Protected by Dolphins

Nov. 1, 2005

Never underestimate the value of a good fender in New York City. Driving in New York City isn’t as simple as it once was. Getting from point A to point B can involve many construction detours in between.

Never underestimate the value of a good fender in New York City. Driving in New York City isn’t as simple as it once was. Getting from point A to point B can involve many construction detours in between. Nowhere can reconstruction cause more delays than on Manhattan’s Franklin Delano Roosevelt East River Drive—known locally as “the FDR.” Constructed by the Works Projects Administration as part of the New Deal strategy to provide work for the unemployed, the FDR was built during World War II when steel was in short supply and automobile traffic was not. The FDR serves as a major artery connecting Manhattan to the Bronx and Queens through the Triborough Bridge in the north and to Brooklyn through the Brooklyn-Battery Tunnel in the south. The FDR also provides access to several important points along Manhattan’s East Side, including all of lower Manhattan, the United Nations, the midtown business district, the Upper East Side and the Queensborough Bridge. Hugging the East River, the FDR is now used by more than 150,000 vehicles every day. Like many other aging roadways, the FDR has another important characteristic: It’s crumbling.

Constructed primarily of reinforced concrete, the FDR’s underpass at Sutton Place is a region where space constraints required the FDR’s width to be narrowed by stacking the southbound lanes on top of the northbound lanes.

“This section of the FDR has taken a real beating over the years. Timber and steel were being used to shore up columns. And there was extensive leakage, so the whole structure was top-heavy and seismically unsound,” explained engineer-in-charge Tom Bowers of the New York State Department of Transportation (NYSDOT). “But closing a lane on the FDR—the traditional approach for most roadwork—was not an option here. This section of the FDR is already badly congested, and doing the repair work one lane at a time would have made matters worse. Leave it to New York state to do something so complicated and challenging. But then again, what do you expect? This strip of real estate is hemmed in on one side by a city that never sleeps and on the other side by Mother Nature.”

The “something” that Bowers refers to is NYSDOT’s unique, award-winning $136 million repair solution known as the “FDR Outboard Detour Roadway.” Carrying three lanes of northbound traffic out over the East River, this temporary roadway allows the contractor to shut down an entire section of permanent roadway for major demolition and reconstruction work. The effort entails the rehabilitation of the bridge and viaduct superstructures, including the highway roof structure and retaining walls; retrofitting for seismic resistance; and lighting, signs and drainage. Affecting a 1.28-mile stretch of the FDR, the five-stage project will be completed in April 2007.

Shining fender

Providing a seamless roadway during repairs, the 1,900-ft-long outboard roadway essentially functions like a coronary bypass. The northbound lanes get diverted at 54th Street and reconnect with the FDR near 63rd Street. The southbound lanes switch between the two levels, depending on which level of the underpass is being rehabilitated. Not just an elegant project approach, this innovative temporary roadway solution trimmed a 12-year project down to a five-year undertaking. But there was a hitch. While creating a temporary roadway extending over the river solved the traffic flow problem on land, it created new problems in the water.

Aside from being a considerable maritime challenge for any engineer, the East River also is a vital waterway for New York City and the region. With its heavy shipping traffic, the river provoked considerable concern about wayward vessels striking the roadway. Given the constant volume of traffic on the FDR, a sizable ship ramming the temporary roadway could be disastrous. To overcome the hazard—having an unprotected element in the path of maritime traffic—NYSDOT took the direct approach: they protected it with a fender system, the marine equivalent of a huge bumper.

The fender system is a major engineering feat that makes the entire project possible.

“[It] had to meet several criteria,” explained Joe Klein, FDR East River Drive fendering system project manager for DMJM Harris, the marine experts tasked with designing the structure. “First, the permits require the roadway and fendering system to be temporary; they need to be easy to remove once roadway reconstruction is complete. The design also had to contend with water depths ranging from 40 ft to 65 ft and with greatly varying subsurface conditions. In addition, it had to span two pairs of subway tunnels. But there was one more critical criterion. Although most high-capacity fender systems can be designed to be sacrificially damaged when a severe collision occurs, this fendering system had to bounce back and remain fully functional to defend the roadway after all but the most severe collisions.

“The system we put in place meets those criteria by taking advantage of the narrow geometry of the channel; it limits the feasible range of an errant vessel’s heading. Because the roadway runs parallel to the channel, the only threat to the roadway is the lateral component of ship velocity. With the ship approach angle limited by the narrow channel, the lateral component is comparatively small. Recognizing this, the system does not try to slow the parallel-to-channel motion of an errant ship. Instead of trying to stop a vessel on a collision course, the system is designed to deflect it back toward the channel and out of harm’s way. To do this, the system provides a continuous, smooth impact face parallel to the channel to avoid snagging the parallel-to-channel motion of the ship.”

No small achievement, the $17.7 million fendering system features 13 barge-like pontoons called dolphins. Each dolphin is 12 meters long, 6.1 meters wide and 5.5 meters deep.

