WA18-03 CS051818 BIRKHOFF, HENDRICKS & CARTER, L.L.P.
PROFESSIONAL ENGINEERS
Texas Firm F526 RPLS Firm No. 100318-00
]]910 Greenville Ave.. Suite 600 Dallas,Texas 75243 FaY(214)461-8390 Phone(214)361-7900
MEMORANDUM
To: Kerit�Collins, P.E.
Directo�of Public Works, City of Cop �
From: Derek B. Chaney, P.E., R.P.L.S.
Date: May 18, 2018
�
Subject: Water/Wastewater Master Plan & Impact Fee Update
Benefits of Water Model Conversion from Steady-State to Dynamic Simulation
As requetsed in our meeting with the City Staff on Tuesday, May 1 St", we are providing a summary below of the
benefits that could be expected with a Dynamic as compared to a Stready-State Water Distribution System
Model.
1. On a fundamental level, a dynamic/extended period simulation (EPS)water model provides a more
accurate, and realistic output result than a steady-state/static model. The dynamic model requires input of
a diurnal curve created from maximum daily and maximum hourly water demand records. This time
variable curve allows the model to report results across various times and usage conditions.
2. Operational Settings: The dynamic model allows creation of pump settings based on input from the City's
operator. For example, a typical pump setting would cause Pump 1 to turn on when EST levels dips below
a specific elevation and would cause the pump to turn off when the tank level is replenished to the desired
elevation. This allows us to review and confirm that the City's EST's are deep-cycling, and if necessary,
provide recommendations for pump setting adjustments that could optimize the system operations.
3. EST Cycling: A typical 72-hour simulation allows us to evaluate the system"s facilities(elevated/ground
storage and pumping)to provide adequate capacity over a range of different demand conditions.
Typically,the initia124-hours tests the ability of the EST's to discharge adequate flow volumes to meet
maximum hourly demands,the 2"d 24-hours tests the ability of the pump station to refil(ed/replenish the
EST's during maximum daily flow conditions, and the 3�d 24-hours tests the system's ability to respond to
a new maximum hour event the following day.
4. Water Quality Modeling: Without a dynamic model, water quality(e.g., residuals)cannot be obtained.
When paired with residual information collected in the system, a dynamic simulation can be calibrated and
used to determine the locations of low residual and excessive aging of water. Analysis can then be
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