This project's unassuming name belies a groundbreaking approach to water filtration, called Riverbank Filtration (RBF), which uses the natural properties of materials like gravel and sand to pull contaminants from drinking water. In theory, RBF is a cheaper, more sustainable alternative to chemical treatments, but it had never been applied to a project of this size in the United States, or to a system as complex as the one proposed by the Louisville Water Company, which serves some 700,000 customers. Water flowing from the Ohio river is filtered through the riverbank and gathered in various collector wells. It then seeps into a central tunnel, leading to a treatment plant. Aside from requiring fewer chemicals, engineers believe the water's stable temperature will mean fewer water main breaks. The final system yields 60 million gallons per day, and has real potential to become a model for RBF systems around the world.