The Application of Television Borehole Logging to Ground Water Monitoring Programs

Borehole television has been successfully utilized to gather in situ information on boreholes and wells in several ground water monitoring programs. Borehole television surveys are proposed as a viable alternative to other downhole instruments in the subsurface investigation stages of a ground water monitoring program. The borehole television camera used by the authors was originally developed for use in the examination of nuclear reactor cores; the camera has since been modified for use in borehole investigations. The lens attachments are capable of looking sideward or downward and include built‐in lighting assemblies. Use of the camera, lenses and various support equipment are discussed. The in situ characterization of fractures that can provide pathways for contaminant migration poses a significant challenge. Borehole television inspection can provide information on the frequency, size and orientation of these fractures. Vertical correlations of rock cores in areas where voids are present (i.e. deep mining or karst topography) can also be simplified by this technique. In addition, borehole television can also be used to check monitoring well integrity. Casing inspections are especially useful where construction details are not known. Well screens may be inspected in place to determine if rusting has enlarged the screen openings or if screens have been damaged during emplacement or well development operations (i.e. surge block, air jetting, etc.). This information may prove to be very valuable in the decision to decommission a well. Examples of these successful applications in ground water monitoring programs at several Superfund hazardous waste sites are presented.