COMPARISON OF INTERIM MITIGATION MEASURES TO REDUCE VAPOR INTRUSION RESULTING FROM RELEASES OF TETRACHLOROETHENE AT DRY CLEANERS

Releases of tetrachloroethene (PCE) from dry cleaners can result in plumes of contaminated soil vapor that extend more than 200 feet laterally in all directions away from the source area. These plumes frequently underlie both commercial and residential buildings, and pose a risk because of vapor intrusion. Regulators are increasingly requiring interim mitigation be performed to reduce PCE concentrations in the short term while a permanent solution is developed. Typical interim mitigation measures include changes to the building’s air handling system, desktop or air handling carbon filtration, floor coatings, sub-slab depressurization, and soil vapor extraction. Interim mitigation activities from several dry cleaning sites will be presented in terms of effectiveness, regulatory acceptance, costs, and response of adjacent property owners/tenants. The most effective and cost effective interim strategy was found to be modifications to the air handling system to increase the flow of outside air. While simple, rapid, and effective, this strategy puts the financial and operational burden on third parties.