In situ remediation of contaminated groundwater has received significant attention throughout the environmental industry. One of the challenges with in situ techniques is the delivery of the amendments to the areas that need remediation. In situ remediation techniques require a detailed understanding of the subsurface geology and hydrogeology to be effective. Several approaches have been applied to remediate groundwater contaminants in situ; however, most techniques reported in the literature have been small pilot-scale tests. Presented here is our experience applying an in situ remediation technique over 48 acres of a 70-acre closed mineral processing facility. The initial groundwater nitrate-as-nitrogen (nitrate-N) concentrations ranged from 10 milligrams per liter (mg/L) to 2,200 mg/L. Based on the approach described here, the nitrate concentrations have decreased an average of 41 percent across the site and have allowed for postremediation compliance monitoring beginning three years after treatment began. © 2005 Wiley Periodicals, Inc.