Numerical simulation of field methods for estimating hydraulic conductivity and concentration profiles

Abstract

The estimation of hydraulic conductivity and concentration profiles is important for groundwater quality studies and for planning remediation action. A simple and economical way is to use existing wells, provided that appropriate sampling techniques are available. The reliability of some new techniques (Separation Pumping (SEP), Packer-Baffle Systems (PBS), Multi-Port Sock Sampler (MLPS or BMS)) is studied in this paper by using numerical models to simulate flow and mass transport to the sampling device. The results of testing the methods in different hydrogeological environments as well as in the laboratory were analysed in order to understand —from a hydraulic point of view—the reasons, why these techniques succeed or fail to give reliable results. Important factors influencing the flow and transport in the system are identified and discussed. The investigation showed that SEP which can be used to estimate hydraulic conductivity as well as concentration profiles, gives reliable results. In order to obtain reliable results by means of PBS the hydraulic conductivity must be known and the sampling rate must be adjusted to it. However, experience showed that further problems can arise in the field. Multi-Port Sock Samplers give reliable results if the concentration profile around the borehole is not disturbed owing to vertical flow in the gravel pack or owing to the installation of the device.