Last year, Eastern Kentucky faced an unprecedented environmental challenge. Following several days of heavy rainfall, up to 8 inches overnight, combined with the steep mountainous topography, the region experienced intense flash flooding. Rivers and creeks surged to record high water levels, damaging over 100 bridges, washing away roads, and destroying numerous homes. In total, over 10,000 homes were affected.
To address this calamity, FEMA, in partnership with the Kentucky Transportation Cabinet, initiated a plan to quickly repair the roadways, and bridges and develop new neighborhoods on old mine spoil sites. But what exactly are these sites?
UNDERSTANDING MINE SPOIL SITES
Strip mining in mountainous areas with coal seams consists of removing mountain tops and contouring around the mountainside to expose the various coal seams. As a part of the mining to expose the coal seams, the soil materials (sandstone, limestone, shale, and siltstone) are wasted in valleys and on previously mined benches creating generally flat areas of land in normally mountainous terrain. These leveled terrains seem ideal for construction projects like subdivisions, but they come with their own set of challenges.
Although the mine spoil sites had been identified as a potential development site for some time, last year’s flood presented an opportunity to find alternative housing for some of the homes that were continuously destroyed through repeated flooding.
VECTOR ENGINEERS: NAVIGATING THE INTRICACIES OF MINE SPOIL SITE DEVELOPMENT
With a history of work on mine spoil sites dating back to the 1990s, Vector Engineers, a subsidiary of CTL Engineering, has significant experience working with mine spoil sites. In particular, Dr. Wayne Karem has written several research papers about the settlement of mine spoil sites through water infiltration in his role as an Adjunct Assistant Professor at the University of Kentucky. This expertise made CTL a natural choice for geotechnical consulting on several potential rebuilding sites in the aftermath of the floods.
CHALLENGES AND SOLUTIONS IN DEVELOPING MINE SPOIL SITES
Developing on mine spoil sites is no easy task. Because loose bedrock had been previously placed on old mine benches, the ground is unstable and subject to movement. Before development can begin, CTL Engineering’s geotechnical engineers needed to identify the spoil sites, and create a plan to allow for future development.
Identifying Mine Spoil Sites & Defining the Risk: The first step is understanding the mining and backfill history. A mine spoil site may have considerable variations in fill thickness and depth to competent bedrock. Additionally, depending on the composition of the fill, there are areas of stiff and soft zones that are prone to differential settlement. Vector/CTL utilizes geophysical testing by sending sound waves through the ground to differentiate between soil, mine spoil fill, and bedrock. This is followed up with soil test borings and rock coring to confirm the findings of the geophysical testing.
Mitigating the Risks and Dealing with Settlement: Once areas of the fill are delineated, Vector/CTL provided engineering analysis and empirical expertise to assist the owner in reducing the risk of detrimental differential settlement issues so that the proposed residential development would provide a long-term housing solution.
Despite the challenges, once properly engineered, these mine spoil sites will offer breathtaking panoramic views of the mountains.
With support from FEMA and local government, Eastern Kentucky could witness a transformation in land previously deemed undesirable. The first housing development to build new housing for individuals displaced by last year’s flooding started earlier this year. As interest in developing former mine spoil sites grows, there is also an opportunity to attract industrial development in addition to the residential development already taking place.
While last year’s devastating floods inevitably left scars, innovative approaches like developing mine spoil sites offer opportunities for new growth in Kentucky.