Erosion and Sediment Control
Case Studies for Successful Coal Ash and Mined Land Rehabilitation in the Southeastern United States Using Engineered Soil Cover Systems
Design and construction of cost-effective cover systems are critical to successful rehabilitation and closure of coal ash and mining projects. Traditional cover system designs typically have involved comprehensive specifications for placement of highly specialized barrier and drainage systems with 12-18 inches (305-457 mm) of cover soils, that are then capped with 4-8 inches (102-204 mm) of a “vegetative soil layer” that is “capable of supporting the growth of vegetation”. A sustainable stand of vegetation will provide enduring control of erosion, capture precipitation to reduce and improve stormwater runoff quality, improve visual aesthetics and foster carbon sequestration while releasing oxygen into the atmosphere. Fertile and productive soils are essential to the development of sustainable vegetative covers.
Soil Health is defined as the continued capacity of soil to function as a vibrant living ecosystem that sustains plants, animals, microorganisms and ultimately, humans through nutrient cycling, filtering and buffering functions. One vexing issue facing successful restoration of coal ash and mining sites is the lack of available and suitable soils to cover coal ash and mining waste to create viable environments for establishing sustainable vegetation.
Obtaining acceptable soils can be problematic as most closure sites rarely have salvageable topsoil after decades of operation. The costs of procurement, transportation and placement of suitable offsite soils can be exorbitant on large closure projects. Fortunately, emerging technologies, such as Biotic Soil Technology (BST) and prescriptive agronomic amendments can make marginal soils suitable for vegetative establishment with significant cost savings to utilities, mining companies and other stakeholders. Biotic Soil Technology (BST) is a generic term to define products engineered to incorporate a consistent weed and pathogen free source of organic materials with potent doses of biostimulants and biological inoculants to replicate and accelerate early pedogenic processes that often may take years to naturally occur on denuded sites.
The Southeastern US has a long history of mining with the first American gold rush actually beginning in 1829 in the north Georgia Mountains. Beyond an abundance of sand and gravel operations as well as hard rock quarries, the Southeast has also been home to many types of clay and phosphate mines. In addition, the region has long been the site of many coal burning power plants, many of which are being shuttered or converted to natural gas in the aftermath of the massive Tennessee Valley Authority (TVA) Kingston Fossil Plant coal ash impoundment failure in 2008. This and other uncontrolled ash releases have led to more stringent ash disposal regulations, coupled with enhanced air and water quality legislation.
This paper presents an overview of soil testing requirements, guidance for the use of BST and other agronomic formulations, and descriptions of complementary erosion control techniques with case histories documenting successful and cost-effective coal ash and mine cover systems in the Southeastern US. In addition, these case studies will describe and detail longer term performance monitoring techniques to demonstrate sustained improvements in Soil Health.