The condition of the current bridge led officials to decide to build a new Sakonnet River Bridge, right, rather than attempt to repair the existing structure, left.

The Providence Journal / Frieda Squires Frieda Squires

PROVIDENCE — The replacement for the Sakonnet River Bridge will be built later and cost more than it was supposed to.

However, the state Department of Transportation’s new director, Jerome F. Williams, says he has taken Steps to cut the cost increases, so that the bridge can be built less expensively than it might otherwise have been.The new bridge will, like the current rusting one, carry Route 24 from Tiverton across the Sakonnet River to Portsmouth. It will be built immediately south of the existing one. Williams said he hopes to advertise for bids in January and start construction next spring.

It will be the first major project to go out for bid since Williams, a former official in the state Department of Administration, took over as director of the DOT at the beginning of the year.

Hoping to encourage competition, the DOT is considering Two versions of the bridge, one using steel as the primary material, the other concrete.

The agency said it estimated the cost of a new bridge at $118 million in 2001 for construction using either material, plus allowances for engineering supervision and change orders during the project.

But Williams said that when he got to the agency, the estimated cost of a steel bridge had risen to $189.5 million and a concrete one to $211.8 million, increases of 60 percent and 79 percent, respectively. He blamed the higher cost estimates on increases in the cost of building materials.

Williams said he ordered a speedy — 60-day — reconsideration of the plans, asking the Federal Highway Administration for help and getting advice from a group of bridge experts.

The review included basic decisions on the project, some of them dating back years. The most fundamental was whether to replace the bridge rather than repair the existing one. That produced the same answer: it’s better for a number of reasons — cost, avoiding traffic jams — to build a new bridge.

But in other areas, Williams said, his review has produced major savings — $34.5 million off the cost of a new steel bridge, and $23 million off the cost of a concrete one — without reducing the bridge’s usefulness.

That leaves the overall cost estimates, including construction, engineering and change orders, at $155 million for a steel bridge and $189 million for a concrete one, Williams said. By the DOT’s figures, Williams’ review has cut the increase in the estimated cost of the cheaper, steel bridge by almost half, although it still amounts to an increase of more than 30 percent.

The DOT once said it would begin construction of the new Sakonnet River Bridge by the fall of 2005, with completion by the end of 2008. More recently, it had said it would advertise for bids last December, and begin construction this spring.

Kazem Farhoumand, the DOT’s chief bridge engineer, said the 13-month delay to January was caused when it was discovered that the soil at the bridge site wless supportive than expected. The new bridge is to be built with steel piles, driven deep into the river bottom to support the concrete piers that will hold up the bridge deck. A second round of pile testing is going on now on the Portsmouth side of the river, he said.

The bridge is a critical part of the state highway system. It carries Routes 24 and 138 between Portsmouth and Tiverton and links Newport and Aquidneck Island to Fall River, Boston and the rest of southern and eastern New England. Built in 1956 to replace a stone bridge, it carried about 10,000 vehicles per day in the early 1960s. Now, about 43,000 vehicles cross it daily.

One reason for replacing rather than repairing the bridge is that there’s no convenient detour for traffic to use during repairs. That means slow construction, traffic tie-ups, or both.

Another is the complexity of repairing the existing bridge, whose major elements include truss spans at either end of a 375-foot steel arch 65 feet above the main channel.

“It’s like an Erector Set,” Farhoumand said. He said the DOT’s consultants said that repairing the bridge would amount to building a new bridge in the same place as the existing one. It could cost as much as a new one, or more if the work were done only at night to avoid causing “massive” traffic backups, he and Williams said.

Whether steel or concrete, the new bridge will look like the new Jamestown Bridge rather than the existing Sakonnet River Bridge, Farhoumand said. The steel version would be built of “tub girders,” long steel boxes similar to the ones the DOT has been installing across Route 95 in Providence for the ramps in the new Route 195-Route 95 interchange. The concrete version would be built of long box girders, too, but of concrete.

Either kind of girder would span the distance between the bridge piers, with the road deck built on top. There are to be three sets of piers in the Sakonnet River, with more on shore on each end, holding up the girders.

The cost-saving changes will make some visible changes in the bridge, but Williams said it won’t damage its usefulness.

“We’re not reducing the size of the bridge,” Williams said. “We’re not taking away the usability of the bridge.”

One feature that survived the cost-cutting is the 13-foot bicycle and pedestrian walkway path along the bridge’s northern edge. The DOT had looked at narrowing the bridge to a width of 76 feet and eliminating the bike and pedestrian lane.

Farhoumand said the new bridge will remain its original width, 96 feet, including the bike and pedestrian lane.

“We looked at everything, but we didn’t want to lose the bike path,” Williams said.

Some of the bridge’s decorative treatments will change. For example, the pylons, decorative columns that rise above the bridge’s sides, will be simplified and moved toward shore, where they will be cheaper to build, Farhoumand said.

One change drivers may notice is that the downward slope of the bridge from Tiverton to Portsmouth won’t be constant from one end to the other. Farhoumand said engineers prefer a slope without any bumps in it, partly because it makes the road drain better. He said that’s important because water on bridges freezes more quickly than on roads. But it will be cheaper to include a relatively flat stretch in the middle of the bridge, Farhoumand said, so drivers going from Tiverton to Portsmouth may notice a downward slope, a flatter section, and then another downward slope.

Another change that probably won’t bother anyone while saving millions of dollars is shortening the bridge on the Tiverton end by essentially supporting more of the highway with dirt rather than an expensive bridge. Farhoumand said that can be achieved by building a longer embankment. He said it would save $10.8 million on the concrete version and $16.4 million on the steel version.

That change will shorten the new bridge from 2,850 feet to 2,265 feet. And reduce the number of spans from 15 to 10.

The bridge will also be built a few feet lower than the original plans, meaning shorter piers and less cost.

blandis@projo.com