A Remedial Investigation was conducted at the Great Falls Air National Guard Base during April, May, and July 1996. During the period four IRP sites were investigated (IRP Sites 1, 6, 7, and 8) . The investigation consisted of drilling 14 soil borings and installing 10 monitoring wells. At Sites 1 and 6, no contaminants in the soil or groundwater were found above State and Federal cleanup levels; and a Decision Document to support no further action is recommended. At Sites 7 and 8, no contaminants were found in the soil above State and Federal cleanup levels; and a Decision Document to support no further action with respect to soil contamination is recommended. At Sites 7 and 8, groundwater contamination above State and Federal cleanup levels was detected. The contamination included petroleum hydrocarbons, chlorinated solvents, and dissolved metals. It is recommended that an Engineering Evaluation/Cost Analysis be prepared to evaluate remedial alternatives for the groundwater at Sites 7 and 8.