Green Infrastructure Helps Coastal Wetlands

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North Carolina Coastal Federation rain garden
Credit: North Carolina Coastal Federation
North Carolina Coastal Federation rain garden
In coastal North Carolina, stormwater managers are looking to green infrastructure to solve stormwater problems.  One successful green infrastructure project in Wilmington is the Wade Park Wetland. It was a $4 million joint project by the city of Wilmington, New Hanover County, and the state of North Carolina. The 17-acre park is on the site of a former wastewater treatment plant. Before the plant was constructed, the area was a natural wetland.

Completed in 2007, the wetland at Wade Park helps clean stormwater before it runs into the Hewletts Creek watershed and also reduces flooding in the area. The largest wetland in the area, it receives runoff from 590 acres, which is about 10% of the Hewletts Creek watershed.

The project began when New Hanover County bought the land in 2005 with money provided by the North Carolina Clean Water Management Trust Fund (CWMTF). Wilmington’s Stormwater Services Division installed the 12-acre wetland starting in 2006. The project diverts runoff from two outfalls bordering the property into the wetland before the water enters Hewletts Creek.

The Wade Park Wetland also provides habitat for native and migratory birds and animals. The remaining 5 or so acres of the land were made into a public park after the wetland was completed.

Wade Park Wetland

The city of Wilmington and its nearby beach towns are fortunate to have the University of North Carolina at Wilmington close. Dr. Michael Mallin, professor of biology and marine biology, works with the city, the North Carolina Coastal Federation (NC Coastal Federation), and other entities on stormwater issues.

Mallin led monitoring efforts in 2009 and 2010 to see how well the Wade Park Wetland was handling stormwater volume and pollution. According to a study first published in the November 5, 2012, issue of the Journal of Environmental Quality, the results were quite favorable.

The sampling covered eight storms and showed that the Wade Park Wetland retained and/or removed 50 to 75% of the inflowing volume of runoff. The average load reduction for fecal coliform bacteria was 99%, with an overall concentration reduction of more than 90%.

Another green infrastructure project in Wilmington involved converting city property into an operations center for the Street Sweeping Division of the Public Works Department. Solar panels added to the roof eliminated almost all the power bill for the center.

“A portion of that property directs runoff to a new bioretention area, about three-quarters of an acre, and that’s in a very industrial area,” says Mayes. “Previously stormwater just sheeted off. Now it infiltrates.”

Pier at Wrightsville Beach

About 10 miles from Wilmington is the town of Wrightsville Beach. It is on a narrow island several miles long, which is connected to the mainland. One of several barrier islands, it lies between the Intracoastal Waterway and the Atlantic Ocean.

Wrightsville Beach stormwater officials team up with their counterparts in Wilmington.

They also work closely with the NC Coastal Federation, North Carolina State University, the University of North Carolina at Wilmington, and other agencies.

In this section of coastal North Carolina, pollution carried by stormwater runoff has closed shellfishing waters, some for years. Periodically—usually after a big storm—swimming areas off Wrightsville Beach and other places are closed. Mayes says results from lab tests allow these beach areas to reopen for swimming in less than 48 hours, but the closures interfere with tourists and residents alike.

Wrightsville Beach

“People want to come here for shellfishing, swimming, boating, all sorts of recreational activities. Livelihoods depend on it, so our waters need to be clean,” says Mayes.

Skrabal says, “Wrightsville Beach is a real destination for athletic events, especially triathlons and swimming events. People are exposed to the water, so there is increasing attention to it and the desire to get [rid of] polluted water.” SW_bug_web

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