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AWWA Webinar Program: Hydraulic Modeling of Unidirectional Flushing (UDF) – American Water Case StudiesThursday, April 21, 2016

Copyright © 2009 Bentley Systems Incorporated

Modeling Water Distribution System Flushing

Tom Walski, Ph.D., P.E.

James Chelius, P.E. and Jian Yang, Ph.D., P.E.

2 | WWW.BENTLEY.COM | © 2013 Bentley Systems, Incorporated

Moderator

Keith Raymond

Marketing Manager

Bentley Systems, Inc.

Keith Raymond is the marketing manager for Bentley

Geospatial products. Previously in product management for

geospatial and foundation application, Keith has been with

Bentley for more than 20 years.




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Ask the Experts

Submit questions any time throughout this broadcast by using the

question pane at the lower right of your screen.

Tom Walski

Senior Product Manager


James Chelius

Director, Engineering

Asset Planning

American Water

Jian Yang

Senior Planning Manager

American Water




• Purpose of flushing

• Types of flushing

• Case Study

• Flushing tips

• Steps/terminology in WaterGEMS

Overview


• Scour deposits and films

• Rapidly improve water quality in area– Low Chlorine

– Taste and Odor

• Respond to complaints– Turbidity

– Taste and Odor

• Test hydrant operation

Purposes of Flushing




• Conventional– Open hydrants one at a time

– No valve operation

• Uni-directional (UDF)– Close valves to direct flow

– May use multiple hydrants

– Improves/controls scouring velocity

– Several steps to set up

• Can base on shear stress = γSR (preferred) or velocity

Types of Flushing


American Water Presentation



Hydraulic Modeling of Unidirectional Flushing

(UDF): American Water Case Studies

James Chelius, P.E. and Jian Yang, Ph.D., P.E.

American Water – Corporate Engineering

April 21, 2016

2016 AWWA Bentley Live Webinar

American Water is the largest water

and wastewater services provider in

North America, headquartered in

Voorhees, NJ.

American Water provide services to

approximately 15 million people in

more than 1,600 communities in 47

states and in Manitoba and Ontario,

Canada; and employs nearly 6,800

water professionals.

American Water owns or operates

300+ drinking water systems and

200+ wastewater facilities.

We treat and deliver over a billion

gallons of water daily

The company conducts over one

million water quality tests each year

for over 100 regulated parameters,

and up to 50 types of water-related

tests each day.



13

• Key rules of flushing

• Hydraulic modeling of UDF case studies

• Summary – cost/benefits, and key metrics

Presentation Outline

1414

Key Rules of Flushing

1. Ensure adequate pressure (e.g. >20 psi) to protect

public health Most state rules require minimum 20 psi under all flow conditions

No specifics where to monitor and duration, is <20psi for a second OK?

How to ensure – field monitoring and hydraulic modeling

2. Ensure adequate flushing velocity (e.g. >5 fps for UDF)

Ellison et al., 2003, Investigation of Pipe Cleaning Methods, AWWA Research Foundation, Denver CO..



15

1. Ensure 20 psi - Potential Contamination near DS

15

Overall 56% (18/32) of samples near water pipes were positive for viruses:

enteroviruses, Norwalk, and Hepatitis A virus (Karim et al. 2003, JAWWA)

Sewage Pathogen Levels

• Meta-analysis of occurrence levels in

literature

Pathogens/Indicator Geometric

Mean Q0.025 Median Q0.0975

Cryptosporidium 2.58 101

2.03 10-3

2.84 101

2.41 105

E coli O157:H7 3.19 103

1.57 10-7

5.21 103

2.47 1011

Norovirus 1.59 104

1.98 10-4

2.38 104

1.39 1010

Cryptosporidium

N=14

LeChevallier et al., 2012, Effective microbial control strategies for main breaks and depressurization. Project #4307, Water Research Foundation,

Denver CO.

