This technical note argues the importance of incorporating nonlocal dispersion effects when modeling contaminant travel times. Using the transport theory of Di Federico and Neuman <1998>, expressions for nonlocal contaminant travel times and breakthrough are developed. They show that nonlocal travel times are significantly faster than their local (Fickian) counterpart and that nonlocal breakthrough occurs significantly earlier than Fickian. As an illustrative example, nonlocal breakthrough curves for Nevada's fractured welded tuffs, a common rock unit found at the U.S. Department of Energy's Yucca Mountain Project, are approximated using the electrical-hydraulic conductivity correlation theory and measurements of Purvance and Andricevic <2000a, 2000b>. At the 5 km compliance point the approximation shows that nonlocal contaminant breakthrough occurs ~5 times earlier than what is predicted by the Department of Energy's Fickian model. ¿ 2001 American Geophysical Union