Comprehensive VI Assessment as Part of RCRA Corrective Action
Many liquids are composed of carbon-based volatile organic compounds (VOCs). Because they readily evaporate, VOCs in soil and groundwater can enter a building through openings in the floor and contaminate indoor air in a process known as “vapor intrusion” (VI). Since the release of EPA’s draft Vapor Intrusion Guidance in 2002, VI has been one of the primary environmental concerns at many older industrial facilities.
As part of the RCRA Corrective Action program, Cox-Colvin conducted a multi-year investigation of the VI pathway at a RCRA permitted primary metals manufacturing facility in northwest Ohio. PCE and TCE in groundwater, soil, and utility backfill beneath the operating area of the facility resulted in numerous sources of vapors beneath or adjacent to multiple buildings, all of which required evaluation. Using groundwater data and site-specific geotechnical and hydrogeologic data, the groundwater to indoor air pathway was determined to be incomplete, eliminating many of the buildings. Deep soil gas sampling adjacent to VOC sources in soil and sediment and within utility backfill eliminated additional buildings from further consideration. Subslab sampling conducted in conjunction with indoor air sampling and modeling at the two remaining areas then showed the VI pathway to be acceptable. Johnson-Ettinger modeling relied heavily on the turnover rate for air within the buildings due to large scale air handling equipment.
The comprehensive VI demonstration and report was approved by Ohio EPA with no revisions required. Cox-Colvin then developed an annual inspection program to identify changes in building use, from air exchange rates to floor penetrations, to be implemented by the facility.