(San Diego, California) The Department of Defense manages hundreds of buildings that reside over volatile contaminant groundwater plumes. At one very large (172,000 sq. ft.) facility located in San Diego, the client was struggling with understanding why after spending years of investigation and mitigation, they still had a TCE vapor intrusion issue. VaporSafe® was deployed for a one-week monitoring campaign. Every day dramatic increases in concentrations were observed in the late morning. It was determined that this indoor concentration increase coincided with a drop in barometric pressure and resulting increase in pressure differential between the subsurface and indoors.
Lesson: Upward vapor flow can be caused by drop in barometric pressure and increase in pressure differential. This has significant implications with respect to conventional monitoring methods. For more information, see Hosangadi et al., 2017