In this study, a Life Cycle Assessment (LCA) was conducted on a project to clean up a heavy metals-contaminated site located in central Italy (Tuscany) in order to define the less impactful solution. The study evaluated the contamination in the soil, derived from the leaching of backfill materials composed of quarry aggregates and sintered granules referred to as “Keu”, a waste derived from the pyrolization of sewage sludge from the Tuscan tannery district, rich in chromium. Three action scenarios were compared, namely the no-action scenario, an excavation and landfill disposal scenario, and a permanent material capping and sealing scenario. The LCA results show the lowest impact for soil capping operations due to the high impacts of heavy metal emissions and landfilling of materials for the first and third scenarios. The third scenario has the lowest impact for ten of the eleven categories analyzed by the CML-IA baseline method. The only exception is the ozone layer depletion category due to the binder synthesis process used for the pavement to protect the membrane. Future studies could be devoted to the study of Keu, through extensive characterization, as well as a study of the fate of this material in landfills to define an appropriate process for future LCA analysis.