This article provides a case study done by the EPA to showcase the potential impacts on groundwater from the use of green infrastructure. The design of green infrastructure actually increased the risk of flooding and erosion when large volumes of stormwater overwhelmed the treatment plants. Water quality index analysis indicated that groundwater quality at the sites of interest were unsuitable for human consumption, and the concentrations of organic compounds were not a regulatory concern. The data collected from these case studies can be used by state and local agencies to understand at what conditions groundwater quality by or may not be adversely impacted by green infrastructure. Observed geochemical processes, movement of water within the system, and potential for changed to groundwater chemistry provide new information for communities and city planners to consider and use in their GI planning, and potentially their water treatment processes.