During the concept comparison and selection phase of capital projects, decision makers compare development options and select one option to carry forward to detailed engineering. This effort is often complicated by uncertainty in one or more of the critical inputs. Therefore, project teams typically investigate how different assumptions about the uncertainty influence optimal decisions. In cases where initial investment decisions are costly to change, the analysis of facility flexibility increases in importance. The goal is to find the optimal balance between initial capacity and the allocation of space and other resources for future expansion. This paper reports the results of a research project in which the authors develop an integrated asset model for a hypothetical deepwater asset and use the model to investigate various aspects of facility design under uncertainty. The method produces estimates for the optimal initial capacity, the likelihood of expansion, the expected size of expansion, and the willingness to pay for the option to expand. The approach is systematic; the model solves quickly and, thus, enables a wide scope of uncertainty analysis. The graphical output is intuitive and facilitates communication between the facility engineer, subsurface engineers, and management.