The uppermost fiber optic grid will be transposed 90 degrees from the lower grid for maximum spatial resolution and monitoring efficiency. SNL plans to optimize monitoring with the close-coupled cover and shallow vadose zone monitoring system to demonstrate landfill cover performance. NTS operates two disposal areas for low-level wastes, Areas 3 and 5. Moisture movement in this zone is a complex and highly nonlinear process. Soil moisture migrates upward through the top 40 to 50 meters through advection and diffusion, with evapotranspiration being the primary driver in the top meter of soil.
Water is essentially static or moving slowly downward in the deeper sections.
NTS has in place a mature vadose zone monitoring program that has been collecting data for more than 5 years. The NTS strategy has been to track contaminant migration, primarily tritium, by sampling soil gas and monitoring water movement in the vadose zone. A neutron probe field calibration facility has been successfully operating for more than one year, producing accurate calibration data for the different type of borehole casings and serving as a shallow vadose zone monitoring location. To date, all these monitoring systems have proved to be robust and have performed exceptionally well with only minor problems and limitations. All data collected from these systems indicate NTS to be ideal for waste disposal.