ANCIENT LANDSLIDE DEPOSITS IN THE APPALACHIAN REGION BELFRY LANDSLIDE

When exploring subsurface conditions in the Appalachian Region, one can expect to encounter bedrock near the surface of steep valley flanks, deep alluvial deposits along some of the major streams and land disturbed by past and recent coal mining activity. The bedrock conditions are predictable unless the project is underlain by unusual geologic features like Pine Mountain where a fault zone presents adverse dips and changing lithology. The thickness and consistency of the alluvial deposits are not unlike those encountered along other major streams surrounding the region and available mine records provide useful information relative to mine related land disturbance. However, what is not well documented is the presence of deep colluvial deposits that sometimes are in excess of 80 feet in thickness and can only be addressed by a thorough geotechnical exploration.

The Belfry Landslide occurred along the west flank of Pond Creek directly below an abandon deep mine. A geotechnical exploration encountered deep colluvial deposits along the hillside, well above the floodplain but directly above US 119. Although the landslide did not affect US 119, a slightly different alignment of this road would have intersected almost 90-foot deep colluvial deposits, which by the nature of their deposition are only marginally stable. This paper discusses the scope of the geotechnical work performed to evaluate the stability of the hillside and formulate recommendations to mitigate the disturbance, and actual repair work information provided by the government agency responsible for the abatement measures.