Green infrastructure life cycle assessment: A bio-infiltration case study

This paper presents life cycle assessment (LCA) as a methodology to evaluate environmental, economic, and social performance of green infrastructure stormwater control measures (SCMs). A case study examining a bio-infiltration rain garden at the Villanova University Campus is offered to demonstrate this methodology. The scope of this analysis is cradle to grave benefits and impacts of green infrastructure. Metrics used in this case study to evaluate benefits and impacts include carbon footprint (global warming potential), acidification potential, human health cancer impact, human health non-cancer impact, respiratory effects, eutrophication potential, ozone depletion potential, eco-toxicity, smog formation potential, labor impacts, and life cycle economic costs. Results of this bio-infiltration rain garden case study show that the construction phase is the main contributing life cycle phase for all adverse environmental impacts, as well as total life cycle cost and labor impacts. The majority of these construction phase environmental impacts are attributed to the use of silica sand as a soil amendment for the rain garden media and the use of bark mulch to provide ground cover, repress invasive vegetation, and establish target vegetation. The bio-infiltration rain garden operation phase was found to provide significant avoided environmental impacts relative to the construction phase impacts. These avoided impacts are attributed to urban forest benefits from rain garden vegetation, benefits due to stormwater runoff pollutant treatment by the practice, and benefits to combined sewer systems due to reduced stormwater volume through infiltration and evapo-transpiration. Consideration of multiple rain garden decommissioning phase scenarios makes a case to support the onsite reuse on rain garden media at the end of the practice life.