When you step aboard a tugboat, no matter the size or the horsepower, you will not be going fast. But how about a trip down the Chesapeake at 1-3 knots — from Baltimore to Portsmouth, Va.? That’s about 170 miles. Now, how about taking that trip six times, towing a sealed, semi-submerged, 350′ rectangular tube with a 25’6″ draft?
That’s exactly how crews involved in the movement of the first six sections of the new Midtown Tunnel for Norfolk, Va., spent the month of June. Tampa, Fla.-based Dann Ocean Towing, known for taking on complex projects, coordinated the delivery.
The new 4,200′ two-lane tunnel under the Elizabeth River is being constructed in 11 segments. The tubes are being fabricated by the tunnel’s general contractor SKW Constructors at the old Sparrows Point shipyard in Baltimore. This tunnel is not a typical steel shell, concrete-lined tube, but a cast concrete rectangular tunnel. Casting was completed on the first six sections in early June and Dann Ocean assembled a fleet of tugs to assist in shifting them from the graving dock to a lay berth nearby.
“It was a tricky move,” according to Stephen Dann. The tubes cannot make contact with the tugs except at certain points. “Each piece weighs approximately 16,000 tons. Because of [their weight]and their draft, they are slow to turn and very difficult to maneuver on sailing and docking.”
For the trip down the bay, the tubes were towed by the 3,000-hp Express Marine tug Honor with the 2,700-hp Stephen Dann made up with pushing gear on the stern.
SKW, a joint venture of Skanska, Kiewitt and Weeks, is now working on the next five segments at Sparrows Point. Once they are complete, the nail-biting shifting and the excruciatingly slow tows will start all over again.