This document summarizes the in-situ remediation of hexavalent chromium, antimony, and nickel contamination at a site using sub-micron ferrous sulfide slurry. The remediation involved injecting nano-scale ferrous sulfide into soils and groundwater to chemically reduce the contaminants of concern to less soluble and mobile forms. Initial contaminant levels in soil and groundwater exceeded regulatory limits by several orders of magnitude. Post-treatment sampling over multiple quarters indicated that contaminant levels decreased significantly and met cleanup goals following the in-situ chemical reduction process. The remediation took approximately two years compared to estimated times of 15-20 years for other proposed methods, and cost nearly 50