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Search on for sinkholes

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By Mark Scohier, Staff writer

Recent rains are a welcome reprieve for Florida's sensitive and often over-burdened ecological systems. Lakes, wetlands, rivers and springs — all subject to the effects of development, farming, drought and a changing climate — are, for a time, replenished.

But rain, when it comes in large doses such as the 16.7 inches that fell in Chiefland last month alone, can bring with it unwelcome changes, especially in areas with relatively low groundwater levels.

Sinkholes, though not uncommon in the state, become more prevalent when rainwater eats through limestone already weakened from below by low aquifer levels. The water in the aquifer acts as a support, pushing up with hydrostatic pressure on the rocky ceiling.

In Chiefland this week, the Florida Department of Transportation is investigating several potential sinkholes on state roadways.

Gina Busscher, FDOT district two public information officer, said last week that FDOT is doing tests on areas along County Road 347, Alternate Highway 27, both near Chiefland, and along State Road 24 in both lanes about 4 miles west of Otter Creek. 

Workers there are drilling with a probe to test for voids beneath the highway after it was noticed that depressions were beginning to form, she said. Crews should know by the end of the week if sinkholes are developing.

On Sunday, a 100-foot wide sinkhole opened beneath a Lake County resort a few miles away from Disney Land, prompting reporters from around the state to seek answers from the Florida Geological Society.

Clint Kromhout, an FGS geologist, said in a teleconference phone interview with the media Monday, that sinkholes are to be expected in a state made up of several thousand feet of porous limestone.

"Over time, " Kromhout said about rain in Florida, "it steadily dissolves that limestone, creating a void space."

Kromhout, when asked, also said low groundwater is a factor in the creation of sinkholes.

"Aquifer levels can certainly be a part of the equation," he said, explaining that sinkholes in Hillsborough County in 2010 were the result of low groundwater from agricultural use coupled with lots of rain. The same situation occurred in parts of the state last year after Tropical Storm Debbie came through.

Those sinkholes, he said, are part of the reason the Florida Department of Emergency Management approached FGS last year to do a study of sinkhole vulnerability.

The three-year study will at first concentrate on Suwannee, Hamilton and Columbia counties and then branch out through the rest of the state.

"Hopefully, it will lead to a better understanding of sinkholes."