Investigating two-dimensional soil gas transport of trichloroethylene in vapor intrusion scenarios involving surface pavements using a pilot-scale tank.

In this study, we investigate the soil gas concentration attenuation with diffusive transport in lateral and vertical transport in cases with surface pavements with a pilot-scale tank. Three scenarios were investigated, one with a completely open soil surface and the other two involving partially paved soil surface. The results, on the one hand, indicate that the soil gas concentration generally decreases linearly and exponentially in the vertical and horizontal transport directions, respectively, generally in accordance with available modeling studies. On the other hand, our experiment shows that low-permeability ground covers can increase shallow soil gas concentrations beneath the pavement by at most 3-4 times, inducing higher subslab concentration than that below open ground surface, even if the latter is obtained at a closer location to vapor source. For cases with uniform soil properties, our study suggests exterior soil gas sample should be taken at a depth below the building foundation by half of the building footprint size, if the vapor source is laterally extensive relative to the building footprint, or by 1 m and 2-3 m for slab-on-grade and basement scenarios, respectively, if the vapor source is located laterally away from the building.