Green infrastructure practices serve as decentralized alternatives to traditional wet weather controls in urban areas where land is limited and sewer infrastructure is often stressed to capacity. Green infrastructure attempts to restore natural hydrologic processes and decreases the quantity of runoff, reduces peak flow rates, and improves water quality. In addition, green infrastructure can improve air quality, reduce urban heat island effects, create urban habitat, add aesthetic beauty to neighborhoods, increase property values, and improve public health. Because of these benefits and many others, numerous metropolitan areas are now pushing for investments in green infrastructure to supplement or replace traditional “gray” infrastructure.
Washington, D.C., sought to reduce its volume of wet weather runoff to ease the burden on existing sewer infrastructure, decrease the number and volume of CSOs, reduce streambank erosion in urban streams, and improve water quality. The District wanted to consider green infrastructure practices to help achieve these goals; but before making a significant investment, they needed to get an idea of the extent of their benefits and opportunities for implementation.
LimnoTech worked with the Casey Trees organization to develop the Green Build-out Model and later the Enhanced Green Build-out Model to calculate potential reductions in stormwater runoff and CSO discharges associated with the application of green infrastructure practices. Findings showed significant reductions in stormwater runoff volume (up to 26% annually) and CSO discharge volumes (up to 43% annually) across the City under the most intensive implementation scenario.
The research provides an innovative and powerful planning tool for stormwater management in the District. The original Green Build-Out Model study received a 2007 Honor Award in Research from the American Society of Landscape Architects. LimnoTech has used the analysis results to guide a three-year green infrastructure retrofit demonstration study being undertaken with a coalition of District government agencies and nonprofits. The goal of this effort is to provide further proof of the stormwater management benefits of green infrastructure and to investigate the logistics required to make large-scale green investments across the City.