Pressure Management: Baseline to Optimized Utility Case Studies … › ncer › events › calendar...

Pressure Management: Baseline to Optimized

Utility Case Studies

Mark W. LeChevallier,

Minhua Xu, Jian Yang, and David Hughes

2 2

Importance of Maintaining Adequate Pressure

Fundamental to providing safe drinking water Loss of pressure can allow intrusion of

contaminants in to the distribution system

Fluctuations in pressure can affect the physical integrity of pipes Pressure spikes can result in leaks,

main breaks, and premature failure

Pressure management can save money Reduced energy costs, system maintenance, leakage,

customer complaints, water quality problems

Physical

Integrity

Hydraulic

Integrity

Water

Quality

Integrity

National Research Council. 2006. Drinking Water Distribution Systems Assessing and

Reducing Risks. National Academy of Science.

@ Copyright 2013 Water Research Foundation

3

Pressure Management – Optimized Distribution Systems

Distribution System Optimization consists of thee focus areas: Disinfectant residual, Pressure management, Main breaks

Impact most of the 19 categories examined

Optimized Pressure Management Goals >0 psi during emergencies

>20 psi under max day and fire flow conditions

>35 psi under normal conditions

<100 psi under normal conditions

Within +/- 10 psi of average, >95% of the time

Optimized Pressure Monitoring A minimum of two pressure recorders in each pressure zone

placed at the minimum and maximum pressure locations

Friedman et al., 2010. Criteria for Optimized Distribution Systems. Water Research

Foundation, Denver CO.

Disinfectant

Residual

Pressure

Management

Main

Breaks

Optimized System


4 4

#4321 Pressure Management: Baseline to Optimized

Task 1: Conduct a utility survey

Determine prevalence of distribution system attributes leading

to undesirable pressure variations

Task 2: Conduct baseline and optimized pressure monitoring

Conduct 12 month baseline (existing) and optimized pressure

monitoring at 24 participating systems

Task 3: Integrate pressure management with other distribution

system activities

Demonstrate how the cost of an optimized pressure management program can

be offset by cost reductions in other system operations (backflow sensing

metering, water quality, model optimization, main break/repair activities,

customer complaints, etc)

Task 4: Develop best practice guidance

Strong utility focus on best practices and strategies for

pressure management.


5

Task 1: Utility Survey

Zoomerang online survey

Distributed to ~330 water utilities (36 responded)

One third each: small, medium, and large systems

Surface/Groundwater/Both: 47%, 19%, and 33%

5

Minimum Median Maximum

# of service connections 414 20,000 475,371

Total population 1,040 77,600 2,500,000

Retail service area (miles2) <1 28 1,300

Total lengths of water mains 16 300 5,500

Average daily delivery (MGD) 0.2 11 245


http://www.zoomerang.com/

6 6

Survey – Low Pressure Criteria/Goal

Most States have some requirement for maintenance of pressure

6

During Fire Flow

Pressure

(psi)

Percentage

(%)

0 2.7

20 95.0

30 2.7

Pressure

(psi)

Percentage

(%)

0 21.0

0 to 20 2.6

20 68.0

30 2.6

No

requirement 5.3

During Emergency Conditions

Most have a minimum requirement of at least 20 psi

Highly variable after this point

6 @ Copyright 2013 Water Research Foundation

7

Survey – High Pressure Criteria/Goal

0%

10%

20%

30%

40%

50%

60%

70%

No

requirement

65 85 95 110 125 150 175 200 320

Allowable Maximum High Pressure Maintained in Distribution System (psi)

Pe

rce

nta

ge

- No requirement or variable (65-320 psi)

7


8

0%

5%

10%

15%

20%

25%

30%

Wat

er m

eter

Fire h

ydra

nt

Pum

p st

atio

n

Sto

rage

tank

PRV s

tatio

n

Sys

tem

inte

rcon

nect

ion

Wat

er p

rodu

ctio

n fa

cility

Oth

er

Routine Pressure Monitoring Locations

Pe

rce

nta

ge

13%--Targeted locations

87% --Convenient locations

8

Survey – Pressure Monitoring

Pressure monitoring locations


9


Smallest pressure zone – Are the routine monitors

permanently installed ?

17% 11%

17%

11% 43%

67% 78%

57%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

1-6 7-11 >11

# of Pressure Zones

Perc

en

tag

e

Yes

No

Some are permanent, but some are not


10


0%

5%

10%

15%

20%

25%

30%

35%

Never 1-6 Months Annually 3 - 5 years As needed

Pressure Transducer Calibration Frequency

Pe

rce

nta

ge

10

What? You’re supposed to calibrate these things?

