I was roaming around the internet, reading some of my usual blogs when I wandered over to DeputyDog (I click on the links a lot). He has some wonderful photos of "7 Amazing Holes" - large mines, "glory holes", and sink holes.
One thing led to another, and I came upon stories of mine pillars collapsing and causing sinkholes, which pull buildings and roads down into the ground due to land subsidence .
"Land subsidence also occurs in areas of underground mining where removal of material causes overlying surface rock to sink or collapse. Although the locations of underground mines are often denoted on topographic and geologic maps, the potential subsidence hazard from a mine requires evaluation by a geologist."Tar Creek, OK is one town that has been subjected to sinkholes and threats of mine collapse for years. There are also the real toxic threats from the dust to the air and acid mine water that contaminates the water table. While it was zinc and lead mined there, gypsum , used primarily in wallboard, has its concerns also:
"Similar to land subsidence due to underground mining, subsidence can also result from chemical weathering of soluble rocks (e.g. limestone, dolomite, gypsum). As groundwater flows through limestone, a chemical reaction causes the rock to dissolve, eventually forming cavities within the bedrock. As a cavity near the surface increases in size, the overlying materials can sink or collapse and create a depression on the land surface."
"In the early 1980s, landfills in British Columbia were found to be producing toxic gas and leachate from concentrations of gypsum debris that had been buried for as little as two days."One would think that the Town of Clarence would want to shield itself from future lawsuits. There can be all kinds of studies, but that doesn't mean that the earth won't do it's unpredictable thing and shift. Then again, Amherst is off the hook for it's sinking homes.
The prevailing thought just might be that if they're insurable, and the Town's not liable, go for it. Add to the tax base and services needed, subtract from green space. Just think twice before buying a house there.