Field determination of the hydrologic properties and parameters that control the vertical component of groundwater movement

The vertical movement of groundwater through geologic formations generally constitutes the shortest pathway for transport of contaminated fluid from polluted aquifers to the accessible environment. If such movement is encouraged by unfavorable conditions such as an upward hydraulic gradient or relatively permeable zones, it could jeopardize the safety of an underground nuclear waste repository. In this report, a description has been attempted of some of the conventional techniques for measurement of the properties and parameters which control the vertical movement and travel time of groundwater. The most important properties and parameters which control the vertical movement and travel time of groundwater are the effective porosity, hydraulic conductivity, and storativity of the geologic media, and the distribution of hydraulic head within the formations around the repository. Given a candidate repository site, a thorough knowledge of the magnitude and variation of these parameters within the adjacent geologic formations is essential in evaluating the safety of the site. Determination of these parameters in aquifers has been a routine task for hydrologists for several decades. In tight formations or scarcely fractured media which have little or no significance from a water supply point of view, conventional methods are not reliable. During recent years when the need for further information has increased, some new techniques have been developed. However, these methods are far from complete and in some cases there is much room for improvement