CHARLESTON — It started as a 3-inch hole in the asphalt.

Concerned that the palm-sized pit could be the result of a leaking pipe, Steve Jones probed it with a five-foot steel rod and found a chasm.

“I thought, ‘I wonder what caused that?’” said the Oregon Institute of Marine Biology’s on-staff building contractor. “It went all the way down to nothing in several different directions, and we kind of went ‘uh-oh.’”

He and OIMB officials suspected a flaw in the storm-water system under the school’s parking lot. But when a backhoe expanded the hole to see what was what, a different story and deeper mystery emerged.

“We started digging and digging and digging until we found wood. One piece had a big square spike in it. That was when we knew we had something.”

After the discovery of the obviously man-made structure, OIMB Director Craig Young called the director of the Coos Historical & Maritime Museum in North Bend. In turn, she called the U.S. Bureau of Land Management and State Parks.

Enlarging the hole, researchers found the rotting wood formed a shape akin to a culvert, a boardwalk or a small-gauge train track. Rough-hewn planks sandwiched supporting logs, connected by long, rust-caked spikes.

The representatives from BLM and State Parks gave their opinions. The structure was obviously old enough to warrant a more educated opinion. OIMB needed to determine whether it contained historical significance, and if it could be torn up. OIMB’s staff was anxious to repair the hole in front of the school’s maintenance shop.

“It probably couldn’t have been in a more inconvenient spot,” Jones said.

Young contacted Tom Connolly, research director at the University of Oregon’s Museum of Natural and Cultural History. Museum archaeologists expanded the hole to a 30-foot trench. They concluded it was an old culvert, and therefore not much of a find. They filed a report with the State Historical Preservation Office and left it at that. SHPO officials agreed to let OIMB pull out the wood, as long as workers saved a piece for display.

But Young, who spent the better part of a day in the hole, disagrees with their conclusion.

A stream bed on old maps suggests a culvert might have been used in that area. But the structure didn’t match that function. It likely would have blocked the water instead of serving as a conduit.

“We think now it was a boardwalk. It was probably one of the first boardwalks in Charleston,” Young said.

Although located in the middle of campus today, it likely would have been over beach sand and within 100 feet of shore. People would have used the walkway to get from building to building rather than slog through soft sand.

Young has a 1930s photograph showing a similar boardwalk design.

“We expect this is the same, but about 50 years older,” Young said. “This could be the oldest structure in Charleston that still exists that we know of.”

He placed its construction between 1850 and 1890, when builders would have used cut nails like those found jutting from the rotting wood. He is unsure whether it would have run near the shore or from building to building. There are no Charleston photos from that era, nor anyone who remembers.

Recalling stories of Jedediah Smith, who camped on or near OIMB land in the early 1820s, Young said the campus has a rich history, including being the site of the first U.S. Coast Guard Station.

“It’s a very interesting place historically. This just adds one more piece of the story (of OIMB),” Young said.

The boardwalk — if that’s what it is — probably remained visible in the 1920s, Young said. A 1923 Coca-Cola bottle and fragments of china and glass also were found in the hole.

From descriptions he’s heard about the discovery, Rusty Shield believes it’s more likely a narrow-gauge train track than a boardwalk.

The Charleston Rural Fire Protection District captain said it might have been laid out for hauling rock to the south jetty. Neither he nor Young knows when that would have occurred. The planks seem too hefty to simply support a few people on a stroll, he said.

Young doesn’t entirely disagree. It could be train tracks, though there is no evidence of where the rail would have been attached. Then again, the wood could have rotted away. He also found the design unusual for a train track, since the rails would have been elevated. But Shield said that might have been done to deal with the spongy land.

Jones also has his speculations, believing it could have served either function.

“If it was a boardwalk or a walkway, they did a hell of a job building it,” Jones said.

Whatever it is, a large portion of the wood has been removed, the hole has been filled, and the parking lot was resurfaced this week. The remains of what was found sit haphazardly in a covered area next to the lot.

Jones and Young said there’s more of it in the ground, but it goes beneath school buildings where it can’t easily be extracted. So where it goes and what it meant to the people who built it remain an enigma.

“The mystery continues,” Jones said. “All we can do is guess.”

(Staff Writer Jessica Musicar covers Charleston issues for The World. She can be reached by calling 269-1222, ext. 240; or by e-mailing to jmusicar@theworldlink.com.)