Bonne Terre Mine, Bonne Terre, Missouri  

    Deep underground, the Bonne Terre mine awaits a certain kind of explorer. 
Scuba diver Bob Dulay fits the bill—which is lucky considering Dulay drove 400 miles for the experience. 

The billion-gallon underground lake that used to be a working lead mine draws visitors year-round, but its winter temperature of 58 degrees pulls in the real crowds.

“Where else are you gonna go in the center of the nation in the middle of winter without freezing water or ice diving?” Bonne Terre manager Donna Jones asked.

Dulay and more than 60 other divers set off on this underwater adventure in late February in Bonne Terre, Mo. They traveled from cities as far as Indianapolis and Chicago in hope of an unforgettable experience.

And they found it in the Bonne Terre mine.

Inside the mine, the heavy fog dampens the air, trailing off into the darkness. The humidity closes in oppressively along the descent to the water’s edge. Massive stone pillars support a ceiling more than 100 feet above the water, exposing the large cavern blasted away by decades of mining.

Snug in their skin-tight wetsuits, with pounds of gear strapped to their backs, the divers plunge into the subterranean lake. The water’s clarity makes objects far below seem close enough to touch.

“A lot of times you can see the divers 30, 40 feet under the water, and you can still see the fins and the tank,” Jones said. “It’s crystal clear.” 

This clarity showcases the history that more than 100 years of mining left behind. Mining carts remain on their rails far beneath the surface. Picks and drill bits litter the floor and remain embedded in the limestone walls. The lack of oxygen in the filtered spring water preserves the artifacts.

“It was incredible,” said Dulay, who dived three times that weekend. “I’ve never seen anything like it.”

The St. Joseph Lead Company broke ground at the Bonne Terre mine in the mid-1860s, and at the height of its production, the mine housed an elaborate engineering department, blacksmith shop, machine shop and stables for the work mules. The equipment remains to this day. 

When the mine closed in 1961, the pumps that kept the mine dry were turned off, allowing the cavern to fill with spring water, tour guide Dana Fish said. He said the cavern is filled with more than 275 feet of water, and it requires frequent pumping to keep the water level at slightly less than 100 feet below the cavern ceiling.

Divers explore the cavern in groups of 10. They are allowed to examine the floor and walls of the mine amid the glow of overhead lights strung from pillar to pillar. Illuminating much of the cave, the light system uses more than 500,000 watts of power – equal to the wattage used at the former Busch Stadium in St. Louis, Fish said.

A guide leads each group on one of 24 routes that cover more than two miles of underwater trails. A safety diver brings up the rear of every group, preventing divers from wandering off.

The Bonne Terre staff schedules dives on weekends. A dive requires open-water scuba certification, and two dives cost a minimum of $130.

Although winter is the peak season, Bonne Terre diving is available year-round. The summer lull is perfect for divers who like smaller groups and more space to familiarize themselves with the cave, Jones said.

Boat and walking tours also are an available feature. From the relative dryness of the pontoon boat tour, visitors can see some of the remnants of the mine’s past life.

Despite its one-of-a-kind quality, some divers responded with mixed reviews.

“It was overpriced, overcrowded and inefficient, but I had a good time,” Bryce McKean said.

McKean and a group from a dive shop in Indianapolis traveled to Bonne Terre for a weekend dive. Although he thought the facilities could use improvement, McKean said the cave provides a unique diving experience.

“This close to home there’s not much,” he said. “In the winter, this is about it.”

Yet, the experience is one that draws people of all nationalities from great distances.

“They come from all over the world,” Jones said. “Sometimes we get groups in here that don’t speak English. They usually have a kid who speaks English, so you’ll have to say something and then wait for them to translate.”

International and domestic adventure-seekers alike now glide through the depths that, only a half-century ago, constituted a working lead mine. It operates now as a reminder of a former life and a bridge to a world people only read about in history books.

“It’s totally hard to describe,” Dulay said. “That’s why I take pictures of it. It’s a once-in-a-lifetime opportunity.”