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Approximately 150 Rn‐222 analyses from groundwater wells in fractured lithologies of eastern Connecticut were made to evaluate the intralithologic and interlithologic variability. Although there is a control of Rn‐222 activity in porefluids by uranium (radium) concentration in the host rock, the variability of local Rn‐222 is dominated by site‐specific rock properties. These are (with their contribution to the variability); (i) the specific fracture surface area (>103x), which is functionally dependent on crack width, (ii) the emission efficiency (>102x) which is functionally related to the fracture spacing and (iii) the enrichment of uranium (Ra‐226) on the fracture surface (>102x). Thus, the activity of radon in fractured lithologies is difficult to predict and the measurement of radon activity does not uniquely constrain the geometry of the rock or the chemical inhomogeneity.

Borehole geophysics and horizontal loop electromagnetic profiling (Max-Min) were integrated with regional and site-scale geological and geochemical data to investigate the occurrence of, and possible pathways for, saltwater intrusion near fracture zones on a small island in British Columbia, Canada. An island-wide geochemical study identified a number of coastal wells that are contaminated by seawater; however, the occurrence of high salinity groundwater is spatially irregular due to variable fracturing of the bedrock. To investigate the influence of fracturing on the presence of high salinity groundwaters, geophysical investigations were undertaken at several sites. The nature of the bedrock permeability at these sites, with respect to lithology and fracture zone proximity, is described from geologic and hydrogeologic investigations and supported using surface EM profiling. Fractures and bedding contacts within boreholes, which were suspected to dominate bedrock permeability on the basis of outcrop studies, were identified using borehole video camera in conjunction with normal resistivity, spontaneous potential and natural gamma logs. Flow meter logs, acquired under a variety of aquifer stress conditions including static, tidal and pumping are used to identify potential water transmitting fractures and the locations of entry points for fresh and saline groundwater. The low flow rates measured under the various stress conditions confirm that groundwater flow is minimal and is restricted to mudstone units and single, generally sub-vertical fractures. The low natural groundwater discharge rates near the coast, even at close distances to fracture zones, may be key to the occurrence of saltwater intrusion on many parts of the island.