THE IMPORTANCE OF PROPERTY-OWNER INTERVIEWS IN SINKHOLE COLLAPSE REMEDIATION

Sinkhole collapse is a common, and often costly, occurrence in carbonate rock terrains. Though some collapses occur naturally, most are linked to human activities that involve the concentration of subsurface water flow and the formation of a soil arch. Proper remediation should include excavation to bedrock and exposure of a principal conduit, proper construction of a filter plug, and correction of the fundamental cause. Case studies often show a leaking storm water pipe, roof gutter, or water main as the culprit, but one should be aware of more sophisticated causes.

One such case involved a seemingly minor 1 square meter collapse adjacent to a home in Pennsylvania's Cumberland Valley. The small collapse opened after an exceptionally wet period and was located 2 meters from a broken roof gutter seam. Excavation created a pit that slowly filled with water, which with sufficient head pressure, blew-out a soil pipe that drained the pit in seconds. Abandoning the gutter idea, a homeowner interview identified an abandoned in-ground pool, French drain, municipal water service break, abandoned septic system, and street maintenance as a series of seemingly unrelated items that were pieced together to reveal the cause.