Dottorato in INGEGNERIA AMBIENTALE E IDRAULICA

Titolo della tesi: New methodology for estimating the hydraulic conductivity of soils through low flow purging operations in monitoring wells or piezometers

The remediation activities in a contaminated site are the more targeted (effective and cheaper at the same time) the higher is the spatial resolution of the hydrogeological parameters necessary for the characterization of the site. Hydraulic conductivity (K) plays a key role for estimating the contaminant time of travel (ToT), considering the mechanism of advective transport, i.e. the most conservative condition (worst case). This is especially true for alluvial aquifers, where a site-specific environmental health risk analysis (required by the reference legislation) could be difficult to reach in the absence of previous data. According to the procedures, widely accepted for groundwater sampling, during the purging of the wells related to a monitoring network, the chemical-physical parameters are usually checked, to determine the start of the sampling procedure after their stabilization. The approach presented in this PhD thesis proposes to use groundwater level data in monitoring wells, easily measurable during the low flow purging and sampling (LFPS) procedure, to determine the aquifer hydraulic conductivity. Since the purging and sampling are carried out using low flow pumps (with flowrates ranging between 0.1 and 1 L/min) to avoid the displacement of contaminants from one point to another, the stress imposed on the aquifer, as well as drawdown, is supposed to be limited. For a rather wide range of the parameter, mostly typical of alluvial aquifers, it is possible to use the collected data to estimate the horizontal hydraulic conductivity (KH) in the monitoring point. This procedure allows to obtain a greater spatial resolution of the parameter, with cascading potential positive effects on characterization, such as providing a detailed knowledge of the study area and a rich database for the subsequent modeling of the site, avoiding further investigations and reducing times and costs for stakeholders.