1. Source Zone Remediation: The State of the Practice

Chlorinated solvents are widespread groundwater contaminants whose physical and chemical properties make them difficult to locate and treat within the subsurface. In particular, remediating chlorinated solvent source zones has proven technically challenging, costly and contentious. Nevertheless, there has been a concerted effort over the past 20-25 years to remediate these source zones, involving development of several in situ technologies. This chapter summarizes the knowledge gained from these efforts, and serves as an introduction to the entire volume. The chapter first summarizes the evolution of the conceptual model of DNAPL source zones, and then describes the current model of a 5-stage life cycle, with a long final stage of back diffusion and desorption. The chapter then summarizes the development of the important remediation technologies, followed by an overview of the current state of the practice. The chapter includes brief summaries of the remaining chapters, and concludes with a summary of the current needs, both for research and for the highly-qualified personnel required to manage groundwater restoration in the future.