PUBLICATIONS--Report, "Borehole geophysics applied to ground-water investigations," In Reply Refer To: January 26, 1989 WGS--Mail Stop 411 OFFICE OF GROUND WATER TECHNICAL MEMORANDUM NO. 89.01 SUBJECT: PUBLICATIONS--Report, "Borehole geophysics applied to ground-water investigations," by W. Scott Keys The attached subject report, recently released as Open-File Report 87-539, pending publication in the Techniques of Water-Resources Investigations (TWRI) series, provides comprehensive information on geophysical logging techniques that are widely used in ground- water hydrology or that have significant potential for application. The report is an update of the TWRI (released in 1971) by Keys and MacCary entitled "Application of borehole geophysics to water-resources investigations." This recent report emphasizes those techniques that have changed most since 1971, and includes dicsussion on some newer logging techniques, such as the acoustic televiewer, that have become widely used since 1971. The report provides guidelines useful for selecting the logging techniques most appropriate to obtain the information needed for the rocks and fluids penetrated and indicates the required borehole conditions and potential limitations of each technique. The logging techniques discussed include: spontaneous potential, resistance, resistivity, gamma, gamma spectrometry, gamma-gamma, neutron, acoustic velocity, acoustic televiewer, caliper, fluid temperature, conductivity, and flow. For each logging technique, the following topics are discussed: principles and instrumentation, calibration and standardization, volume of investigation, extraneous effects, and interpretation and applications. Multiple-choice tests are supplied at the end of some sections on related types of logging techniques to help the reader determine whether significant points are understood answers to those tests are given at the end of the report. We recommend that this report be distributed to technical and management personnel concerned with ground-water studies. Eugene E. Patten Chief, Office of Ground Water Attachment Distribution: A, B (w/o attachment) S, FO, PO