The George Washington University
Vision and Mission for Sustainability at GW
The George Washington University envisions a future with resource systems that are healthy and thriving for all. In efforts to enhance our campus, our nation's capital and the world at large, the GW community is building a greener campus, providing research and intellectual discourse on policies and pathways to sustainable systems, and equipping students with the skills and knowledge to contribute to a sustainable future.
Prior to the Square 80 improvements, the site functioned primarily as a parking lot with tertiary spaces used for a pedestrian walk and trash collection for the residents of Guthridge Hall, Strong Hall, and 2109 F Street. These uses yielded the site with a 93% impervious surface.
The primary design objective for Square 80 was to create a large central open space for student and faculty recreational use while enhancing the main pedestrian connection from F to G Streets. STUDIO39 Landscape Architecture was chosen to design Square 80 and transform the underutilized spaces used for trash collection and parking into social gathering spaces. The final objective was to harvest 100%
on site rainwater for irrigation, maintenance, and amenities. Once the sustainability design practices were established, including the use of native plants, GW also wanted to use the space as an outdoor classroom for its Landscape Design & Sustainable Landscapes program.
Sustainable Sites Initiative
The Sustainable Sites Initiative™ (SITES™) is a partnership of the American Society of Landscape Architects, the Lady Bird Johnson Wildflower Center at The University of Texas at Austin, and the United States Botanic Garden with an objective to transform land development practices with the first national rating system for sustainable landscapes. Square 80 Plaza is one of over 150 pilot projects within the Sustainable Sites Initiative's pilot program. The U.S. Green Building Council (USGBC), a stakeholder in the initiative, anticipates incorporating these guidelines into future iterations of LEED Green Building Rating System™.
Native plants are those that are indigenous to a specific region. The majority of the plants used here are native species. The remaining plants, with the exception of the lawn, are non-invasive, adaptive species that tolerate regional soils and climate. The planting design respects the establishment period (the first growing season), after which, the trees, shrubs, grasses and groundcover would no longer
require supplemental irrigation. The harvested rainwater can then be completely allocated to the open lawn.
Pervious paving allows water to move vertically through the paving material to slowly infiltrate and recharge groundwater. It can be designed to detain or convey water. Including pervious paving in any urban setting creates a cleaner environment, and can save on costly stormwater vaults and other filtration systems. At this plaza, excess water that does not infiltrate the soil below the paving is collected into a pervious PVC underdrain and channeled to the underground cistern for storage and reuse on site.
Roof Water Collection
While street level rainwater is addressed with various bioretention and reuse techniques, rooftops are another rainwater source deserving of attention. Utilizing existing gutter and downspout systems, rainwater can be rerouted to rain barrels and cisterns. Both of these components provide a means to reuse water on site that would otherwise flow into storm drains polluting natural waterways, and preventing groundwater recharge. A rain barrel and vortex separators are utilized for collecting roof water from Guthridge Hall and 2109 F Street.
Rainwater harvesting benefits the natural environment by eliminating the reliance
on potable water, thus preserving this valuable resource. Harvesting all the rainwater on site reduces the amount of stormwater that enters into sewer systems eventually contaminating the local waterways. Throughout the site, the plaza design implements numerous Low Impact Development (LID) practices in order to clean, store and reuse the rainwater harvested. LID practices strive to maintain and enhance the pre-development hydrologic regime of urban and developing watershed. Examples include: pervious paving, biofiltration planters, rain gardens, bioswales, and roof water collection.
1 Pervious Paving
2 Biofiltration Planters
4 Rainwater Irrigation Pump
5 Rain Barrel
6 Rainwater Fountain
7 Rain Garden + Bioswale
Underground cisterns are waterproof tanks that provide rainwater storage for reuse and distribution on site. Using cisterns for rainwater harvesting, making it possible to eliminate the reliance on potable water. In the plaza, all storm water collection systems convey water to three underground cisterns - 8,000, 10,000, and 15,000 gallon capacities, respectively. The stored water is then redistributed to either the irrigation system or the rainwater fountain feature at the center of the plaza.
Biofiltration planters capture runoff from impervious surfaces such as sidewalks, roads, compacted lawns, roof downspouts, etc. They allow the water to infiltrate through the amended soil into the native subgrade effectively recharging groundwater. The soil and plant material filter pollutants from the water, recharge groundwater system, and prevent polluted water from reaching natural waterways. Runoff flows into trench drains and is conveyed to the depressed biofiltration planters where it is retained and allowed to slowly infiltrate into the amended soil.
Rain Garden + Bioswale
A rain garden is a shallow planting bed that collects water runoff from impervious surfaces such as sidewalks, roads, compacted lawns, roof downspouts, etc. The water is filtered, retained for a short time, and released slowly through the amended soil into the native subgrade effectively recharging groundwater. A bioswale is a wide, shallow, landscaped channel with a slight gradient, designed to capture surface water during a rain event, with infiltration functions similar to a rain garden. The sloped surface in the courtyard conveys rainwater to the rain garden. The bioswale acts as the rain garden's overflow, conveying water to an area drain and ultimately to the underground cisterns for storage and reuse on site.