by Jason Feldman

The Franklin Delano Roosevelt Drive, known to most New Yorkers as "the FDR Drive," was built when its namesake sat in the White House.

It was constructed as part of the New Deal's Works Projects Administration, created primarily to give work to the unemployed. World War II - and a steel shortage - came along as it was being built.

No wonder the FDR needs some work.

"It was primarily constructed of reinforced concrete with some use of steel on the east line columns, said Neil Porto, associate and senior project manager for Daniel Frankfurt Engineers and Architects, the project's New York-based design engineer. "The concrete shows deterioration. In some cases, timber and steel are being used to shore up columns. There is extensive leakage, and it's top heavy so it is seismically deficient.

"The roadway is severely deteriorated. It has lost about 80 percent of its structural capacity, and express buses are no longer allowed on the roadway. The program is to get the FDR Drive back to HS-20." Under the auspices of the New York State Department of Transportation, work began late last year on a $138 million project to reconstruct the FDR from 54th to 63rd streets.

Preventing Hemorrhage
Despite its age and decrepitude, the FDR Drive, running along the East River from Harlem to the southern tip of Manhattan, is one of the city's major traffic arteries.

It connects to the Bronx and Queens through the Triborough Bridge in the north, to Brooklyn at the Brooklyn-Battery Tunnel in the south, and provides numerous points of access to Manhattan's East Side as well as to every one the city's East River bridges. About 130,000 vehicles travel it everyday.

Closing the drive while reconstructing it was not an option. Even shutting some lanes while working on them, as is traditionally done, would have resulted in a traffic nightmare.

The solution has been the construction of a temporary outboard detour roadway and fendering system in the East River. Once the detour is in place, the construction team will be able to close sections of the old highway without interrupting traffic flow. Additional benefits include a faster schedule and a reduction in night work.

The outboard roadway has three segments:

• An elevated structure, to be constructed over the East River from East 53rd Street to East 59th Street.
  
• An elevated structure that serves as the exit to East 61st Street for the Northbound Roadway. The 61st Street exit is critical for traffic flow to the Queensborough Bridge.
  
• An at-grade portion from East 59th Street to East 64th Street.

The outboard roadway will be supported on 60- to 100-ft.-long caissons socketed to rock. A precast concrete deck will be placed on top of the caissons. Drilling the 64 caissons was difficult, said David Vosseller, project manager of Cranford, N.J.-based Weeks Marine Inc., the project's marine contractor in a joint venture with Whitestone, N.Y.-based Slattery Skanska.

"The rock slopes 45 degrees, which made it tough to ensure the shaft location during the drilling," Vosseller said.

The river's current also played havoc with shaft location. "The typical flow of the river is 3.5 knots; if you throw piece of wood into the river you would have to run to keep pace with it," Vosseller added.

To combat the sloping rock and keep a level platform during the drilling, the drilling platform was set up on hydraulic jacks. As soon as the platform was level, bores were drilled anywhere from 30 ft. to 80 ft. down to bedrock.

A temporary caisson was then lowered to the rock and filled up to 10 ft. with concrete. "If the roadway were a permanent structure the whole shaft would have been filled," Vosseller said.

Placed on top of the caissons will be an 1,800-ft.-long composite steel superstructure with a precast concrete deck, said Jason Stern, project manager for Earthtech TAMS Consultants Inc., the New York-based consulting engineer for the outboard detour roadway.

"We chose steel because it was the most economical solution," he added. "Precast was chosen because it was the fastest to place and it gives us better quality. In addition, the precast roadway eliminates the chance that loose concrete will fall into the water. The concrete deck will be overlaid with 1.5 in. of asphalt."

Protecting the Outboard Roadway
Because the outboard detour roadway will be built in the East River, there was concern about wayward vessels striking the roadway. To alleviate the risk, a fendering system will be constructed that will deflect ships away from the roadway.

The fendering system will consist of 13 18-ft. by 20-ft. by 20-ft. structures called dolphins. "They are basically a two-story building that will be secured by four rock anchors and chains," Vosseller said.

The rock anchors consist of 17-in. H-piles that are drilled straight into bedrock and connected to chains. Connected to the dolphins will be a 250-ft.-long, 10-ft.-diameter pipe with bracing inside.

Vosseller said connecting the chains in the current was difficult. "We have six divers attaching the chains to the dolphins and the rock anchors," he added.

Each link of the chain weighs nine tons.

The Start of Something Big
After the outboard detour roadway is complete by April, northbound traffic will be diverted to the detour and work will begin on the Southbound Viaduct Structure. The Southbound Viaduct Structure consists of a 27-in.-thick reinforced concrete slab supported on the west side by a massive concrete retaining wall.

On the east side, longitudinal edge girders support the slab; the majority of the columns are reinforced concrete. The east girders are supported on pairs of slender steel-riveted steel columns spaced 45 ft. on center. The columns extend down to concrete piers at the lower level, which are supported on piles or rock.

This structure will have to be removed with the not-inconsiderable task of chopping through 27 in. of reinforced concrete, said Jerome Daraio, senior project manager for Slattery Skanska. Daraio said that during the removal stage, a shield will be placed under the structure to ensure safety.

The replacement structure will consist of longitudinal steel stringers supporting a standard New York State Department of Transportation concrete deck. Design engineer Porto said the deck will provide better performance and will be more easily maintained.

During this period, the roof deck will also be rehabilitated. While the roof deck is being rehabilitated, parks on 56th, 57th and 58th streets will be rebuilt. This work is scheduled to last 21 months.

Afterwards, traffic will be detoured through the new southbound roadway while work will begin on the northbound section. This eight-month job includes the removal of the protective shield over the roadway; new drainage and lighting; repair and seismic retrofit of walls, roof and columns; construction of a new barrier; and paving.

When that part of the job wraps up, traffic will be placed back on the northbound roadway and the $40 million temporary detour roadway will be removed.

"Without that roadway, it would have been a 12-year job instead of five years," Dario said.