G N I D L UI B L A C I E9 R S T A C C T E N L E E M S H OW ON EPLACE T G N I R R R R A A H E . G R H K. C T I W L AST AND S GR
RTN N D PA ITH A M S , M E SHA
K.R. Harrington Electrical Building and Switchgear Replacement LOCATION
Nashville, Tennessee C L IENT
Nashville Metro Water Services SERVIC ES
Mechanical, Electrical and Plumbing Engineering Structural Engineering Water and Wastewater
I K .R. HARRI NGTO N E LECTRI CAL BU IL DING A N D SWITC H G E A R RE PL AC E ME NT
Located at the confluence of the Cumberland River and Stones River, the 35-year-old water treatment facility was completely engulfed by the floodwaters in 2010.
n May 2010, Nashville experienced a flood of epic proportions that inundated the city with nearly 14 inches of rain in just 36 hours. The event resulted in significant damage and destruction of private and public facilities, including the K.R. Harrington Water Treatment Plant— one of two 90-MGD water treatment plants that provides potable drinking water to the Nashville metropolitan “GS&P has worked at K.R. Harrington since 1988 when area and its surrounding communities. the firm was hired to design a plant expansion, so we had Located at the confluence of the an in-depth knowledge and understanding of the system’s Cumberland River and Stones River, operations from our past experience. Just prior to the the 35-year-old water treatment facil- flood, we had been selected to design the replacement ity was completely engulfed by the of the plant’s existing switchgear, which had outlived floodwaters, shutting the plant down its anticipated life cycle. Before we could get started on and exposing weaknesses in the project, the flood event the overall water treatment dramatically changed the A planned electrical project’s original purpose and water distribution system. system upgrade for the GS&P engineers worked with and scope. Metro Water Services’ (MWS) “Getting the plant back facility turned into a engineering and operational in operation and online as comprehensive floodstaff to assess the condition quickly as possible was an of the facility and helped enormous effort unto itself. mitigation effort to expedite the recovery of its During that process, we protect the plant from operations within 30 days of determined there were several future flood events. the superflood. Joe Whitson, things we had to do to make executive vice president of sure the facility would not GS&P’s Water Resources market, fail under another flood, and were tasked by Metro Water explains how a planned electrical Services with fully protecting the entire plant’s electrical system upgrade for the facility turned supply and distribution system from a 500-year flood into a comprehensive flood-mitigation event in addition to replacing the original switchgear. effort to protect the plant from future Previously, the majority of the facility was only protected flood events: to the 100-year flood elevation.”
To replace the plant’s existing switchgear and keep the facility operational required the installation of a new electrical building on the site. The new facility is a two-story building designed to stand 2 feet above the 500-year flood elevation.
NEW ELECTRICAL BUILDING
EXISTING ELECTRICAL SUBSTATION
A PHASED APPROACH To replace the plant’s existing 4,160-volt switchgear and at the same time keep the facility operational required the installation of a new electrical building on the site. This presented the design team with one of the project’s biggest challenges. “Site space was limited due to several factors, including an existing electrical generator building and substation as well as raw water lines,” says Dale Mosley, senior vice president of GS&P’s Water Resources market. “The flood plain along the Stones River also presented limitations. Because we lacked the area needed for the building footprint, we had to make the structure two stories.” Designed to stand 2 feet above the 500-year flood elevation, the first floor of the new building would house four 2,500 kW diesel generators relocated from the existing electrical building and allow space for two future generators. The upgraded switchgear and variable frequency drives (VFDs) would be situated on the second floor.
“The plant’s four existing generators had been partially submerged in the flood. A big part of the project was relocating those generators to the new electrical building,” says Mosley. “Each generator weighed several tons, so extensive coordination was required to move them to the first floor where they’d be safe above the flood level. To keep the plant operating with emergency backup, we kept two of the existing generators running while we moved the other two generators to the new building. Once the relocated generators were operational, we then transferred the remaining generators. This phased approach was absolutely critical because it allowed the plant to remain online throughout the extensive construction, and supplementing Nashville’s drinking water, which was being produced at the Omohundro Water Treatment Plant.”
SECOND FLOOR – SWITCHGEAR AND VFDS
K .R. HARRI NGTO N E LECTRI CAL BU IL DING A N D SWITC H G E A R RE PL AC E ME NT
FIRST FLOOR – GENERATORS
“It was a remarkable achievement to have a project of this scope and size and be able to replace the plant’s entire electrical system—the cables, the switchgear, and the instrumentation and controls—without shutting it down,” adds Whitson. “We essentially replaced the facility’s brain and nervous system while it kept on working.” In addition to being flood-resistant, to meet stringent International Building Code requirements, the new electrical building was also designed to be earthquake-resilient. “The building and the equipment inside were specifically designed to withstand natural disasters such as an earthquake and still remain in service,” says Mosley. “The structural steel superstructure and metal insulated panels allow movement during a seismic event. So, if there’s a major earthquake in Middle Tennessee, the facility will remain intact and be fully operational. “From an aesthetics standpoint, GS&P selected a metal building type that complements the color of the plant’s mostly brick structures. From a distance, you can’t tell it’s a metal building on the far end of the facility. It simply blends in with the rest of the plant.”
