AFTON MOUNTAIN - From tunnel darkness beyond the flashlights' reach echoed a rhythmic "poc, poc, poc, poc."

The sound mimicked the noise a metal canteen might make jostling against a hip.

"Is someone walking there?" asked Gene Whitesell in a low voice, wondering aloud.

Whitesell and two companions walked deeper into the abandoned railroad tunnel, a 19th-century engineering marvel. Each man wore chest-high waders. Sections of the nearly mile-long tunnel now trap water weeping or pouring through rock.

Eight years of brutish, dangerous labor shouldered by Irish immigrants or slaves cut this passage through Afton Mountain in the 1850s for steam locomotives. Claudius Crozet, a French-born engineer once described as the best mathematician in the United States, guided the work at the Blue Ridge Tunnel. (Related item: Claudius Crozet: From Napoleon's army to the Blue Ridge)

Today, motorists by the millions cross over the tunnel on Interstate 64 and never know the tunnel is there. At Rockfish Gap they drive over Crozet's marvel and speed past, also, the Appalachian Trail and entrances to Skyline Drive and the Blue Ridge Parkway.

Officials in Augusta, Nelson and Albemarle counties would like to capture some of these travelers - believing both that the Blue Ridge Tunnel is a treasure worth sharing and that disposable-income travelers will share some treasure, too.

Toward this end, Whitesell's Roanoke-based landscape architecture and planning company, the Whitesell Group, is working with Nelson County officials and others to create an interpretive trail through the tunnel. To build clamor for the plan, which already has garnered $638,000 in funding, Whitesell and colleague Suzanne Gandy have repeatedly taken journalists and state and local officials on tunnel tours.

Many emerge with similar reactions. Awe is commonly reported. And more than a few fight to articulate sensing somehow the presence of the men who labored with hand tools and gunpowder in the tunnel between 1851 and 1858.

Dan Mahon, greenway coordinator for nearby Albemarle County, is a descendant of Irish immigrants. Mahon said when he visits the tunnel he allows his imagination free rein.

"You can hear the workers. You can hear what it must have sounded like in there, with the hammers and hand drills and picks," he said.

Mahon once visited the Blue Ridge Tunnel with his son and renowned Irish fiddler Frankie Gavin. Mahon played tin whistle, Gavin fiddled and the son played the bodhran. Their music echoed off the hand-hewn stone.

Maureen Corum, Nelson County's director of economic development and tourism, said the tunnel elicits many feelings.

"You can sense Crozet's tenacity and his mathematical genius," Corum said. "And I feel the people who worked there."

Abandoned since 1944, when trains shifted to a newer, larger tunnel nearby, the Blue Ridge Tunnel is owned by CSX Corp. College and high school students sometimes trespass there, leaving behind graffiti and beer cans. Corum said Nelson County is negotiating with CSX to buy the Blue Ridge Tunnel for a nominal fee.

Whitesell said he's walked through the 4,277-foot tunnel, and crawled through the section that requires crawling, about 15 times. Inside, the air is consistently cool, in the low to mid-50s. One blistering summer day when Whitesell entered the egg-shaped western portal, a red-tailed hawk burst from the cool interior and startled Whitesell witless.

On the recent visit, deep inside the tunnel, Whitesell swung his flashlight from wall to wall, searching for the source of the mysterious "poc, poc, poc, poc." The answer revealed was anticlimactic - the sound resulted from the steady drip of groundwater onto a partially filled beer can.

Crozet's work crews battled "the interference of water" with pumps and a 2,000-foot siphon designed by Crozet. The engineer, the contractor and workers endured many other challenges and hardships as they labored in the cause of facilitating trade and transportation for the Shenandoah Valley: poor ventilation, falling rock, labor strife, financial woes, sniping editorial writers, a cholera outbreak in 1854 and more.

In 1855, Crozet wrote of work "so very hazardous that many of the hands left it" and described rock so hard it "frequently dulls drills before any perceptible impression can be made."

History suggests the Irish workers were more expendable than the slaves because the latter were considered a tangible asset by slaveholders.

Workers dug from opposite sides of the mountain. They finally "holed through" on Christmas Day 1856. Subsequent excavation revealed that the tunnels mated nearly perfectly, being merely inches (or less) off center - an engineering feat that became part of Crozet's legend.

