Monitored Natural Attenuation (MNA) has become an effective alternative to the more active remediation methods for the in situ treatment of contaminated subsurface environments. This low-cost technology requires a high degree of certainty in the conceptual site model and the underlying reactive transport processes. In order to gather site specific information, site characterization studies must be performed; however, the expense of these studies detracts from the low-cost nature of MNA. Additionally, existing aquifer assessment methods, which range from simple laboratory batch and column studies to large-scale plume studies, suffer from several disadvantages; including the likelihood that the small sample cores are not representative of the heterogeneous subsurface system, the disturbance and possible contamination of cores during collection, the inability to reproduce the exact in situ condition in the laboratory, and the long required time frame. Hence, cost-effective site characterization techniques are required which provide a level of information suitable for demonstrating that in situ processes are present for MNA to be a viable treatment option. Developers of such techniques can not advance without integrating the latest technology in several different research areas such as laboratory methods, field techniques, groundwater mathematical, numerical, and inverse modeling techniques, management and optimization systems, as well as cost-benefit studies.