Hindcasting vs. Historic Reconstruction

The goal of my article was not to review the Camp Lejeune (CLJ) modeling studies. Rather it was to use the CLJ problem as an example to highlight issues related to model complexities and to spark an open debate on when, where, and why we should limit model complexity. I would like to first thank Maslia and his nine co-authors for contributing to this debate. I believe this is an important debate given the fact that our understanding of contaminant transport processes is limited. For example, Konikow (2011) reviewed the current state of knowledge and concluded that the classical transport equation does not always adequately represent what we see at the field scale, and in such cases, commonly used numerical models are solving the wrong equation! He went on to recommend that the secret to successful transport modeling is simply to lower expectations (of the public and sponsoring agencies). Konikow’s (2011) review make a case that we still do not fully understand conservative tracer transport in groundwater systems. Chlorinated solvent transport mediated by biogeochemical reactions is clearly a more complex problem. On the basis of my own experience in developing computer codes and applying them to model various types of laboratory and field datasets (Clement et al. 1997, 2000, 2004), I believe that bioreactive transport modeling is still in its infancy. With this background, in the sections below I provide my point of view on the issues/questions raised by the authors.