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FEMA to assess Florida's vulnerability to sinkholes
By Pat Andrews
posted Aug 12, 2013 - 4:27:54pm
The collapse of a Lake County resort has Central Floridians worried about the possibility of more sinkholes, threatening homes and businesses.
About a third of the three-story Summer Bay Resort in Clermont collapsed into a sinkhole around 3 a.m. Monday, Aug. 12, The Associated Press and other news services reported. The hotel was evacuated, and no injuries were reported.
Volusia County has had its share of sinkholes in the past — including one that opened up near Deltona High School, swallowing a chunk of Howland Boulevard and forcing the evacuation of 20 homes in the area.
This January, a smaller sinkhole in DeLeon Springs gobbled up a tree, fencing and power lines, but not nearby homes.
By the afternoon of Aug. 12, the Florida Department of Environmental Protection reported being swamped with requests for information.
In response to questions, DEP offered the following information about sinkholes:
The entire state of Florida sits on top of several thousand feet of limestone — Limestone is a rock that can form with natural void spaces called porosity. Porous and permeable limestone makes great aquifers, which provide millions of gallons of fresh drinking water for residents and agriculture.
The most significant factor in the development of sinkholes is the dissolution of the limestone underlying Florida by naturally acidic groundwater.
Sinkholes are a natural and common feature of Florida's landscape — They are only one of many kinds of karst landforms, which include depressions, caves (both air-and-water-filled), disappearing streams, springs and underground aquifer systems, all of which occur in Florida. Thousands of naturally occurring sinkholes can be seen throughout the state of Florida, including many that connect underground to springs, rivers and lakes.
Sinkholes that cause great holes form when surface sediments collapse into underground voids.
In response to questions about the danger of sinkholes, DEP responded:
A sinkhole opened in my neighborhood... should I be concerned? — Although sinkholes in Florida 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 might be prudent. Unless the sinkhole is very large, and extends to your property, there’s likely to be little reason for concern.
Should a sinkhole open in an area near you, the hole should be immediately cordoned off and clearly marked to protect traffic. Contact local law enforcement to report the hazard, and call your city or county road department to initiate repair work. If the road is private, repair of the hole is usually the responsibility of the landowner or property owners’ association.
Is there a safe area of Florida where there is no chance of sinkholes? — Technically, no. Since the entire state is underlaid by carbonate rocks, sinkholes could theoretically form anywhere. However, there are definite regions where sinkhole risk is considerably higher. In general, areas of the state where limestone is close to the surface, or areas with deeper limestone but with a conducive configuration of water table elevation, stratigraphy, and aquifer characteristics, have increased sinkhole activity.
The News Service of Florida reported that the Federal Emergency Management Agency (FEMA) will funnel nearly $1.1 million to an assessment of Florida's vulnerability to sinkholes, according to the state Department of Environmental Protection.
The request for the project stemmed not from the Aug. 12 sinkhole, but from last year's Tropical Storm Debby, which brought heavy rain to the state and led to the formation of sinkholes.
The assessment will start in Hamilton, Columbia and Suwannee counties in north Florida.
Later, a model will produce a statewide map showing sinkhole vulnerability, a DEP news release said.
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