Dann performed the “wet” towage of 11 tunnel elements for the new midtown tunnel constructed by SKW Constructors in Norfolk, VA.
Running beneath the Elizabeth River, the midtown tunnel connects the cities of Norfolk, VA, and Portsmouth, VA.
Each element measured 350’ x 54’ x 28.5’ and drafted between 25-26’ and had a displacement of approximately 15,000 tons.
The elements were built in the graving dock at Sparrows Point in Baltimore, MD, and “wet” towed to Portsmouth, VA.
The tunnel elements were coated with a waterproof membrane that tugboats were not permitted to make contact with. Contact was limited to 8 steel protective grillages.
Dann worked closely with SKW representatives and the USCG to ensure the project was completed safely and successfully. Dann developed the towing plan and met with the USCG to ensure safe transit from Baltimore Harbor to the Chesapeake Bay, thus reducing the need for channel closures and limiting the impact on maritime commerce in the Port of Baltimore.
Float Out – June 9, 2014
The project occurred in two phases. The initial 6 elements were transported in June of 2014. The graving dock allowed for the construction of a maximum of 6 elements. For SKW to meet their scheduling requirements, the “float out” was required to occur during a 12-hr. period. It was imperative the elements be removed on one tidal sequence so construction could begin immediately on the next 5 elements.
The water depth at Sparrows Point allowed for minimal under keel clearance and the date of June 9th was chosen based on the predicted tidal height.
To make matters more interesting, this tidal sequence required the operation to be performed at night.
The route from the graving dock also made for a tricky movement. All of the elements had to be turned 90 degrees in a limited area and then pass through a narrow bottleneck to get to the temporary lay berth.
For this evolution to occur in this time frame, it required a total of 9 tugboats. As no one company had nine tugs available of the varying sizes required to perform this operation, Dann provided logistical support coordinating without outside tug vendors to ensure the safe handling of the elements.
Dann provided senior port captain to handle piloting duties. As this was not a “normal” vessel, the handling characteristics of the elements were unknown and Dann had to learn the peculiarities of moving the tunnel elements on the fly.
The planning paid off and by morning the last of the element was beginning the 220 nautical mile voyage down the Chesapeake Bay.
All 6 elements were moved successfully to Portsmouth and Dann was again chosen to transport the remaining 5 elements in March of 2015.