After more than a month of closures, Lost River Cave reopened the underground park for boat tours Monday.

“Everybody here has a smile on their face,” Rho Lansden, the cave’s executive director, said Monday.

Six weeks ago, furrowed brows might have been the expression of choice. On March 30, Lost River Cave staff discovered a gasoline odor emitting from the cave and suspended boat tours.

The Kentucky Department of Environmental Protection began an investigation last month. Due to karst-related challenges, the Kentucky Energy and Environment Cabinet declared a state of emergency to provide the resources needed to solve the mystery, and hired a contractor to examine nine nearby gas stations’ underground storage tanks – the expected source of the release.

Kevin Strohmeier, the response coordinator for the department’s Environmental Response Branch, said that although the investigation is ongoing, the cave is safe for visitors.

“We have been getting minimal detections to non-detects with (a vapor and gas monitor) for well over a week. This is our standard indication for outdoor air that there is no risk-based threat from volatile organic compounds,” Strohmeier said via text.

Gasoline exposure can harm human, plant and animal health. Gas stations regularly cause air and soil pollution when gasoline drips onto the ground or vapors escape open gas tanks. When the fuel evaporates, it emits compounds such as benzene, a known human carcinogen, according to the National Institutes of Health.

Throughout the investigation, the environmental experts involved reiterated that the data has not indicated any safety threat.

Jason Polk, director of the Center for Human GeoEnvironmental Studies at Western Kentucky University, has been monitoring air quality once or twice daily during the investigation. He agreed that the cave’s air quality is safe – and was probably never unsafe.

“It’s always been within safe levels for exposure,” Polk said, especially for short durations of time.

In the past week, the levels dropped to near-zero or zero – so the threat is essentially nonexistent at this time.

But both the investigation and monitoring will continue. If air quality does change, the experts involved will know immediately, Polk said.

Since the levels never exceeded safety standards, the state did not recommend that the cave suspend tours, according to Strohmeier.

Lansden, however, wanted to ensure that the cave was “absolutely” safe before allowing visitors back underground.

“We are very happy. We have had an entire week without any smell of gasoline, so we feel comfortable reopening the cave and resuming tours,” she said.

This caution came with a cost. The nonprofit lost nearly a tenth of annual income.

Unlike state and federal parks, Lost River Cave doesn’t receive tax dollars. It’s self-funded with variable income. For the past two decades, the cave has reserved non-essential annual funds into a rainy day fund with the goal of avoiding staff layoffs in unpredictable situations, such as flooding-related closures.

“We’re purposely very conservative financially,” Lansden said. “We depend on the cave tour proceeds. When we will look at our project to-do list this year, we’ll be taking things off the list. Repair and maintenance, those will be the first to go.”

The closure also prevented cave staff from training new hires for summer tours, though everyone will be caught up before Memorial Day, the cave’s first major weekend, Lansden said.

Despite the setback, Lansden expressed excitement to regain normalcy at the cave.

But she emphasized that she wanted this situation prevented in the future.

“I’m anxious to see what the investigation turns up,” Lansden said. “All of us that live in Bowling Green are concerned about the safety of our cave systems (and the groundwater) that we live on top of.”