We will be attending the 2018 FSAWWA Fall Conference being held at the Omni Resort at ChampionsGate in Orlando, Florida from November 25-29! Our team will be presenting on important topics in utilities, water quality, water conservation, water supply, and asset management. Below are more details about each presentation. We look forward to seeing you there!
Developing an Efficient Flushing Program for Water Conservation and Quality
Presented by Cameron Crandell, City of St. Cloud, and David Yonge, Jones Edmunds
The City of St. Cloud periodically flushes the potable water distribution system to improve water quality (reduce water age and maintain a chlorine residual) and remove sediment and scale that builds up over time. Water main flushing is a common practice but municipalities are being tasked with meeting increasingly stringent water quality regulations while also maximizing water conservation efforts in their systems. An efficient flushing program is necessary to meet these two conflicting goals. For many municipalities, the distribution system flushing program has not been designed and implemented to accomplish specific goals. Instead, flushing is done reactively to address water quality issues or complaints. This paper discusses how Jones Edmunds used the City’s existing water distribution system model and GIS data to develop a unidirectional flushing plan developed for specific water distribution system zones to achieve improved water quality. Hydraulic modeling was used to determine the specific zones, the flushing volume and duration, and to confirm adequate system pressure is maintained during flushing events. GIS data was also reviewed to identify proper stormwater collection was adjacent to the proposed unidirectional flushing location to allow discharge of the flushed water and prevent flooding to roadways and private property. The development and implementation of the unidirectional flushing program increased the City’s flushing effectiveness by improving water quality and optimizing water usage.
Maintaining System Knowledge with Asset Management
Presented by Tom Tibbitts, St. Johns County Utility Department, and Mark Nelson, Jones Edmunds
How many farewell parties did you attend this year? Did you find that retiring employees and changes in organizational structure left a dent in the operation of your Utility? Institutional knowledge is the glue that holds many Utilities together. With a wave of retirements and the occasional restructuring facing utility departments, the challenge becomes documenting that institutional knowledge. Despite inevitable change, the underlying duties remain – the infrastructure and assets will still need to be operated, maintained, and checked so that normal functions don’t skip a beat. Having a firm grasp on the location and functionality of the assets within your Utility infrastructure system can save some of the headaches of passing along knowledge when someone leaves your staff or when a reorganization leaves people with new job duties. More and more municipalities are turning to systems which integrate spatial data in GIS with a robust asset management system to help document workflows, conditions, and tasks. Cityworks Asset Management System is being used throughout the State to help capture institutional knowledge in standard procedures and workflows and GIS-enabled datasets so that staff are never wondering what the status of a specific infrastructure asset may be, or what the next task is. This presentation will look at a case study where Cityworks has organized spatial information and operational functions to keep a Utility running smoothly.
SWRUSA Potable Water Pressure Reducing Valve Stations Study
Presented by John Behr, Polk County, and Erin Hunt, Jones Edmunds
Polk County provides potable water to the Southwest Regional Utility Service Area (SWRUSA) service area. The SWRUSA potable water system pressure reducing valve (PRV) stations are configured to allow water to automatically flow from the east side of the water system that is served by the Pollard Road Water Production Facility (WPF) to the west side of the water system that is served by the Imperial Lakes WPF and the Turner Road Re-Pump Station. If the potable water service is unexpectedly lost at the Pollard Road WPF (e.g., due to a master control system PLC failure), a significant portion of the east SWRUSA potable water system will depressurize and may experience system pressures less than the regulatory minimum allowable value (i.e., 20 psi).
Traditionally, Demand Driven Analysis (DDA) is used to mathematically simulate demands in water distribution systems. In DDA, system demands are only a function of time and assumed independent of the system pressure, and consequently may lead to inadequate pressure results in abnormal conditions. However, a Pressure Dependent Analysis (PDA) based hydraulic model incorporates the relationship between pressure and demand. PDA can help to more realistically simulate a water distribution system’s dependency on the available pressure to supply water, and if the pressure drops below a required pressure the water demand is unable to be supplied. PDA framework assumes a fixed demand above a given threshold pressure, zero demand below a minimum pressure, and demand changes based on an orifice equation for intermediate pressure.
In this project, a PDA-based hydraulic model was used to determine the expected water system performance following a loss of water service at the Imperial Lake WPF or the Pollard Road WPF. In addition, modifications to the performance of existing PRVs to automatically flow from the west side to the east side of the water system to reduce the severity of the east water system depressurization were evaluated.
The results showed that under normal operation conditions pressures obtained from DDA and PDA are similar. However, under pressure-deficient conditions PDA provides more realistic results by taking into account impacts of pressure changes on system demand. Using PDA, the existing PRV stations to be modified, the pressure settings, and the expected water system performance following a loss of water service at the Pollard Road WPF were determined.