Scientific literature review to inform recommendations on best practices for implementing green infrastructure stormwater practices.
(February 2015) Academic report by the University of California Berkeley Law Center. Well-implemented green stormwater infrastructure (GSI) keeps stormwater local. It works by infiltrating or evaporating precipitation where it falls or capturing it for later use. The goal is to minimize the quantity and maximize the quality of urban runoff that flows to local waters. The EPA and state water quality authorities are already beginning to require GSI for Clean Water Act compliance in some stormwater permits and combined sewer overflow (CSO) consent decrees.
Information limitations impede decision making by perpetuating uncertainty about GSI performance and the life-cycle costs of GSI. Accurate information about both is essential for those contemplating implementing GSI in their communities.
Actual performance data for GSI are still very limited. Available data come from relatively few GSI installations that cover a limited range of site conditions and geographic areas. Again bioretention data are illustrative. Although bioretention systems are one of the most common forms of GSI currently being implemented, bioretention monitoring results reported in peer-reviewed literature and the ISBMPD come from just 40 field sites in the United States; about 78% of these sites are on
the east coast, and more than one third are in North Carolina.
Over the coming decades, GSI will be increasingly important for stormwater management. However, developing best practices for using GSI—and demonstrating its role in regulatory compliance—will require more thorough understanding of performance maintenance needs, and costs. Uncertainty about the life-cycle costs or the effectiveness of green- and gray-infrastructure options makes it hard to accurately compare them.