How is uncertainty quantified in site characterization?

• A. Through confidence intervals, probabilistic modeling, sensitivity analyses, and scenario planning
• B. Through deterministic single-value estimates
• C. By assuming worst-case scenarios only
• D. By ignoring variability and using average values

Answer: (A)

Uncertainty in site characterization is quantified using probabilistic approaches that describe how likely different conditions could be. This means moving beyond a single fixed estimate to expressions of risk and spread. Confidence intervals give a range around an estimate with a stated probability, showing how precise or imprecise the value is. Probabilistic modeling uses distributions for uncertain parameters and propagates that uncertainty through models to produce a range of possible outcomes rather than one answer. Sensitivity analyses reveal which inputs most influence the results, helping focus data collection and reduce overall uncertainty. Scenario planning explores how outcomes change under different plausible future conditions, capturing the effect of different drivers and events.

Relying on a deterministic single-value estimate hides variability and misrepresents risk. Focusing only on the worst-case scenario can overstate risk if that outcome is unlikely. Ignoring variability and using average values erases the tails of the distribution where extreme events may lie, potentially underestimating chances of significant impacts.