Daniel Walsh, senior technical advisor at LaBella Associates, is a geochemist with over 30 years of experience regulating environmental protection in cities. He founded and operated the NYC Clean Soil Bank, the first urban soil bank in the U.S. He is also an adjunct senior research scientist at the Lamont Doherty Earth Observatory and The Climate School at Columbia University. Cities need clean soil and other fill materials for earthworks projects, ranging from large-scale flood protection in waterfront areas to urban green infrastructure and community gardens, but the high cost of clean fill, limited supplies and uncertain chemical quality can obstruct this important work. Studies show that excavation during urban construction produces large quantities of clean soil that is a valuable but often overlooked natural resource in cities. With basic planning to promote a circular soil economy, this soil can be retained within the city and used as a low-cost fill to supply urban earthworks. In urban areas, soil is excavated to make room for underground parking and basements and often disposed of at commercial facilities located outside the city at a high cost. At the same time, public and private construction projects within the city are purchasing clean fill to reshape or elevate urban land — also at high cost and often from the same commercial vendors that take exported soil. Without local policy in place, this regional commercial marketplace maximizes construction costs, truck transportation, fossil fuel consumption, greenhouse gas and other pollutant emissions, and traffic congestion. Soil banking is an innovative way to retain and reuse surplus soil within cities to create a low-cost supply of fill material that can lower construction costs, assure chemical quality and improve availability. Soil banking can also direct soil reuse to government earthworks projects, at low- or no-cost to the city, to