But more work remained, including trimming and grading, brick arching for sections of loose rock, and the laying of track. The first train passed through in April 1858.

In 1976, the American Society of Civil Engineers designated Crozet's Blue Ridge Tunnel a Historic Civil Engineering Landmark. The society said the tunnel "represents the culmination of civil engineering technology based on manual drilling methods."

Crozet reported that construction of the Blue Ridge Tunnel cost $488,000, or more than $9 million in today's dollars.

The Whitesell Group estimates conversion of the tunnel into a safe, passable and partially lit interpretive/recreational trail will cost at least $1.7 million. Gandy said the tunnel "has been combed by structural engineers, geologists and other professionals and it has been deemed sound - at this stage."

Gary Rogers is a professor in the civil and environmental engineering department at Virginia Military Institute, where Crozet is considered a founding father. Rogers has studied the tunnel for years and describes it as "a fascinating piece of our engineering history." He said he believes the tunnel is stable, noting the absence of fallen rock on the tunnel floor.

In the 1950s, a doomed scheme to store natural gas led to construction of two concrete "plugs" inside the tunnel. Now, traversing the tunnel end-to-end requires crawling through each of these bulkhead plugs via short lengths of a small-diameter pipe. If the project goes forward, the plugs will come out.

Whitesell and Gandy have drummed up support for the tunnel effort in many quarters. Mahon is a fan. As is Bob Munson, planning bureau manager for the Virginia Department of Conservation and Recreation.

"I think it's an exciting, unique, dynamic opportunity," Munson said. "We have lots of trails in Virginia on the surface of the ground, but few that go underground."

Munson said the Blue Ridge Tunnel's location is ideal - close to I-64, the Appalachian Trail, the TransÂAmerica Bike Trail, the Blue Ridge Parkway and Skyline Drive.

"So, if we can bundle these all together in a unique place, I'd say we have a pretty good investment," he said.

Corum said Nelson County depends on tourism, which she said provides about one-third of the county's revenue. A tunnel trail could lure visitors from I-64, she said.

"You're talking about heritage tourists, eco-tourists, college kids and many others," she said. "There are so many facets we can market."

Phil Dulaney and his family's corporation, Skyline Swannanoa, own more than 600 acres atop Afton Mountain. Dulaney said he is a history buff and believes the Blue Ridge Tunnel project has merit.

"I think it's better than just having the thing sit there," Dulaney said. "I've known all about Crozet since I was 10 years old."

But Dulaney said he hopes the project won't hurt adjacent landowners, including his friend Bruce Tyler, a lawyer who lives and works near the village of Afton.

Tyler said he first opposed the project because he believed access to the tunnel would affect his property. Now, Tyler's objections focus, he said, on the maintenance costs he fears Nelson County taxpayers will bear if the trail effort proceeds.

Gandy has cited a state maintenance figure for surface trails of $2,500 per mile per year. She said actual maintenance costs could go higher and said an anticipated master plan will estimate such costs more precisely.

Tyler described Gandy's estimates as "crazy," noting the county's costs would include liability insurance and maintenance, and expenses for security and lighting inside the tunnel.

"It's a loser for the county," Tyler said, noting his belief that the bulk of any economic benefits will go to Waynesboro and Augusta County instead of Nelson County. The tunnel's western entrance is in Augusta County.

Like Dulaney, Afton landowner Roger "Bud" Carter, who said his family has lived on Afton Mountain's east slope since the late 1890s, expressed tentative support for the trail plan. Born in 1939, Carter recalls the era of steam, when he heard the "chuk, chuk, chuk" of locomotives fighting the grade.

He expressed admiration for Crozet and the tunnel diggers.

"When the Lord made the seven natural wonders of the world he had a lot of power behind him, but when Crozet came in and engineered this feat he had only the power of men," Carter said.

Carter worries that tourists who have never known back-breaking work won't comprehend the awe he feels in the tunnel's presence.

"If you are a sentimental person - and I am a very sentimental person - you have to wonder how many people will respect it. When I go down there, even now, I stand and I marvel. I marvel because I have worked in my life, believe you me."