[en] This report presents an analysis of the impact of subsurface contamination resulting from a series of hypothetical leaks or accidents involving Hanford high-level radioactive defense waste. Estimates of the amounts and concentrations of radionuclides reaching the Columbia River through the Hanford unconfined aquifer flow path were obtained by means of predictive models. The results of the study showed that the spatially averaged concentrations of ⁹⁹Tc, ³H, and ¹⁰⁶Ru in the ground water as it discharges into the Columbia River are at all times far below the respective ERDA Manual Chapter 0524 Concentration Guides for uncontrolled areas. Upon entering the Columbia River, additional large dilutions of the water containing trace quantities of contaminants will occur