Third rock slide in three weeks rumbles on Signal

Mountain roads with rocky bluffs on one side and steep drops on the other may be pretty places to drive, but a series of slides in the last three weeks are rocky reminders of the dangers.

"Any time you're driving on roads with rock bluffs, there can be a tendency for one to roll off," said Hamilton County Director of Highways Harold Austin. "A lot of times it's when there's a lot of rain or a real cold freeze and thaw."

On Thursday morning, a small rock slide toppled onto the W Road on the side of Signal Mountain, closing the road. And local road crews were called out twice earlier this week to remove boulders from Cummings Highway up Lookout Mountain.

The local slides, coupled with the massive rock slide on U.S. 64 in the Ocoee Gorge this week and another large slide late last month on Interstate 40 near Asheville, N.C., point up the toll that weather and earthquake tremors can have on the region's mountainous roads, according to highway officials.

Tennessee Department of Transportation spokeswoman Julie Oaks said more than 15 inches of rain since Sept. 1 and several small earthquakes last week near Cleveland probably contributed to the Ocoee rock slide, which will close U.S. 64 for at least three weeks.

On Thursday morning at the top of the W Road, Wilbourne Markham and his wife, Constance, waited with curiosity at the barrier to the closed roadway.

"We came up yesterday and said we thought we wouldn't be surprised if a tree or something fell on this road," Mr. Markham said.

"This could happen on the W any time," Mrs. Markham said.

LOOKING FOR TROUBLE

Mr. Austin and other highway officials say road workers are on constant alert to inspect all roads whenever they drive or perform normal maintenance.

"We've got supervisors out on the roads every day. If they see a rock or tree that's about to fall, they go ahead and do something about it," Mr. Austin said. "It is a thing they do daily."

Ms. Oaks with the transportation department said regular drivers can help, too.

Small rocks that have fallen onto a road from a nearby rocky bluff can be a telltale sign of impending trouble, she said.

"Absolutely anytime (drivers) see rocks on the highway they should call the Tennessee Highway Patrol," she said. "They will contact us (at the Department of Transportation.)"

Ms. Oaks said highway workers often do pre-emptive work, and part of clearing U.S. 64 will involve taking down rocks that look suspect.

Ray Rucker, who works with the local Tennessee Department of Transportation office, said highway officials now are monitoring an area above Cummings Highway on Lookout Mountain.

On Tuesday night, they were called about a rock in the road on Cummings Highway, and workers tied a chain around the boulder and pulled it out of the road, he said. Then Wednesday morning a larger boulder came down with a few more rocks, blocking one lane of the highway, he said.

"There's some debris still up here that looks like it could come down," he said. "We're going to monitor it and, when we get a chance, we're going to go up there and see what it would take to pull it on down."

Mr. Austin said members of his work crew were able to use their hands to remove about a wheelbarrow full of rocks from lanes near the top of the W Road on Thursday.

He said they found no reason to worry about another slide, but since the road already was closed, they took the opportunity to do some regular maintenance and ditch cleaning for the rest of the morning and early afternoon.

A safer future

Ms. Oaks said federal highway rules require any new road built through a slide-prone area to be safer than older ones.

U.S. 64 and I-40, as well the local mountain roads, all were built in the 1960s. Federal Highway Administration rules now require wide rock-catching areas between slopes and the roadbed.

"With catchment systems, you actually plan for rocks to fall," said Steve Hall, TDOT's assistant chief engineer for operations.

In the meantime, there are other ways highway officials can stabilize slopes and bluffs over roadways, said Greg Duncan, TDOT director of maintenance.

In some places -- Monteagle Mountain, for example -- highway workers have installed drain pipes deep in the rock to carry water from behind the bluffs, hopefully preventing the water from washing away the ground that the rock sits on.

They also placed concrete at the bottom of steep slopes to hold the rock base in place, Mr. Hall said.

The transportation department also may use a process called "rock nailing," in which anchors are driven into sound rock in order to help "hold one that is not so stable," Mr. Duncan said.

Ms. Oaks said not even budget cuts have slowed TDOT efforts to evaluate potential slide sites.

"We continue to monitor and evaluate the sites as we always have," she said.

In September, the department awarded a $3.6 million contract for rockfall mitigation along I-40 in Putnam County, she said.

"We have also requested approval from the Federal Highway Administration to authorize the use of Highway Safety Improvement Program funds to address rockfall mitigation sites."

EARTHQUAKE ZONE

The Appalachian region is prone to earthquakes. U.S. Geological Service records show the East Tennessee Seismic Zone through East Tennessee and Northwest Georgia is the second shakiest area east of the Rockies. But most tremors are too small to be felt by people. The shakiest area east of the Rockies is the New Madrid Seismic Zone, which runs from Memphis to Missouri, according to earthquake experts.