Covering Up History Makes Room for the Future


Story Number: NNS170818-11Release Date: 8/18/2017 12:02:00 PM
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By Jennifer M. Zingalie, Norfolk Naval Shipyard Public Affairs

NORFOLK (NNS) -- Since the 20th century America has seen many changes especially in the realm of warfare and technology.

At that time Norfolk Naval Shipyard (NNSY) had been building ships for approximately 150 years and had already been through three major wars.

During World War I Dry Dock 6 and 7 were constructed for the U.S. Shipping Board Emergency Fleet Corporation. Then, steamships were becoming the primary means to ship people and goods due to improved speed and fuel efficiency and when the docks were completed in 1920, merchant ships were first to enter. The goal was to support commerce, in the interest of the United States, while helping Europe rebuild after suffering from the remnants of war.

The dry docks were built as a pair each measuring more than 465 feet in length. Both opened Oct. 31, 1919 with a grand ceremony attended by King Albert and Queen Elizabeth of Belgium as well as a distinguished party from Washington, including the Secretary of State and Secretary of the Navy.

Eventually the docks were given over to the U.S. Navy for use.

Fast forward to the 21st century where modernization has grown exponentially and Dry Dock 6 and 7 are no longer relevant. In fact, the docks fall approximately 500 feet short in their ability to support the modern day fleet. That's because for a dry dock, size matters and that isn't bound to change any time soon. Consider a new class of ship, the Gerald R. Ford-class aircraft carrier, the replacement for Enterprise and Nimitz-class, soon to be delivered to the fleet, which is 1,092 feet in length.

"You'd have to lengthen the docks extensively for them to be relevant -basically combine them and then double the lengths. That would be a very expensive Military Construction Project, about $1 million per foot," said Moises Finale, structural engineer and NNSY Dry Dock Program Manager, who has been on the Dry Dock 6 and 7 project for almost four years.

"They are also a detriment to the Navy assets around them, it just makes sense to demolish them as it allows us to better take care of those surrounding facilities."

Dry Dock 6 and 7 sit right in the middle of Dry Dock 3 and 4; having the most impact on 4 because the foundation is no more than five feet away, explained Finale.

"Water weighs approximately 64 pounds per cubic foot. If I fill the docks and leave them sit there--overtime it would start to settle and immediately impact DD4," said Finale. "Whether the dock is active or passive, if one moves the other moves."

What ultimately causes the domino effect is a structure underneath the dry docks that most never get to see or experience. The docks have a vast tunnel system that resemble something like an underground city, explained Finale, some reaching as far down as 70 feet. In turn, the tunnels along with an intricate pumpwell system, serve in the watering and dewatering process.

At NNSY, all of the dry docks are interconnected through these tunnels. The shipyard maintains these tunnels and pumpwells to ensure ongoing operation and safety standards are being met to support the fleet. "That is the beauty of this yard, to touch one thing is to touch many other things," said Finale.

Because the shipyard has not docked a ship in DD6 and 7 in several years, the Navy performed a risk assessment on them and determined, since adapting them was too costly, closing or demolishing them would be most cost efficient and beneficial to the integrity and safety of the docks surrounding them.

Before the demolishing process could begin, however, the docks would need to be dewatered. Typically the process would go something like, valves open, water pours into a space underground, the pumps pick it up and send it back out to the river. Although, normally straight forward, the openings underground, where the water would flow, had been closed off by concrete due to the lack of use.

To further complicate things, about seven years ago, a severe storm came through Hampton Roads and a decision was made to fill Dry Dock 6 and 7 in order to maintain the integrity of their caissons (watertight retaining structures that allow water to be pumped out of an area to create a dry working environment).

To do this, the shipyard decided to put a cofferdam right outside the apron of Dry Dock 6 and 7, explained John "Sunshine" Frazier, dry dock engineer.

A cofferdam is a temporary enclosure built within, or in pairs across a body of water and constructed to allow the enclosed area to be pumped out.

"The cofferdam was constructed by round, steel piles driven into the ground, followed by sheet piles attached between them to create a wall between the river and the dry docks so they could be pumped down," said Frazier.

The concrete apron acts to support the pile structure and works to prevent undermining, basically to keep the base material from washing out."

Once the pumps were placed inside the cofferdam the dewatering process began June 10, and lasted about a week.

Emptying the docks is just the beginning, said Finale. The remaining openings underground will also be filled in to ensure all points where water once flowed will be sealed.

Demolishing a dry dock does not mean the use of implosion or a wrecking ball. Put simply, the docks will be filled in. This will be done using piles (a structure driven into the ground to support weight over top of it), concrete, engineered dirt and a layer of asphalt to top it all off.

"After a lot of studies and finite element analysis, we found the safest method for the fill in was to use the piles to reduce the magnitude of the settlement," said Frazier. "They reduce the risk of Dry Dock 6 and 7 moving at all-because of general or distributed weight."

Once the docks are filled in, it will be almost as if they were never there and the shipyard will gain approximately 1.83 acres of land back that can be used as lay down for ship repair for the surrounding projects.

When work of this magnitude needs to be completed it is not an easy task and affects multiple departments, schedules, contractors and projects. The work completed, and which still needs to be done on these docks, is no exception. It isn't just the docks that touch each other at the shipyard but the several dozens of people, at all levels, involved in the ongoing work.

"This is a huge project in the middle of two other dry docks, in a very busy sector of the shipyard. The coordination has been astronomical," said Finale.

He and his team have worked closely with Naval Facilities Engineering Command (NAVFAC) as well as the shipyard's Public Works Department and two current projects, the La Jolla (SSN 701), which is being converted into a training vessel, and USS Rhode Island (SSBN 740), which is at the yard for an 27-month Engineered Refueling overhaul.

"At times it felt like we were never going to get started but we worked with everyone and as problems arose we would solve them. We tackled issues one at a time and before you know it things started to happen," said Finale.

The success we have seen so far has been a culmination of a lot of people working together and we haven't even broken ground yet."

Although the 20th century has long passed and the docks will soon be gone, their purpose served--their foundation will remain. As history continues to write itself and advances made, ships will continue to come in and out of the shipyard. Dry Dock 6 and 7 demolishment helps pave the way towards the shipyards future and the mission of the Navy in the 21st century and beyond.


For more information, visit www.navy.mil, www.facebook.com/usnavy, or www.twitter.com/usnavy.

For more news from Norfolk Naval Shipyard, visit www.navy.mil/local/nnsy/.

 
 
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