Tracer injection and observation experiments are the best field methods available to characterize advection and dispersion in aquifers. Near Mobile, Alabama, single and two-well tracer experiments have been conducted in a confined sandy aquifer. Multilevel observation wells were designed, constructed, and operated in eleven different experiments.

Data have been selected from all the results which demonstrate observation well behavior. Isolation of sampling zones is shown to be necessary. Drilling mud remnants in or near the observation well are shown to invalidate measurements. In an experiment where an inflatable packer system suddenly failed, the loss of vertical integrity is shown in the electrical conductivity signals. Finally, mixing within sampling zones, sampling zone lengths, well installation, vertical integrity, and vertical integrity testing are discussed with an emphasis on desirable design characteristics.