The recent spate of sinkhole activity in Southwest Florida -- including a fatal sinkhole in Tampa earlier this month -- has shed light on the state's geologic anomaly. But how do sinkholes impact state economic factors like property insurance and home sales?
A 2010 data call and statistical analysis by the Florida Office of Insurance Regulation -- undertaken in response to "the office identifying increased sinkhole claims as one of the cost drivers affecting homeowners rates" -- shows a sharp increase in reported sinkhole losses in the state between 2006 and 2009. According to the report, "total sinkhole costs over the sample period amounted to approximately $1.4 billion and increased from $209 million in 2006 to $406 million in 2009."
The report looked at three types of sinkhole claims: collapse sinkholes ("frequently triggered by fluctuations in underground water"), subsidence sinkholes (generally slow and gradually forming), and clay shrinkage (vary with "seasonal and annual precipitation changes"). The most common claims were subsidence sinkholes, paying out an average of $140,094.
The bulk of claims were in regions well known for sinkhole activity, including Hernando, Pasco, Hillsborough, and Pinellas counties. There was a slight but impactful increase in claims activity in Miami-Dade and Broward counties: Miami-Dade accounted for 1.5 percent total claims in 2006-2009 and 2 percent in 2010. Meanwhile, Broward accounted for 1.4 percent in 2006-2009 and 2.2 percent in 2010.
Of the increase in these two counties, the report states: "Not only are the number of claims on the rise, so is the total loss and expenses. This is statistically significant due to the fact that this area is generally not subject to sinkhole activity." (Read the report in its entirety here.)
The Florida Legislature responded to the issue in 2011 with the passage of SB 408, property insurance reform that tightens up the timeframe for insured homeowners to make a sinkhole claim, outlines investigation protocol, and limits the structures that may be covered under a sinkhole claim. It also "allows an insurer to require a property inspection prior to issuing sinkhole loss coverage" while repealing the electronic database of sinkhole activity. (Homeowners can read SB 408 here.)
South-Florida-based forensic realtor, Larry Lowenthal has in the past been retained as an expert witness on sinkhole-related lawsuits in the Tampa area. He likens the ground in that part of the state to "Swiss cheese" but doesn't forsee sinkholes as an immediate threat on "this coast."
"I don't see it as having an impact on this half of the state," said Lowenthal, who has been active in the Florida real estate business since 1990. "They do occur here, but they are pretty rare."
Indeed, South Florida's geological makeup is less likely to lead to the type of sudden, deep sinkholes seen on the state's Southwest coast. But as water use and development increase in South Florida, that risk factor could fluctuate. A Miami Herald story from earlier this month quotes Florida sinkhole expert Bill Fernandez on sinkhole formation:
'When they take water out of the ground it's like taking air out of a balloon,' Fernandez said. 'When you suck water out of the ground, you change the hydrostatic pressure underground and that's what can cause sinkholes.'
The story also quotes State Geologist Jonathan Arthur who says there are a lot of variables involved in the naturally-occuring phenomenon, but "moving a lot of dirt around for development can also trigger sinkholes."
No matter where in the state, prospective and current homeowners should perform due diligence before purchasing a home. Lowenthal said the old notion of "all you have to check for is termites" is dated. While "the law requires full disclosure of all defects," buyers looking in areas known for sinkhole activity or suspected sinkholes should consider ordering engineering surveys and ground soil tests. (He also suggests an increase in radon inspections for prospective buyers.)
"Science Friday" host Ira Flatow recently interviewed Randall Orndorff, a geologist with Virginia-based U.S. Geological Survey. Orndorff said current testing procedures for sinkholes haven't been "completely successful." He said home owners concerned about potential sinkhole damage should watch for changes like cracks in walls or foundation, changes in door frames, and cracks in soil.
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