This 1 hour course discusses subsidence problems associated with past underground mining activity. Typical problems include cracks in foundations and walls, jammed or broken windows, and broken water, sewer, and gas lines. Information is also provided about conditions such as expansive soils or brick thermal expansion that may produce problems frequently mistaken as being caused by subsidence. Detailed advice is provided as to what to do when subsidence problems are suspected and what help is available for property owners faced with these kinds of problems.
The course is based on specific conditions in Illinois, but many of these same conditions also exist in Indiana, Kentucky, Ohio, Pennsylvania, and West Virginia. These states are underlain with coal deposits that lie so far below the surface that they can be extracted only through underground (rather than surface) mining. Many of these mines were dug well over one hundred years ago in areas that were uninhabited or sparsely settled at the time. Today these areas are home to residential subdivisions and retail centers, some of which now sit above abandoned mines. As the coal pillars and timbers that originally supported the mine roof collapse from age and water damage, the roof comes down, and the soil and rock overlying the mine sink. The surface of the land above the mine subsides, and any structure lying on the surface is liable to damage from the subsidence.