Observed deep movement of 137 Cs implies similar movement of other contaminants normally considered to be readily adsorbed. Preferential flow is common in vadose zone environments, but vadose zone characterization at Hanford has not adequately defined preferential pathways for use in predictive modeling. Development of more representative simulation models requires better characterization of the vadose zone. Vadose zone characterization is needed to help estimate the distribution of contaminants in groundwater. Contaminant transport in the vadose zone at Hanford is poorly understood.
Percussion drilling is a relatively low cost method of obtaining logging data.
The drilling-resistance measurements requested by the Panel seem to provide useful information about formation properties. It is imperative that a comprehensive characterization of the vadose zone be undertaken to give clear focus and definition for computer simulations. Steps should be taken to minimize and monitor drag down during drilling. Drilling through known contamination zones should be avoided by slant drilling, unless deliberate sampling and analysis of the zones is undertaken. Hanford should obtain a capability for accurate logging of formation temperature.