From the flux measurements we can deduce that the vertical spread of the pollution to the deeper layers (>10 m-bgl) is negligible. The shallow parts of the soil generally contain more oxygen to support BTEX biodegradation. In addition, the permeabilities measured in shallower layers are more suitable for possible addition of nutrients and oxygen or for recirculation of groundwater. The most suitable biodegradation conditions based on the flux measurements were found in plumes 1 and 2, mainly because mass fluxes were relatively lower there. In plume 29 the permeability is suitable, but the higher fluxes may be more toxic and inhibit biodegradation. If dilution and degradation rates are higher than the pollutant mass discharge, its load will decrease over time.

The results of the water flux measurements showed that groundwater moves 2x to 4x faster in the shallow layers between 5.4 and 6.2 m-bgl. The highest velocities were measured in plume 2 and 29. Between 10.1 and 11.6m-mv a slight increase in speed was observed. The lowest velocities were measured between 6.2 and 10/2 m-bgl and in the deepest measurements at 12.6 and 13.2m-bgl. The measured flow rates are show in the figure above per plume and as a function of depth.

The dominant pollutant flux was determined for xylenes (maximum 640 mg/m²/d), especially in the shallow wells of plume 29, but also in plume 1, despite the lower groundwater velocities measured. Except for one xylene flux of 66 mg/m²/d measured at 10 m-bgl, pollutant fluxes are decreasing rapidly with depth.The measured mass fluxes for xylenes are shown in the figure below per plume and relative to depth.