Commonly employed techniques for the installation, purging, and sampling of monitoring wells are examined. The degree to which hollow‐stem augering disturbs the near‐borehole environment, and how this may result in the movement of contaminated solids or fluids from one stratum to another is discussed. The desirability of driving temporary casing to shield one stratum from another, and to improve the general quality of the monitoring well installation (especially the effectiveness of the filter pack emplaced), is argued. A call for further testing of sampling devices, based on limited field comparisons and a lack of reports of conclusive tests elsewhere, is given.

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Three case histories are presented to illustrate the problems encountered using some monitoring well installation, purging, and sampling techniques. Hollow‐stem auger‐ing was found to pose problems during the installation of monitoring wells in terms of potential for cross‐contamination of strata, the inability to emplace an adequate filter pack, the potential for smearing natural clays into sand and gravel strata, and the possible need for excessive purging of sediments that accumulate between sampling events. Cable tool drilling was found to allow construction of high quality wells, but was slow and expensive. Concern over the potential for increased emissions of noxious vapors from the borehole when drilling with the air rotary method prevented its use in situations where highly contaminated strata were likely to be encountered. A hybrid drilling technique, augering with temporary casing, was able to provide the advantages, and minimize the disadvantages, of the foregoing drilling methods. The installation of vertically separated clusters of monitoring wells lent important insights into the potential movement of a contaminant plume. Detailed aquifer tests provided needed information on the hydraulic behavior of the subsurface strata occupied by the plume so that potential pathways of contaminant transport could be more accurately identified. Obtaining reliable data from such tests depended greatly on the ability of each monitoring well to act as a high quality hydraulic observation well. The selection of drilling and installation techniques that ensured minimal disturbance of the near‐borehole environment provided the best guarantee of such performance.