Singleton’s Award-Winning Work On The Corbalis Treatment Plant

Singleton Electric team at work on the Corbalis Treatment Plant.

A Q&A with David Singleton, VP of Preconstruction at Singleton Electric Company, Inc.

Singleton Electric’s work on The Corbalis Treatment Plant received awards for two Craftsmanship Awards from The Washington Business Congress, earlier this year.

What is the Corbalis Treatment Plant?
The Corbalis Treatment Plant in Herndon, Virginia is a critical resource for the citizens of Fairfax County. The plant produces and distributes potable water to residential and commercial customers within the Northern Virginia area. The rated capacity of the plant is 225 million gallons a day.

What was the scope of the electrical needs and requirements for this job?
This was a power infrastructure replacement project. Corbalis has been in service since the early 1980s and has expanded twice while operating on the original power distribution infrastructure, leaving the plant susceptible to unplanned power outages. Due to the critical nature of the plant, it was a contract requirement to maintain power and controls to production equipment throughout the project. The major power distribution equipment was replaced during two winter low water production periods from November 1st through March 31st in 2018 and 2019.

Why or how did the Singleton team’s expertise align for this type of project and scope of work?
Singleton has performed power and control upgrades on water and waste water treatment plants for over 50 years. We have an extensive history in the replacement of major infrastructure systems while maintaining power and controls to critical operations.

Singleton has done several waste and water treatment plant jobs, how does the Corbalis job compare in size, difficulty, etc.?
The Corbalis project was typical in size but had significant challenges due to the critical nature of the work. The project documents included 131 pages of detailed constraints while performing work on a given system. Some of the systems were so crucial to plant operations that the durations given for outages were measured in minutes. 

What made this job unique?
An extremely technical electrical infrastructure upgrade at an operating plant.

 Please expand on the technical and more complicated specifications of the Corbalis job.
On this project there were various control systems throughout the plant, ranging from motor controls to a complicated 5kv automatic transfer scheme between (3) new 5kv switchgear lineups, fed from (2) new 35kv substations. Many of the systems are connected to the plant’s existing SCADA system. All work was completed while maintaining the plant’s production throughout the project. Many of the control wire runs are in excess of 500’, ranging from 14AWG to 6AWG control wiring. New controls were connected to various existing instruments and pump systems in multiple buildings throughout the plant. Existing conduits were reused in many areas. This required countless hours of research, investigation of existing in-service systems, planning and coordination to perform the work during minimal outage durations. We pulled over 500,000 feet of control wire and cable to perform this work.

Were there any unexpected discoveries or bumps in the road that required adjustments to plan or scope?
A month prior to the low demand period in 2018 we were notified that the delivery of the first 34.5kv/4.16kv transformer would be delayed nearly 3 months due to flood damage at the plant caused by Hurricane Florence. To mitigate lost hours, Singleton worked closely with the Fairfax Water staff to develop a modified sequence of work that would allow us to meet the March 31st deadline.

Singleton was honored for power, generation, distribution and switchgear as well as special systems for electrical work by the Washington Building Congress, for this job, could you tell us more about those specifics?
The major power equipment includes:

  • (2) 34.5kV/4.16kV substation transformers and (2) 34.5kV pad mount switches with local and remote controllers.
  • (3) 4.16kV switchgear lineups with remote breaker control panels monitored from the SCADA system.
  • The (3) lineups are connected together with tie breakers by a combination of bus duct and cables and are controlled by an automatic transfer scheme.
  • (9) 4.16kV SCADA controlled starters

Singleton Electric craftsmen replaced the 5kV feeders and control wiring to 9 finished water pumps ranging from 1,000 to 1,750 horsepower as well as replacing and reconfiguring the plant wide 5kV distribution feeders totaling over 65,000 feet of new medium voltage cable. This work involved the following:

  • (4) 4.16kV/480V oil filled pad mount transformers
  • (3) 125V dc battery power and charging stations
  • (2) 480V Motor Control Centers
  • (2) 480V switchgear lineups

In addition to the major work performed under the low demand periods, Singleton performed the equipment upgrades to 13 other production critical buildings during the peak demand season. The equipment included:

  • Installation of a 750kW emergency generator package to provide service to the Water Quality Improvement Center and Facility Support Center during outages.
  • (6) 480V Motor Control Centers
  • (2) 480V switchgear line ups
  • (7) 4.16kV/480V oil filled pad mount transformers
  • (15) Automatic transfer switches

 About how many electricians did you all have to man the job?
On average 14 and peaked at 25 during the low demand periods.

Did you have any JATC apprentices working on the job site during the time? If so, what was their experience?
We used residential trainees. They assisted in all aspects of the project, conduit runs, cable/wire pulls, gear placement and terminations. 

What are you most proud of with regard to your team, the work done or anything else specifically, with regard to this project?
Our teams ability to adjust from a sequence of work that took 6 months to develop was a significant accomplishment. They worked extremely long hours on a compressed schedule while installing work with superior craftsmanship.

What else is there to share about the Corbalis job?
The success of the project can only be attributed to the team work by all parties. Fairfax Water, Jacobs, W.M. Schlosser and Singleton all worked together to complete the project ahead of schedule.

Was all work completed in the timeframe, as planned as well as the budget
Absolutely.


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