In a broad-scale risk analysis of hazardous waste isolation by incorporating it into rock, the principal failure scenario is for the waste material to be dissolved out of the rock by groundwater, to be carried with the groundwater close to the surface, and then to be ingested by humans. Based on average conditions and average rock behavior, the probability per year for an atom of this waste rock to be dissolved in groundwater and, after it reaches the surface, the probability of it being ingested by a human via various pathways are negligible. These pathways include potable water derived from rivers and from wells, freshwater fish as a food, agricultural use of irrigation, deposition by rivers of silt that is later used for agriculture, and—after the material has reached the ocean—human consumption of seafood. The time delay between waste burial and human ingestion, courtesy of common geologic features and processes, is the key to effective long-term isolation.