GIS LINKS FIELD EFFORTS AND MODELING RESULTS FOR EFFECTIVE SEWER SYSTEM ANALYSIS

The City of Columbus, Division of Sewerage and Drainage (DOSD) used a comprehensive approach to address sanitary sewer overflows, stormwater flooding and water-in-basement occurrences in the Clintonville and Walhalla study areas. Project goals included reduction of inflow and infiltration, reduction of basement and surface flooding and improved system operations and preventative maintenance.To accomplish this, a thorough understanding of the existing conditions of the stormwater and sanitary sewer system was required. System condition information came from an extensive SSES field investigation program, a historic record review and responses by residents to a questionnaire. Using record plans, survey information, a geographical database and the results from a 60-meter flow-monitoring program, a MOUSE model of the system was developed. Results from the field investigations, maintenance and service records, questionnaire responses and the results from the model were converted into ArcView GIS themes. This provided a means of comparing model results directly with field conditions.The approach generated a substantial amount of data, which was managed by the GIS and used for sewer system analysis. Sub-basins were developed around flow monitor locations and were systematically studied for such factors as structurally deficient pipes and manholes, maintenance problem locations, I/I sources, the hydraulic operating condition and the interaction between the storm and sanitary systems. The analyses identified problems in both the local sanitary systems and in the main trunk sewers.Neighborhood projects with cost estimates were developed from the analyses utilizing the GIS. Analysis of the overall operation of the Clintonville and Walhalla basin was conducted to identify and develop solutions to problems that affected multiple sub-basins. The recommended plan was comprehensive. It addressed maintenance needs, structural problems and capacity issues in addition to I/I sources.