The goal of the Department’s Sewer Rehabilitation Program (SRP) is to investigate, identify and correct failing sewer infrastructure in order to decrease inflow/infiltration (I/I) of rain water into the system and extend the life of the sewer system assets.
The Brentwood Water and Wastewater Department’s ongoing SRP program dates back to the early nineties. The activities to rehabilitate sewer pipelines and manholes included, line inspections via closed circuit video and point repairs with chemical grouting. However, beginning in 2006, the SRP program was redefined and expanded to fulfill requirements of an Agreed Order issued to both Metro/Nashville Water Services and the City by the Tennessee Department of Environment & Conservation. That same Order created a sewer moratorium in the Little Harpeth River basin.
The redevelopment of the program now includes a comprehensive, $30 million dollar corrective action plan that extends through the year 2019 and is aimed at eliminating sewer overflows by reducing storm water infiltration and inflow, or I/I, into the sewer system through pipeline and manhole rehabilitation and repair.
The programs approach is to identify problematic areas and prioritize rehabilitation tasks through system flow monitoring and video inspection. Projects to be completed by private contractors during the multi-year program include, rehabilitation of approximately 100,000 linear feet of trunk and collection sewer lines primarily by relining pipes and manholes and an upgrade to the Department’s sewer pumping station.
Pipe “relining” was selected as the primary rehabilitation method because of its minimal impact to above ground property. Pipelining is mostly a trenchless process and therefore less destructive to the surrounding above ground property. The contractor installs a felt or fiberglass based liner through an existing manhole and into the underground pipeline that is being rehabilitated. Air is typically then applied to inflate the liner and then the liner is cured via ultraviolet light or hot water. Once cured in place, the new liner seals up all cracks and points of infiltration and future surface or ground water is prevented from entering the section that has been rehabilitated. The rehabilitated pipe then has a new life expectancy of approximately 50 years.
To date, the Department has eliminated an estimated 700+ million gallons per year of infiltration and inflow resulting in a reduction of sewer system overflows by about 90%, reducing operational cost and increasing the life of the system infrastructure. In September, 2014 the below Program Report was prepared by CH2M Hill Engineers and submitted to, and approved by the State's Department of Environment and Conservation (TDEC), which outlines the City's progress to date and the next phase of work to be completed. Highlights of the work to date are also included.
In 2015, the City engaged CH2M Hill Engineers to assist with the implementation of the Phase III requirements, including project oversight and compliance reporting. Below is the PowerPoint presentation, very similar to the one provided to TDEC in August 2014, that provided an overview of rehabilitation program and the Phase III requirements to the City Commission.
The Board awarded a contract in 2017 to SAK Construction, for continued pipe lining work through CY2019 (Phase 3) in the following areas: Maryland Farms, Brentwood Country Club and along the trunk sewer beginning near Wildwood Drive and working west to Hillsboro Rd.