SPRING VALLEY — On a recent hot July day, spelunker John Ackerman of Lakeville unlocked the door that leads to Spring Valley Caverns, the state's largest privately owned cave and the largest cave on his farm north of Spring Valley.
Inside the stone structure, backpacks littered the floor, left behind by children exploring the cave with guides from Quarry Hill Nature Center in Rochester.
They're the reason Ackerman worries about a nearby BP pipeline.
Ackerman fears that if the pipeline would break, fumes could kill people exploring the cave and the hazardous material would wreak havoc on the cave's fragile eco-system, as well as on the creek that flows into Bear Creek and eventually the Root River.
The cave entrance, located in woods near Fillmore County Road 1, was discovered in 1966 by a young farmer who had recently purchased the property.
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An early commercialization effort never panned out. When Ackerman purchased the farm in 1989, he knew there was a nearby pipeline, but he had no idea that the cave would run five miles underneath it.
Back then only half a mile of passageways were accessible, but with the help of explosives about five miles of the cave is now open.
Off and on since 1994, Ackerman has corresponded with officials with Amoco, which merged with BP in 1998, in hopes that the company will send workers out to inspect a section of pipeline that lies directly under a flowing stream that dumps into his cave.
"One would hope they would have just a hint of curiosity regarding a potential catastrophe just a few miles from their terminal," Ackerman said.
Ackerman believes the pipeline has never been physically inspected since it was built.
But BP officials say they last inspected the pipeline in July 2009 and found no problems.
"Operating the pipeline safely is top priority for us," BP spokesman Ronald Rybarczyk said. "Our intention is to prevent issues before they arise."
The Minnesota Office of Pipeline Safety records show that office completed inspections in 11 of the past 15 years of the pipeline.
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Ideally, Ackerman would like the company to move the pipeline, but he's only asking that they install a shut-off valve in the cave's vicinity.
"Everyone knows we need oil and gasoline, but when the pipeline was laid in the 1940s, people didn't know anything about karst features," Ackerman said, referring to the geography of the land characterized by numerous caves, sinkholes, fissures, and underground streams.
The pipeline was commissioned in 1948 and transports finished products like gasoline or diesel fuel from Dubuque, Iowa, to a New Star terminal in Roseville.
The section that concerns Ackerman runs directly under a blind valley, where flowing surface water abruptly drops into the ground, travels underground and reemerges at the surface.
Hundreds of feet away from the cave's entrance there's a grove of trees with a creek meandering through it.
"Sometimes the water rushes and other times it's merely a trickle," Ackerman said.
Two markers, one on either side of the grove, indicate the pipeline's path.
Ackerman believes the flowing water could be slowly eroding it.
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"The pipeline isn't buried very deep," Ackerman said. "A farmer nicked it with his plow before I bought the land."
University of Minnesota geology professor Calvin Alexander, with the help of his students, did two dye traces in 2006 and discovered that the water flows through the cave and re-emerges about 2 miles away, near Fillmore County Road 1. The water from the cave eventually flows into Bear Creek, which dumps into the Root River.
