As part of a DoD 2016 sampling event, PFOS and PFOA contamination was discovered in active supply wells; a soil/groundwater at a former fire training area (FTA); a small arms range, and an airfield sanitary landfill in shallow overburden aquifer, deep bedrock aquifer, and hydraulically-connected seeps across the 107,000-acre installation. Weston performed a PFAS expanded site investigation and a subsurface investigation to characterize on-base contamination and evaluate off-base sources to determine the potential risk to local drinking water supplies to Watertown, NY military and civilian communities. While conducting sampling and well installation, we performed value engineering screening in real time to achieve 3 major milestones, 22 minor milestones, and 114 schedule activities on time and budget. Weston installed and developed 14 bedrock and 8 overburden MWs; performed borehole logging; and collected24 soil samples ( 8 locations with 3 soil samples at each location), surface water samples at 12 river locations, and seep samples at 6 river locations. We reduced average sample collection times by at least 50% and reduced the potential for cross-contamination by using PFAS-approved HydraSleeves™. We managed all PFAS chemical analyses at an ELAP and NYSDOH NELAP-certified laboratory. Weston demonstrated that the base’s supply wells were not at risk despite PFAS exceedances at the FTA. Our final determination assured USACE that public health was not at risk, thereby eliminating future costs for remediation of the Army supply wells and Watertown surface water drinking supply to 45,000 people.