Companies drilling Pennsylvania's Marcellus Shale natural gas reserves say they've spent more than $400 million to repair the roads. Increased truck traffic in rural areas of the state has taken a toll on the state and local highways.

Drilling companies have to get permits to haul water and supplies over the state's roadways. Those permits require them to fix the damage caused by heavy loads.

"There is wear and tear on the roads from traffic, which the key is getting ahead of those repairs, doing as much proactively as opposed to reactively and increasing the communication," says Katherine Klaber, president of the Marcellus Shale Coalition.

Klaber says the drilling industry has spent $411 million on roads since 2008. Each year, the state Department of Transportation spends about $4 billion on repairs across the state.

Dennis Buterbaugh, a spokesman for PennDOT, said the department inspects the roads before--and after--the repairs are done.

"If there has been an issue where a roadway is not brought up to our satisfaction, then their permits are pulled," he said. "There have been instances where those permits were pulled."

The department issues hundreds of permits to natural gas drillers. In the past nine months, PennDOT has revoked 25 of those permits for improper road repair.