This book addresses the need to predict and control fluid movement in the subsurface. It demonstrates how to conduct realistic assessments of contaminant plume structure and achieve contact between injected reagents and target compounds. It describes both the advection-dispersion and continuous random walk theories of mass transport as well as explains the practical implications of each theory in remedial system design. This book provides an arsenal of relevant theories and practical applications to aid practitioners and regulators in the prediction of fluid movement in the subsurface.