Project of the Year

FDR Drive Outboard Detour Roadway

By Tom Stabile

A mile and a quarter of detour roadway is seldom the stuff of great acclaim. But the FDR Drive Outboard Detour Roadway left the awards jury marveling at everything from innovative engineering to smooth execution.

"The ingenuity of the FDR Drive project is what gets the kid in all of us excited," one judge said.

The temporary detour opened in May after 18 months of construction as the anchor of a $136 million project to rebuild the deteriorating highway. The signature of the $40 million detour portion, which runs from 51st to 64th streets, is the half-mile "outboard" built over water from 53rd to 60th streets.

"The whole concept of building a temporary bypass out in the East River and then taking it back down again afterwards is pretty unique," said David Vosseller, marine project manager for Weeks Marine of Cranford, N.J., which built the roadway in a joint venture with Slattery Skanska of Whitestone, N.Y.

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The detour carries two lanes of northbound traffic, allowing the project team to shut down one section of the permanent roadway at a time for major demolition and reconstruction. Among rebuilding tasks ongoing through 2007 are replacement of bridge and viaduct superstructures, rehabilitation of the highway roof structure and retaining walls, and retrofitting for seismic shoring, lighting, signs, and drainage. The highway, also known as the East River Drive, funnels 150,000 vehicles daily along Manhattan's east side, and is a critical artery linking bridges and tunnels up and down the island.

Observers from many vantage points, including the awards jury, have said none of that work would have occurred without the detour. That's because there was little appetite among city and state leaders for the more standard reconstruction approach - shutting down lanes, stomaching traffic backups, and likely requiring most of the work to take place at night. The jury noted how residents in the upscale East Side neighborhoods near the proposed work pushed hard to prevent a scenario that would have flooded local streets with traffic.

"It's also 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," a juror said. "Complex to execute technically without question, but also because of all of the work they had to do beforehand."

That backdrop explains why the New York State Department of Transportation sought other solutions, eventually turning to New York-based Daniel Frankfurt Engineers & Architects. Its president, Neil Lucey, said a highlight of the outboard detour approach is eliminating nearly all of the nighttime work.

"You could say under a conventional plan you'd have 20 more times nighttime work," Lucey said.

More Bridge Than Highway

The roadway's basic design impressed the jury. "From a technical standpoint, it's innovative," one juror said. "It's head and shoulders above the rest."

The 22-pier bent detour bridge section sits atop 64 steel pipe caissons socketed into the river bedrock. Those hold the steel superstructure supporting precast concrete panel slabs, a layer of asphalt, and a corrugated metal panel roof to shield noise and light.

The idea of a detour over water grew from a floating highway concept state transportation authorities had considered, Lucey said. His firm teamed with three other New York-based consultants - Earth Tech/TAMS, DMJM Harris, and Sam Schwartz Co. - to design an over-water detour with a protective fender system in the busy East River shipping channel.

"What made it possible was that the transition back to the land was there," Lucey said. "At the north end, it's the old 60th Street heliport, and at the south end, at about 53rd Street, there's a little disabled vehicle turnout."

That was enough. The team conjured up a temporary structure - more bridge than highway, Lucey said - that could keep the road's existing design speed, stay within the planned budget, gain necessary permits from agencies like the U.S. Coast Guard, and handle wind, currents, and ice. It planned a structure 10 to 14 ft. above mean sea level - higher than the permanent northbound lanes - and an alignment addressing all of those factors, as well as features such as subway tunnels below at 53rd, 60th and 63rd streets, the Queensboro Bridge above at 59th Street, and critical entry and exit ramps.

The study and design phases ran from 1998 to 2001, said Neil Porto, senior project manager for Daniel Frankfurt. Construction started in November 2002, with the joint-venture contractor splitting most over-water work to Weeks and most land work to Slattery.

Slippery Challenges

The team encountered the choppy East River early on. It has five to seven feet of tide variation and flows at 3.5 to 4.0 knots - close to 5 m.p.h. - which is a significant speed for marine work, Vosseller said. Sometimes those flows were in one direction on the surface and another below.

But Weeks had ample water work experience and resources, said Tom Bowers, engineer in charge and project manager for the department of transportation. For the over-water portion, Weeks met varying river conditions with one barge setup using anchors on the north side and another using a jack-up system that stabilizes against currents and waves on the southern half. Meanwhile, having multiple setups allowed the team to always be building at least two sections of the roadway.

