Minerals Exploration Methods Modified for Environmental Targets

Abstract

In recent years, several traditional mining exploration methods have been successfully modified for use in the environmental geophysics field. In these cases, ``successfully modified' refers primarily to acquiring data fast enough, and therefore economically efficient enough, to accommodate the relatively small budgets that are available in most environmental studies. For example, transient electromagnetics (TEM) methods have been increasingly applied to environmental problems, particularly in unexploded ordnance (UXO), underground storage tank (UST) and utilities detection. Small, in-loop, cart-mounted TEM measurements are excellent for these deep metal detection applications. A major research effort is now underway to use, among other methods, multi-component, multi-time-gate mobile TEM systems (measuring Hx and Hy, as well as the standard Hz) in order to discriminate targets of interest (UXO, for example) from non-UXO objects such as metallic debris. A second good example is the induced polarization (IP) method. Although resistivity has been used extensively in shallow environmental applications, IP data acquisition has always been too slow, and therefore too expensive, for most environmental targets. Multichannel receivers, multiplexers, and laptop computers now allow us to acquire IP data at rates of 2500 to 3000 data points per day (in the dipole-dipole configuration, for example), providing low cost, high density data. IP data have been shown to be particularly useful in delineating buried waste, such as at old landfills. In numerous surveys, resistivity data have provided useful information on buried, back-filled pits and trenches, while IP data have been used to discriminate which of the pits and trenches located with resistivity actually contain waste material.