Green first approach for wet weather programs

Abstract

Many United States and Canadian cities have recently started to initiate combined sewer overflow (CSO) and sanitary sewer overflow (SSO) control projects to comply with their regulatory mandates (permits and consent decrees). The capital costs of these projects are estimated to be in hundreds of millions of dollars. Both conventional gray and new green infrastructure solutions are generally required but some communities are more interested in a green first approach that requires realizing the full potential of green solutions before committing to gray solutions. This paper suggests that green infrastructure is not a panacea and green first does not mean green only. Comparing the life cycle costs and hydraulic performance of green and gray solutions is essential in the justification of a green first approach. A good green first approach should maximize the strengths and minimize the limitations of both the gray and green solutions. This paper compares green and gray infrastructure and discusses green vs gray cost and performance comparison approaches and tools. Real world examples are included and relevant software tools and models are summarized.