Very Low Frequency (Vlf) Geophysics: A Case Study On Locating Bedrock Wells In Water Bearing Fracture Zones For Use In Contaminant Migration Interception

A Very Low Frequency (VLF) geophysical investigation was performed during June 1995 at an industrial facility in Waltham, MA. The VLF survey was used to locate ground water monitoring wells in water bearing bedrock fracture zones at the site to determine contaminate migration pathways and improve ongoing remediation of the ground water. The bedrock at the site consisted of Granodiorite and Gabbro-diorite and brittle fracture analysis indicated bedrock was permeable and highly fractured. Historical releases of chemicals have reportedly occurred at the site.<br>Previous investigations indicated contaminated ground water exists in the bedrock at the site. The objective of using VLF geophysics was to increase the likelihood that water bearing fractures in the bedrock were intercepted during drilling, and that the most conductive zones were intercepted. The VLF geophysical survey consisted of six days of field work by<br>two geophysicists, covering 5,290 meters of geophysical survey line, and nine days of data interpretation, to select the proper drill targets. Three separate VLF stations were used to collect<br>the data. The data was collected and interpreted using the ABEM WADIcTM' instrument and SECTOR software.