Scott Lake: The Formation and Investigation of a Large Sinkhole Occurrence in the Mantled Karst of West-Central Florida

On June 13, 2006, several large sinkholes developed within Scott Lake, Polk County, Florida. Due to potentiometric head differences between the lake and the underlying Floridan aquifer, one of the sinkholes drained the entire lake over a seven-day period. Slope failures affected the shoreline and damaged residential properties and other structures. The exposed lakebed revealed two large cover-subsidence sinkholes aligned along a northwest trend, along with multiple circular topographic features consistent with older, in-active (paleo) sinkhole features. Investigation of residential structures along the lakeshore found minor to significant settlement damage related to the slope failures and soil raveling. Standard Penetration Test (SPT) borings showed significant stratigraphic disruptions in the subsurface, suggesting the recent sinkhole activity was associated with reactivation of the pre-existing paleo-sinkhole feature(s). Remediation of damaged properties included compaction grouting to stabilize deeper raveled soils, in combination with foundation underpinning and shallow chemical grouting. The size of the sinkhole features and rapid draining of the lake require substantial cavernous permeability within the Floridan aquifer. Periodic reactivation of paleo-sinkhole features and development of new sinkholes are part of the cycle of formation of lake basins within the mantled karst upland areas in Central Florida. It also provides a mechanism for the transport of large amounts of fine organic sediments into the subsurface.