The Mountaineer

Geologist says massive slide probably won’t be the last

Those who were around decades ago when the path for Interstate 40 was first carved through the Pigeon River Gorge said they knew then that problems would be coming. They were right. 

Since construction of the interstate was completed in 1968, numerous rock slides have occurred like the recent catastrophe that left a massive pile of house-size boulders blocking all lanes of traffic just inside the Haywood County line.

Crews are working every day to secure the area around the slide, so clean up can begin. For days, crews have been blasting the slope with dynamite and ammonium nitrate explosives to remove all loose rocks and overhanging boulders that could potentially slide. Blasting will continue for several weeks before any material is hauled away from the site.

Meanwhile, following the blasts the N.C. Department of Transportation Photogrammetry Unit is flying over the site to take aerial photos of the area, which are used to determine how much material remains to be removed from the face of the mountain. Reference points painted on the ground give engineers measuring points. Using the photos with the points, they can then calculate the size of the area.

While no official timeline has been established, officials estimate it will be at least four months before the road is re-opened to traffic.

The Oct. 25 rockslide wasn’t the first, and it likely won’t be the last.

“The whole north side of the Pigeon River is going to be prone to future rock slides for as long as it’s there, until they all fall down,” said Jim Reynolds, associate professor of geology at Brevard College. “It’s because of the way the fabric of the rock is situated. There are a lot of planes of weakness, and they are all pointed down toward the road. So, when the water gets in there it degrades the strength of the rock —changes the minerals to clay minerals, which are slippery — and lubricates the rock. Eventually the weight of the overburden is greater than the strength of the rock and it all starts sliding.”

Following a 1997 slide of similar proportions, Reynolds said he predicted it would only be a matter of time before the mountain slid again. He’s making the same claim now.

“I will make the prediction now that it will happen again,” he said, “just because that’s the way the rocks are.”

It’s not the type of rocks, said Reynolds. It’s mainly the angle of the rocks that causes them to slide.

“If you look at the rock there’s lots of flat surfaces that are sloping toward the road and each is a plane of weakness. There are thousands of weaknesses in the rock,” he said.

Ralph Rathbone grew up on Fines Creek, near the dam. He remembers when the interstate was built.

“We were all excited about having a highway up through there,” he said. “But some of the old people realized there would be problems … And slides have been a problem from just about the very beginning of it.”

When the decision was made to build the interstate, several routes were considered, said Rathbone, including a path routed through Madison County along the French Broad River.  Each route would have posed similar problems.

“Yule Taylor, owner of Taylor Motor Company, and I went to Asheville to a meeting when they were discussing the possibility of building the road down the French Broad (River), and we went to try to persuade them differently and we did. I think there were about 628 people from Haywood there. It was a big bunch of people.”

Among other reasons, “we got it to come to Haywood County because it was much easier to do than the French Broad would have been, and it was more practical,” Rathbone continued. “Engineers from Raleigh said the most feasible route to take was through the Pigeon River Gorge.”

At that time, however, little was known about building interstate highways, particularly through steep, rocky terrain, said Reynolds.

“When the road was built, the world really didn’t know how to build interstate highways, and that was the first one to (cut) through the mountains,” said Reynolds. “The whole thing was a learning process, and they have learned very well how to take care of this.”

Since the 1950s when construction on the interstate began, much has changed, he added.

“If building the interstate today, they would terrace it to make it safe,” said Reynolds. “It’s one of those things we didn’t know when we were building then. Now, we know and we would sure do it differently if we built it today.”

One way to prevent future slides would be to terrace the rocks throughout the slide prone areas — an unlikely option due to cost, said Reynolds.

“It’s terribly expensive,” he said. “So, the public has to decide are we going to put up with this every few years or spend a fortune to make sure it doesn’t happen again?”