Years of direct disposal of solvent wastes into a septic system at the American Eagle Airlines facility at Dutchess County Airport in Wappinger, NY resulted in a plume of chlorinated solvents dissolved in the groundwater. The plume progressed from the septic system to the right of the building to the pond seen at the top left. Chlorinated solvent vapors from the plume were migrating and collecting in the office areas on each side of the hangar. CEMCO personnel were retained to assess vapor conditions and migration and prepare a remedial plan. A soil gas survey was conducted around the site to assess the dominant paths of vapor migration and based on the results three main routes of vapor entry were discovered.

The first pathway was along the septic system soil pipes. Vapors were preferentially migrating through the coarse pipe backfill and entering the building sub-slab area. This was addressed by excavating a small portion of the pipe trench and constructing a vapor barrier with geotextile and concrete.

The second pathway was via vertical migration from the dissolved groundwater plume beneath the building. Two Vapor Mitigation systems were installed in the office areas along the sides of the hangar. Each of the systems comprised three concrete floor penetrations evacuated by a PVC pipe system. The pipes were routed outside the building and connected to a single fan via a manifold. Exhaust after the fan was discharged above the roofline. Air testing for volatile organics confirmed the negative pressure exerted below the floor slab eliminated the vapor infiltration. The system was kept on line throughout the period of soil and groundwater remediation at the site. After several years of operation the levels of solvents in the office areas reduced to non-detectable levels and the systems were removed.