Scaling DNAPL Migration From the Laboratory to the Field

When dense nonaqueous phase liquids (DNAPLs) are released into the subsurface, an important problem is identifying where the DNAPL is and if it is still moving. This question is perhaps most important at sites where thousands of cubic meters of DNAPL were released over decades. While large DNAPL releases are outnumbered by smaller DNAPL spills, the most significant risk to the environment and human health may be associated with large DNAPL spill sites. To our knowledge no laboratory studies have examined DNAPL migration over the length and time scales associated with large DNAPL releases. In this investigation a laboratory tank experiment was conducted to examine DNAPL migration over these scales. Modified inspectional analysis was used to develop relationships for scaling observations from the laboratory model to four hypothetical spill scenarios in the field, all of which had large DNAPL releases. One scenario was compared to an actual DNAPL spill site. The length and time scales of DNAPL movement predicted from our analysis were consistent with those predicted from a numerical model of this site. The methodology developed in this work may prove useful for scaling results from other laboratory investigations of DNAPL migration to field-scale systems. Our results also challenge the common conceptual model of a stationary DNAPL source with only a migrating aqueous phase plume when large DNAPL volumes are released.