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Metro Water Services Chemical Feed Upgrades

Situated on the Cumberland River, the Omohundro and K.R. Harrington water treatment plants are the two 90-million-gallons-per-day conventional surface water treatment facilities that provide potable drinking water to Metropolitan Nashville. In May 2010, the K.R. Harrington plant was completely engulfed by the Nashville Flood. Through a unified effort, GS&P and Metro Water Services (MWS) were able to return the crippled facility to operation in less than 30 days. 
 

Showcase TEN | Metro Water Services – Chemical Feed Upgrades from Gresham, Smith and Partners on Vimeo.


Due to age, the chemical feed systems at both the Omohundro and K.R. Harrington plants had reached the end of their useful life cycles. Because repair kits and replacement parts were becoming obsolete and expensive to obtain, MWS contracted with GS&P to upgrade the alum, carbon, fluoride, lime, polyphosphate, polymer and permanganate chemical feed systems at the facilities. From preliminary design through construction and startup, GS&P and MWS approached the overall project as a team, working together to design the new systems, select key feed system components, and manage the social and economic impacts during the replacement and installation of the systems. The team established goals for the project that included continuity of operations under flood conditions, energy efficiency, reliability, maintainability, operational flexibility and consistency between the plants. 

During the design phase, the most complex part of the project was making all seven chemical feed systems similar despite each chemical possessing different properties and functions. MWS desired comparable equipment at both water treatment plants for ease of maintenance and to allow operations staff to move between the plants without requiring additional training on the chemical feed equipment. Pumps and instruments were evaluated to see which equipment would work best for the client’s needs, and a range of sizes and construction materials were used to accommodate the seven chemical dosage rates. A single brand of peristaltic pumps ultimately provided the optimum solution. The new system included four different sizes of peristaltic pumps, all with variable frequency drives (VFDs) that allow operational flexibility in flowrate so that minimum and maximum needs at the plants could be met. The VFDs also helped deliver the optimal amount of each chemical, thereby improving efficiency. 

Having experienced the negative impacts of the K.R. Harrington shutdown during the 2010 flood, another key project goal was keeping the existing chemical feed systems in operation while constructing and switching over to the new systems. To achieve this, the team provided a detailed plan for the construction sequencing, startup and commissioning of each chemical system in the construction documents. Constant communication between operations staff, management, maintenance staff, GS&P engineers, the resident project representative and the general contractor was also critical. To mitigate future flooding risks, both facilities were designed above the 500-year flood elevation plus 2 feet—the preferred level of protection for critical facilities as set by the Federal Emergency Management Agency (FEMA). 

Installed without interrupting either plant’s operations, the new state-of-the-art chemical feed systems at Nashville’s Omohundro and K.R. Harrington water treatment facilities not only enhance efficiency and chemical feed accuracy, but are flexible enough to meet both current and future water quality standards. 

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Project Info

  • Client: Metro Water Services
  • Location: Nashville, TN , USA
  • Market: Water Resources, Water Treatment Plants
  • Services: Civil Engineering, Environmental Engineering, Mechanical, Electrical, Plumbing (MEP), Structural Engineering, Water and Wastewater
  • Team:
    • William J. Whitson , P.E. PIC
    • J. Dale Mosley PM
    • Ron Abraham , P.E., BCEE
    • Kenneth D. Baker
    • Eric Bearden, AIA
    • Andrew Bratcher
    • Randall S. Booker Jr. , Ph.D., P.E.
    • Adrienne Ciuba, AIA
    • Anthony N. Coles
    • Randy M. Curtis , P.G.
    • Tracey Curray
    • Seth Dobyns, P.E.
    • Clae Fuller
    • Amanda Haider
    • David A. Johnson , P.E.
    • Scott Kibby, EI
    • Terence S. Mulvaney, RLA, CLARB
    • Jason OGG, EI
    • Michael Robertson
    • Christopher A. Temple
    • Akeem Turner, P.E.
    • James R. Wilson , P.E., LEED AP
    • Johnathan C. Woodside, P.E., LEED AP O+M, C.E.M., GBE
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