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Crews work on the left lane of the northbound I-91 bridge over the Saxtons River on Nov. 30. 

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WESTMINSTER — A failed expansion joint in a bridge that spans the Saxtons River and Route 121 has led to the closure of a southbound travel lane on I-91.

According to information from the Vermont Agency of Transportation, the southbound lane of the northbound bridge was closed on Tuesday after the failure was discovered. A further investigation revealed two other expansion joints on the bridge showed “signs of deterioration.”

Southbound traffic has been detoured on to the northbound bridge while the deck of southbound bridge is replaced.

The bridges are part of a deck replacement project affecting both north and south lanes of travel.

It is believed the joint failure is due to southbound traffic using one of the northbound lanes during construction and hitting the joint opposite from the regular direction of travel, states information from the AOT. The travel also resulted in damage to the concrete easement of the joint.

“Inspection of the northbound joints determined that they appear in good condition,” states an email from Jeremy Reed, AOT construction engineer. “Based on what we could see, the joints in the northbound lane look OK.”

Reed said weather dependent, the southbound travel lane will reopen late Thursday. Southbound traffic is being detoured off the highway and onto Route 5 while the repairs are made.

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The I-91 bridges were built in 1963 and consist of 7 and 8 span cast-in-place decks on rolled steel beams. The 35-foot wide bridge structures are 534 feet and 542 feet in length, respectively. The current project will replace the existing decks and repair the piers and pier caps.

According to a fact sheet about the existing bridges, they have a substandard width, approach rail and bridge railing. All these conditions will be addressed by the project.

The superstructure beams are in good condition, but the concrete deck components are only in fair condition. The substructures are in fair to poor condition, as a result of the deteriorated deck sections above, which allow water and salt to seep onto the bridge seats, damaging the pier caps.

VTrans evaluated alternatives for rehabilitation of Westminster I-91 Bridges 21 N&S in an engineering study completed in October 2014. The study assessed the proposed design criteria for the bridge and roadway alignment, right-of-way impacts, hydraulics and wetland and archaeological resources. Several alternatives were considered including no action, repair and rehabilitation, deck replacement, superstructure replacement and full bridge replacement. Because of the structure’s age and condition, the study recommended a deck replacement with phased construction.

Both bridge decks will be completely removed and replaced, as will the substandard bridge and approach rails. Deck joints will be replaced to provide additional protection to the steel support beams. Deteriorated and loose concrete on the piers will be removed and repaired. The steel superstructure will be repainted in coordination with the deck repairs.

A new electrical protection system will be installed to slow future concrete and reinforcing steel deterioration, triggered by deicing salts and moisture. The new decks will be the same length as the existing ones, but will be widened slightly on each side, resulting in two 4’-8” wide shoulders and two 12-foot travel lanes for each bridge. The new decks will feature F-shape concrete bridge rail with Heavy Duty Steel Beam approach rails.

Updates will be provided as the work progresses.

Bob Audette can be contacted at raudette@reformer.com.