Nevada Test Site 2005 Waste Management Monitoring Report Area 3 and Area 5 Radioactive Waste Management Sites

Environmental monitoring data were collected at and around the Area 3 and Area 5 Radioactive Waste Management Sites (RWMSs) at the Nevada Test Site. These data are associated with radiation exposure, air, groundwater, meteorology, vadose zone, subsidence, and biota. This report summarizes the 2005 environmental data to provide an overall evaluation of RWMS performance and to support environmental compliance and performance assessment activities. Some of these data (e.g., radiation exposure, air, and groundwater) are presented in other reports (U.S. Department of Energy, 2005; Grossman, 2005; Bechtel Nevada, 2006). Direct radiation monitoring data indicate that exposure levels around the RWMSs are at or below background levels. Air monitoring data at the Area 3 and Area 5 RWMSs indicate that tritium concentrations are slightly above background levels. There is no detectable man-made radioactivity by gamma spectroscopy, and concentrations of americium and plutonium are only slightly above detection limits at the Area 3 RWMS. Measurements at the Area 5 RWMS show that radon flux from waste covers is no higher than natural radon flux from undisturbed soil in Area 5. Groundwater monitoring data indicate that the groundwater in the uppermost aquifer beneath the Area 5 RWMS is not impacted by facility operations. Precipitation during 2005 totaled 219.1 millimeters (mm) (8.63 inches [in.]) at the Area 3 RWMS and 201.4 mm (7.93 in.) at the Area 5 RWMS. Soil-gas tritium monitoring continues to show slow subsurface migration consistent with previous results. Moisture from precipitation at Area 5 has percolated to the bottom of the bare-soil weighing lysimeter, but this same moisture has been removed from the vegetated weighing lysimeter by evapotranspiration. Vadose zone data from the operational waste pit covers show that precipitation from the fall of 2004 and the spring of 2005 infiltrated past the deepest sensors at 188 centimeters (6.2 feet) and remains in the pit cover. Precipitation did not infiltrate to the deepest sensor on the vegetated final cover at U-3ax/bl. Water drained from all Area 3 drainage lysimeters that received three times natural precipitation, but there was no drainage from the lysimeters that received only natural precipitation. Biota monitoring data show that tritium is the primary radionuclide accessible to plants and animals. Other human-produced radionuclides in the tissues of plant and animal samples from both RWMSs were not found at concentrations higher than in biota samples collected at control locations. This suggests that sampled animals did not intrude into the waste and that waste did not move to where it is accessible to plants or animals