CANTON – The venerable Gilbertville Bridge was closed Wednesday, but its usefulness is not over yet.

Guilford Rail System employees were busy replacing about 30 traditional wooden ties with concrete ones at the north side of the bridge, as part of the $4.4 million bridge construction project. Work was expected to continue Thursday.

Concrete ties and panels are being installed to provide greater support for the traffic on Route 140, said Guilford spokesman Joe Bunevith. Lots of heavily loaded logging trucks use Route 140 and cross the railroad tracks before crossing the bridge.

Concrete ties are relatively new to Maine, and are used only when extra strength is needed, said Bunevith. He knows of only one other place in the state that uses them – a bridge in downtown Saco.

The old ties at the foot of the bridge will be reused.Along with the tie and rail replacements, the grade was raised about 3 feet so drivers will have a better view when coming off the bridge.

The nearly 70-year-old, steel-trussed bridge is expected to open sometime Thursday, but it will be used only a few more weeks after that.

Maine Department of Transportation resident engineer Catherine Mettey a new, wider and slightly longer steel girder bridge is scheduled to open by the end of July.

The multimillion-dollar state project is on schedule and on budget, Mettey said, despite a slowdown during the December flood.

When the new bridge opens, the old bridge will be dismantled.

The old bridge’s two spans will be separated, with the north span loaded onto one barge and floated to the north shore, and the south span loaded onto another barge and floated to the south shore. There, bridge contractors Reed and Reed of Woolwich will cut up the sections with huge cutting shears, then sell the metal as scrap.

Mettey said the old bridge must be down by the end of August.

She said traffic will not be stopped when the changeover occurs. This week’s bridge closure is the last one she expects at the site.

The new bridge has three spans instead of two, is about 10 feet higher over the river than the current one, and is about 8 feet wider to accommodate a sidewalk/snowmobile path.

The Gilbertville Bridge was named for brothers Charles and Zimeri Gilbert, who owned sawmills in that section of Canton during the late 19th and early 20th centuries.