MODELING VOC MIGRATION FROM A LIQUID WASTE DISPOSAL SITE, LOS ALAMOS NATIONAL LABORATORY

A numerical model of VOC transport is presented that includes complex physical processes and site specific boundary and initial conditions. Henry's Law fractionation, vapor phase diffusion as a function of water content, and surface boundary layer effects are simulated. Topography, geology, and anthropogenic factors (i.e. asphalt) are included. The model results are compared to an extensive data set from the site that includes over 100 quarterly vapor sampling ports. Correlation between model and data is quite good (r2=0.973) showing that the conceptual model of transport is adequate to explain the behavior of the subsurface VOC plume. The modeling indicates that the plume has reached a near-steady state with respect to the atmospheric boundary and should not grow significantly through time. This result has implications for the style of remediation that will be implemented at the site, allowing less drastic measures (i.e. source removal) to be taken. Natural attenuation with the addition of passive vapor venting is likely to be the most viable alternative for site remediation.