$2.8M culvert replacement on Route 4 to continue into fall

Staff report

Traffic is reduced to one lane on a portion of Route 4 as a sewer line is moved and an existing pipe culvert is replaced with a concrete box culvert near Spring Hill Road in Killington. 

The $2.8 million project, which started in June, is expected to be done this fall. 

The contractor, J.P. Sicard, Inc., is currently moving an existing sewer line deeper and higher uphill to accommodate the larger culvert, which will be about 12 feet long and 8 feet high.

The sewer line will be encased in a metal sleeve under the culvert in case it needs to be replaced in the future. 

The contractors are also moving the new culvert about 30-40 feet downhill and constructing new channels to maintain flow inside the existing culvert during construction.

“That took some coordination with engineers,” Agency of Transportation Project Manager James McCarthy said.

The previous culvert, a 6-foot long asphalt-coated galvanized pipe, constructed in 1965, had a rating of 3 and was in “serious” condition for 10 years, according to the Agency of Transportation. 

While most culverts in the state are inspected every five years, this one was inspected every year due to its deteriorating condition.  

“Quite often we see sinkholes when the culverts get into that condition,” McCarhy said. “Typically, there’s a lot of perforations in the bottom of it, the galvanizing wears off.”

The new concrete box culvert is currently being pre-fabricated in New Hampshire and will be installed under phased construction.

“They will excavate and put in half the concrete box and then put the traffic on top of the concrete box and do the other half,” McCarthy said.

The Agency of Transportation evaluated alternatives for rehabilitation or replacement of the bridge in an engineering study completed in March 2020. This study assessed  the right-of-way, hydraulics and community concerns. The agency  considered installing a culvert invert, a spray-on liner, a new four-sided box culvert and a new concrete rigid frame.  

“Given the age of the structure, site constraints, existing geometry, and current conditions, the engineering study recommended a full replacement with a concrete box culvert,” according to the Agency of Transportation website, vtrans.vermont.gov.