Decontamination Systems Information and Research Program

The following paragraphs comprise the research efforts during the second quarter of 1998 (April 1 - June 30.) These tasks have been granted a continuation until the end of August 1998. This report represents the last technical quarterly report deliverable for the WVU Cooperative Agreement - Decontamination Systems Information and Research Program. Final draft technical reports will be the next submission. During this period, work was completed on the Injection and Circulation of Potable Water Through PVDs on Task 1.6 - Pilot Scale Demonstration of TCE Flushing Through PVDs at the DOE/RMI Extrusion Plant. The data has been evaluated and representative graphs are presented. The plot of Cumulative Injected Volume vs. Cumulative Week Time show the ability to consistently inject through the two center PVDs at a rate of approximately ten (10) gallons per hour. This injection rate was achieved under a static head that varied from five (5) feet to three (3) feet. The plot of Extracted Flow Rate vs. Cumulative Week Time compares the extraction rate with and without the injection of water. The injection operation was continuous for eight hour periods while the extraction operation was executed over a pulsing schedule. Extraction rates as high as forty-five (45) gallons per hour were achieved in conjunction with injection (a 350% increase over no injection.) The retrieved TCE in the liquid phase varied to a considerable degree depending on the pulsing scheme, indicating a significant amount of stripping (volatilization) took place during the extraction process. A field experiment was conducted to confirm this. A liquid sample was obtained using the same vacuum system used in the pad operation and a second liquid sample was taken by a bailer. Analyzation of TCE concentration showed 99.5% volatilization when the vacuum system was used for extraction. This was also confirmed by data from the air monitoring program which indicated that 92%-99% of the retrieved TCE was being transported in the gas phase. Data on the recovered TCE concentration for the pulsing schemes implemented in the field were collected. Based on the TCE concentration in the liquid phase, the optimum schedule for recovery during an extraction only scenario is one hour on - seven hours off - one hour on which allows for the recharging of the groundwater with TCE by the process of diffusion. With injection utilized, the optimum schedule for the operation is one hour on - three hours off - one hour on, which allows for the optimum recovery of TCE in an optimized amount of liquid. Uranium (U) was recovered in conjunction with TCE removal. Although specifically not targeted, the PVDs indiscriminately retrieved the subsurface contaminants on the order of 65-95 pCi/L. The field work was completed on surfactant augmented injection. Circulation and data reduction from this sequence of testing is ongoing