Texas leads the nation in the number of fatalities caused by trench collapses, with three this year alone.

The last such accident in Corpus Christi happened four years ago where one worker was killed.

A trench rescue demonstration was held Thursday in Robstown.

One of the biggest surprises for many of the people who watched was how little chance there is of surviving a trench collapse.

"I was pretty amazed about the rescue part of it. That there wasn't much success in rescuing," said Jessie Green. He works for the City of Corpus Christi digging trenches daily for repair and maintainance of City services.

The other surprise was that you could not use equipment.

"You have to use your hands to dig with versus if you had some type of vacuum system to help out. And using your hands in this clay around here, yeah, no success rate at all," Green said.

At a 2013 trench collapse in the King George Place subdivision, the wall of an eight-foot trench fell in, trapping and killing a worker.

According to the National Occupation Safety and Health Administration, or OSHA, there were 11 deaths in both 2014 and 2015 each, and then 23 were killed in trench collapses last year. There have been two in Texas last year and three more this year.

Josh Rungee with Lone Star 811 Call Before You Dig said the biggest factors against survival were weight and time.

"It's about 100 pounds per square foot, so a cubic yard is about 2,700 square feet," Rungee siad. "So it's 2,700 pounds per square yard, which is about two standard truckloads of dirt."

A worker could only last for a few minutes under that dirt.

"So by the time the rescuers get to the scene, come up with a plan of action and start executing that plan of action, time's against that victim," said Mario Vasquez with Houston-based National Trench Safety. "Especially if they're buried completely. They can't breathe, so more than likely they're going to expire."

The experts said the only way to keep workers from dying is prevention involving proper digging and bracing to keep the walls from collapsing.

Thursday's demonstration was the third annual of its kind involving collapsing trenches. Organizers hope to hold one again next year.

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