The dragonflies are in abundance and even a few fish have been seen. These tentative signs of life are the first indications of hope for a new stream reclamation project on Duke's campus.
The unnamed stream runs along Campus Drive and connects to Sandy Creek. For many years its condition has deteriorated. During heavy rains, instead of calmly flowing horizontally into a floodplain, the energy of the water flow dug vertically into the soft stone base. The result was a steep, narrow stream poor in wildlife and water quality.
"When your campus streams get degraded like that, sedimentation carried downstream dramatically increases," said Ryan Lavinder, a civil engineer with Duke University Utility and Engineering Services. "Going in and restoring this stream is a good thing for water quality and aquatic life. And the problem with a degraded stream like this is once it starts to occur, it just gets worse and worse and worse."
On the surface, the project seems simple. The contractors tore up much of the tree and plant life on the stream's edge, most of which were invasive species, and dredged out the land to create a proper floodplain. River bends now have a more stable radius. Logs, recycled from the cut-down trees, are buried across the stream and the stream's descent has been slowed. All of this reduces the stream's vertical energy and allows the floodplain to do its job.
Part of that job is reduce foreign nutrients, including nitrogen and phosphorus, common pollutants in an urban stream that affect water quality. One goal was to restore the stream's natural ability to mitigate the effect of the nutrients, said Angela Gardner, a water resources consultant with John R. McAdams Co. who assisted Duke with the project.
The plants and soil of the floodplain interact with the pollutants in the water, Gardner said. "The soil contacts bacteria that transforms these nutrients and releases nitrogen into the atmosphere rather than retain it in the water as [polluting] nitrates," Gardner said. In its current degraded state, the stream was too steep and energetic for any of that interaction to occur.
Using contractors who are experts in stream reclamation, the project is progressing in three sections. Work is nearly complete on the central section that runs from a culvert at the intersection of Swift Avenue and Campus Drive to a culvert that flows underneath Campus Drive near the Freeman Center for Jewish Life. Work is now two-thirds complete on the north section that runs from the Freeman Center toward East Campus.
In this audio slideshow, Lavinder and Gardner discuss what the bulldozers are doing and why they believe the reconstruction will make for a more lively, healthy campus stream.