MEC&F Expert Engineers : SINKHOLE STATE: Acid rain from hurricanes or tropical storms is expediting the creation of sinkholes in Florida

Sunday, May 13, 2018

SINKHOLE STATE: Acid rain from hurricanes or tropical storms is expediting the creation of sinkholes in Florida









OCALA, Fla. – All around some members of a Florida community, solid ground is suddenly opening up.

A sinkhole drained an entire pond. At least a dozen people were forced from their home when giant holes swallowed up land near them. One woman scrambled out of her home in the middle of the night after hearing a loud crack.


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Sinkholes are not uncommon in Florida, but the frequency of the ones opening up in a community in Ocala the past two weeks is alarming officials and residents who live there.

In Winchase townhomes, more than a dozen sinkholes have opened around a retention pond—a pool designed to hold storm water runoff from streets to prevent flooding.

“When they first started opening up it was really scary, and we weren’t sure whether we should stay here or stay with a friend or family member,” said Maren Pinder, a mother of two who lives in the quiet community 80 miles northwest of Orlando.

The massive depressions have drained the pond, pulled water out of another one nearby and forced the evacuation of eight nearby homes, with some overlapping and intersecting to become larger.


“The crews testing the soil said they’re still assessing the land before they can develop a plan to repair everything,” said resident Maren Pinder. (Fox News)

The holes began appearing on April 25. Residents said they saw them burst open when water started exploding into what looked like a geyser shooting out of the now-empty pond.

“My husband said that when he was leaving for work the day it happened, he felt a depression in the road. It was soft on the concrete so it was no surprise to him that there was a sinkhole there later in the day,” Pinder said.

According to the Florida Geological Survey, more than 400 sinkholes have been reported in the state since Hurricane Irma hit on September 10, 2017, a sudden spike from previous years. Meteorologists predict the upcoming hurricane season could be just as destructive – causing a ripple effect the causes the ground to give way.

Locals say there was another sinkhole epidemic here in 2012, which cost the Homeowner’s Association thousands of dollars to fill and secure.

“The 2017 hurricane season was extremely active…we saw Hurricanes Harvey, Irma, Maria and Nate,” said Brian LaMarre, meteorologist-in-charge at the National Weather Service Tampa Bay. “What we’re looking at for the 2018 hurricane season is actually another above normal season.”

Dr. Anthony Randazzo, co-principal of Geohazards, Inc. and professor emeritus at the University of Florida, advises engineers and architects of sinkhole and other ground risks before construction projects begin.

He says weather and other factors contribute to the risk of sinkholes.

“This is a natural phenomenon, but it’s exacerbated by the fact that we have a rapidly growing population in Florida occupying land areas prone to sinkhole activity,” he said. “So we should see more and more sinkholes develop with time, particularly when they’re triggered by large storm events.”


The Sunshine State has more sinkhole activity than any other state in the country. The city of Ocala sits in a part of the state known as "sinkhole alley," and it all has to do with what lies beneath.

Florida’s bedrock is made up of a porous layer on limestone, which Randazzo compares to a block of swiss cheese. He says it can break down over time as it interacts with acid naturally found in rainwater, causing anything above to collapse.

Randazzo said the process creates caverns in the limestone and has been going on for thousands of years, long before Florida was Florida, but can be accelerated by heavy rain from a hurricane or a tropical storm.

“Central Florida has limestone close to the surface that dates back millions of years, parts of Florida farther south have younger limestone which is deeper under the surface and not as permeable,” he said, adding that the holes in the limestone existed long before the development was built.

"Sinkhole alley" accounts for two-thirds of the sinkhole-related insurance claims in the state, according to a Florida Senate Insurance and Banking Committee report.

In 1981, a crater near Orlando grew to 400 feet across and claimed five sports cars, most of two businesses, a three-bedroom house and the deep end of an Olympic-size swimming pool.

Crews are using underground radar and drilling machines to dig up to 100 feet down for soil samples in hopes of figuring out a solution to the cratered lunar landscape.


They have told residents the holes cannot be filled until testing is completed.

The Ocala Fire Rescue Department and the city's engineer, as well as the county's Emergency Management Department, have been investigating the sinkholes to try to prevent them from happening again.

Randazzo said preconstruction reviews of soil are not extensive enough and do not involve geologists to the extent that they should, adding, “as a result the underlying conditions that could produce a sinkhole are oftentimes missed and the construction goes on and then years later the structure experiences sinkhole activity.”

“I don’t know a whole lot about sinkholes, but you would think if they had fixed the one back in 2012 that would prevent future sinkholes here,” Pinder said. “I’m hoping this time around they fix it so we don’t have to worry about those sinkholes happening anymore.”

A worse-case scenario is that these sinkholes continue to grow and eventually merge into one massive crater, something neighbors describe as their worst fear.