Seven HDD Crossings in Hampton Roads Harbor, Virginia
A 10-mile pipeline that connects the north and south sides of Hampton Roads Harbor — made possible through onshore and marine horizontal directional drilling — allows Virginia Natural Gas (VNG) to expand capabilities to serve a growing customer base and will also open new doors for HDD projects, industry experts say.
The project’s onsite work began in May 2008 with the final land-to-water shore approach completed and tie-ins of the 24-inch steel product pipe now under way. At the heart of the project were seven HDD crossings completed by Mears Group Inc. working closely with the prime contractor, Weeks Marine Inc.
Of those seven, one was a record length 7,357-ft crossing beneath the Elizabeth River and three were rare water-to-water drills under Hampton Roads Harbor that required the contractors to adapt to marine conditions.
It was a combination of the multiple crossings, water-to-water crossings and the challenges that the contractors overcame that made this the 2009 Trenchless Technology Project of the Year for New Installation.
Perhaps the most important water-to-water crossing was the 3,003-ft bore spanning the 53-ft-deep Newport News shipping channel, one of the world’s busiest commercial and military shipping lanes.
VNG senior project manager Les Flora, P.E., said HDD under the waterways was the only practical way to complete the marine crossings since governmental agencies would not grant permits for techniques, such as open-cut dredging due to environmental and shipping concerns.
Flora said, “The only way we could get a permit was to HDD... I’m sure that what the contractors have learned on this project will be of great interest to those in the industry.”
Flora said the project’s original design called for trenching across the majority of the harbor, but that plan was revised after entities such as the Army Corps of Engineers indicated that permitting would not be possible.
Instead, VNG looked to HDD techniques to cross the marine sections of the project, areas that include environmentally sensitive areas such as clam sanctuaries and oyster beds and shipping traffic that includes U.S. Navy ships that utilize the fueling station on Craney Island.
Flora said that by utilizing HDD techniques, the amount of material needed to be trenched decreased by about two-thirds the original planned quantity.
The marine environment created unique hurdles for the contractors to overcome: strong tides and currents, storms and sonar equipment from passing ships and submarines that momentarily fooled with steering readings.
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