Table 2 shows various estimates of volumes of liquids that have leaked from these four tanks. Efforts to establish a scientifically-sound approach to contamination of the vadose zone, begun recently by Undersecretary of Energy Ernest Moniz, must continue to receive high priority and attention. A thorough reconsideration of tank waste retrieval and tank decommissioning is also needed, since current plans appear to rely on groundwater models that have been invalidated by recent investigations and disclosure of data regarding radionuclide migration and leaks. An important part of DOE's tank management involves pumping liquids from the single shell tanks into double shell tanks in order to prevent further leaks. The process faces challenges, however.
Liquids are present in the tanks as supernatant and interstitial liquid.
Supernatant can be somewhat straightforwardly pumped from the tanks. But interstitial liquid occurs in the pore spaces of the saltcake and sludge and is more difficult to pump. In fact a considerable amount of liquid might remain in the pores even after extensive pumping. Therefore, it is difficult to ensure against leaks until the tanks are completely emptied. Although removing the liquids from single shell tanks is desirable in order to prevent further leaks, it also creates new concerns such as increasing the temperature in the tanks being emptied and changing the chemistry of the double shell tanks into which the liquids are being pumped.