Prioritizing Collection System Repairs with Limited Information

Sewer Collection systems can contribute substantial pollutant loading to receiving waters during wet weather events due to Sanitary Sewer Overflows (SSOs). The implementation of the Total Maximum Daily Load (TMDL), the National Pollutant Discharge Elimination System (NPDES) Phase I Stormwater Program and other Non Point Source (NPS) reduction programs have identified water quality issues associated with SSOs. A new program being implemented to address these issues is the Capacity, Management, Operations, and Maintenance (CMOM) program; the goal of this program is to minimize SSO events, this is accomplished by many facets of the program, including development and implementation of a system that prioritizes maintenance needs, including infiltration/inflow (I/I) investments in repairs to the collection system. This paper describes an ongoing I/I reduction project in the Morning Creek basin in the southern portion of Fulton County, (Atlanta) Georgia. This basin consists of approximately 3800 manholes and 230 kilometers of pipeline divided into 14 separate sewersheds (defined by the location of a sewer flow monitoring station). The project uses a process called the "find and fix" approach which combines engineering analysis with construction of repairs of identified defects. Defects that cause I/I are identified, and then assessed to determine the most cost-effective investments from a flow reduction perspective. This process differs from the traditional approach to I/I reduction in that it is flexible in terms of information required for the analysis. Several tools were adapted to this project, including a Decision Support System (DSS) and a Geographic Information System (GIS)-based hydraulic model. A DSS is used using InfoNet (Wallingford Software), the DSS assists in the integration of GIS information, asset management databases, CCTV (Closed-Circuit Television) of sewer lines, manhole surveys and inspections, and hydraulic model information. These tools are employed in an illustration of the prioritization process; tracing the analysis of from the entire basin to evolution of specific work order for repairs.