WA18-03 CS051818 (2) - � Kent Collins, P.E.
Benefits of Water Model Conversion from Steady-State to Dynamic Simulation
May l8, 2018
performed to pinpoint the root causes of water quality issues and provide feedback to the City for potential
system changes that may improve the issues being experienced.
5. Time-variable analysis of system pressure and velocity: A dynamic model allows location and diagnosis
causes of low or high system pressures or pipe velocities. With a dynamic model,these results are
reviewed throughout the 72-hour simulation. In some cases, this provides information that allows the City
to make judgement calls that couldn't otherwise be made. For example,the worst case (maximum) pipe
velocities may exceed 6-8 feet per second in a certain area. However, further review may show that this
condition only occurs briefly (e.g., for one hour) and then returns to normal velocities for the balance of
the simulation. In a static simulation, only the worst case would likely be presented, which can make
results appear worse than they really are. The dynamic model may also identify low pipe velocities that
would not be noticed in the static model.
6. "What If' Development Analysis: With the dynamic model in place, at present, or at any point in the
future, we (or the City with training)can provide a prompt and realistic "What if'Analysis to determine
what effect a potential development or major system change(e.g, interconnect)would have on the
distribution system.
7. Fire-Flow Analysis: The fire-flow analysis capabilities are more robust in a dynamic simulation. Across
the 72-hour simulation, we typically generate a color-coded fire-flow results map showing minimum
residual pressures(red is less than 20 psi, yellow is 20-30 psi and green is greater than 30 psi). The
dynamic model fire flow analysis also allows for verification of maximum velocity during a fire-flow event
(We generally like to see no greater than 10 feet per second). In a"What [fl'analysis,this might cause us
to recommend that a developer put in a 10-inch line rather than the standard 8-inch line to ensure velocities
are maintained below that 10 feet per second threshold.
8. In summary, conversion of the City of Coppell's water model to a dynamic simulation will provide for a
better product,with extended capability beyond what can be provided with a static model.
We are available to discuss these benefits further at your convenience and are standing by to begin the model
conversion efforts at the City's direction.
cc: „�Michael Garza, P.E.
George Marshall, P.E.
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