Despite large holes in the road, Brevard just doesn’t get sinkholes

by Michael Mosher on October 9, 2017

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After a large hole appeared this week on Knox McRae Road in Titusville, social media accounts were abuzz with claims a sinkhole with an appetite for asphalt had formed in the street.

Titusville police also took to social media, to report a “possible sinkhole” last week. Instead, it was a pothole on South Street. On State Road 528 near Industry Road, a broken water line resulting in a hole in the ground also was mistaken for a sinkhole.

Fears about sinkholes in Brevard County were fueled by a 25-foot-wide, 15-foot-deep sinkhole forming in Apopka, taking with it a couple’s long-time home.

But geologists and government officials said Brevard residents shouldn’t be worried.

Washout from Hurricane Irma’s heavy rain is pulling the ground from underneath roadways or sidewalks, causing them to implode in places.

“We don’t have sinkholes in Brevard County,” said county spokesman Don Walker. “We’ve had culverts collapse, washouts and emergency road closings.

“Because of our geological makeup, we don’t have sinkholes.”

Kevin Cook, Titusville’s director of public works, echoed Walker’s comments after possible sinkholes were reported by residents on Indian River Avenue, Knox McRae Road and Sisson Road.

“Given the amount of water that has submerged some areas, it’s usually related to a utility or stormwater pipe,” Cook said. “With the impact of the hurricane, people do have a little fear when they see things like that open up.”

Water from Irma opened up problems not seen there before, he said, such as erosion of vulnerable culverts. But the washouts that have occurred are not sinkholes, he said.

What is a sinkhole?
A sinkhole is a specific geologic event that occurs when acidified rainwater eats away at underground limestone creating cavities in the earth and allowing the ground’s top layer to cave in. Rainwater can become acidified as it interacts with natural compounds in the atmosphere or carbon dioxide in the soil, according to the Florida Department of Environmental Protection.

Reports from The Florida Geological Survey show that dozens of sinkholes have been reported in the interior of Central Florida over the years, nearly all of them inland or on the west coast of the state.

But in Brevard County? None.

What keeps the Space Coast safe?
Geologist Dr. Randall Parkinson said it’s all about the limestone on which the Space Coast rests.

Limestone here is a young and vibrant 120,000 years old, Parkinson said. Compare that to the elderly limestone found beneath other parts of the state that’s between 15 and 25 million years old.

Older limestone has had more time to dissolve, creating those caverns that end up giving way and swallowing houses.

“Our limestone is thin. It’s not everywhere. It’s too young to have matured to that level,” Parkinson said, comparing older limestone to Swiss cheese. A heavily pock-marked chunk of coquina makes for a good microcosm of what happens in the limestone, he said.

Urban areas, humidity and dry seasons are all factors when it comes to sinkholes, according to Parkinson.

Groundwater naturally fills many of those cavities, sustaining the necessary pressure to prevent cave-ins, but when people use lots of water and drain it elsewhere, the lack of replenishment can be like removing the columns from beneath a ceiling.

Sinkholes require a narrow set of geological conditions, Parkinson said.

And Brevard County just doesn’t have them.

 

Full article…here

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