Interceptor Maintenance Cleaning Plan: Evaluating Sewer Cleaning Needs May Yield Combined Sewer Overflow Abatement The Metropolitan District – Hartford, Connecticut

The purpose of the Interceptor Maintenance Cleaning Plan (IMCP) was to provide a tool to the Metropolitan District (district) for better sediment management and removal in the interceptors of the Hartford combined sewer system (CSS). A report was developed to characterize the CSS under existing conditions and prioritize critical interceptors that should be regularly cleaned or closely monitored and cleaned as needed.The goal of the proposed cleaning was to reduce combined sewer overflow (CSO) discharges by restoring and maintaining the design capacity of the CSS. Computer modeling had predicted that reducing current sediment depths to a maximum of six inches would reduce CSO volumes by 14 percent system wide (from 63 million gallons to 54 million gallons) for the 3-month design storm, and by 11% system wide (from 93 million gallons to 83 million gallons) for the 1-year design storm.This Interceptor Maintenance Cleaning Plan was a product of extensive data collection efforts and multiple analyses. A comparison of the data gathered, teamed with information gathered from previous studies, computer modeling, workshops, and additional investigations with the district, led to key findings.