The objectives of this study include: determining routes and severity of pathogen entry into the distribution system; evaluating the effectiveness of existing utility practices in protecting the system from intrusions; and, recommending monitoring and control strategies. The approach includes a literature review and a survey of utilities' current operation and maintenance practices. An Expert Panel was used to rank the importance of each pathogen intrusion pathway. The ranking process was conducted twice during the project duration, once after the literature review and once after field monitoring and modeling is completed. Based on the initial ranking of pathways, field monitoring studies were conducted to validate the occurrences of pathogen intrusion and to evaluate existing and proposed control strategies. Hydraulic surge modeling was conducted to characterize transient surges and their role in contributing potentially contaminated water to the distribution system. Includes tables, figure.