The practice of “approximate original contour” in the central Appalachians. I. Slope stability and erosion potential

Abstract

Surface mining for coal disturbed hundreds of thousands of hectares in the Appalachians by the mid-1970s. The mined landscape created by typical “shoot-and-shove” mining methods during this era led to severe water-quality and land-use problems. Enacted in 1977, the Surface Mining Control and Reclamation Act (SMCRA) required that all mining spoil be stabilized and returned to “approximate original contour” (AOC) wherever possible. This requirement is controversial in the steeply sloping Appalachian (U.S.A.) mining region. The major goal of this research was to objectively evaluate the long-term slope stability and potential erosivity of central Appalachian AOC landforms. Many AOC backfills in this region face long-term stability problems. The major factors leading to backfill instability are: (1) excessively steep and/or convex fill configurations; (2) excessive seepage leading to loss of fill strength; and (3) inaccurate estimation of spoil shear strength parameters and fill safety factors. Slope failures may occur both within and beyond the five-year bond release period mandated by SMCRA. Steeply sloping siltstone spoils are particularly prone to erosion losses, and rapid revegetation is essential for the stabilization of AOC slopes. Widespread implementation of alternative landforms which utilize hollow fills for excess spoil disposal while still eliminating the highwall would greatly reduce the potential for slope failures and erosion by reducing total backfill slope areas and lengths.