Landsliding in Allegheny County, Pennsylvania

Book excerpt: Man should proceed with caution if modifications such as loading, excavation, or changes of the water regime are contemplated for slopes in Allegheny County, especially those slopes described on the map as highly sensitive to disturbance by man. Features indicative of unstable slope conditions include: cracks in buildings, yard walls, and pools; doors and windows that jam; fences and other linear features bowed out of line; tilted trees and utility poles; cracks and steplike ground features; hummocky ground; and water seeps. Geologic factors related to the landsliding process include rock types, layering, fracturing, and attitude; nature of soil cover; permeability of rocks and soils; and steepness of slope.