Bonne Terre Mine: Billion Gallon Lake

Bonne Terre, Missouri

We've been in big mines before. We've been in boats in caves before. But we've never before been in a boat in a big mine while the water around us boiled with the bubbles of scuba divers. Like a surfacing pod of subterranean whales, they suddenly appeared. "I have to be careful where I turn the boat," said Dennis, our guide and captain. "I don't want to run over the divers."

We were afloat in Billion Gallon Lake, the centerpiece of Bonne Terre Mine. The mine is a giant hole underneath the town of Bonne Terre, hacked out of solid rock over 101 years by the St. Joseph Lead Company. In 1962 the mine shut down and turned off the pumps -- and groundwater began pouring in.

By the time Doug and Cathy Goergens bought the place in the 1970s, water had submerged the three lowest levels of the mine, filling roughly 88 miles of passages. Its surface, now at the floor of level two, has 17 miles of navigable shoreline.

A Billion Gallon Lake was just fine with the Goergens, who turned their waterlogged underworld into the "world's largest fresh water dive resort." Adventurous scuba divers come from across the globe to enjoy water as clear as a swimming pool's and to explore a "ghost town" of submerged junk left behind when the miners walked out. "We had two guys here the other day from the Netherlands," said Dennis. "I don't even know where the Netherlands is."

For everyday terrestrial visitors, the Mine offers an hour-long walking tour through cavernous rooms -- supported by rock pillars 50 feet high -- and a boat ride on the lake. Dryness, however, is not an option. The splash of water-on-rock is everywhere in the mine, as underground springs continually bubble in. Dennis showed us a collection of old mining equipment, set on the cave floor in 2004 -- already encased in a hard shroud of milky-white calcium left behind by the non-stop dripping.

It's not exactly the magical formations you'd find in some natural caves, but certainly something you won't see anywhere else.

Dennis pointed out a tree root growing down through a drill hole in the roof and an underground garden where at least two couples have been married. He tumbled a small rock down a mine chute so that we could hear its surprisingly loud clatter. "Imagine when they dumped a ton of ore," Dennis said. "A lot of miners went deaf."

Bonnie the Mine Fish.

The towering walls of the mine glittered in the beam of Dennis's spotlight, but he assured us that the sparkly lead was harmless. The Ty-D-Bowl blue color of the water, he said, was from light refraction, not contamination.

The walking tour ends 120 feet below the parking lot at the dock of Billion Gallon Lake. Dennis took a moment to toss a worm to Bonnie, the lake's only known fish, then we hopped aboard the boat. The lake's surface is smooth (except for the gurgling air bubbles of the divers).

We puttered around the stone columns that rise out of the water, 375 feet deep in parts. Dennis pointed his light down to ore carts and other mining debris submerged in the clear lake. We asked if any dead miner skeletons had turned up. Dennis said no, but added that only "a slight percentage" of the drowned 88 miles of passages had been explored. He also said that an energy drink company had sponsored an event, "Depth Charge," where jet skis had hauled wake boarders around at up to 35 mph. We guessed it may have been one reason why a billion gallon lake has only one fish.

Eerie plant growth experiment is spot where a 1975 wedding was held.

Dennis said that he'd lived in Bonne Terre all his life, so we wondered if he'd ever been afraid that the mine might cave in and swallow the town. Doesn't this part of Missouri have a history of earthquakes? Dennis said that he was assured that the billion gallon lake would act as a shock absorber -- and once you accept that scuba divers and jet skiers cavort in the ground beneath Bonne Terre, it sounded perfectly reasonable to us, too.