VA city’s artificial wetland the real deal in slowing stormwater pollution
Waynesboro installation uses ponds to filter runoff from 330 acres of a residential neighborhood
Historically, cities and towns relegated stormwater treatment to the unseen places: The backs of buildings, the edges of town. A pond that held runoff containing the detritus of urban life — water mixed with heavy metals and fertilizer, motor oil and animal waste — was not the prettiest town amenity.
But Waynesboro, VA is bringing stormwater treatment to the forefront. Recently, the city of 21,000 installed a 10-acre “constructed wetland” in its center. Mimicking nature as best as it can, it filters runoff from its natural drainage basin — 330 acres of mostly residential neighborhood. The beneficiary is a mile or so to the east: the South River, which flows through the city and eventually to the Shenandoah’s South Fork 15 miles away.
This constructed wetland works by forcing runoff to cascade gradually downhill through an array of three ponds — four, if you count the highest elevation, the “sediment forebay,” which captures mud from the runoff before it enters the vegetated ponds. According to Waynesboro’s stormwater manager, Trafford McRae, the city will likely have to dredge the forebay every two to three years.
By the time the water reaches the bottom pond and is piped to the river, it has spent enough time in the wetland to allow natural processes — chiefly absorption in the underlying soil and mud, uptake by plants and microbial processes — to remove most of the polluting nutrients.
Built on what had been a grassy “detention basin,” or large stormwater collection pond, in the city’s Jefferson Park neighborhood, the new wetland is expected to remove around 300 pounds of phosphorus and 1,700 bounds of nitrogen annually from the runoff that passes through it. That’s a very small fraction of Waynesboro’s total nutrient contribution to the river, but it’s moving the city in the right direction, according to McRae.
“I think the wetland — along with other activities, such as additional retrofits we have completed and street sweeping — will get us to our goal,” he said, for reducing phosphorus, the river’s primary nutrient stressor.
The $1.6 million project was funded by a grant from the Virginia Department of Environmental Quality’s Stormwater Local Assistance Fund and a low-interest loan from the DEQ’s Virginia Clean Water Revolving Loan Fund. Waynesboro is the first city in the valley to take on a stormwater project of this kind, though it might be the last to do so with help from the state, at least for the time being. Virginia legislators earlier this year, looking for places to tighten the state’s budget, chose not to renew stormwater local-assistance funding.
Stormwater runoff is a significant contributor of nutrient pollution in the Bay, pouring tens of millions of gallons of nutrient-laden water into the creeks and rivers of the Bay watershed.
Fertilizers and yard and pet waste are typical sources of urban phosphorus and nitrogen pollution, which is sluiced without filtration from impermeable surfaces such as roofs, roads and parking lots into storm drains. The overabundance of nitrogen and phosphorus getting into streams and rivers promotes an unnatural level of algal growth, which in turn robs the water of dissolved oxygen, making it inhospitable, if not deadly, to fish and animal life.
“Waynesboro has turned a boggy field into a community park with thriving wetlands,” said Rebecca LePrell, Virginia executive director of the Chesapeake Bay Foundation — which has promoted the project in its publications. “This is a truly transformative project,” she said. “What Waynesboro has done is cost-efficient, effective and benefits the whole community. It is an example for other localities around Virginia that need to reduce polluted runoff.”
LePrell expressed great disappointment in the Virginia General Assembly’s decision to end the SLAF funding, without which the Waynesboro project couldn’t have happened. “These projects do much more than just reduce pollution,” she said, noting that constructed wetlands beautify a neighborhood and may also control flooding.
The local government is strongly on board as well. “More and more, the city council and our community recognize that the South River and its tributary streams here are among our most valuable resources,” said Waynesboro Mayor Bruce Allen. “We’re home to an urban trout fishery, we’re installing boat launches and trails along the river, and the South River is a designated blueway. Completing the Jefferson Park retrofit is part of a mindset and a local culture we’re promoting here for protecting water resources.”
The project was completed late last year. Because of the dry winter and early spring, the ponds were only half full by mid-April, but the region has since experienced heavier rainfall, and McRae said he is hoping for a wet fall and winter, which would put the ponds at full capacity by next spring.
To date, the new landscape has yet to attract wildlife, barring a few geese and the occasional killdeer cautiously exploring the shallows. But McRae said he expects a wide variety of wildlife to make use of the new wetland — including songbirds, waterfowl, frogs, turtles, deer and small mammals. And with any luck there will also be bats — houses have been built for them — which will help control the inevitable explosion of the mosquito population.
Among the new residents, no doubt, will be nonmigratory Canada geese, which explains the plastic fencing surrounding each pond. It’s there to keep the waterfowl from waddling ashore to graze on the surrounding grass, or nesting in the area, adding their waste to the runoff that needs to be treated.
In some areas around the ponds, contractors planted water-tolerant Japanese millet, a nonnative plant that serves the temporary purpose of making the soil more welcoming to the native water lovers that will eventually take its place: bald cypress, river birch, smooth alder, silky dogwood, American holly, serviceberry, cardinal flower and milkweed.
It will be a few years before the revamped Jefferson Park’s new plant life will serve as active wildlife habitat, but as the trees, shrubs and wetland vegetation begin to mature, it’s expected to appeal to both wildlife and the local human population. To enhance the latter, the city plans to add a community garden, signage explaining the park’s history and present function, and walking trails.
“We’re hoping to rename it ‘Mulberry Run Wetlands,’ ” McRae said, to acknowledge the creek that was known by that name long ago, before it was piped underground downstream at the site. “Hopefully, in 10 years we’ll see a thriving wetland habitat that is used by Waynesboro citizens to enjoy, as well as being a valuable educational resource.”
- Category: Pollution
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