After the first iteration a stable Nickel plume was confirmed. Most measured values were less than 0,5 mg/m²/day, which was a factor of 30 lower than the water flux expressed in cm/d at corresponding depths. Because of this, further active remediation of residual Nickel contamination was no longer deemed necessary by the supervising authority. A risk- based management approach was approved for coming years, which could probably avoid an extensive and expensive remediation process.

Subsequently, in the second and third iteration, only CVOC’s were measured. Before the flux measurements, unexpected results were found in the concentration measurements (in P43). The stratification of the pollution was different than expected.

By adding flux measurements, it was possible to interpret these results with more certainty and to adapt the contaminant transport model accordingly. The groundwater flow model has been calibrated according to these results.

• Relevant CVOC's mass present and migrating down gradient. Nickel mass is stable.
• Preferential pathways related to heterogeneous soil permeability found.
• Focused mitigation measures possible. Remedial monitoring and design needs to be differentiated for stable Nickel and migrating CVOC's