“We tethered the dolphins to the river bottom [bedrock] with a series of rock anchors and chains,” explained Boris Levintov, DMJM Harris’s principal engineer on the project. “The chains maintain the elevation of the dolphin no matter what the tide level, but allow it to move laterally in response to a collision. The depth and elevation of the dolphins maintain tension in the chains, even in low-water conditions. As the tide rises, the increasing buoyancy causes higher tension levels in the anchor chains.”

Berthing process

To avoid excessive tension in extreme high-water conditions (which might arise because of a storm), the dolphin deck is set at an elevation only slightly above mean high water, limiting buoyancy by going awash whenever such an event occurs.

Long sections of internally stiffened floating pipe—called berthing beams—extend from one dolphin to the next. Rising and falling with the tide, they slide on vertical guides provided in the face of each dolphin. The berthing beams provide the continuous, smooth impact face that is required to deflect any errant ship back toward the channel. Fitting together seamlessly, the elements of the system provide maritime protection as well as a solution as unique as the outboard roadway itself. “This was innovation by necessity,” explained Ed Schmeltz, a DMJM Harris senior vice president and director of the firm’s marine business. “As far as I know, nothing like it has ever been done before. It was created, however, for a very good reason. First, the roadway needed to be protected. That meant working in the East River, which imposes some very challenging constraints. It has fast currents, varying depths and subsurface conditions and two subway tunnels in the project area. In addition, this is a heavily used waterway. In a way, it’s almost the marine equivalent to the FDR itself in terms of traffic. But we had a unique advantage here: We know the East River and its marine environment. This isn’t our backyard; it’s our front porch. Our founder began the firm with a project in the East River. So we knew exactly what we’d be wrestling with. That familiarity helped us develop this fendering system, which we consider to be the optimum, unobtrusive way to protect marine traffic, the roadway and the traveling public—which is the ultimate goal of the project and NYSDOT.”

Constructing the roadway and fendering was no picnic. “The East River has tide variations of 5 to 7 ft, and it flows at 3.5 to 4 knots. That’s almost 5 mph. That may not sound like a lot on land, but in the water that’s a serious current to reckon with,” explained David Vosseller, marine project manager for Weeks Marine of Cranford, N.J. (Weeks built the roadway in a joint venture with Slattery Skanska of Whitestone, N.Y.) “And sometimes the river flows in one direction on the surface and another direction below the surface. So that presented some unique difficulties. But the fast current wasn’t the only challenge.

“There was little or no soil on top of the bedrock. That made it much harder to drill. And the rock itself sloped on a 45° to 50° angle. To prevent the drilling equipment from skittering down the slope, we had to develop an entirely new drilling method. This project required quite a bit of innovation on everybody’s part to get the job done.”

NYSDOT’s Bowers acknowledged both the effort and the expertise involved, noting that Weeks had the water work experience and resources to come up with solutions—such as the use of two full barge setups in the water, plus a barge system for the fenders—that saved a lot of time.

All-star league

The unusual approach has paid off. Not only has NYSDOT found a quicker way to rehabilitate the FDR, they’ve done it in a way that will cause virtually no interruption for New York drivers and the neighborhoods bordering the FDR. That achievement has not gone unnoticed. Dubbed the “Project of the Year” by New York Construction News, the project was described by one juror as being “in a league of its own for the innovation and the thinking and the cooperation they had to elicit from the United Nations, from the Coast Guard, from the neighbors. . . . The ingenuity of the FDR Drive project is what gets the kid in all of us excited.”

Driving in New York City is challenging. Find the gas pedal. Find the brake. Find the horn. Crawl from point A to point B. Deal with everything in between. But for drivers on the FDR and the surrounding side streets, driving could have become much more difficult. Without the inventive FDR outboard detour roadway, traffic on Manhattan’s East Side would have come to a veritable standstill while work progressed. The FDR outboard detour roadway sidestepped that considerable annoyance. But the outboard roadway would not be viable without protection in the water, without the state-of-the-art, singularly designed fendering system. And as most New York drivers know, never underestimate the value of a good bumper in New York City.

Sponsored Recommendations

The Science Behind Sustainable Concrete Sealing Solutions

Extend the lifespan and durability of any concrete. PoreShield is a USDA BioPreferred product and is approved for residential, commercial, and industrial use. It works great above...

Proven Concrete Protection That’s Safe & Sustainable

Real-life DOT field tests and university researchers have found that PoreShieldTM lasts for 10+ years and extends the life of concrete.

Revolutionizing Concrete Protection - A Sustainable Solution for Lasting Durability

The concrete at the Indiana State Fairgrounds & Event Center is subject to several potential sources of damage including livestock biowaste, food/beverage waste, and freeze/thaw...

The Future of Concrete Preservation

PoreShield is a cost-effective, nontoxic alternative to traditional concrete sealers. It works differently, absorbing deep into the concrete pores to block damage from salt ions...