Gas pipeline highway crossings use conduits, vents - WBOY.com: Clarksburg, Morgantown: News, Sports, Weather

Gas pipeline highway crossings use conduits, vents

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Although the investigation into the explosion that hit Interstate 77 at Sissonville on Dec. 11 has only just begun, some early signs are that it was at or near the highway and it was natural gas–related.

The natural gas pipeline running through there has been identified as a 20-inch or 30-inch Columbia Gas Transmission pipeline.

Natural gas pipelines cross highways and other roads all across the state.

Obviously this could be a dangerous combination, but problems are rare and that's because there are standards for how it's done.

The general design is to make the crossing in such a way that roadway disturbance can be minimized.

"What we generally will do is, the pipeline will be inside another larger pipe, conduit," said West Virginia Department of Transportation Secretary Paul Mattox.

"If at some point in the future a company would have to change out lines, it's easier to do, rather than dig up the road to replace the pipe," Mattox said. "So generally they'll put in a conduit pipe and put their pipe through that conduit."

Dennis Xander, president of Denex Petroleum Corp. in Buckhannon and also of the Independent Oil and Gas Association of West Virginia, provided a little more detail.

"If it's 20-inch pipe, you would probably put a 24- or 30-inch line in first, like a sleeve, and run the gas line through that," Xander said.

The casing or conduit has a rubber seal at each end, with vents welded onto the casing.

"Driving down the road, you'll see often see pipes sticking up vertically with a hook on the top, like a candy cane — that's a vent," he said. "It's welded onto a piece of pipe, and through that piece of pipe is a gas line or a water line. It serves as both a marker to locate the line and as a vent."

Other standards specify depth under the roadway for various crossings.

Highway crossings require permits from the DOT.