ILC Dover deploys new inflatable tunnel plug


Program manager for Department of Homeland Security John Fortune explains how the Resilient Tunnel Plug operates after inflation at ILC of Dover on Tuesday. (Delaware State News/Marc Clery)

FREDERICA — ILC Dover’s motto is: creating what’s next. On Tuesday, the company made it clear that inflatable tunnel plug technology and other anti-flooding solutions is what’s next.

The high-performance flexible material design, production and engineering firm, headquartered in Frederica, hosted a tour and demonstration to showcase their new resilient tunnel plug — a project they’ve been working on with Department of Homeland Security, Pacific Northwest National Laboratory and West Virginia University since 2008.

The concept was cooked up originally in 2007 when the DHS began brainstorming possible technologies capable of protecting tunnels from flooding in light of climate change, rising sea levels, increasing storm intensities and possible terroristic threats explained John Fortune, the program’s manager with DHS.

In 2012, Hurricane Sandy caused massive flooding in New York City’s subway system. It impacted seven tunnels and several stations. The South Ferry station, which flooded with 15 million gallons of salt water, was closed for almost five years and racked up restoration costs of $350 million. These hazards and costs are the ones DHS hope to see mitigated by the new tunnel plug and associated technology.

“We started looking in 2007 for a way to protect tunnels from flooding due to natural hazards or man-made ones,” he said. “When the idea of an inflatable tunnel plug came up initially, a lot of transportation experts were telling us that it probably couldn’t be done. But, we were funding some high risk, innovative programs at DHS and we reached out to Pacific Northwest Labs and West Virginia University to give it a try.”

Senior Design Engineer with ILC Dover, Jon Hinkle, shows a completely inflated Resilient Tunnel Plug at ILC of Dover on Tuesday. (Delaware State News/Marc Clery)

After a year of work on a concept plug, the project team deployed a prototype in one of Washington D.C.’s metro system tunnels. The test successfully met the projects main criteria and encouraged DHS to pursue it further.

“The test proved three things to us that were crucial: that we could fold the deflated plug up and store it compactly without affecting train functions, that we could inflate it fully within minutes and that it was capable of fully sealing off the tunnel,” said Mr. Fortune. “However, what the test didn’t do was prove that the plug could hold back flood water sufficiently. Our plug was made out of lightweight material — we needed it to be made out of a high strength fabric, that’s why we decided to include ILC Dover.”

ILC Dover is well known for its work in material science and engineering, perhaps gaining most renown for designed and manufacturing space suits since the Apollo era. The project team was confident that ILC Dover’s background in high strength fabrics would transform their prototype into a usable and widely distributable product.

Greg Holter, an engineer with Pacific Northwest National Laboratory outlined the six main criteria they wanted the tunnel plug to achieve when the development was moved to ILC Dover.

• It needed to be compact and easily fold-able so it can be easily stored.

• It needed to have operational readiness and be able to deploy quickly.

• It needed to be made with the strongest material available to withstand the tremendous pressure floodwaters apply.

• It needed sealing capacity against a variety of surfaces and tunnel shapes.

• It needed to be designed for integration into existing tunnels and transit system — intuitively designed for installation.

• It needed long term reliability and reusability.

According to Dave Cadogan, director of engineering and product development at ILC Dover, the firm has more than met those expectations with their design.

“Our plug is 16 1/2 feet in diameter, 32 feet long,” he said. “It weighs about 1,700 pounds and when inflated, it gets pressurized to 17 PSI. When folded, it fits into a very small container that’s essentially 4 1/2 feet by 3 1/2 feet. It’s like an airbag that conforms to the shape of the tunnel.”

Mr. Cadogan says that the material the plug is made of is where it really shines.

“The inside layer is a urethane coated nylon which holds the air, outside we have a Vectran material webbing,” he said. “The way it’s woven together make it extremely resilient. It can sustain a fair amount of damage as well because of the way that it redistributes load.”

ILC Dover built a test tunnel specifically to examine the performance of the plug. The half tunnel is designed in a way to simulate a flooding subway tunnel and allows engineers to pressurize water behind the inflated plug to gauge its performance.

From a fully stowed position, the plug can inflate to its target 17 PSI in about 12 minutes, which was within the response time desired by the DHS. Testing has shown that although a small amount of water does sneak past the plug as the flood water pressure rises, the standard subway tunnel pumps are able to divert the amount of water that escapes at an acceptable rate.

Ten years and about $15 million taxpayer dollars after the project started, the day these resilient tunnel plugs will be deployed seems to be approaching.

“Back in February and March, we did three very important validation tests and the plug performed acceptable every time,” said Mr. Fortune. “Several of the tests were for one hour, but one of them was for three weeks straight to see how the plug performed over a length of time. We’re at a critical point in the project. It’s a proven technology and could be rolled out in a matter of months. We believe that it will save money, property and potentially lives.”

Although there are several parties interested in the tunnel plug, ILC Dover is keeping the unit and installation prices confidential in the face of competing technology.

Adjacent projects

Since getting involved with the project, ILC Dover has been a part of the conversations with various transit authorities and tunnel operators about the eventual uses for the plug. In 2013, this blossomed into some complimentary products that are already in use in New York City.

“We were talking to the New York Transit Authority in 2013 and they were very interested in the plug, but they also really wanted to look in to more ways to stop flood waters at the surface before the got into the tunnels,” said Mr. Cadogan. “They had us look into other options which led us to develop three other types of solutions we call: Flex-Gates, Flex-Walls and Flex-Covers.”

Because cities like New York City have so many openings to their tunnel system they need to cover or block during storms, getting every one covered is often a manpower and cost struggle, said ILC Dover officials. Existing equipment used to block up tunnel vents and entrances during a storm often have to be stored elsewhere and hauled to the opening and installed before a storm.

The flexible gates, walls and covers ILC Dover designed are made of high-strength fabrics, can be deployed quickly, can be customized to fit a variety of openings and be stored at the point of use — solving many of the issues transit authorities face.

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