In a matter of seconds, the earth opened under Jeff Bush’s bedroom and swallowed him up like something out of a horror movie. About the only thing left was the TV cable running down into the hole.
Hillsborough County Fire Department firefighters responded about 11:00 p.m. Thursday to 240 Faithway Drive in Seffner, Florida to a report of a sinkhole with one man missing and one man entrapped in the sinkhole. A hole about thirty feet across at the earth’s surface opened beneath the bedroom floor — leaving only a mattress visible.
“The bedroom floor collapsed and my brother-in-law is underneath the house.”
— 9-1-1 call
Hillsborough County sheriff’s Deputy Douglas Duvall arrived first and found Jeremy Bush desperately trying rescue his brother, Jeffrey Bush, from the hole. Jeffrey was not visible, but his brother thought he heard him scream for help in the downward flowing sinkhole, which is often caused by dissolving limestone from dynamic levels of the underground water table. Dirt and clay and parts of the floor were still falling into the hole as Jeremy tried to get in the hole and rescue his brother when Deputy Douglas Duvall pulled him out to rescue him. Five adults, a child, and two dogs were in the house when they said it felt and sounded like a car hit the home. Everyone else and the dogs got out of the house safely.
Cover-collapse sinkholes occur where a solution cavity develops in the limestone to a size such that the overlying cover material can no longer support its own weight. Collapse is generally abrupt when this occurs and is sometimes catastrophic. Collapse sinkholes provide dramatic local changes in topography. They may occur in any areas of soluble rock; however, they are less likely to occur in areas of deeply buried rocks.
Collapse sinkholes generally occur in areas where the limestone is near land surface and the limestone aquifer is under water-table conditions. Ground-water circulation is most vigorous at and just below the water-table where solution of the limestone is accelerated. Accelerated solution also may occur at certain depths where bedding planes in the limestone or changes in rock composition concentrate the flow of groundwater.
Limestone is commonly exposed in the vertical or overhanging walls of collapse sinkholes shortly after they form. The sinkholes generally are circular in shape and the walls may be round and smooth, but mostly they are irregular in shape because of the influence of joints and fractures in the rock. Surface drainage, erosion, and deposition of sediment into collapse sinkholes will eventually smooth the sides and reduce their slopes until they may become indistinguishable from other types of sinkholes.
The type of sinkhole is likely a Cover Collapse Sinkhole, which involves a cover of clay over unstable limestone with empty pockets, which can fill with the supporting clay leaving nothing to support the floor of the house. The process of dissolving limestone and the formation of a void is known as suffosion. The dynamic land mass (about 10 percent of earth’s landmass) is known as karst.
Houses on either side of the affected house were evacuated Friday. About noon an underground camera was dropped into the stormwater pipes. About 2:30 p.m. positioned drilling equipment at the front of the house. Rescue workers, engineers, and sinkhole experts have concern that the hole is much bigger than the 30-foot hole exposed at the surface with risk that the whole neighborhood could be engulfed by the sinkhole. The earth below the house is described as a “very large, very fluid mass.” The house is possibly on top of a 100-foot cavern, where engineers have actually had difficulty determining the margins of the cavern. At least 16 verified sinkholes are confirmed within a one mile location of the home.
Only three men are known to have died from injuries caused by a sinkhole.
Sinkhole information from ABC News with graphic presentation of how sinkholes form, and a representation of the collapse of the Seffner home.
Officials say a sinkhole that swallowed a Florida man is seriously unstable and they think it will grow. Hillsborough County Administrator Mike Merrill says no one can go into the house because they are afraid of losing more lives.
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See also …
Tampa Bay Times Seffner sinhole 911 call: ‘Bedroom floor just collapsed’
Sinkholes, from USGS Water Science School
(Show US map with areas prone to sinkholes)