The possibility of the light non-aqueous phase liquids migration in the layered porous medium

The light non-aqueous phase liquids (LNAPLs) percolating into the soil and groundwater present a threat to the subsurface environment. When LNAPL is present on the groundwater table the initial step of remediation should be its recovery. Proper design and monitoring of LNAPL recovery require an estimation of the actual LNAPL thickness or LNAPL specific volume. These parameters are mostly calculated on the base of the apparent LNAPL thickness (LNAPL thickness measured in the monitoring well). This apparent thickness can be even several times greater than the actual LNAPL thickness in the porous medium surrounding monitoring well. This difference depends on the properties of soil and the properties and amount of LNAPL on the water table. The major aim of this study was to investigate if LNAPL present in the observation well can contaminate the high permeable soil lenses lying below the LNAPL layer on the groundwater table. Results show that the considerable amount of LNAPL penetrated the high permeable soil lens that was hydraulically connected to the well. Additionally, the free product percolation into the high permeable soil lens has influenced the value of apparent LNAPL thickness. Such a situation can complicate the estimation of the actual thickness or specific volume of LNAPL on the groundwater table.