RECOMMENDATIONS FOR LEVEL-DETERMINED SAMPLING IN WELLS

Level-determined samples of groundwater are increasingly important for hydrogeological studies. The techniques for collecting them range fro m the use of purpose drilled wells, sometimes with sophisticated dedic ated multi-level samplers in them, to a variety of methods used in ope n wells. Open, often existing, wells are frequently used on cost groun ds, but there are risks of obtaining poor and unrepresentative samples . Alternative approaches to level-determined sampling incorporate seve n concepts: depth sampling; packer systems; individual wells; dedicate d multi-level systems; separation pumping; baffle systems; multi-port sock samplers. These are outlined and evaluated in terms of the enviro nment to be sampled, and the features and performance of the methods. Recommendations are offered to match methods to sampling problems.