As a result of the May 2010 floods in Nashville, the KR Harrington Water Treatment facility site was heavily damaged by contaminated flood waters. The power distribution systems at the site were knocked off line and had to be cleaned, repaired and temporarily put back in service. This plant is one of only two facilities supplying Nashville with clean drinking water.
Two primary types of construction were built:
A. Vertical Seismic Category IV Electrical Powerhouse Structure
B. 5kV, 480V / 277V, 208V /120V Power Distribution System
The Electrical Powerhouse structure is two stories, built on steel H-piles, driven by an 80 ton crane, to an average depth of 40 ft. for the building and ductbanks supports. The building footprint comprises of approximately 17,100 square feet and over 1,000 linear feet of ductbanks, supported by 194 H-piles.
The project began September of 2012 and was completed December 2014, 849 Calendar Days. The Facility remained on-line and operation throughout construction. Multiple service change-overs were completed depending on sections of the plant that was ready to be brought on-line with the new equipment.
The conditions of working in an existing fully operational critical service facility, for the City of Nashville, in excess of two years was a task within itself. Wolfe & Travis Electric was the Electrical Contractor for the original plant construction in 1976. The site conditions consisting of existing underground electrical and water services, working with the various operational stages of the plant and environmental restraints. Maintaining water supplies from the Cumberland River, processing water to City of Nashville and providing the TVA requirements for load sheading at peak times, all makes this one of the most unique and challenging projects in our company’s 48 year history.
Meeting the challenge of a difficult job is in fact, what we did! The project involved relocation of the power services to two feet above the 500 year floodplain of the historic May 2010 floods and the replacement of the existing power distribution system.
The facility operations must be maintained at all times 24 hours / 7 days a week. The project was divided into workable phases and coordinated with plant operational requirements. Yearly rain schedules, river levels, and freezing weather conditions dictated certain times of the year that work could be performed on selected sections of the project. This made a scheduling a critical part of the daily activities. Daily and weekly schedules were provided and approved by the construction teams so the facility could switch services and control the up to 90 Million Gallons a Day water flow to Nashville as required.
Coordination issues, safety and project planning was handled in a bi-weekly project meeting at the site. Each day a site review was made by the on-site engineer for compliance. An overall sequence of operation was created and the schedules built upon that effort.
Our Superintendent worked daily with the facility managers to discuss installation options and plan the next day’s work. Our effort was not only to install what was designed but to install it in the best manner possible for quick access and future rearrangement possibilities’. Raceways, Manholes and cable tray management are all a part of the “Constructability” service that we provided. This effort gives the Owner exactly what they want for their day to day operations and the ability to easily expand systems for future integration’s and understands why and where things are installed.
Creating a diverse infrastructure was the key to the project. Installations had to be completed and ready for incorporation when the plant released areas of work.
The ductbanks and manholes were all coordinated with the existing 48” water lines and new electrical services were installed with H-piles driven into the ground to support the weight of the ductbanks. Soil erosion techniques were implemented around the building perimeter and where the ductbanks crossed the site.
A special 5 kV cable was installed that is more resistant to water penetration in all new underground services. A new “Cable Bus” system was installed to feed the replacement Motor Control Centers in the original Plant.
During this effort, the H-piles for the new Seismic Category IV Electrical Powerhouse Structure were installed and the building made ready for the sequence - the installation of the new State-of-the art 5kV paralleling main-tie-main switchgear, interlocking power management controls and extension of the 65kV switchyard for our service.
Our team provided a detailed Coordination and Arch Flash Study of all the power distribution equipment to confirm the components and their settings were compatible with the new system. This also provided the safety requirements of the gear and what type of safety clothing must we worn when working in live operational environments.
Relocation of the existing four 1.7 mega-watt diesel generators in sequence so that the facility would never lose operational power was scheduled around possible load shed or active weather patterns. The existing generators had to be removed from the existing building and relocated to the new electrical power house on the first floor. Expansion of fuel oil system and interlock controls had to be installed for a controlled load based engine start-up. A system as large as this, with 99% efficient power factor and load ranges, required extensive adjustments and repairs to the existing generator units. New exhaust and make-up air louver system was installed to support the generator start-up and run requirements.
New installation of the 5kV, 2,500 H.P. variable frequency drives for the finish water pumps and relocation of the 800 horsepower raw water pump drives. Relocation of all other 480V existing drives and the eight new motor control centers for various plant operations.
Tying all these systems together is a new supervisory control and data acquisition (SCADA) system. It was installed and interlocked with the existing operation and tied to a new 5MR remote load shed system for TVA.
A complete system wide testing and commissioning effort was performed. Switchgear switching performance, Generator start sequences, switchyard switching and load shed systems were all tested under several real life scenarios’. Third Party testing of all the 5kv cables and their terminations was completed and inspected. Nashville Electric Service provided a mock power outage test for emergency capabilities.
This project in its entirety is required to supply potable drinking water for the use of the community of Metropolitan Nashville Tennessee. Local contractors and suppliers were used for materials and labor from the surrounding area.
It was an honor to have the opportunity to return to a project that our company originally completed 1976.
Working in a fully operational facility has its challenges for normal expansion projects, but this project was much more, it was a complete replacement and expansion of the Power Distribution System.
To do this required a new 2 story Electrical Power House based on a Seismic Category IV Structure, New 5kV “Double-ended” Paralleling Gear, relocation of all the facilities Emergency Power Generation plant and reconnection of the 2500 horsepower pumps and systems with the state-of-art SCADA controls.
We are proud of all the efforts by our staff and our subcontractors.