The numerical simulation of contaminant spreading in the vadose zone as well as the modeling of remediation scenarios requires, in general, very sophisticated model concepts. Particularly, compositional and nonisothermal effects increase the complexity of a model significantly. This makes the solution of large systems computationally costly. To save computation time, it is reasonable to adjust the required model complexity to the complexity of the relevant physical processes. The relevant physical processes governing the system's behavior can change for distinct time scales. This can be taken into account by models that are adapted to the respective processes, which can be coupled sequentially.