This open access book synthesizes important advances in the assessment and management of soil and groundwater systems contaminated with petroleum hydrocarbons, especially in the form of light non-aqueous phase liquids (LNAPLs). LNAPL characterization and remediation is challenging due to the multi-phase, multi-component nature of the problem and the various physical, chemical, and biological processes involved in a dynamic and heterogeneous hydrogeological setting. This book focuses on the current state of practice of LNAPL characterization and remediation and seeks to provide information and a framework that would allow some of these complexities to be better addressed by contaminated land practitioners, researchers, and regulators.