DIMOCK TWP. - Everywhere Tim Ziegler travels dirt tracks and gravel roads in rural Pennsylvania, he sees an insidious threat of pollution beneath his tires.

Sediment is the largest pollutant by volume in the commonwealth's streams, degrading water quality, smothering natural vegetation and destroying fish habitat.

Worn dirt roads and their ditches are a potent source of grit and Pennsylvania has more than 20,000 miles of them.

Ziegler has driven many of those stretches, spreading the gospel of drainage. He works for the Center for Dirt and Gravel Road Studies at Penn State University, which helps townships, companies and other agencies build and maintain unpaved roads in an environmentally protective way. Its toll-free number is 1-866-No-To-Mud.

The highest density of dirt roads in the state coincides with the richest spots for Marcellus Shale natural gas drilling and Ziegler's work in recent years has focused on that intersection.

Shale development presents both a challenge and an opportunity for rural road infrastructure: Heavy haulers rut the roads, but posted and bonded thoroughfares have to be returned to their prior condition and companies routinely strengthen the roads before they run trucks on them or improve them beyond their previous state.

The Marcellus Shale Coalition calculated that its member companies spent more than $411 million on road construction in Pennsylvania between 2008 and the middle of 2011.

The problem, Ziegler said, is that much of the companies' attention and money has been spent reinforcing the roads' surface while leaving the old drainage infrastructure in place. The hardened, widened roads increase the amount of runoff during rainstorms, exacerbating existing sediment pollution pathways and adding to the likelihood and severity of flash flooding in nearby streams.

"There's an opportunity that we're losing here," he said.

During a recent field trip to a reinforced stretch of road in Susquehanna County, he demonstrated that roads built without protective drainage in mind are also less likely to last.

Like many Pennsylvania gravel roads renovated to withstand thousands of drilling-related truck trips, Hunter Road in Dimmock Twp. is not strictly gravel anymore. The surface has been solidified with cement.

But the improvements constructed in 2010 are already starting to show wear. A jagged rut snakes under one tire track, a washed-out pile of the new road material threatens to clog a stream pipe that steers a small tributary under the road, and the rush of stormwater where one ditch intercepts another has undermined the road base, leaving the concrete jutting a foot or more over open air.

At the valley intersection of three steep roads, more than a mile of road surface plus half of a gas well pad drains to one small stream.

That system, and its impacts, are only associated with one pad among the thousands built or planned in the state, Ziegler said.

"We've got to look at how we're going to handle this with such an intensive, widespread development across the rural landscape."

Many solutions are known and affordable, especially for companies already investing in road-repair projects.

Roads should be constructed with several drainage cross pipes and diversion points to interrupt sheets of water and disperse the flow in a way that more closely mimics nature, he said.

Together, the improvements "cut one big watershed" - the uninterrupted ditch - "into lots of little watersheds."

The center has cooperated with several companies, including Range Resources, Enerplus and Carrizo Oil and Gas among others, to offer tips and suggestions on proper drainage infrastructure.

But Ziegler looks at the effort and money invested in already-cracking Hunter Road and sees much room for improvement.

"It's just a matter of looking at things a little differently," he said.

Contact the writer: llegere@timesshamrock.com