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Rock stabilized, U.S. 250 will reopen all lanes under Afton Mountain

If the plan comes together and the mountain doesn’t mind, U.S. 250 below Afton Mountain will have all of its lanes open to traffic once more.

On April 11, The Virginia Department of Transportation started a preventive project to shore up a section of Afton Mountain just beneath the scenic view overlook near mile marker 100 on Interstate 64 and above U.S. 250 in Nelson County.

Crews expected the work to take a month, but the project is finishing nearly two weeks ahead of schedule.

“Expect alternating lane closures in the eastbound and westbound lanes with flaggers on U.S. 250 (Rockfish Gap Turnpike) throughout the day,” VDOT officials said in a statement. “Work crews will be removing all barriers in place for the project, and the goal is to reopen all lanes on U.S. 250 by [Thursday] evening.”

Once the barriers and equipment are removed, all three lanes of U.S. 250 will open to traffic, and both the scenic overlooks on U.S. 250 and Interstate 64 at mile marker 100 will open to the public, officials said.

Engineers first identified the area as a possible problem spot during the spring of 2021. VDOT constantly monitors rock outcroppings near roadways by watching for rock movement and comparing photographs, taken over time, to detect changes.

The process to stabilize the mountainside involved drilling deep into the rock with bolts to secure a special mesh which will keep the outcropping in place. It will about $197,000, VDOT officials said.

Early last May, a nearby outcropping of rock began dribbling a few rocks onto U.S. 250. Within days the outcropping let loose tons of soil, rock and debris to shut the road down.

The rockslide occurred in an area of geologic instability where a past rockslide already had occurred. According to geologists who studied the rockslide, the rock along the highway is unstable due to the cuts that were made into it in order to put the interstate over the top of U.S. 250 in the early 1970s.

Cuts were also made into the mountain in the 1930s to put U.S. 250 over the mountains.

The rock is schistose greenstone, a fine-grained foliated metamorphic rock that formed in sheets as it went through hundreds of millions of years of continent creation and tectonic processes.

Greenstone rock lies in layers, or foliation, which is its weakness. Hard impacts can make the rock split along its layers, making it prone to slides once it has been exposed for a period of time.

Geologists say that the rock rots when exposed to weather and elements. Rain, snow and sun slowly break down minerals, leaving the rock to decay and crumble. For greenstone, that creates something akin to clay between the rock layers, which make it even more susceptible to sliding.

Source: www.dailyprogress.com

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