Peering down into the manhole, the construction workers did not see the darkness they expected.
Instead, they saw several people huddled underground, gazing up into the sunlight of the street. The workers called down: Did the group need rescuing?
“It’s OK!” came the reply from underground. “We’re scientists.”
A dozen scientists, science writers and students from as far away as Venezuela, all in town for the annual Science Online science communication conference, came to Raleigh a day early for a different type of pre-conference workshop: a journey to the center of the Earth. Or, make that a journey into Raleigh’s subterranean storm tunnels, something most people never think about.
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Scott Huler, a former News & Observer reporter and now a blogger, wrote a book about Raleigh’s infrastructure called “On the Grid.” With Huler as their guide, the scientists, clad in customized Science Online hard hats, ducked under sewer pipes, maneuvered around tree branches and spelunked several miles through the tunnels directly underneath Raleigh.
Storm tunnels prevent city streets from flooding by collecting excess water and rain through storm drains. Raleigh’s tunnels funnel all the water to the Neuse River.
Essentially, storm tunnels were made using creeks that engineers covered and buried as the city developed. Early engineers built some of Raleigh’s tunnels using the city’s bedrock as a natural floor. Some large cities with older infrastructure collect sewage and stormwater through the same pipes, but Raleigh has separate systems for each.
The tunnels themselves are about 8 feet high and 10 to 20 feet wide. They are covered in a layer of standing water, with drain pipes leading back up to the streets in all directions.
The average person walking by the tunnels would not give the nondescript openings a second glance. However, the locals on the tour were not the first Raleigh residents to see the storm tunnels up close: They are filled with graffiti, raccoon pawprints and even graffiti about raccoons.
Experts on call
Everyone on the tour had a phone that could connect them to the outside world, but when they had a question, they only had to look to a person next to them. The tour had its own resident experts to answer everyone’s questions every step of the way: Anne Jefferson, an urban hydrology professor from Kent State University, knew what type of bedrock made up the tunnel floor. Emily Finke, a geology education specialist from the Cincinnati Museum Center, explained what caused a unique stalactite formation.
Some of the participants pointed out that the tunnels have their own artificial coral reef: a grocery cart flipped over in front of a side drain creates a natural barrier in the stream, just like rocks in a river.
Several miles of tunnels later, the group emerged into the sunlight of Pigeon House Creek. A resident who had never been in the tunnels called down to the group splashing past her in the creek below and asked what they were doing.
Despite living nearby for years, she had never gone into the tunnels, and that’s probably for the best. When it rains, the tunnels fill quickly, taking in water from every street in the area. Without a map or a tour guide, the cave-like tunnels could be dangerous.
Bringing tunnels alive
Jefferson studies city streams and urban watersheds for a living, but she had never actually been in one underground. She showed videos of the experience to her geology students when she returned, bringing the tunnels alive for them more than reading about them in a textbook would.
Imagine yourself walking along a stream, surrounded by the canopy of large trees, she tells her students. Next, imagine yourself in the dark in a concrete tunnel: It is the same stream you pictured the first time, just several hundred years later.
“I just don’t understand why people don’t do more of this, don’t just constantly say, ‘Hey, that’s a stream. Where does it go? Where does it come from? Where does it start? Where does it end?’ ” Huler said as he held back a branch so tour participants could step into another tunnel. “My 8-year-old was over the moon when we were down here. So I hope I’m teaching him.”