An employee of Long's Asphalt Inc. of Quarryville uses a roller to compact the Driving Surface Aggregate, a special recipe developed in the 1990s that resists erosion and traffic wear. (Daily Record/Sunday News - Bil Bowden)
Approximately 300 miles of dirt and gravel roads still exist in York County, and North Hopewell Township recently received federal stimulus funds to pave a few of its own with a special rock mixture.

Crews with Long's Asphalt Inc. of Quarryville are laying the mixture, known as Driving Surface Aggregate, on five roads: Line, Blymire Hollow, Spring, Huson and Deer.

The $750,000 project will be completed by the end of November, said Jason Snyder, township engineer and senior engineer with Rettew.

"We're really hoping to be an example product with this with the Commonwealth," he said.
What is the special mixture?

Driving Surface Aggregate was developed by Penn State's Center for Dirt & Gravel Road Studies in the 1990s to provide a wearing course for unpaved roads and help reduce runoff into streams.

Unlike other aggregate, this recipe includes a higher percentage of rock fines, said Tim Ziegler, field operation specialist with the Penn State center.

The various sizes of rock lock together when compacted to produce the most dense and durable surface possible. The material must be delivered and placed at an optimum moisture so it will reach maximum compaction, Ziegler said.

He compared it to building a sandcastle. If it's too dry, the sand remains like a dust. If it's too wet, the sand is sloppy. But it's just right, the sand will compact and support itself, Ziegler said.
What are the material's benefits?

It resists erosion and traffic wear, Ziegler said.

Plus, municipalities have found they can get longer maintenance cycles. Some have not had to grade or reshape roads for years, said Gary Peacock, watershed specialist II with the York County Conservation District.

"It helps the township budget, and it helps the environment at the same time," Ziegler said.

The aggregate should help reduce sediment flowing into the east branch of the Codorus Creek and eventually lakes Redman and Williams, Snyder said.
How is it applied to roads?

It's put down just like asphalt, Snyder said. Crews use pavers and rollers. North Hopewell Township also is using a geogrid, a reinforcing fabric for the road.

"It acts like a big snowshoe actually, and it distributes the load so we don't get rutting in the roadway," Snyder said.
Have other municipalities in York County used it?

Yes, about half a dozen, Peacock said.

About $842,823 has been spent with funds through the York County Conservation District, Peacock said. The material was on about 16.12 miles of road by the end of 2008.

North Codorus Township and its roadmaster, Nelson Brenneman, were among the first on board with the product.

Brenneman has estimated that using the material on some township roads has saved the municipality about $250,000 over five years, Peacock said.

"That's a big deal," he said.

Learn more

To learn more about Driving Surface Aggregate, visit www.dirtandgravel.psu.edu.

Municipalities interested in using the material for road projects can call Gary Peacock at the York County Conservation District at 840-7430.


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