[Subsidence is the motion of a surface as it shifts downward. Land subsidence can lead to many problems including changes in elevation; damage to structures such as storm drains, sanitary sewers, roads, railroads, canals, levees, and bridges; structural damage to public and private buildings; and damage to wells. Most commonly, subsidence causes an increase in flooding potential.]
During the first half of the 20th century extensive underground coal mining took place beneath the city of Red Lodge. Workers created rooms in a checkerboard or grid pattern, leaving pillars of un-mined coal to support the mine roof and the surface. Although a common mining method, over time if the roof of a subsurface mine collapses, it causes the ground above to sink, shift, or subside.
Over the years in the Red Lodge area, instances of crop failures or mine-related subsidence occurred. In 2011, two property owners reported to the Montana Department of Environmental Quality (DEQ) that ground subsidence was affecting their houses. The DEQ awarded Pioneer a contract to conduct a drilling investigation in the area to determine whether the surface subsidence is related to the collapse of underground mine workings. Pioneer will determine the best locations to drill borings, oversee the drilling, evaluate potential vibrational effects on adjacent homes, develop a 3D model, analyze all the information, and provide recommendations to DEQ on a path forward.
For more information contact: Tim Ranf (tranf@pioneer-technical.com)
Pioneer is currently conducting quarterly monitoring of ground movement and home foundations using survey methods and inspections in the same area.
