Presented by: Joe Langston, PE, LEED AP BD+C

Operational Benefits of Developing an Unidirectional Flushing Model

April 15, 2013

• What is Unidirectional Flushing (UDF)?

• Why Implement an Unidirectional Flushing Program?

• Creating a Model for Unidirectional Flushing.

• Unidirectional Flushing Model Utilized as an Efficient Tool for Operation & Maintenance of a Water System.

Overview

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• What is Unidirectional Flushing?

• Defined: •  Unidirectional - Moving, functioning, in single direction -

Other examples of objects moving, functioning in a single direction (HOPEFULLY):

What?

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•  Improve Hydraulics: •  Scour walls of pipe - remove sediment - controls

erosion

•  Improve Water Quality: •  Shear biofilm - improve residual - improve taste

Why?

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• Possible treatment inconsistencies at intake and plant.

• Cross-connection issues (illegal taps, non-functioning BFP’s, etc.)

• Water main/infrastructure leaks.

• Water main breaks.

Potable Water is Not Sterile

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•  How complex is the water system?

•  Type of modeling software available or that is compatible with current hydraulic modeling software.

•  What are limits of existing hydraulic model (accuracy)?

•  How reliable is the current hydraulic model (PRV’s, Altitude Valves, Pumps on or off)?

Thoughts on Creating a Model for Unidirectional Flushing

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•  Bentley •  SELECT – includes flushing simulation module for WaterCAD

and WaterGEMS.

•  Innovyze •  InfoWater, InfoWorks, H2OMap, etc. •  InfoWater UDF add-on software (more extensive and user

friendly), InfoWorks WS has built-in UDF function.

•  Infrastructure Management System (IMS) •  By HURCO, not modeling software. •  Maintenance program for valve & hydrant exercising, fire flow

testing, flushing/UDF, and C-factor testing.

•  Manual Method •  For less complex water systems.

Unidirectional Flushing Software

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If current hydraulic model is deemed reliable:

•  Verify Model Calibration.

•  Identify Water Quality Problem Areas.

•  Verify Existing Structures (hydrants).

•  Identify Clean Water Sources.

•  Determine how Flush Zones will be delineated (with realistic flushing goals and capabilities of maintenance personnel and equipment).

Creating a Model for Unidirectional Flushing (cont’d)

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• Utilized InfoWater UDF add-on software.

•  Size: The water distribution system serves over 65,000 people daily.

•  Primary physical features included in UDF program: •  Water mains 6-inches and larger. •  Three (3) booster pump stations. •  Seven (7) storage tanks (ground and elevated). •  Twelve (12) Flush Zones. •  Approximately 870,000 linear feet of pipe to be flushed.

Case Study: Complex Water Distribution System in North Carolina

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Overall Water Distribution System – Clean Water Sources

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High  Pressure  Zone  

• Tasks Include:

•  Flush Zone (FZ) Delineation.

•  Map preparation to determine basis for labeling/identification and pipe sizes from valves and hydrants for Unidirectional Flushing Model.

•  Identification of loops – determine isolation valves to be closed and hydrants to be open for routine flushing exercises.

•  Development of flushing program. • What is the intent/goal?

Unidirectional Flushing Model

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Identified Flush Zones

11  1  2  3  

4  5  

6  

7  8  

9  10  

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• Flush Sequences: •  Each Flush Zone has a target of 40 to 100 Flush

Sequences, to optimize field operations. •  Must start with clean water source, or previously

flushed pipe. •  Target velocity of 3 to 10 feet per second. •  Must maintain minimum pressure of 20 PSI. •  Must use one fire hydrant to flush, or a maximum of

two hydrants. •  Target of 1,200 linear feet of pipe per flush, max. of

2,500 linear feet in each sequence.

Unidirectional Flushing Model

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• Factors to consider when determining Flush Zones and Flush Sequences:

•  What are the goals of flushing? •  Characteristics of Flush Zones (neighborhoods, work

week, pressure zones). •  Sensitive Areas. •  Large Users. •  Water Quality and Low Pressure Issues. •  Valves Available. •  Fire Hydrants/Blowoffs Available.

Unidirectional Flushing Model

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Flush Zone 1 – “Red” Sequence Area

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Field Journal – Flush Sequence 1

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Field Journal – Flush Sequence 2

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Field Journal – Flush Sequence 3

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Field Journal – Flush Sequence 4

Top of generated Field Journal shows:

•  Current Flush Sequence highlighted orange

•  Previous Flush Sequence highlighted green

•  Valves to close (red circle and X)

•  Valves to open (green circle and X)

•  Hydrant to flush (highlighted green)

Map can also show pipe diameter, velocity through each pipe section, name of each valve operated, and name of hydrant flushed.

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UDF Field Journal Flow Data

Bottom of generated “Field Journal” shows: •  Water lines to flush •  Valves to close •  Velocity •  Time for flushing •  Volume

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• Aids in providing: •  Utilized with current flushing program to maintain

water quality standards (Improve taste and residuals).

•  Provides maps and records of each loop to aid in a flushing program (Valve, water main closures, etc.).

Unidirectional Flushing Model

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The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again.

The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again.

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• Helps identify: •  Expected travel paths of water through the water

distribution system (controlling direction of flow). •  Required volumes to be flushed on the ground.

• Be aware of water volume to be flushed/surroundings.

Unidirectional Flushing Model

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•  Hydrant Flushing Lesson Learned in Alabama

Be Aware of Surroundings

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One Mad School Teacher!

     Be  Aware  of  Where  Flow  will  Go!!  

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Unidirectional Flushing Model is a Tool to Enhance O&M

•  Used to educate customers.

•  Create Standard Operating Procedure (SOP) for UDF Program.

•  Can be utilized with valve turning program.

•  Can be utilized with hydrant maintenance program.

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• Unidirectional Flushing Model can be an important O&M tool for water systems.

• Unidirectional Flushing: • Water efficient. • Better scouring of pipes. • Reduces bacterial growth. • Controls erosion. • Aids in identifying repairs • Improves water quality.

Conclusion

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Mr. Brannon Richards, PE (Old North Utility Services)

Mr. Jamie Gregg, PE, LEED AP BD+C (Dewberry Engineers Inc.)

Acknowledgements

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Questions?

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