In many cases, the application of in situ techlogies evolved as a necessity from a cost perspective. However, the basic understanding of the mechanisms and theory behind these techlogies was treated as a black box. Although we have seen some tremendous successes in the application of remediation techlogies over the past several years, we have also seen many cases in which a techlogy has been incorrectly or inappropriately applied. In most cases, this misapplication has been the result of a poor understanding of the basic concepts and mechanisms behind the techlogies. Without proper understanding, the potential for misapplication of techlogies remains a serious ecomic and technical threat.