Site characterization is the method used by cleanup programs to establish the nature and extent of contamination and subsequently any risks potentially posed by contamination at sites. During site characterization, sampling and analysis plans are implemented, and field data are collected and analyzed to determine the nature and extent of threats to human health and the environment.

Risk assessment activities are ideally intertwined with site characterization activities, with an eye on informing the risk management decisions that need to be made. Therefore, site characterization activities are ideally designed to support risk assessments, which in turn support risk management decision making.