1616

2. Ensure Flushing Velocity >3ft/s, Ideally >5ft/s

• Flushing 1 kg of sand of difference sizes, weigh how much left

Sand tested (conservative compared with peat/clay sediments);

Threshold velocities (2.5-3.0 ft/sec) and removals (2.5-3.0 log);

E.g., 2-log removal = 99% removal

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0.0 1.0 2.0 3.0 4.0 5.0 6.0

Log

rem

ova

l

Flushing Velocity (feet/sec)

Flushing Sand Log Removal

2-4 mm Sand

0.5-2 mm Sand

0.25-0.5 mm Sand

Below a threshold

velocity, flushing cannot

remove the sediments.

LeChevallier et al., 2012, Effective microbial control strategies for main breaks and

depressurization. Project #4307, Water Research Foundation, Denver CO.



1717

When Two Rules Conflicting:

1. Never compromise pressure.

If needed, compromise

flushing velocity.

2. If not monitored in field, the

impact of the flushing can be

assessed by hydraulic

modeling.

Use hydraulic modeling to reduce

needs of field monitoring.

Pressure 20 PSI

Velocity 5 FPS

18



• Summary – cost/benefits, and key metrics




1919

Tools needed for UDF planning and modeling

• Data requirements

• Calibrated hydraulic model, accurate pipe/hydrant/valve maps, existing

flushing program, historical customer complaints, etc.

• Software

• Hydraulic modeling software (WaterGems used in the case studies)

• ArcGIS

• Microsoft Office Excel and Adobe Acrobat PDF Writer

• Iterative 3-step process: modeling, field logging, and mapping;

• Recommended Reading List

• WaterRF #2668 “Investigation of Pipe Cleaning Methods”

• WaterRF #2606 “Establishing Site-Specific Flushing Velocities”

• AWWA C-651 Disinfecting Water Mains

2020

How a UDF program looks like?

• Consists of flushing groups (or areas) and sequences (or events)

• Two case studies used to demo the product and key considerations

Sys A (~100 miles pipe), system-wide UDF;

Sys B (~1,600 miles pipe), localized UDF

• Maintain a clean water source (or flushed main) and the

strongest possible network behind

Source

of Water

Land marks and

background

street map are

removed for

security

purpose.



2121

How a UDF program looks like?

• Flushing group/area consists of sequences/events

• Each sequence: one page of a field map (even) and one page of field

log (odd)

Each group or

area has about

1-day worth of

flushing.

2222

UDF Field Book – Flushing Map

Land marks and

background street map

are removed for

security purpose.

Valve/Hydrant

Operations

Potential Low

Pressure



2323

UDF Field Book Should Show

• Hydrants to be flowed

• Valves to be open and closed

• Recommended duration and volume

• Reminder to open valves when done

• Place to record observations

2424

Case Study System A

• 38 areas, 431 sequences, and ~100 miles pipe to be flushed

• Flushing volume estimated 3.2 MG, or $2,000 production cost if

assuming $600/MG

UDF

Summary

Flushing

Group/Area #

Number of

Flushing Sequence

Flushing Pipe

Length (mile)

Estimated Flushing

Volume (kGal)

Estimated Flushing

Time (minutes)

1 11 2.6 74 65

2 7 3.1 166 90

3 12 4.0 136 115

4 13 3.8 217 89

5 10 3.2 157 85

6 12 3.3 71 100

7 6 2.0 32 73

8 8 2.3 27 60

9 15 3.6 159 87

10 6 2.1 76 39

11 13 2.9 91 88

12 9 1.6 29 73

13 15 3.2 79 84

14 11 2.9 103 75

15 12 2.4 70 86

16 5 0.7 15 21

17 16 2.8 34 106

18 13 3.3 27 98

19 11 2.0 45 51

20 12 2.8 91 63

21 11 1.5 34 30

22 12 1.5 49 36

23 17 2.2 75 54

24 9 1.9 89 51

25 10 2.6 81 80

26 14 2.7 49 89

27 14 2.1 70 53

28 10 2.5 102 71

29 10 3.1 153 79

30 8 3.3 133 61

31 8 5.4 187 101

32 19 2.4 81 40

33 17 4.1 91 80

34 14 1.5 70 39

35 9 2.7 77 73

36 10 2.0 52 61

37 10 2.3 68 51

38 12 2.7 53 54

Average 11 2.7 85 70

SUM 431 101 3,213 2,650

Flushing

Group/Area #

Number of

Flushing Sequence

Flushing Pipe

Length (mile)

