Metro Nashville Receives CAP/ER Approval

In late August 2017, the U.S. Environmental Protection Agency (EPA), in conjunction with the Tennessee Department of Environment and Conservation (TDEC), approved the Corrective Action Plan / Engineering Report for Sanitary Sewer Overflows (CAP/ER). The CAP/ER outlines Metro Water Services' plan to address sanitary sewer overflows (SSOs) in Davidson County and is one of two key pillars of the Clean Water Nashville Overflow Abatement Program. The other pillar, the Long Term Control Plan (LTCP) remains under review by EPA and TDEC and describes the combined sewer system and recommended improvements.

Both the CAP/ER and the LTCP were submitted to EPA and TDEC, in September 2011. The approved CAP/ER and the Addendum to the CAP/ER, which provides updated project information, can be found in the public documents repository.

The CAP/ER targets conditions that cause overflows within Metro Waters Services' sanitary sewer system. Defective existing infrastructure and capacity limitations can create conditions that allow sewage to escape the system before it can reach a treatment facility. When that happens, SSOs occur that may contribute to the impairment of area creeks, streams, and rivers and may pose a risk to human health.

Development of the CAP/ER began in 2008 with a characterization study of Metro's sanitary sewer system based on extensive monitoring and modeling to understand the existing system's limitations. The need for improvements to address both current and future sewer capacity needs was then assessed, and potential alternatives were evaluated with the most efficient and cost-effective solutions being recommended for construction.

The CAP/ER's recommended projects include rehabilitation of sewer pipes, associated manholes and service laterals to reduce extraneous sources infiltration and inflow; upgrades to the system to add conveyance capacity; and construction of storage facilities to hold excess flows during rain events.

Even prior to the final approval of the CAP/ER, the Clean Water Nashville Overflow Abatement Program has made substantial progress to reduce wastewater overflows to the environment and improve water quality by constructing over twenty projects. Additional projects are currently under design.

The Clean Water Nashville Overflow Abatement Program is tasked with providing dynamic benefits to the community by designing and constructing these projects at an estimated cost of approximately $1.2 to $1.5 billion. These benefits include:

  • Renewing and improving aged infrastructure that, in some cases, was installed between 75 and 100 years ago;

  • Making a strategic investment in infrastructure that will benefit future generations of Nashville;

  • Enhancing the environment for Nashville;

  • Improving water quality in the Cumberland River and its tributary watersheds throughout Davidson County; and

  • Providing major engineering and construction projects that boost the local economy.

  • Metro Water Services is required to complete CAP/ER projects within 11 years from the approval date or August 2028.

Julie Flynn