An overview of groundwater hydrology; a technology review of equipment, methods, and field technologies; and a methodology for estimating groundwater contamination under emergency response conditions are provided in this book. It describes the state of the art of the various techniques used to identify, quantify, and respond to groundwater pollution incidents.Interest in the causes and effects of groundwater contamination has increased significantly in the past decade as numerous incidents have brought the potential problems to public attention. Protection of our groundwater resources is of critical importance, thus making the book both timely and relevant.Part I assesses methodology for investigating and evaluating known or suspected instances of contamination. Part II surveys groundwater fundamentals, state-of-the-art equipment, monitoring methods, and treatment and containment technologies. It will serve as a desk reference and guidance material. The information will supply input to developmental efforts leading to more efficient, durable, and cost-effective monitoring and remedial action technologies. Part III details possible emergency response actions at toxic spill and hazardous waste disposal sites. It provides a rapid assessment methodology for performing such an evaluation within a 24-hour emergency response time frame.