Hooven

Trihydro Corporation, a prime contractor to a major integrated petroleum refining company with historic operations across the United States, has responsibility for the remediation of groundwater impacted by hydrocarbons at a site in Ohio. One of the key issues to be resolved as the groundwater remediation program moved forward was the potential for subsurface vapor intrusion into indoor air in a residential neighborhood adjacent to the site. Light, non-aqueous phase liquid (LNAPL) hydrocarbons from the former refinery operations were present at one time beneath a portion of the community. The U.S. EPA Region 5 required an assessment of the potential for vapor intrusion, and Trihydro wished to ensure that the sampling and analysis program would provide the best practicable data quality. Background concentrations of some gasoline constituents (such as benzene) can exceed risk-based target concentrations for inhalation exposures, so it was clear from the beginning of the project that a forensic analysis could be required to ascertain the source of certain vapors. Resolution of any off-site vapor intrusion issues is part of long-term strategy for redevelopment of the original refinery site for recreational, commercial, and/or manufacturing uses.