Economic Considerations of Borehole Geophysics for Hazardous Waste Projects

In environmental or hazardous waste investigations, simple homogenous subsurface geologic conditions have historically been assumed. In reality, heterogeneous conditions predominate. The costs of remediation and the consequences of incorrect remediation are increasing rapidly. These investigations often require the collection of extensive amounts of data to evaluate the problems sufficiently to recommend and execute appropriate remedial action.

Borehole geophysics can be used to obtain valuable data including information on geologic conditions and in-situ physical parameters in drill holes. The amount and benefit of this information is determined by the logging suite, borehole conditions, geologic parameters, interpreter experience, and application of current technology.

Typical costs for drilling and geophysical logging associated with different types of environmental investigations vary considerably. These costs are a function of the types and quantity of the desired data, whether the geophysical logging and analysis will be performed in-house or by an outside consultant, and the operational field environment.

Five case histories demonstrate the application of borehole geophysics to hazardous waste investigations and provide qualitative evidence as to its cost-effectiveness. The primary conclusions indicated by these case histories are that: (1) geophysical logs assist in well construction efforts; (2) borehole geophysical logs provide in-situ physical measurements not available from other methods; and (3) costs associated with borehole logging can be justified by consideration of the total cost of drilling, completion, and monitoring and the implications of inadequate understanding of the subsurface in a remediation program.