"No one dreamed they would have two full barge setups in the water, plus a barge system for the fenders," Bowers said. "That saved a lot of time."

A major task for the barge crews was installing the caissons. But before they could proceed, the team had to make sure it didn't bore into the subway tunnels. Bowers said Slattery's infrastructure expertise - and its ongoing contracts with the Metropolitan Transit Authority in those same tunnels - was a big help.

In addition to helping the team precisely locate the tunnels to avoid damaging them with caisson boring, Slattery was able to piggyback the drilling schedule onto an already planned subway service outage for other work the company was overseeing in the East River tunnels. That saved months of negotiating with the MTA, Bowers said. The intricate work also helped the team plan for some land-based portions where the temporary roadway will place partial loads over the tunnel sections.

That planning set the table for one of the biggest technical challenges - digging holes for the 54-in. diameter steel caissons. Besides the fast current, the team had tough conditions at the river bed, where there was little or no soil on top of the bedrock, making it harder to drill. And there were other complications, Vosseller said.

"Trying to install and develop the sockets was hard, because the rock itself sloped on a 45 to 50 degree angle," he said. "We had to develop a method that was going to prevent that drilling equipment from skittering down that slope."

Despite the challenges, the Weeks team of divers, drillers, and other crews completed about one caisson every 2.5 shifts, working one shift a day. The procedure started with drilling about 55 ft. into the bedrock - already 25 ft. under the surface - and inserting a 90-in.-diameter casing as a slot for the core barrel drill. From there, the team placed a 79-in. diameter casing in the hole, and within that, developed a 74-in. diameter socket down to the drilled bedrock. The team then placed the 54-in. caisson in that socket and filled the entire casing with concrete up to the river bed. Above the bed, the caissons are hollow up to the superstructure, and they have a steel plate cap to connect with the superstructure.

On the portions of the fender and detour road installations under the Queensboro Bridge, the team had to shorten the crane booms in order to have enough headroom, Bowers added.

Decked and Fendered

Once caisson installation finished on a particular stretch, the next phase of installing the steel superstructure would begin. That framework consists of transverse steel-cap beams and 100-ft. long longitudinal steel girders.

Waves of work crews would roll behind each completed stage, so installation of the precast concrete deck followed as superstructure work finished. Right behind the deck came asphalt surface paving, followed by sound barrier panel installation. "It took a lot of project coordination, a lot of scheduling," Bowers said.

In tandem with the detour are other features, such as an elevated roadway serving as a temporary exit ramp for East 61st Street, and an entrance at 60th Street that rebuilt a ramp to the old heliport. "We're maintaining all the vital ramp connections," said Daniel Frankfurt's Porto.

Another technological highlight is the fender system out in the river. Porto said DMJM Harris designed the system, the first of its kind, to gently guide errant ships back into the East River channel, and away from the detour road.

The $28 million system consists of a 10-ft.-diameter floating fender beam "guardrail," in sections 250 ft. long, connected by 13 floating barge-like "dolphins." These 18-ft.-deep, 20-ft.-wide, and 20-ft.-long structures, encased in metal with a hardened black plastic exterior, stay in place amid changing currents and tides thanks to four rock anchors, some running 120 ft. deep, tied to each one with chains. Divers did a lot of the heavy anchoring work, Vosseller said.

Quick Lifespan

For all of its innovation, the temporary roadway will have a short existence. Built to last 10 years, its role is merely to buy time for crews rehabilitating the permanent roadway, particularly a stacked section where the northbound lanes are above southbound ones. Work began on that portion in earnest this year, with the installation of a demolition shield over the old northbound lanes, to which crews have diverted traffic heading south in order to begin work on the old southbound lanes.

Porto said a major point of pride is how the detour portion came together with almost no impact on the traveling public. "It was only when the crossovers needed to be connected that there was some weekend work during those times," he said.

Once the reconstruction work is done in 2007, however, the detour will leave little mark after the team disassembles it. Bowers said there are already plans for the sections to journey south by barge, where they will meet a watery grave - joining old New York City subway cars off the Atlantic coast in an artificial reef.