole, Mears brought in a second 160,000 pound drilling rig which was set up on the exit side of the crossing and used to assist the 660,000 pound rig with reaming operations. Once the hole had been suitably expanded to 32-inches, the pipeline was connected and pulled back under the Elizabeth River. The pullback process lasted approximately 22 hours from the time the pull head initially entered the hole on the exit side until it reached the entry pit at the rig.
Installing the pipeline using HDD methods presented many challenges typical of projects this size. During the reaming phase an old oyster bed was encountered that contributed to the collapse of the hole, which ultimately resulted in a break of the drill stem on the entry side off the 32-inch reamer. Through the experience of the Mears management team, which included Site Supervisor Mike Vidomski and Operations Manager Bob Stern, the situation was quickly dealt with and the project was not significantly delayed.
There were also challenges in finding a suitable location to fabricate a 7,500 foot-long segment of pipe. Les Flora, project manager, VGN, Risa Durrett, construction manager, VNG and Carolina Palmer, project manager, Weeks Marine, worked together in resolving this issue which was handled in the end by fabricating the pipe in two offset segments. The first segment was constructed on the Navy’s Carney Island fuel terminal, while the second was welded along the South edge of the Craney Island project. The two segments were then joined just prior to pullback and managed by cranes and cradles, suspending the pipe over an existing pipeline and access road below. The project was an overall success due primarily to the experience of the contractors involved and the cooperative efforts of the entire project team.
Mears Group: (800) 632-7727, www.mears.net