ABSTRACT
At the start of many investigations, subsurface mapping of aquifer thickness and configuration is often lacking. The subsurface is mapped from logs of wells and, in some places, with the aid of geophysical survey techniques. The logs collected from well drillers, well owners, public-agency files, and oil and gas exploration companies are useful. If possible, wells for which no logs are available should be logged by
geophysical equipment and correlated with known geology in the vicinity of the well.
