With more than 1,300 feet of earth overhead and few openings the conditions are unfriendly at best, fatal at worst.

That is why safety is foremost on everyone's minds at the Cargill Salt mine at Avery Island.

At the first level, the air is cool, even a little damp with just a hint of salt. This level is 500 feet below the ground, and marks the location where mining here began.

Currently the 1,300 and 1,600 feet levels are being actively mined. At that depth, miners are working more than five football fields below the earth's surface.

Visitors are rarely allowed inside the mine's belly.

The ramp leading down to the lower surfaces is cavernous. Typically according to Mine Supervisor David Swisher, mining areas are not so large.

“In coal mining, you could have men working on their hands and knees in 36 inches of space,” Swisher said. “In salt, what you are mining is all around you. The only thing limiting you is ground stability.”

Mining mechanics

To ensure that stability, Cargill independent consultants use rock mechanics to make sure that an area is mined only while it is safe, Swisher said.

Consultants prepare a mine model on a computer, Swisher explained, and “mine it out.” All the factors, like pressure and temperature, are programmed into the computer model. This prefix to actual mining, he said, gives a pretty exact idea of how much mining can be done in any particular area before that area is in danger of collapsing.

“In old times,” he said, “it was trial and error.”

“They mined until it caved in, and then they knew they had gone too far. With experience it became easier to predict when to stop.”

Another factor mandating when mining has to cease in an area is temperature. The deeper the mine, the higher the temperatures. The Avery Island mine, Swisher said, may contain salt to a depth of 40,000 feet. But currently, there are no plans to mine it past the 2,100 feet level. Doing so would be impossible because of the heat.

Mining process

At 1,300 and then 1,600 feet salt is being actively mined here. The air is filled with the sounds of workers moving salt. A crusher rumbles as the big chunks are broken down. A ball-bearing squeaks as the conveyor belt it moves hauls half-inch pieces of salt up the production shaft. Miles of conveyor belts traverse the mine in an elaborate system that looks like blood veins.

Each portion that is mined, is first undercut, drilled, shot, scaled and then undercut again. The undercutting involves a special machine — looking like a gigantic 20-foot long chainsaw — that cuts straight through the salt wall. The face of the wall comes off in a 20 foot deep section with a little help from a “shot” of ammonium nitrate fuel oil ignited by a booster charge. The charges are inserted in holes drilled into the face.

After the salt is loaded and hauled to the crusher, the area is “scaled” to remove any loose sections. Weak sections in the ceiling are bolted with metal bars driven into the ceiling to bolster its strength and keep it stable.

Then, the entire process starts again. Each shot Swisher said, can produce between 1,800-2,500 tons of salt — the weight of about 945 Chevy Suburbans.

This mine produces 2.5 million tons of salt annually, Swisher said.

The air is thick with salt, and the mineral is all-pervasive. It coats clothes and equipment. It leaves its grains in hair, eyes, nose, and ears. It whitens eyebrows and eyelashes with its grainy powder.

Unlike coal, salt dust is not a health hazard but it does increase wear and tear on machinery and cause vehicles to rust. Because of salt's corrosive qualities, a complete machine and repair shop has been erected 1,300 feet below ground.

Equipment used in the mine is brought down in pieces and assembled. But it is never taken out, Swisher said.

“Once it is brought down here it stays here,” he said. “We put it up a dead end in a part that is not being mined any more and eventually it is buried.”

Because salt is flexible, it is always moving. Occasionally an abandoned tunnel will contract and shut off again without actually caving in, Swisher said. This is how abandoned parts go to their graves.

Mining dangers

Even though salt mines are less likely to cave in than other types of mines, mining of any kind is an inherently dangerous profession. Every miner is required to wear a safety hat, glasses, and steel-toed boots and carry a battery-powered lamp and a self rescuer kit to convert carbon monoxide to carbon dioxide in case of a mine fire.

“Safety is of primary importance down here,” said Joseph Collins, who works in mine production at Cargill. “When you work so far underground, you have to be careful. Others are depending on you, like you depend on them.”

As workers exit the mine, they return lamps their original locations “tag in.” They hang circular tags on a board. Workers place their tags black side out when they are in the mine, and white side out when they have left the depths of the white-walled caves. Brass tags with names and numbers are returned to the hooks as well.

“In case of a disaster or a fire,” Swisher said, “these tags will at least let rescuers identify your body.”

An accident in a mine — especially a fatal one — is something no miner should ever have to witness, said Lynn Bayard, maintenance supervisor at the mine.

“There are no second chances,” Bayard said. “All you have is yourself and a lot of luck.”