Mountain Research has expertise in completing geologic site evaluations to determine if damage to a structure or property is caused by a true karst sinkhole or can be attributed to other causes.
The term “sinkhole” is used by many to explain a surface depression. However, depressions in the ground surface may be created by various causes, not all of which are natural. A true geologic sinkhole is defined as a circular depression in a karst area. The term karst defines a type of topography that is formed primarily over carbonate rocks affected by dissolution and chemical weathering and characterized by sinkholes, caves, and underground streams.
The difference can be important because many insurance companies will only cover true karst sinkholes. Depressions in the ground that are not karst in origin can be caused by a variety of issues such as, but not limited to, mine subsidence, decomposition of organic material, underground utility failures, or settling of improperly installed fill material. In some cases a natural karst sinkhole may be triggered by manmade influences such as a roof drainage discharge or a leaking underground utility.
Mountain Research’s sinkhole investigation includes background research and a site inspection. The background research consists of geologic and cultural investigations for resource based geology, mining, underground utilities, and historical development evaluations. The on-site inspections are to substantiate the geology and other findings, to interview local authorities and landowners, and observe other features. Mountain Research professional geologists will make a final determination based on the findings.
If karst sinkhole activities are confirmed, other confirmatory investigations may be suggested and initiated. Defining a karst sinkhole feature through geophysics or geotechnical drilling can yield evidence to delineate the size and geometry of the issue.
If damage to a structure is identified as a karst sinkhole, Mountain Research can assist with obtaining proper mitigation experts to stabilize the ground and structure. Each sinkhole is different and the type of stabilization requires custom determination by an expert. Typical mitigation techniques include soil grouting or underpinning.
Several States including Florida, Texas, Alabama, Missouri, Kentucky, Tennessee, and Pennsylvania are significantly underlain by carbonate bedrock and are prone to sinkhole damages to property. Much of this damage occurs in areas of denser development. Large areas of Central and Eastern Pennsylvania are underlain by carbonate rocks prone to karst.
Sinkholes in Pennsylvania – PADCNR Educational Series 11
PADCNR General Sinkhole website