Surge Modeling Improves Water Service and Eliminates Pressure Fluctuations
- Crystal M Broadbent, P.E., David Briley, P.E. - Hazen and Sawyer
- Karen Brashear - City of Goldsboro
A 12 mgd water system was experiencing significant water pressure fluctuations in a specific area. System pressures fluctuated by approximately 50 psi. This part of the system served several major institutional facilities; a neuro-medical center, a major state mental health hospital, and two correctional facilities. Low pressure and inadequate fire flows around the medical center were also experienced. Due to these concerns, potable water at the medical center was being provided by a neighboring water system.
The City worked with a consultant to determine the causes of the deficiencies and develop alternatives to mitigate the pressure fluctuations. After studying the distribution system model and discussing operational data with the City’s engineering staff, the project team suspected that the cause of the pressure fluctuations was a laundry facility operated by the Department of Corrections. Pressure loggers were installed within the distribution system to record pressures. A surge model was created and calibrated to the field data. The model matched the field data when simulating the operation of the washing machines which filled rapidly at certain times of day. This confirmed that they were the cause of the fluctuations. After evaluating several alternatives, a surge bladder tank was determined to be the most effective solution. A 5,300-gallon surge bladder tank was installed in the fall of 2011 near the laundry facility. Since the tank’s installation, pressures stabilized allowing the City to serve the medical center again, and potential wholesale users. Model calibration, field data collection, pressure logging equipment, and sampling locations were critical to the project success.
This case study will help other utilities understand how surge modeling can solve pressure problems.
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