In October 1982, the first phase of a sewer system evaluation survey was completed for the City of Alameda, California. The objective of this phase was to determine which portions of the city’s collection system would require intensive field investigations to locate specific sources of infiltration and inflow (I/I). This was accomplished by a sewer flow monitoring program and subsequent cost-effectiveness analysis of the data. The techniques used to ensure accurate data collection during the 32-day monitoring period will be presented. Also, a new methodology that was developed for this study to analyze the flow monitoring data will be discussed.