In the wake of the death of a man whose bedroom was swallowed by a sinkhole, the Florida Department of Environmental Protection's Florida Geological Survey this weekend reported the protocol for handling sinkholes in an urban area.
Sinkholes could occur on and around Gasparilla Island although officials say it's not happened so far.
"I've not heard of any," said Bonnie Pringle of the Gasparilla Island Water Authority.
Sinkholes are a natural, common feature of Florida's landscape, which sits atop several thousand feet of limestone, a porous rock that can form with natural voids. Where voids connect in limestone the rock is permeable.
The good news is porous limestone makes great aquifers and provides millions of gallons of fresh drinking water.
The bad news is sinkholes develop when limestone is eroded by naturally acidic groundwater.
Sinkholes form in karst terrain from the collapse of surface sediments into underground voids. Florida has many kinds of karst landforms, which include depressions, air- and water-filled caves, disappearing streams, springs and underground aquifer systems. Thousands of naturally occurring sinkholes connect underground to springs, rivers and lakes.
Solution and cover-subsidence sinkholes are nearly invisible to the naked eye while collapse sinkholes show an abrupt change in topography.
QUESTION: My yard is settling. Do I have a sinkhole?
ANSWER: Maybe. But a number of actors can cause holes, depressions or subsidence of ground surface. Expansive clay layers in the earth may shrink upon drying, buried organic material, poorly compacted soil after excavation work, buried trash or logs and broken pipes all may cause ground depressions to form.
These settling events, when not verified as true sinkholes, are "subsidence incidents." If the settling affects a dwelling, testing by a licensed engineer with a licensed geologist on staff or a licensed geology firm is in order. Property insurance may pay for testing, but in many cases insurance may not cover damage from settling due to causes other than sinkholes.
QUESTION: A sinkhole opened in my neighborhood. Should I be concerned?
ANSWER: Although sinkholes sometimes occur in sets, most are isolated events. The bedrock underlying the state is honeycombed with cavities of varying size, most of which will not collapse in our lifetimes. A quick inspection of your property for any sinking or soft areas is prudent. Unless the sinkhole is large and extends to your property, there's likely little reason for concern.
QUESTION: What should I do if I find a sinkhole?
ANSWER: The hole should be immediately cordoned off and clearly marked to protect traffic. Report the hazard to law enforcement to and call your city or county road department to initiate repairs. If the road is private, repair of the hole is usually the responsibility of the landowner or property owners' association.
QUESTION: Is there an area of Florida where there is no chance of sinkholes? ANSWER: Technically, no. The entire state is underlain by carbonate rocks so sinkholes could form anywhere. However, there are regions where sinkhole risk is considerably higher. In general, areas of the state where limestone is close to surface, or areas with deeper limestone and a conducive configuration of water table elevation have increased sinkhole activity.
To report a sinkhole, go to www.dep.state.fl.us/geology/forms/Subsidence/SIR-quick-form5.htm or call (850) 488-9380.