Laboratory Simulation of VOC Entry into Residence Basements from Soil Gas

Pollutants in groundwater can be a source of exposure to residents of houses overlying contaminated aquifers. Volatile compounds may migrate through soil gas and enter below-grade basements under negative pressure. A three-dimensional apparatus was built to simulate intrusion of volatile organics from groundwater into residence basements. Three reference soil materials were used to fill the model, each with different air permeabilities and organic matter contents. A simulated basement was equipped with holes in the floor, which were sealed in three configurations to represent different size cracks. Experiments were run on each soil, with each hole configuration, at several levels of depressurization. Soil permeability was found to be the overriding factor controlling advective TCE intrusion into basements. Soil porosity as well as particle size and shape distribution will dictate the diffusive migration of TCE through the soil profile and toward the building superstructure. Basement crack size does not appear to be a significant variable, and degree of depressurization is only significant in terms of dilution at higher rates of flow. The experiments also served to verify previous hypotheses proposed by mathematical models and field experiments.