Sanitary Sewer Overflow (SSO) Program

Objectives

The Sanitary Sewer Overflow (SSO) program is MSD’s centralized program for managing the investigation, prioritization and rehabilitation of the separate sanitary sewer system in order to abate sanitary sewer overflows and basement backups. This program represents MSD’s proactive approach toward eliminating excess inflow and infiltration (I/I) from the separate sanitary collection system. MSD’s SSO Program has the following goals:

• Eliminate and/or reduce the frequency/volume of recurring SSOs caused by excessive I/I.
• Eliminate basement flooding caused by sewer backup as a result of excessive I/I.
• Reduce MSD expenditures to construct, maintain, and operate sewage collection and treatment systems impacted by existing I/I.
• Assure compliance with the Kentucky Division of Water (KDOW) regulations governing sanitary lateral extensions and wastewater treatment plant upgrades.

History

Although sporadic flow monitoring, sanitary sewer evaluation studies (SSES), and sewer rehabilitation projects have been conducted in the past, these projects were always reactive in nature and addressed the symptoms at “hot spots”, and did not necessarily investigate the root causes of the I/I problem. With the advent of the centralized I/I program in 1998, MSD began systematically evaluating the condition of the sanitary sewer infrastructure and conducting rehabilitation construction in a proactive manner. Fiscal year 1999 marked the first “wave” of sewer rehabilitation construction designed as a result of the new program.

Program Elements

Structuring the SSO Program into a single, centralized function has allowed MSD to focus efforts on long-term, system-wide I/I reduction and SSO mitigation through a systematic program of flow monitoring, field investigation, hydraulic modeling, and infrastructure rehabilitation. Priorities are set based on the previously listed objectives. The result has been the creation of a 15-year plan that includes a deliberate process of pre-investigation system-wide, by sewershed. Activities include:

• Flow monitoring
• Hydraulic computer modeling of the system sub-basins as required (for capacity analysis and predictive rehabilitation construction planning).