TOP 10 ROADS: Mountain rescue

October 06, 2011

The battle on Rte. 15 in Lycoming County, Pa., went way beyond the uphill mark. In fact, some may say it even intensified after the peak.

The main north-south corridor through mountainous central Pennsylvania carried two generations of pavement along with enough curves to last a lifetime. It was time for a rebirth.

“In both directions heading down the mountain you were on a 1930s vintage windy road, which really was not consistent at all with the other sections of highway to the north or south that had been improved over the years,” Dave Hamlet, project manager for Gannett Fleming, told ROADS & BRIDGES.

Motorists also endured a throwback alignment going up Rte. 15, where there was still a 1930-style road alongside another two lanes that were constructed in the 1970s. Gannett Fleming and prime contractor Trumbull Corp. had their work cut out for them, but in the end the team knocked out the No. 1 project on the 2011 ROADS & BRIDGES Top 10 Roads list.

“I sure hope this does not end up being a once-in-a-lifetime opportunity, but right now it kind of feels like that,” remarked Hamlet.

On top of the hilly, twisting landscape, there also was an environmentally sensitive stream to deal with, and it called for a creative approach. Gannett Fleming decided to break the project into three sections (southern, mountain top and northern) and modeled alternatives for all of them. Crews slid the alignment of the southern section up the hill in order to make the route straighter and to minimize impacts to the stream. The highlight of the mountain top segment was the construction of a diamond interchange, and the northernmost portion of the project was smoothed out much like the southern section.

This 9.8-mile stretch of Rte. 15 also carried a few at-grade intersections, which are a rare sight on a highway-type facility. They were replaced with grade-separated interchanges.

The existing two lanes of pavement going down the mountain were removed and recycled. According to Hamlet, design calculations in the new pavement assumed 15% recycled asphalt.

The new road consists of an 11-in. sub-base, 11-in. hot-mix asphalt (HMA) base course, a 2.5-in. HMA binder course and a 1.5-in. HMA surface course. All three lifts were Superpave and used a PG 64-22 binder.

Since the area was susceptible to landslides, Trumbull Corp. avoided deep excavations, and the threat was the reason a portion of the alignment was raised. A short retaining wall also was built on the southern section.

The project also featured a two-span, 270-ft-long continuous prestressed concrete bridge carrying Green Mountain Road.

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