Sponsored by the Natural Attenuation Task Committee of the Environmental and Multi-Media Council of the Environmental and Water Resources Institute of ASCE. This report provides the regulatory framework, scientific and engineering principles, and applications of natural attenuation for the remediation of contaminated sites. Natural attenuation is a process that relies on the natural assimilative capacity of a site to reduce or stabilize contaminates to desirable levels. It is becoming an increasingly popular, cost-effective remedial alternative for many contaminated sites. The report describes in detail sites contaminated with petroleum hydrocarbons and MTBE, chlorinated solvents, polycyclic aromatic hydrocarbons, metals, and radioactive wastes. Topics include: Ømajor pollutants; Øextensive review of literature; Øexamples of applications of natural attenuation; Øsite characterization and monitoring requirements and procedures; and Øbasic scientific principles on physical, chemical, and biological processes. Environmental engineers and scientists will find this book full of information on basic principles to summaries of natural attenuation applications.