Environmental remediation includes many activities that require measurement and monitoring of parameters such as contaminant concentrations, media characteristics, and systemic parameters. In recent years, there has been an increase in the number and types of sensor technologies used during site remediation. These include technologies that are used for performing real-time and continuous measurements, remote monitoring, remote operation, and system automation. The U.S. Environmental Protection Agency (EPA) prepared this report to provide an overview of several types of sensor technologies and a summary of selected experiences with using the technologies during site remediation activities. The report highlights the applications, implementation, strengths and limitations, and lessons learned from actual projects that have used one or more sensor technologies as part of an overall site remediation strategy. Appendices one through seven provide case studies for specific sites that have used sensor technologies during site remediation activities. This report does not provide guidance on the selection of a specific type or vendor of sensor technology; these technologies are most cost-effective under specific environmental, chemical, and physical conditions. Numerous site-specific considerations, such as site geology, soil, and aquifer characteristics, chemical, physical, and biological parameters of affected media, and chemicals of concern, among many others, can impact the overall cost-effectiveness of a system.