A New Application For Geophysics: Monitoring At The Dig-Face During Waste Site Excavation

There are many hazardous waste sites throughout the United States that have been mandated by<br>law to undergo remediation. That process has been painfully slow and expensive, partially due<br>to the inadequacy of the waste characterization schemes that have been counted on to define the<br>extent and nature of site contamination. Conventional characterization efforts simply fall short<br>of providing the level of information on buried waste that is consistent with human safety during<br>clean-up operations. Preliminary design has been completed for a new technology, called Safe<br>Step Remediation, that addresses this problem. The key component of the Safe Step approach is<br>a Dig-face Monitoring System. The monitoring system produces waste characterization data in<br>small, careful increments. Each new characterization increment drives a new increment of<br>excavation.<br>Dig-face monitoring poses some new challenges for geophysicists. One challenge is to meet<br>performance requirements for quantitative, exact interpretations that go well beyond those that<br>apply to most conventional geophysics. In dig-face monitoring, interpretations directly and<br>continuously protect site workers by guiding the removal and handling of dangerous materials.<br>Several unique aspects of the dig-face monitoring application should enhance capabilities for<br>making these accurate interpretations. First, within the Safe Step Remediation approach, the<br>monitoring system will be able to make an extraordinary set of measurements. These<br>measurements will be made on multiple planes as the excavation progresses and will include<br>close-up measurements made in the immediate vicinity of hazards. Second, and even more<br>important, the physical retrieval of targets following each increment of characterization generates<br>a unique opportunity to validate interpretations continually. This provides a basis for steadily<br>improving the quality and accuracy of interpretations over time.