Prior to the requirement of returning mine land to approximate original contour, vertical rock faces, called highwalls, were left as the last cut of the strip mining operations. Some highwalls exceed 100 feet in height. Depending on the rock strata composition, highwalls can be unstable. As a result, highwalls can present a significant danger when in close proximity to occupied structures, public roads and frequently visited sites.
Structures built below highwalls may be damaged by falling rock. Highwalls are inherently unstable due to the deterioration of the geologic formation by weathering and erosion. Building near a highwall can also increase safety concerns. Injuries can result from pedestrians walking above or below highwalls and rock faces giving way causing physical harm.
This particular highwall was created as a result of mining coal. Coal deposits occur in three main regions in Virginia: the Southwest Virginia Coalfield, Valley Coalfields, and the Eastern Coalfields. the Southwest Virginia Coalfield contains extensive deposits of low- to medium-volatile bituminous coal hosted by Pennsylvanian-age (about 299 to 323 million years old) sedimentary rocks. Since the 1950s, virtually all of Virginia’s coal production has come from the Southwest Virginia Coalfield, an area of about 1,550 square miles that encompasses all of Buchanan and Dickenson counties, most of Wise County, and portions of Lee, Russell, Scott, and Tazewell counties. (Virginia Department of Mines, minerals, and Energy). While you cant see coal in the highwall because of the retaining wall you can look across the street and see signs of coal.
As with other highwalls in the area with time they become weaker with the effects of erosion that can help lead to runoff and rockslides. Erosion is the process by which earth is worn away by usually wind, water, or ice. In the case of this highwall the effects of wind and rain water lead to the erosion of the highwall over the years which in turn lead to the falling of rocks and boulders onto the sidewalk and roadway that made this area troublesome for pedestrians and motorists.
The project involved incasing an Old Abandoned Mine Highwall with a segmented retaining wall with a terraced design made from Redi-Rock. The Abandoned Mine Land Highwall had became a danger to vehicles and pedestrians due to rockslides. The need for a safe route from downtown to the elementary school and hospital was needed and this project offered the chance to fix the problem areas. Redi Rock is an architectural-grade concrete block made to look like natural stone. This particular retaining wall has the look of limestone. The blacks that made up the wall segments were formed off site and delivered to the site where they were placed immediately. The new terraced wall consisted of 5 tiers that were made up of a total of 8,816 Individual blocks. Each block weighed between 2,400 and 3,200 lbs, making the walls weight over 21 million pounds. If you were to stack the blocks end to end they would stretch 6.5 miles. The adjoining sidewalk is 3,900 linear feet long. To help fill in the space between the tiers in the wall over 2,000 tons of gravel was used. That is enough gravel to fill over 1,500 school buses. The project was featured on the cover of the 2016 Redi-Rock International Calendar. The project has been nominated for the Office of Surface Mining National Awards Program and was featured in Virginia Tech's "Save our Towns" series. On October 6, 2015 the City of Norton Celebrated International Walk to School Day by having a ribbon cutting ceremony to celebrate the project being finished.
In order to claim this earthcache please email me the answers to the following questions: 1. When looking at the Highwall what types of erosion played a part in making it unsafe? 2. When facing the City of Norton sign on the retaining wall which side of the highwall looks to have had the most damage from erosion? 3. While a picture is not required feel free to post a picture of yourself at the earthcache.