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The Water's Edge
A wetlands restoration project at the State Botanical Garden of Georgia highlights two pressing issues and the engineering solutions to address them
By Alan Flurry
Walking along the Orange Trail at the State
Botanical Garden, visitors arrive at a branch of the Middle Oconee River; there, joggers and birdwatchers alike will come across the spot where UGA engineering and a local activist organization have come together to address a groundwater problem common in rural and urban areas. The result is a restored wetland, with new plant, bird and aquatic species but also a cleaner river running to the lakes and people downstream.
In April of 2004, community volunteers from the Upper Oconee Watershed Network (UOWN) collected water samples from local streams as part of their annual River Rendezvous event. Samples taken along the Orange Trail Creek at the State Botanical Gardens revealed the highest levels of nitrates of any stream monitored. At the same time, a macro-invertebrate count – whereby the variety and number of organisms are noted – revealed the stream to be one of the area’s healthiest. “It’s got the most species of insects, because they like nitrogen and use it as a food source,” says Mark Risse, UGA professor and extension engineering coordinator for water quality and pollution prevention. High nutrient levels, while healthy in streams, cause algal blooms and biological dead zones in lakes and impoundments.
In response to the report by UOWN, Risse and David Radcliffe of the Crop and Soil Sciences Department at UGA were charged with determining the source of the nitrate. Seven groundwater monitoring wells were installed in the area surrounding the creek and sampled during the summer of 2005. The groundwater runs to the stream through the springs which feed it, plus the runoff following storm events. From three possible sources of nitrate in the local area, the most apparent was one or more of the four wastewater lagoons at the UGA Swine Farm, less than one-half mile from the confluence of the Botanical Gardens’ Orange Trail Creek and the river.
The lagoons, constructed sequentially from the early 60’s to the early 80’s, were determined to be the most likely source of the elevated nitrate levels.
Nitrates: a good element for biodiversity – but not in lakes.
According to Risse, the streams then become healthy and resilient incubators for a variety of insect life – though as the water reaches lakes downstream, a different result occurs. “It makes the water look green and more turbid,” he says. When algae grow in water, it consumes the oxygen that fish and other species depend upon. “So it’s not only an aesthetic issue with the clarity of the water; high nutrient levels have a detrimental impact on a variety of aquatic organisms,” Risse points out.
The relationship between runoff, high nutrient levels and water quality appears to be clear. From recreational lakes to wastewater lagoons on farms across the southeast, similar evidence can be observed of the effects of high biological oxygen demand (BOD) resulting from nutrient-rich, low oxygenated bodies of water.
And yet where the Orange Trail Creek meets the Oconee, UGA engineers and scientists - as experts who are also concerned members of a community - found the path to an elegant solution for treating the groundwater that will add a significant element to Botanical Garden, as well as provide future teaching opportunities. Just off the trail and in view of the river are the remnants of a wetland constructed by beavers many years ago. Risse and Radcliffe proposed to rebuild the wetland, to hold the water from the streams and any runoff so the nitrates coming in will be treated or removed before being discharged into the water.
Over the last thirty years, storm water wetlands have proven beneficial for a variety of reasons. Their construction has been increasingly encouraged, especially in urban areas, to maximize the removal of pollutants from runoff through several mechanisms, including microbial breakdown of pollutants, plant uptake, retention, settling and absorption. Storm water wetlands are an active measure against upstream erosion and nutrient-rich bacteria growth, promoting the growth of plant species which serve to oxygenate the water as it is spread out and stored in the wetland.
“The unique part of this is that we’re building these storm water wetlands in response to a groundwater concern, not particularly for the storm water runoff,” Risse says. And while the Botanical Garden wetland presents an opportunity to hybridize these strategies for a particular purpose with wider benefits, it also presents a teaching opportunity and a chance to look at the economic ramifications of a wider problem for Georgia farmers: wastewater lagoons.
The condition at the heart of the high nitrogen concentration was determined to be the leaking lagoons at the UGA swine center. The entire center is slated to be closed down over the next five years as a new animal science farm is constructed elsewhere. Last year, UGA engineering used the lagoons in a senior design project to measure how much waste is in the lagoons and develop a plan to dispose of the waste and eliminate the lagoons. “We’ve been researching how to close down these lagoons economically because it’s a challenge for farmers all over the state,” Risse says. On farms of all stripes, the lagoons are built, filled to capacity, then another is built. Risse believes people have been overlooking a hidden cost for decades as the number of lagoons increase and the cost of closing them becomes prohibitive. “I work with farmers all over the state who plan on leaving their farms to their children but come to the realization that they’re leaving them a major liability rather than an asset,” he says.
During the week of June 5, the Botanical Gardens wetland dam became a reality. “We think it will go quite far in remediating the situation - we’re hoping to get the nitrate levels well below the maximum of 1 ppm,” said Dr. Elizabeth Little, professor of Plant Pathology at UGA who volunteers her time as Science and Monitoring Chair for the Upper Oconee Watershed Network and who partnered on the project along with Risse and Valentine Nzengung in the Department of Geology. The dam itself was constructed by Risse, Little, Nzengung, UGA water resources staff, student volunteers and employees of the UGA Physical Plant grounds department. A few showers within days of construction in addition to the usual flow from the streams feeding it and the wetlands immediately spread out behind the dam.
As more farmland shifts toward suburban development, the issue of the lagoons as an economic and environmental problem will continue to grow. Making the connection from storm water wetlands to groundwater to wastewater lagoons is just one example of ecological engineers and water quality specialists finding ways to learn in our communities even as they teach and conduct research. The Orange Trail Creek wetlands is a solution that will touch many people and will make up an important new element in State Botanical Garden. “It will be a teaching wetland, ideally,” Risse says, who envisions an ecologist using it to observe the wildlife or bird species which become ensconced there once the changes in the ecosystem occur. The aesthetic appreciation of natural environments is growing to include a respect for nature’s protective mechanisms. This wetland project brings a small part of this growing awareness into the Botanical Gardens experience, one its birds, bees, fish and people can all enjoy.
photos of the wetlands and dam are available at www.plant.uga.edu/faculty/Little/Botanical_Garden.html
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