Estimated Flushing

Volume (kGal)

Estimated Flushing

Time (minutes)

1 11 2.6 74 65

2 7 3.1 166 90

3 12 4.0 136 115

4 13 3.8 217 89

5 10 3.2 157 85

6 12 3.3 71 100

7 6 2.0 32 73

8 8 2.3 27 60

9 15 3.6 159 87

10 6 2.1 76 39

11 13 2.9 91 88

12 9 1.6 29 73

13 15 3.2 79 84

14 11 2.9 103 75

15 12 2.4 70 86

16 5 0.7 15 21

17 16 2.8 34 106

18 13 3.3 27 98

19 11 2.0 45 51

20 12 2.8 91 63

21 11 1.5 34 30

22 12 1.5 49 36

23 17 2.2 75 54

24 9 1.9 89 51

25 10 2.6 81 80

26 14 2.7 49 89

27 14 2.1 70 53

28 10 2.5 102 71

29 10 3.1 153 79

30 8 3.3 133 61

31 8 5.4 187 101

32 19 2.4 81 40

33 17 4.1 91 80

34 14 1.5 70 39

35 9 2.7 77 73

36 10 2.0 52 61

37 10 2.3 68 51

38 12 2.7 53 54

Average 11 2.7 85 70

SUM 431 101 3,213 2,650



2525

Considerations during UDF Planning (1)

1. Localized or system-wide UDF: System B – prioritized by water

quality analysis (See example below)

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LEGEND

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“Hot Spot” Analysis

2626


1. System A: System-wide UDF target to address water quality

complaints and flush out loose deposits



2727


2. Critical – no below 20 psi.

• Exceptions (e.g. near a tank)

• Compromise velocity (<5 feet/sec) if necessary.

3. Field log – list open valves first, then close valves.

• To prevent cutting off water supply to customers

• Keep trace closed valves, none at finishing each group

4. Flushing map - Do not clutter. Hydrant/valve numbers are

needed

• Include street names

• Agree by operators before going forward. QA/QC review.

2828


5. Avoid each flushing length too short/long (~1,600 feet); Flushing

time < 5-10 minutes;

6. Emitter coefficient (K value) – determined from fire flow field tests

• Textbook values may be high

• Reduce K value to simulate throttling the hydrant

7. Group sequences – assuming 15 percent of flush time, and a 7-8

hour day (60 – 70 minutes of flushing per group);

8. Avoid flushing from small to large diameter



29



• Summary – implementation, cost/benefits, and key metrics


3030

To Implement a UDF program

• Labor: a crew of 2-3 operators

• No special equipment/materials needed: pressure gauges,

valve wrenches, diffuser, de-chlorination tablets/mats, etc.

• Minimum water usage: 1-2 pipe volumes

E.g. System A pipe volume ~1.8 MG; UDF volume ~3.2 MG

• Daily production: 2-3 miles (e.g. 100 miles for 40 working days)

• Expected life of benefits: 6 months to 3 yearsFriedman M. 2012, Best Practices Cleaning Mains: Clean, Pig, or Dig.

Opflow (10), American Water Works Association.



3131

Other DS improvements identified during UDF

planning

• 6-inch under-sized pipes by tank

To upsize to 12-inch or larger

• 2-inch DS looping

To upsize to 8-inch

• Others

Lack of isolation valves and

hydrants, etc.

LEGEND

4-INCH OR LESS

6-INCH

8-INCH

10-INCH

12-INCH

16-24 -INCH

Some distribution improvements

(typically identified during master

planning) may be identified during

UDF planning.

3232

To Implement a UDF program

• Discharge/sediment disposal and de-chlorination

Watch out where effluent goes, sandbag if needed

States may have de-chlorination requirements

• Flushing may be perceived as wasteful

System A UDF uses 3.2 MG, estimated ~2% of its NRW;

If really an issue, consider other methods, e.g. pigging/swabbing,

No-Discharge (NO-DES) UDF pilot tested in System B in 2013



3333

UDF Field Guidelines (1)

• Coordinate the flushing program with other

departments

• Prevent pressures below 20 psi. Pressure

monitoring to be conducted for high risk flushing

• Flushing progress from the source outward

towards the periphery.

