A Miles-Long Cave in Kentucky Was a Smelly Disaster. Now It’s Spectacular

There are signs that Indigenous tribes, including the Shawnee, relied on local caves for water and for refuge. In 1850, settlers founded the village of Horse Cave around the cave’s scenic entrance. Soon after, a local dentist tapped the cave’s springs to supply drinking water to the town. (He also later installed Kentucky’s first incandescent streetlights.)

In 1916, a half-mile section of Hidden River Cave was opened to the public for tours, part of a wider wave of cave tourism across America. But those glory days were short-lived.

By the mid-1930s, the cave had become hopelessly contaminated as people dumped sewage into nearby cave passages and sinkholes, not realizing they were contaminating their own water supply. Noxious odors chased away the tourists, and for much of the 20th century the cave fell into neglect, its streams devoid of almost all life. The cave’s yawning entrance became overgrown, nearly invisible to passers-by, closed off by thick vegetation and a tall fence.

The gut punch came in the 1970s, when a metal-plating factory started sending highly polluted wastewater to a local sewage treatment plant, overwhelming the already struggling facility. Waste from a local creamery also swamped the sewage system. The cave’s passages filled with a cheesy foam.

Sandra Wilson, a former mayor who now leads the town’s tourism commission, said she could smell the stench from her office even with the windows closed. Walking past the cave opening was an ordeal, she said. “You just had to hope that you could hold your breath long enough.”

Then some out-of-towners set up shop at a little-used commercial building near the cave’s entrance. The American Cave Conservation Association was founded by caving enthusiasts dedicated to protecting caves and groundwater. They were looking for a project and Hidden River Cave was just the ticket.

Dave Foster, a Virginia cave explorer who came to town to lead the effort, had little experience. But his group had a strong backer, Bill Austin, the cave’s last private owner, who had invited the group to come see if it could tackle the pollution.

“The attitude back then was, ‘Why not let the cave be a sewer?’” said Mr. Foster, who now runs the Hidden River Cave and museum. “We needed to change that.”

Working with hydrologists, biologists, and other experts, the association studied ways to bring the caverns back to life. It quickly became clear that the region’s caves and aquifers were so intertwined that no one town could tackle contamination on its own. It took a decade to get surrounding communities and organizations — Cave City, Park City, Horse Cave and Mammoth Cave National Park — to come together to build a new, state-of-the- art regional sewage system, one that didn’t put treated water back into the caves.

The town also leaned on polluting facilities to treat their wastewater. It lined up state conservation funds to purchase rights to the cave. It negotiated with railroads to obtain the land rights above the caverns, preventing future development. In 2005, the town signed an easement to protect Hidden River Cave permanently.

Ms. Wilson was a town council member when it voted for the new sewage system, which began operating in 1989. There was opposition, she said, from local businesses that objected to increased sewer bills. “They could no longer get rid of their sewage for free,” she said.

Through the 1990s, the stench receded and heavy-metal contamination decreased. Julian Lewis, a biologist who together with his wife, Salisa, started inventorying cave life in 2013, found that cave crayfish, cavefish and other creatures were coming back.

“The cave started to slowly recover,” he wrote in an email. That contrasted, he said, with when he first visited the cave, decades earlier. Back then he saw only so-called blood worms, which had adapted to polluted waters, and strings of grayish sewage bacteria.

Randall Curry, the town’s current mayor, said Hidden River Cave had “gone from being an embarrassment to being a source of pride.” The town had finally realized, he said, that “if you do what you always did, you get what you always got.”

The threats to the cave haven’t completely receded. Some stream sediments still contain what Dr. Lewis called “chemical souvenirs” of decades of sewage flowing through the cave. And he suspects some industries continue to dump sewage

Still, venturing into Hidden River Cave today is a transforming experience. Once an hour, guides lead groups of tourists through a half-mile stretch of passageway fitted with walkways and a 100-foot suspension bridge. The highlight is one of the largest cave rooms open to the public in the United States, Sunset Dome, named for its intricate bands of orange rock.

Excitement is building beyond the cave’s mapped routes, where for the first time in a lifetime, exploration has started again after a decades-long hiatus. There are likely 50 miles or more of uncharted passageways hidden beneath a ridge to the northwest of the cave entrance, said Liam Tobin, a cartographer who has been working to map them.

He’s leading the way for a new generation of explorers. “We’re going to places in our cave system where no one has ever been in the history of our planet,” said Ashlee Warren, an explorer and cave guide. “I never thought I’d get so passionate about a hole in the ground.”

Hiroko Tabuchi covers pollution and the environment for The Times. She has been a journalist for more than 20 years in Tokyo and New York.

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