Green Infrastructure Approaches: A National Perspective

Many Municipal Separate Storm Sewer System (MS4) and combined sewer communities across the country are constructing green infrastructure practices in addition to gray infrastructure to improve water quality and to reduce combined sewer overflows. The projects are prioritized in Environmental Justice neighborhoods and areas of urban flooding where the additional co-benefits from green infrastructure (aesthetics, community engagement, the reduction of heat island effects, as well as stormwater treatment and volume reduction) will improve the neighborhoods and create more resilient, equitable communities. Some communities are taking an area-wide approach, constructing multiple green infrastructure practices throughout tributary areas, in the right-of-ways and on public properties, such as parks, schools and housing developments. These types of green infrastructure projects control stormwater runoff closer to the source. Other communities with more available space for larger green infrastructure facilities are separating combined sewer systems and conveying stormwater to green infrastructure detention/retention basins at the downstream ends of the systems (Figures 1 and 2). Approaches to green infrastructure development also vary by climate. Arid areas of the southwestern United States prioritize stormwater harvesting more highly than water-rich communities in the northeast, and vegetated practices require different local native plant palettes. This presentation will review case studies of these and other approaches to fitting green infrastructure into urbanized settings across the country, including construction challenges, project costs and lessons learned. The case studies include green infrastructure programs for the Cities of Los Angeles, San Francisco, Denver, Tucson, Cleveland, Columbus, Detroit, New Orleans, Kansas City, New York City, Philadelphia, Hartford, Boston, New Bedford, Lowell and Toronto. These case studies are based on CDM Smith green infrastructure planning, design and construction projects over the past 15 years, as well as 2023 interviews with six 'best-in-class' green infrastructure program leaders (Table 1), conducted on behalf of the City of Denver Division of Green Infrastructure (DGI). To learn from the experiences of other established green infrastructure programs as DGI grows, DGI and CDM Smith conducted best-in-class interviews with Los Angeles, Philadelphia, Tucson, Detroit, San Francisco and Toronto to review their perspectives on what worked best in their programs, and how DGI can continue to improve their program moving forward. Common questions about green infrastructure programs are who will maintain it and how will we pay for it? The presentation will include a summary of various ways green infrastructure programs across the country are addressing maintenance, as well as life cycle costs by green infrastructure practice per acre treated.