“It was a remarkable achievement to have a project of this scope and size and be able to replace the plant’s entire electrical system—the cables, the switchgear, and the instrumentation and controls— without shutting it down. We essentially replaced the facility’s brain and nervous system while it kept on working.”
JOE WHITSON, EXECUTIVE VICE PRESIDENT, WATER RESOURCES
FLEXIBLE, EFFICIENT AND RESILIENT Early in the design, GS&P and MWS established four key goals for success: reliability, energy efficiency, maintainability and operational efficiency. Mosley discusses a few of the ways these drivers were incorporated into the new facility:
Above: Load-bearing structural beams known as H-Piles support the entire water treatment plant as well as the new electrical building and the duct bank system. To reduce project costs, GS&P’s design routes the new duct bank system over the existing system where possible to eliminate the need for additional H-Piles and grade beams.
“To increase reliability, we designed redundancy—or backups—into the various electrical systems so if there’s an issue with one piece of equipment it doesn’t shut half the plant down. For example, the upgraded diesel generators transferred from the existing building can produce enough electrical power to operate the entire water treatment plant at the rated 90-MGD capacity. This provides a standby electrical power source for the plant. We increased energy efficiency by installing 4160-volt VFDs on the high service pumps to vary treatment system flow rates to match the water distribution system demands. This allows the plant to alter flows and fill the system during lower-pressure periods, which requires less energy. “The use of VFDs on the high service pumps for flow control add to operational flexibility because of their ability to function by just turning on a switch at the control station. In terms of maintainability, we looked closely at the serviceability and reparability of equipment. We spoke with maintenance personnel about what equipment they liked, what had worked well for them in the past, and what equipment hadn’t worked for them. Using that input and our own electrical system experience and knowledge of plant operations both pre- and post-flood, we helped MWS select equipment that could not only be easily maintained but also quickly restored to service in the event of a failure.”
“To increase reliability, we designed redundancy—or backups—into the various electrical systems so if there’s an issue with one piece of equipment it doesn’t shut half the plant down.” DALE MOSLEY, SENIOR VICE PRESIDENT, WATER RESOURCES
K .R. HARRI NGTO N E LECTRI CAL BU IL DING A N D SWITC H G E A R RE PL AC E ME NT
1 31 A metal building type was selected to complement the color of the plant's existing brick structures.
EXISTING TREATMENT PLANT
READY FOR THE FUTURE Changing course from a standard switchgear upgrade to a major flood-protection effort, GS&P’s design solution provided Metro Water Services and K.R. Harrington staff with a flood-protected, earthquake-fortified, energy-efficient facility that provides the city of Nashville and Davidson County with a reliable source of water. “The key to the way this project is designed is that in the event of a flood, when the water hits a certain level, plant personnel can turn off the entire electrical system and leave the facility. When the water level goes
down, staff can return to the plant, flip a switch, and restart the facility without worrying about a system failure because all of its processes are above water and protected,” says Mosley. “This project defines what we do for our clients,” adds Whitson. “As trusted advisors, we form a bond with our clients and function as part of their staff as they become part of our team. I’m proud of our successful delivery of a complicated project, and that Nashville and Davidson County now has a 90-MGD water treatment facility that is essentially weatherproof.”
NEW ELECTRICAL BUILDING
TE A M
PIC William J. Whitson, p.e. PM J. Dale Mosley PP Wendell Strickland, p.e. PP James R. Wilson, p.e., leed ap
Tisha Bandish Andrew Bratcher Chandra Clonan Anthony N. Coles Randy M. Curtis, p.g. Seth Dobyns, eit Nathan G. Guessetto Amanda Haider Nathan D. Hudgens, p.e. David A. Johnson, p.e. Douglas E. Karaszewski, leed ap Scott Kibby, ei Jeremy Kubac, p.e.
GS&P’s design solution provided Metro Water Services and K.R. Harrington staff with a flood-protected, earthquake-fortified, energy-efficient facility that provides the city of Nashville and Davidson County with a reliable source of water.
Diane Marable Tim A. Rucker, segd John Scannell Kristi M. Schnell, p.e. Jordan Watson
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