3434

UDF Field Guidelines (2)

• Where valve closures isolate pumping, pumps should be

turned off

• Review the order of closing and opening valves to prevent

loss of service to customers

• Some UDF sequences have to be improvised in the field

• Keep fire department informed

• Night time flushing if public perception is an issue



3535

Summary

UDF field implementation

2-3 miles per day

2 pipe volumes

A crew of 2-3 operators

Planning level cost estimate (e.g. System A UDF cost estimate of

~$100K/100mile pipe including planning and implementation)

UDF planning

System-wide or specific areas

Literature optimum flushing sequence length between 1,500-5,000 ft

The shorter the sequence, the higher the velocity (minimum 5 fps)

For an experienced engineer/modeler, ~200 hours to plan a 100-mile

UDF program

36

Questions??

James Chelius, P.E.

Director of Engineering-Asset Planning

American Water

1025 Laurel Oak Road

Voorhees, NJ 08043

phone: (856) 727-6115

fax: (856) 727-6169

e-mail: [email protected]

Jian Yang, Ph.D., P.E.

Senior Planning Engineer

American Water Corporate Engineering

phone: (856) 727-6168

e-mail: [email protected]

Contact Information

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Calibrated

Model

Start Flushing

Manager

Create Study

Create Area/

Set up Options

Create Events

Compute Study,

Area or Event

View Flushing

Results BrowserView Flushing

Area Report

Create

Operator Report

Flushing Steps


• Event– Conventional

– Unidirectional (UDF)

• Area

• Study

• Pipe Run

• Pipe Set/Nodes of Interest

• Scenarios– Representative

– Output

WaterGEMS Flushing Terminology




Flushing Area

Control

output

Set targets

for study


Events in Left Pane

Closed valves

Pipe flow path

Flowing hydrant

Flushing location name




Results from Browser


• Customizable report

• Has pipe run information

Flushing Results Browser - Unidirectional

UDF pipe details





• Set up good color coding

• Color code by max velocity achieved for overall view

• For events, color code – Pipes by velocity (use gray for < 0.01 to show closed)

– Hydrants/junctions by demand

• Roll through events, are they effective?

Flushing Results Browser Tips




WaterGEMS Demo


• Forum http://communities.bentley.com/products/hydraulics___hydrology/f/5925

• AWWA—ACE/WIC

• Water Research Foundation Reports

• [email protected]

Other resources




Take Home Lessons

• Why are we flushing?

• Model gives you x-ray vision

• Water movement not always intuitive

• Sometimes UDF helps


The End

Questions?




Ask the Experts

Submit questions any time throughout this broadcast by using the

question pane at the lower right of your screen.

Tom Walski

Senior Product Manager


James Chelius

Director, Engineering

Asset Planning

American Water

Jian Yang

Senior Planning Manager

American Water


Thank You!




Presenter Biography

Mr. Chelius is director of Engineering Asset Planning for American Water, the largest investor-owned US

water/wastewater utility. He directs American Water’s comprehensive planning program that delivers strategic

engineering masterplans and hydraulic models for the company's 1,600 communities served—plans and

models that assess supply, treatment, and distribution/collection system needs that identify infrastructure

improvement projects forming the foundation of the company’s $1 billion/year capital investment program. Mr.

Chelius has more than 30 years’ experience in the water utility field. He holds a BS in General Sciences and an

MS in Water Resources Engineering from Villanova University. He is a registered professional engineer in

Pennsylvania.

Dr. Yang is a registered professional engineer with more than 17 years of experience in research and consulting

in water quality monitoring and management, water chemistry, hydraulic and water quality modeling, statistical

modeling, and risk analysis. He holds an MS degree in computer science and a PhD in environmental

engineering from the University of Wisconsin at Madison.

Tom Walski has 40 years of experience in water and wastewater design and operation. He is currently senior

product manager for Bentley Systems and has previously served as civil engineer for the Army Corps of

Engineers, distribution system manager for the City of Austin, Tex., executive director the Wyoming Valley

Sanitary Authority, and engineering manager for Pennsylvania American Water. He has written several books

and hundreds of journal and conference papers on many aspects of water distribution systems.

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