Nashville Combined Sewer Overflow (CSO) Program

CTE has been the Program Manager for the Overflow Abatement Program (OAP) for the Metro Water Services since 1990.  The OAP was developed in response to a state order to clean up the Cumberland River's tributary streams that were being polluted by sanitary and combined sewer overflows.  The OAP's objective was to eliminate pollution of the Cumberland River and its tributaries in Davidson County by eliminating bypasses and overflows to Nashville's lakes, rivers and streams.  The OAP, with construction costs in excess of $700 million, has three basic components:  wastewater treatment plant and pump station design, combined sewer projects, and sanitary sewer projects. On November 25, 2002, Tennessee's governor, Nashville's mayor and representatives from the USEPA Region 4 office held a press conference on the banks of the Cumberland River.  At the ceremony, it was announced that 33 miles of the Cumberland River and multiple tributary streams now meet state and federal water quality standards and have been removed from the list of polluted rivers. 

As Program Manager for the OAP project, CTE's role included: overall management of the program plan and schedule, management of sub-consultants who perform design services for projects included under the program, management of the extensive data gathered and maintained under the program, water quality studies which track the progress of the OAP efforts and identify other potential sources of environmental pollution, OAP contracts' management, and construction management and inspection services.  Cleaning up the river was no simple task.  The combined sewer system has an area of about 15 square miles and includes 440 miles of sewer.  The separate sewer system area is about 250 square miles and includes over 2000 miles of sewer.  The first phase of the program was the preparation of a wastewater capacity management plan, mandated by the State of Tennessee as a prerequisite to removing a moratorium on connections to the sewer system. Since 1990, combined overflows have been reduced by 19 billion gallons into the Cumberland River, a reduction of 20 to 1.  Of the 157 sanitary overflows discovered, 122 have been eliminated.  Pump station overflows have been reduced, CSO points reduced from 31 to 8, and 3 billion gallons of inflow and infiltration have been eliminated from the system.  Over 137 projects have been completed or are underway at an expenditure in excess of $700 million. 

The largest project in the OAP, the Central Wastewater Treatment Plant Expansion and Pumping Station, was designed by CTE with estimated costs in excess of $132 million. CTE has developed state-of-the-art procedures, methods and protocols for the determination of water quality in the Cumberland River and its tributary streams. Using these methods, over $100 million was saved by not having to construct massive equalization basins.  The program has been repeatedly recognized on a national basis as an example of abatement done effectively and economically.