The U.S. Botanic Garden – Sustainability Through Stormwater Capture and Reuse
Abstract:Purpose: The United State Botanic Garden (USBG) is located at the base of Capitol Hill and includes the Conservatory and surrounding landscapes; the National Garden and Bartholdi Park. Its mission is demonstrating aesthetic, cultural, economic, therapeutic and ecological importance of plants to the well being of mankind. The USBG has 750,000 visitors per year and is a highly visible component of the National Mall. The USBG and the U.S. Environmental Protection Agency (EPA) Office of Wetlands, Oceans and Watersheds (OWOW) propose to promote the innovative use of sustainable site design practices and the use of soils and vegetation to more effectively and sustainably manage stormwater. By using green infrastructure practices, the USBG and EPA intend to demonstrate that green infrastructure stormwater systems can be beautiful, functional and cost effective to design and manage. This proposed project includes practices such as green roofs, cisterns, permeable pavements and bioretention and infiltration facilities. Reductions in runoff volumes would also help to decrease combined sewer discharges into the Potomac River.
Benefits of Project: (USBG) currently uses and pays for 11.8 million gallons per year of public water for consumptive use, irrigation and water fountains. Based on an analysis of the site, there is the potential to capture up to 7.6 million gallons of rainfall which could be used for irrigation purposes instead of potable water. Under this scenario, the USBG would save approximately 65,000 per year. The majority of rain that falls onto the USBG property runs off the property, into the streets and into the combined sewer overflow (CSO) system. The Washington Area Sewer Authority (WASA) and the DC government charges a stormwater fee for the amount of impervious area which discharges into the CSO for which the USBG is billed monthly. The USBG would like to do their part in reducing pollutant contributions to the Potomac and at the same time, re-use stormwater to minimize the dependence on public water and reduce their water bill. “Greening” their infrastructure would also reduce the impervious area stormwater fee. To accomplish this, opportunities to collect, capture, store, retain, harvest and use and/or infiltrate r rainwater through a series of best management practices (BMPs), concentrating on the most cost-effective alternatives was investigated.
The various measures identified, with specific locations on the site included: rainwater harvest and use technologies, vegetative roofs, soil amendments, porous surfaces (i.e. pavers, blocks, grids, and concrete), roadside bioretention, bioretention /rain gardens, infiltration facilities, rain barrels, cisterns and even a storage tank disguised as a saguaro cactus.
A series of charettes were developed and conducted with a number of interested parties including the Architect of the Capitol, USBG, and US EPA to explain the ideas, pollutant reduction benefits, and long term cost savings.
The Botanic Garden site has high visibility on the National Mall with approximately 750,000 visitors per year and lends itself to an excellent demonstration/education/outreach site. It can serve as a link to its companion project at EPA headquarters, which captures rainwater in rain gardens and in cisterns for water use. A concept report outlining measures and steps (with examples) to eliminate runoff and maximize rainwater use was developed with the objective that it can be utilized as a model for similar public facilities. Educational signs were recommended for the purpose and benefit of each BMP.
Status of Completion: The charettes have concluded and the model report is complete and available. A bioretention area, which had been designed by others previous to this study, has been installed. The installation of the other proposed measures are awaiting funding.
Conclusion: The USBG site could display a combination and wide variety of BMP applications and treatment train concepts to significantly reduce and perhaps eliminate stormwater runoff to improve the quality of stormwater runoff and improve the long-term sustainability of the site. Using a life-cycle approach, the USBG could also demonstrate long-term cost savings. This project also would serve to model an integrated design approach which could include as aspects, rainwater capture and use, reduction in public water usage, cost savings, and public outreach and education.
Document Type: Research Article
Publication date: 2012-01-01
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