UNDERSTANDING FLUID AND CONTAMINANT MOVEMENT IN THE UNSATURATED ZONE USING THE INEEL VADOSE ZONE MONITORING SYSTEM

摘要

DOE has hundreds of contaminated facilities and waste sites requiring cleanup and/or long-termrnmonitoring. These contaminated sites reside in unsaturated soils (i.e. the vadose zone) above thernwater table. Some of these sites will require active remediation activities or removal while otherrnsites will be placed under institutional controls. In either case, evaluating the effectiveness of thernremediation strategy or institutional controls will require monitoring. Classical monitoringrnstrategies implemented at RCRA/CERCLA sites require ground water sampling for 30 yearsrnfollowing closure. The overall effectiveness of ground water sampling is diminished due to thernfact that by the time you detect chemical transport from a waste site, a major contaminationrnplume likely exists in the vadose zone and the aquifer. This paper suggests a more effectivernmonitoring strategy through monitoring near the contaminant sites within the vadose zone.rnVadose zone monitoring allows for quicker detection of potential contaminant transport. ThernINEEL Vadose Zone Monitoring System (VZMS) is becoming an accepted, cost effectivernmonitoring technology for assessing contaminant transport at DOE facilities. This paperrndescribes the technologies employed in the VZMS and describes how it was used at several DOErnfacilities. The INEEL VZMS has provided the information in developing and validating bothrnconceptual and risk assessment models of contaminant transport at the Idaho NationalrnEngineering and Environmental Laboratory (INEEL), Oak Ridge National Laboratory (ORNL),rnSavannah River Site (SRS) and the Hanford site. These DOE sites exhibit a broad range ofrnmeteorologic, hydrologic and geologic conditions representative of various common geologicrnenvironments. The VZMS is comprised of advanced tensiometers, water content sensors,rntemperature sensors and soil and gas samplers. These instruments are placed at multiple depthsrnin boreholes and allows for the detection of water movement in the unsaturated zone and thernsampling of the liquid and gas for subsequent chemical analysis.