The Green Stormwater Infrastructure Decision Tree for Brownfield Sites is a planning tool developed for organizations (i.e., communities, utility organizations, transit agencies) seeking to implement a Green Stormwater Infrastructure (GSI) program on contaminated or potentially contaminated sites (brownfields). It is a tool for assessing risk and managing the unknowns associated with brownfield sites and is designed to be applied by entities that are implementing or intend to implement a larger scale program consisting of numerous sites.