2010-05-07_PERMIT FILE - C2009087 (52)

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0 O. Potential Imoade on Wells and Sperm. T she QAuW. of l mpacts; on r trWdtm § An d Wat 8. Literature Cited Subsidence lllustratlon >f •�+ ~� law this color l Mielpn9hoWing the ypiceieffectso m nce, ncluding captions and photog raphs u ta the types of mina ufood baidence nce that t c can occur , TW Mine Subsidence — An Overview In order to consider potential impacts of underground mining on overlying structures water resources, and surface land a is first necessary to have some understanding of the mechanics of mine subsidence Mina subsidence can be defined as movement of the ground surface as a result of readjustments of the overburden due to collapse or failure of underground mine workings. Surface subsidence features usually take the form of eaher sinkholes ortmughs. • Sinkhole subsidence is common In areas overlying shallow mom-and-pillar mines. Smini occur hom the collapse of the mine roof into a mine opening, resulting in caving of the overlying tNte and an abrupt depre9slon in the ground surface. The MOJOmy of sink Mks usually develop where the amount of cover (vertical balance betvreen the coal seam ant the surface) is less than 50 fed. This type of subsidence is generally localized in extent, affecting a relatively small area on me Ovedying surface. However, structures and surface features affected by sinkhole subsidence tend to experience extensive and costly damages, sometimes in a dramatic fashion. Sinkhole subsidence has been responsible for extensive damage It numerous homes and properly throughout the years. Sinkle ate typically aeaoaated with abandoned mine workings, since MOM active underground mines operate at depths sufficient to preclutle the development of sinkhole subsidence . In accordance with the current regulations, the Department will not authorize underground mining beneath structures where the depth of overburden is less than 100 feet (30.5 m) , unless the subsidence control plan demonstrates that proposed mine workings wal be stable and that overlying structures will not suffer irreparable damage Subsidence those ln induced by room -amt llar mining can Occur over active or abandoned mines. The resultant surface Impacts and damages can be sandar, however the mechanisms that trigger the subsidence are dramatically different In abandoned mines, troughs usually occur when the overburden sags downward due to the failure of remnant mine pillars. or by punching of the claim into a soft mine floor or roof, it Is difficult. 0 not impossible, to predict if or when failure In an abandoned mine might of since abandoned mines may collapse many decades affair the mining k cemplele . if the mine workings were not designed 10 provide long -term support. n To, Potential Impacts of Underground Mining on Structures Damages lo stmames are generally dassifie0 as cosmetic, functional or lit udural. Cosmetic damage refers to slight problems where only the physical appearance of the structure is affected. such as cracking in plaster or drywall Functional damage refers to situations where the structures use has been Impeded, such as jammed doom or windows. More significant damages that Impact structural integrity are classified as structural tlamage. This would include situations where is entire foundations require replacement due to severe clacking of supporting walls and footings