Vapor Intrusion Pathway Screening & Remediation
After a VI investigation has been completed and contaminants have been found above applicable regulatory limits, the responsible party is now faced with remediating the vapor intrusion issue. Remediation of vapor intrusion issues take a considerable amount of evaluation of the source and migration routes of vapors, i.e., how the vapors are entering the building environment. Typically a VI investigation is triggered due to a known contaminant below ground that has the potential for vapors to migrate into a building interior. While this is typically the trigger for the investigation, it is not always the source which is why building inspections are necessary. Since volatile organic compounds are one of the most common indoor vapor issues, a typical evaluation includes an inventory of stored chemical compounds inside the building to determine if these chemical maybe contributory in nature. While this may seem to be a very common sense approach to vapor intrusion, Curren Environmental has been brought into projects to remediate vapor intrusion issues only to find stored chemical (inks, paint, gasoline containers, freshly painted rooms, newly installed tile and carpet) that have found to be contributing sources and in some causes, causes of the indoor vapor contamination.
Once all indoor stored chemicals and operations, have been eliminated as potential sources of VI issues, the next step is the evaluation of exterior contaminants. Both known and unknown plumes of contaminations can be sources of the vapor. It cannot be stressed enough that the subsurface source areas must be evaluated so that a remediation approach can be designed appropriately. Some forms of Vapor Intrusion design planning can include the following:
Ground Penetrating Radar Surveys of the property to locate UST’s former piping that can be conduits of vapor pathways into a building.
Historical research including sanborn maps, aerials photographs and building as built design drawings.
Database lists of neighboring business past and present those maybe unidentified source areas.
Soil and groundwater borings and laboratory analysis to find hot zones. Once source areas are identified, a specific vapor mitigation plan can be designed to address the vapor issues. Vapor barriers, interceptor piping & trenches, vapor sumps and below grade extraction piping are all approaches that can be utilized to address vapor issues. Systems can be both passive and active (extraction blowers) based on site conditions.