Rapid Identification of VOC Source Areas Beneath Large Buildings

At many industrial facilities which operated prior to the early 1980s, it is not uncommon to find volatile organic compounds (VOCs) in groundwater downgradient of large buildings.  Final remediation of groundwater requires locating and assessing the source or sources of the contamination beneath these building.  Many of the sources of VOC contamination in this setting are due to releases which occurred more than 35 years ago.  Standard personnel interview and site records review methods are of little value in this situation, and, in more cases than not, result in the investigation of the wrong areas.  The recent focus on the vapor intrusion pathway in both cleanup and due diligence work has lead to significant advances in the ability to rapidly, thoroughly, and accurately locate and assess VOC sources beneath buildings.  Through these advances, it is now possible to rapidly, and inexpensively collect large amounts of sub-slab vapor data within large buildings in several days.  Plotting and contouring this data on georeferenced aerial photography and historical maps allows the investigator to accurately locate and  assess VOC sources, including individual constituents, magnitude of the source, release mechanism, and in some cases the age of the release.  Using multiple case studies, this session will focus on the use of streamlined sub-slab vapor sampling methods and the interpretation of the data to identify and assess sources of VOCs  beneath large, old, industrial buildings and will examine the reasons why standard methods for identifying sources typically fail.