Abstract

An important aspect of any detailed groundwater quality study is determining the vertical distribution of pollutants. This may be achieved by multi-level sampling from purpose designed boreholes. This study describes a relatively inexpensive system of dedicated sampling where gas-driven water samplers (incorporating vibrating wire piezometers) and unsaturated zone gas samplers are installed in conventional plastic water well casing. One important advantage of this system is that all functional units are housed within a protective screen, which offers both protection and improved potential for satisfactory backfilling. Experiments to determine the performance of gas-driven samplers when collecting water contaminated with chlorinated hydrocarbon solvents indicated that quantitatively accurate results are obtained using short lengths of nylon tubing. However, long lengths of nylon tubing introduced significant negative bias in solvent concentrations and it is recommended that a material with lower absorption properties be chosen to collect deep samples. The system was successfully installed on a contaminated industrial site. Significant variations in solvent pollution profiles together with a substantial vertical hydraulic gradient were defined and such hydrochemical and hydraulic information may be simply collected on a routine basis. Such data could not easily be gained from open boreholes, indicating the potential of the dedicated system in groundwater quality investigations.

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