ABSTRACT
All numerical models calculate an approximation to a specific real-world topic of interest. When used for their intended purpose, they are often useful. However, it is inappropriate to use a model created for one purpose to estimate a solution to a problem not within the scope of the original purpose of the model. For example, an economics model is not suitable for design of a landfill cover. In the same way, it may not be appropriate to use a model developed for design of conventional-barrier landfill covers to estimate performance of an ET landfill cover. The engineer should select a design model that is appropriate for the problem.
