The Pennsylvania Turnpike will replace three bridges and lower a road in Plum and Monroeville over the next four years to prepare for a 7.5-mile, $217 million widening project.

Officials will hold an open house Thursday to display plans and answer questions about the work, which is part of the turnpike’s effort to rehabilitate and expand the length of the cross-state toll road. Some parts of the highway haven’t been upgraded since it opened in the 1940s.

Gary Graham, the turnpike’s assistant chief engineer for design, gave this overview of the work:

The three bridges to be replaced cross above the turnpike. They are on Saltsburg Road (spring 2018) and Unity Trestle Road (fall 2019) in Plum and on Center Road in Monroeville (spring 2020).

Plans call for the new bridges to be built beside the existing structures. That means there shouldn’t be any traffic interruptions until the final few weeks of the work when the new bridges are tied into the existing roadway.

The new bridges have to be longer than the existing structures to accommodate the widening of the turnpike. The turnpike will be expanded from two lanes to three in each direction and have 12-foot shoulders on the far left and far right lanes in each direction.

Hulton Road in Plum will be lowered by two or three feet for several hundred feet on either side of the area where the turnpike passes above it. That is necessary to provide more clearance under the bridge to met current standards.

That project hasn’t been scheduled.

Mr. Graham said the expansion project is at least five years away. It is still being designed and the agency doesn’t have funding for it yet.

The turnpike has followed a similar pattern as it has expanded the highway from the Ohio border to the North Hills, replacing bridges and making other changes on local roads in the years leading up to the expansion project.

The open house is from 6 to 7:30 p.m. Thursday at the Plum High School cafeteria, 900 Elicker Road, Plum.

Ed Blazina: eblazina@post-gazette.com or 412-263-1470.

First Published: February 21, 2017, 5:00 a.m.