A Detailed Look at Costs Associated with Green Stormwater Controls

In the last half decade, the use of green infrastructure (GI) for stormwater management has grown tremendously – often in conjunction with motivating factors such as property owners seeking LEED® certification for new and renovated buildings, compliance with regulatory actions such as consent decrees, or an increased awareness of the need for water conservation. Regardless of motivation, valuable information about GI is being generated at a rapid pace and documented in a growing list of databases. However, one key element is often missing—a detailed look at control-specific costs. Current stormwater best management practice databases frequently lack detailed costs for individual green stormwater controls. Why is so little reported on green infrastructure costs? What factors are driving the cost of green infrastructure? Is there truth to the public perception that “green” is too expensive and study authors are thus hesitant to publish this information?This study is unique in that the cost information is derived from a large program designed to explore the feasibility, including cost, of the use of green infrastructure for combined sewer overflow volume control. The study encompasses a wide range of green stormwater management practices in a variety of settings and at various scales. As all projects were part of the same program, the information was obtained in a consistent manner and is directly comparable. This reduces the uncertainty in the study's results and conclusions.The focus of the study is to gain an understanding of costs to construct a broad range of green stormwater controls in multiple settings. Focal points include the unit costs for the individual types of GI controls, the differences between estimated and actual costs, identification of trends and driving factors for costs, and a preliminary look at the cost benefit associated with the projects as they compare to traditional “gray” projects.