The person in charge of carrying out the $11.3 million Suncook double-decker bridge construction project said work could be completed on time, despite a recent snag that will require the bottom half of the old bridge to be closed.

The upper portion of the old bridge that connects Allenstown and Pembroke on Route 3 is slightly sagging. Traffic use on the bottom half will be sacrificed to shore up the upper level, said Tom Miller, the project’s contract administrator with the state Department of Transportation.

Miller estimated the closure – which will last until the new bridge is complete – will affect about 300 mostly local car trips per day. That’s compared to about 10,000 trips on the bridge’s upper level.

“The traffic down there is minimal,” Miller said. Miller was using traffic counts gathered in 2002, before the double-decker construction project commenced.

“(The closure) is going to be a little inconvenient to the people living down there,” said Allenstown selectmen’s Chairman Sandy McKenney. “It will probably affect more people in Pembroke than in Allenstown.”

Downtown residents are able to cross the Suncook River over the Main Street bridge, which officially opened in January 2006, about three months behind schedule.

Miller said two mild winters have made him hopeful that the new double-decker bridge will open in October as scheduled. “We should make that,” he said.

Miller also said the massive replacement project will likely meet its $11.3 million budget. Funding for the double-decker bridge replacement has come from federal and state sources, and hasn’t required local property taxation in the two towns. The old double-decker bridge was built in 1938 and represents an architectural rarity in the state.

Attempts to sell the bridge for $1 fizzled early last year since buyers would have had to relocate the historic bridge, maintain its integrity and find a suitable use for it.

“It’s just outlived its usefulness,” Miller said of the bridge, which was “red listed” by the state’s bridge task force.

The design of the new bridge follows that of the old bridge, but will handle much heavier traffic loads, said Miller.

“It’s basically a copy of the old bridge, designed wider and taller,” he said. “It should be good for 100 years.”