Tampa engineer explains sand hole that killed 7-year-old girl in South Florida

TAMPA, Fla. - A family's beach vacation turned into tragedy on Tuesday when two siblings were digging a deep hole in the sand, and they were suddenly trapped underneath it.

The 9-year-old boy survived, but his 7-year-old sister didn’t make it.

"The boy was about maybe 3-feet down, but his head was above sand, but his sister was down further, and they tried to dig her out, but the more they dug, the more the sand collapsed," a bystander told WSVN.

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As officials now warn not to dig deep holes at the beach, a geotechnical engineer in Tampa Bay explains the impact of this collapse, and why the depth was dangerous.

"If this hole reached five feet deep, to be safe or have a person in it, it would have to be laid back with a "safe slope" that would make it 10 to 20 ft. across at the top," explained Henri Jean.

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"For every foot you go down into the ground, you put 110 pounds per square foot of depth, so at five feet deep the amount of soil that would be on top of you would be about 550 pounds per square feet. The combination of the weight and the lack of oxygen would result in a very bad situation for anybody down there," Jean said of the potential impact to the little girl.

Jean said without a safe width at the top [around 20 feet], a deep hole can quickly become very vertical and therefore, very dangerous.

"The first thing that you can probably take from this is to never dig anything deep enough to get your head in it," shared Jean.

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