by Christopher Streb, PE
Since the late 2000s, a landscape transformation has been underway in Midtown Atlanta that aims to restore nature and her benefits within the city. On the west side of I-75, the Georgia Institute of Technology has been implementing a core component of a vision established in its 2004 Campus Master Plan: an 80-acre green corridor called the EcoCommons. While the pandemic quieted student life through the better part of the last year, the University forged ahead in its realization of the EcoCommons on 7 acres of land adjacent to the Kendeda Building for Innovative Sustainable Design. Recently completed, the landscape aims to provide a setting for learning, examination, and reflection, while becoming a model of ecological regeneration in an urban setting.
The vision for the EcoCommons is to restore a native Piedmont ecosystem, integrating smart technology to monitor this ecologically performing landscape, and serve as a living laboratory. A historical examination of the site revealed important insights that informed the design and further contextualized the objectives. From the 1930s to 2019, before becoming the EcoCommons, the land was ecologically unproductive, consisting of surface parking spaces and one-story buildings. However, beneath the contemporary veneer lay important stories that reflect both historical events and perspective.
On the western edge of the parcel once stood the Pickrick Restaurant. At this restaurant, three African American students were denied entry into the establishment by the owner, Lester Maddox, and a group of fellow segregationists. Rather than adhere to the law and integrate, Maddox closed the restaurant altogether. The property was acquired by Georgia Tech soon thereafter and the dramatic events that took place there receded into memory. It is now a civil rights landmark.
What also receded into memory long ago is the character of the land before development. Though University engineers and facilities staff were aware of the storm and sewer infrastructure that flowed through the site, how the pipes conveying water disrupted two existing, small headwater stream valleys was easily overlooked. These valleys were filled, the hills between them flattened, the Piedmont habitats cleared, and the soil compacted and covered in asphalt. This seemingly unremarkable site embodies both positive and challenging memories and perspectives of the last century and warrants a place in our collective consciousness.
Land connects us to history. The activities that happened on the land in the past shape what it is today. Whether burned by Native Americans for hunting ground, logged and farmed by European settlers, or re-contoured for buildings and parking, those past management actions leave a memory—just as the land management decisions we make today connect us to the future. With this temporal perspective of landscape, the EcoCommons represents a turning point in the story of this place: from a state of degradation to a process of regeneration.
To transform the land from parking lot to Piedmont habitat, one cannot expect to design and build a high performing, functional ecosystem with heavy construction equipment and contractors within a year. Instead, a truly functional ecosystem develops year after year, in response to climate, topography, soils, species, and disturbances. Informed by this reality, the design of the EcoCommons sought to identify a starting point for the system, a process to manage succession, and targets for habitats and ecosystem services.
Beginning from the ground up, the design mimics the topography of the two stream valleys that once defined the site and daylights the ephemeral streams. Extensive soil borings and testing were performed to characterize on-site materials at various depths. Given the cost of exporting the fill that was placed in the stream valleys, the decision was made to retain the material and recreate a topography that reflects rather than restores historical conditions. This decision presents new challenges.
Soils are built over thousands of years, as they are made by the geologic minerals and processes of the region interacting with native flora and weathering soils are alive, building over time as roots, limbs, leaves, and wood serve as food and fiber for bacteria, fungi, and invertebrates. A healthy soil absorbs and infiltrates rain, recharging the groundwater and supporting plants. And in the Piedmont, soils are primarily acidic. The onsite material had none of these qualities and was better characterized as non-living ‘dirt.’ Having been turned over and moved, any historic structure of the soil is lost. Compacted and without organic material, rainfall is more prone to generate stormwater runoff rather than infiltrate into the ground. Moreover, poor air exchange and lifeless, alkaline soils limit the viability of native flora. Though native soil cannot be made, embarking on restoring the processes that form soil is possible. Compacted ground can be loosened and amended with organic material to jump start soil biology. Additionally, over the ensuing years, organic matter will be left in place and can be added to allow the ecological process to develop and become more resilient.
Another necessary component of regenerating the site ecology is water. Adjacent to the Kendeda Building, which is pursuing the Living Building Challenge, the landscape should be capable of withstanding periods of saturation and drought. A goal of Georgia Tech is to reduce the annual volume of stormwater runoff from the campus by 50%. The EcoCommons sits at the bottom of two small, urbanized catchment basins about 10 times the area of the site. This runoff reduction goal did not only apply to the 7-acre parcel; rather, the EcoCommons is intended to serve as a sponge and evapo-transpiration machine for the drainage area above it. As a result, irrigation is provided throughout the site by using rainfall and condensate harvested in large underground cisterns. Soil moisture sensors installed throughout the landscape keep continuous tabs on the availability of water for plants. If soil moisture drops too low, harvested rain will be used to irrigate. As the plants grow, increasing volumes of water will be evapo-transpired into the atmosphere, helping to cool the site. Finally, as the roots grow deeper and the soils become more porous, it is hypothesized that infiltration will improve with time.
Within the Piedmont region, there are numerous habitats hosting diverse communities. The new topography, amended soil, and water balance influence the potential flora the site can support. Three Piedmont habitats are targeted for the EcoCommons: wetland natural, upland forest, and woodland and open natural. Several old oak trees located outside the grading zone were retained to lend vertical structure to the system. Dozens of native trees were temporarily relocated during construction and now augment the hundreds of new trees that have been planted throughout the site. In time, the habitats are expected to support a broader diversity of insects, including pollinators. In turn, with more food and structure for roosting and nesting, the EcoCommons hopes to attract an ever-increasing diversity of birds and mammals.
The stage has been set for the EcoCommons to be a pedagogic, ecological performing, and regenerative landscape. But the grand opening only represents the first move of a continuous process. To ensure that the site supports greater biodiversity, absorbs stormwater, and functions as a living laboratory, the site has been outfitted with a suite of landscape and climate sensors. This data will be accessible to the University community. Moreover, the data will contribute to the adaptive management of the site. A central point of examination is whether the EcoCommons represents a new paradigm for urban landscapes that rely on natural processes. If successful, it can serve as a model for how landscapes can be designed to be highly sustainable by increasing ecosystem services while reducing maintenance costs (and associated environmental impacts) as compared to traditional university landscapes.
Whether the site performs as anticipated or not, valuable lessons and insights will be derived.
Christopher Streb, PE, is Bioworks Practice Leader and an Ecological Engineer at Biohabitats, Inc.