LNAPL in fine-grained soils: Conceptualization of saturation, distribution, recovery, and their modeling

Authors

  • Mark Adamski,

  • Victor Kremesec,

  • Ravi Kolhatkar,

  • Chris Pearson,

  • Beth Rowan


Abstract

A simple conceptual model is presented that leads to a quantitative description of the behavior of light non–aqueous phase liquid (LNAPL) in fine-grained soil (FGS). The occurrence of large (15 feet) (4.6 m) LNAPL accumulations in observation wells in FGS and of LNAPL located below the water table is explained by macropore theory and capillarity of the FGS. Using soil capillary data, fluid property data, and a simple spreadsheet model, the LNAPL saturation in a soil profile and LNAPL recovery were predicted for a field study site. The predicted LNAPL distribution, saturation, and recovery matched the field observations and actual LNAPL recovery. Measured LNAPL saturations were <2%, while model-predicted values were <3%. The model predicted recovery of ∼530 gallons (2009 L). After 1.5 years of continuous operation, a three-phase, high-vacuum extraction system recovered 150 gallons (568 L) of LNAPL. Application of a model that assumes homogeneity of the soil that is heterogeneous at a small scale may seem to be a misapplication; however, conceptualizing the model domain at a sufficiently large scale (3 to 6 feet; 0.9 to 1.8 m) allows for the FGS to be viewed as a homogeneous medium with small effective porosity.

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