In this paper, we describe approaches to risk determination in underground construction. The center piece of what we describe are the decision aids for tunneling (DAT), which allow one to predict cost-, time- A nd resource probability distributions reflecting uncertainties in geology and in the construction process but also many others. The DAT have been recently further developed so that they can treat linear or networked infrastructure projects such as highways or railroads. Some aspects such as the effect of correlation and individual construction process details have also been recently implemented. In parallel, approaches were developed with which one can determine the effect of exploration and how to best explore for tunnel projects. Philosophically related to exploration is a method with which the tunnel construction process can be continually updated to minimize the geotechnical risks. Finally, it is now possible to combine the DAT with an optimization tool using simulated annealing both for tunnels and for networked infrastructure. Very important is the practical application of all these approaches, and this is shown in the paper.