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
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.