This document summarizes the in-situ remediation of hexavalent chromium, antimony, and nickel contamination at a site using nano-scale ferrous sulfide slurry. The contamination was from a former chrome plating facility and impacted both soil and groundwater. Ferrous sulfide was injected into soils and groundwater to chemically reduce the metals of concern by precipitating or complexing them. Initial concentrations exceeded regulatory limits but post-treatment sampling showed concentrations decreasing significantly below standards. The remedy cost $4.5 million and was estimated to take 2 years, compared to competitor proposals costing over $8 million and taking 15-20 years.