PROVIDENCE -- They finished delivering the city's new bridge yesterday, putting the 80-foot-high, light green arch in place over the Providence River next to the Hurricane Barrier.

You could say it was a natural delivery. Mammoet, the Dutch moving company, largely relied on the tide to gently lower the 5.5-million-pound bridge onto its piers.

The two barges that had carried the bridge here from North Kingstown the day before had spent the night at the head of Providence Harbor, just south of the bridge site.

Yesterday morning, workers from Mammoet and Cardi Corp., the general contractor, aided by two tugs, eased the barges north, between the reinforced concrete piers built to hold up the ends of the steel arch bridge. Mammoet had jacked the bridge up 30 feet before it was loaded on the barges so it could pass over the piers at high tide.

Each end of the bridge's three arch beams had to end up precisely on its respective pier top, so that bolts put through holes in plates under the end of each arch could fit into holes cast in the tops of that pier.

It is a tight spot. The barges had to be inserted between the piers without hitting the Hurricane Barrier, a few feet north of the northeastern-most pier. To get that close, Mammoet had backed up one line of the wheeled transporters it had used to load the bridge until one wheel was hanging over the end of the barge, about two feet from the barrier.

The arch bridge is 400 feet long by 164 feet wide. It was sitting across two 300-foot-long barges held 100 feet apart with sections of crane booms and held rigid with diagonal cables. In effect, Mammoet had built a giant catamaran and put the bridge across it. Because the bridge crosses the river at an angle, the bridge rode on the barges at a matching angle.

Yesterday, the Mammoet crew manipulated the barges into place mostly with four winches, two on each barge, alternately hauling and slacking on cables attached to shore at the tugboat dock on Fox Point, to the Hurricane Barrier and to a barge positioned in the harbor southwest of the bridge.

Directing the show, from the barge closest to the difficult corner of the bridge, was Michael D. Efford, the Baltimore pilot who commanded the tow up the Bay on Sunday. Watching intently, then happily, on shore were three members of the Cardi family, Stephen A., Antonio and Stephen II, whose company is building the bridge as part of an $87-million contract, itself part of the $600-million state and federal relocation of Route 195.

By 9 a.m., the northeast corner of the bridge was about 50 feet south of the Hurricane Barrier and about the same distance from the east bank of the river, where the piers for that end of the bridge stand.

The bridge needed to be moved both north and east, and twisted clockwise, so the falling tide would drop it onto the piers. Slacking one set of cables and taking in others a few inches at a time, the crew on the barges gradually worked the bridge toward its goal.

High tide was at 11:32 a.m. Just after 11, the Mammoet crew was pumping water into the barges, sinking them lower in the water to lower the bridge even as the tide was still lifting it.

When the tide turned, it and the increased ballast in the barges caused the barges to start falling. By noon, Richard Zondag, Mammoet's director of operations, said the arches' east ends had landed on their piers. Those on the other end landed about the same time, and Zondag said the transfer of weight from the barges to the piers had begun.

While it was supported by the barges, about one third of the way in from each end, the bridge's tie beams, the ones that close the bottom of each arch, had bent slightly, their ends drooping down. As the weight shifted to the piers, the lower beam straightened out again.

The bridge had joined the waterfront skyline.

By mid-afternoon, Mammoet and Cardi had moved the barges and the steelwork that had held the bridge up out from under it. Cardi project manager Paul J. Grimaldi said he wanted to make sure the barges didn't go aground as the tide fell or, worse, pick the bridge up again with the next high tide.

Despite its enormous weight, the bridge is really only about half there. It is only a steel skeleton -- the three arches and lower tie beams, and crosswise floor beams that will support the deck. Months of work and many tons of steel and concrete will be added to produce the deck on which cars and trucks will travel.

The DOT plans to open the first part of the project, from Route 95 northbound to Route 195 eastbound, to traffic by the end of next year.

After its dramatic job, Mammoet is done except for cleaning up, leaving the local construction industry impressed at its ability to conduct a complicated heavy moving project, apparently without stress.

"I didn't see one guy running, I didn't see one guy hollering," said one Cardi administrator. "Everything went so smoothly it was incredible."

Not that nothing at all went wrong. A hydraulic line leaked while Mammoet was jacking the bridge up on the pier where it was built, and yesterday a wire rope holding one corner of the pair of linked barges, with the bridge on them, let go when some cable clamps slipped. The crew fixed the leak, and reclamped the eye in the end of the cable, and got on with it.

blandis@projo.com / (401) 277-7487