Case study to derive a critical number of monitoring wells for plume characterization at different quality standards

摘要

The number of observation points required to accurately map a field-scale contaminant plume is rarely known. The aim of this study was to identify the quality of a field site investigation as a function of aquifer heterogeneity and the number of monitoring wells by using virtual contamination scenarios. About 50 observation wells are shown to be needed for a plume mapping at a typical contaminated site scale. Using less monitoring wells leads to a significant decrease in the investigation quality coupled with an increase in uncertainty. This order of magnitude can be used as a first approximate value or upper limit for plume mapping at real sites with similar conditions. Furthermore, the results support existing concepts that investigations near and downstream of the source area could be very useful to increase the quality of a field investigation program. Identifying a steady-state plume, which is one of the most important criteria for accepting monitored natural attenuation at contaminated sites, requires more than 50 observation wells to drop the error below 16 %, at least for the less heterogeneous aquifers.