SULLIVAN'S ISLAND — The traffic lanes and a sidewalk will be wider and the bridge tender's house a bit larger, but otherwise the new $31.5 million Ben Sawyer Bridge will look much like the old one, minus the rust and flaking paint.

During the next two weeks, construction is expected to begin on a new 124-foot-long bridge to replace the old one built in 1945 that connects Mount Pleasant and the island. The contractor is replacing the bridge approaches and the swing span that opens sideways to allow boat traffic to pass on the Intracoastal Waterway. The foundation will be strengthened to better withstand an earthquake.

Islanders made it clear they wanted a more structurally sound version of the existing bridge rather than a modern makeover of the span. The sidewalk on the Charleston Harbor side of the bridge will be widened from 2.5 feet to 5.5 feet. The 12-foot-wide car lanes will increase to 14-feet-wide, said Leland Colvin, state Department of Transportation assistant construction engineer.

The state Office of Ocean and Coastal Resource Management is expected to issue a "land disturbance permit" soon, which will allow construction of the federally funded bridge to begin. When the contractor gets the green light to begin work, trestles will be built on both sides of the bridge approaches that will serve as platforms for constructing the new approaches as well as a foundation on which to slide off the old bridge approaches. The project will be finished in May 2010, Colvin said.

The new swing span, the part topped with a truss that looks like a creation from a giant Erector set, will be built at the old Navy base and shipped in by barge. The old swing span will be lifted off and the new span put in place. The DOT Commission awarded the bridge contract to PCL Civil Constructors of Tampa, Fla. The bridge will close for a week in early November while the old approaches and swing span are removed and the new ones are slid into place atop the strengthened foundation, Colvin said.

Ben Sawyer Bridge inspectors have found numerous structural issues over the years. A year ago, the bridge closed for 72 hours so rusty steel beams supporting the 5-ton bridge tender's house could be replaced. Traffic was rerouted to the Isle of Palms Connector, the alternate route off Sullivan's Island.

In 2004, transportation engineers reduced the gross weight of vehicles allowed to cross the bridge from 30 to 20 tons after an inspection of the structure found "fairly significant deterioration" of floor beams and stringers. In 1989, the bridge truss was left pointing skyward at a 45-degree angle after Hurricane Hugo in 1989. It was eased back into place and continued to serve as the main route off the islands until the connector opened more than a decade ago.