Changes in the regulatory landscape, coupled with budget-constrained environments, are driving local governments to search for new or evolving strategies and investments that deliver more value than conventional stormwater management practices.
In light of this challenge, green infrastructure (GI) is getting more attention as a stormwater management strategy. GI is described as a more holistic and multifunctional approach to stormwater management that can deliver benefits across the triple bottom line, mitigate water quality impacts, improve quality of life and enhance climate resiliency (US EPA, 2015). The list of direct and indirect benefits arising from GI is fairly consistent across sources, but the scale and value of these benefits are not. Careful examination of peer-reviewed published literature, combined with existing guidance documents and studies, provide options for quantifying and monetizing the wide array of GI benefits. The various sources are diverse. They employ different valuation and assessment methodologies. Existing resources do not provide a unifying framework or standardization. Consequently, the methods require multi-disciplinary technical knowledge (engineering, economic and bio-physical) that stormwater managers do not generally have.
This document is intended for smaller local governments with stormwater programs that are responsible for regulatory compliance with municipal separate storm sewer system (MS4) obligations (e.g., Phase 2 communities). It outlines an approach to holistically evaluate the benefits of implementing green infrastructure. The guidance places emphasis on first understanding the goal and scope for assessing benefits. It uses the goal and scope to step the user through: (1) differentiating between direct benefits and co-benefits of GI, and (2) understanding when and how these benefits need to be characterized, quantified or monetized. This document is not intended to be a “how to” measure benefits for conducting benefit-cost analysis, but rather an approach to tailor benefits and co-benefits identification and to inform decision making and stakeholder engagement. The report is organized into three sections with attachments.
The first section introduces the concept of green infrastructure and describes some of the most common GI practices. The second section discusses the range of benefits and co-benefits often attributed to GI. The third section outlines an approach to assessing the benefits. Finally, the attachments provide case studies that illustrate how this guidance can be used.