Monitor calibration


11


0%

5%

10%

15%

20%

25%

30%

35%

Seconds Minutes 1-5 Minutes 15 Minutes 1-12 Hours Day Other

Data Recording Frequency for Permanently Installed Pressure Monitors

Pe

rce

nta

ge

11

Monitor recording


12

Pressure monitoring data in 1-hour interval

0

10

20

30

40

50

60

70

80

90

Pre

ssu

re (

psi

)

Fire Station #38 - Low Pressure Avg

Fire Station #16 - High Pressure Avg


13 13

Pressure monitoring data in 2-minute intervals

0

10

20

30

40

50

60

70

80

90

100

Pre

ssure

(psi

)

Fire Station #38 - Low Pressure MaxFire Station #38 - Low Pressure MinFire Station #16 - High Pressure MaxFire Station #16 - High Pressure Min

Much more

variation


14

Task 2: Optimized and baseline monitoring

Approach

Select a study pressure zone

Choose two optimized monitoring locations

Conduct baseline and optimized pressure monitoring over 12 months

Optimized pressure monitoring

A minimum of two pressure loggers at the min/max pressure locations

(WaterRF #4109)

Baseline pressure monitoring

Existing pressure monitoring (e.g. SCADA pressure monitoring at pump

stations or PRV stations)

A “baseline” monitoring may be already “optimized” (e.g., lowest pressure

at monitored tank, highest pressure at monitored pump or PRV station)


15

Optimized monitoring location selection

15

• Use hydraulic model, historical pressure data, operational

experience, and/or customer complaints

Area with min/max pressures or min/max elevations

Far away from tanks/pumps

Hydrants

Alternative locations

not subject to freezing

• Pressure recording rate

No less than hourly data

Most in minutes interval

Impulse reading


16

CO-1

Optimized Low

Monitoring

Location

Optimized High

Monitoring

Location

System has

6 pressure

monitors in

test zone


CO-1 – Importance of monitor placement

Conventional monitors still do not capture the full range of

pressures within the system.


Impact of Monitoring Location: VA-1

Optimized low

pressure location Conventional

Monitoring

(SCADA) at

Tank 591

Optimized high

pressure location


Impact of Monitoring Location: VA-1

Low pressure events captured at optimized low pressure monitoring

location but missed by conventional monitor. Pressure in system is

much higher than anticipated


20

CA-1

Optimized

Low Pressure

Monitoring

Optimized High

Pressure

Monitoring


0

20

40

60

80

100

120

140

160

1/31/12 0:00 1/31/12 4:48 1/31/12 9:36 1/31/12 14:24 1/31/12 19:12 2/1/12 0:00

Pre

ssu

re (p

si)

Conventional Monitoring - Verde Del Arroyd

CA-1 – Detection of a Low Pressure Event

Jan. 31, 2012: Pressures dropped due to a break on a 4" main;

Monitoring of tank levels not as sensitive as pressure monitoring

0

20

40

60

80

100

120

140

160

1/31/12 0:00 1/31/12 4:48 1/31/12 9:36 1/31/12 14:24 1/31/12 19:12 2/1/12 0:00

Pre

ssu

re (p

si)

Conventional Monitoring - Toro Treatment

Conventional Monitoring - Verde Del Arroyd


22

TX-1

Conventional

Monitoring (SCADA)

at Tanks


Impact of Monitoring Location: TX-1

Conventional monitor shows average 55 psi, while optimized

monitoring ranges from 40 to 120 psi


24

Task 3: Integrate pressure management with other

distribution system activities

System specific

Purpose

Estimate benefits of optimized pressure management

Examples

Link optimized pressure monitors to SCADA for real-time monitoring

Collect case study and operational experiences

Assist hydraulic model calibration

Conduct spatial analysis of pressure, main breaks, backflow events, etc.

Correlate low pressures and water quality

Evaluate water distribution energy efficiency


25

Change pump settings: WI-1

Conventional

Monitoring

(SCADA) at

pump station

Optimized low

pressure location

Optimized high

pressure location

25

Conventional monitor at pump

discharge point shows >145 psi, while

optimized monitoring locations are 60-

80 psi.



• Existing pressure met all pressure criteria

• Propose to reduce the VFD pump setting by 7 psi

(~10% pressure reduction)

Expected benefits: 1. Cost minimal to implement the pressure reduction;

2. Reduce water loss by ~10-15%;

3. Reduce main break frequency;

4. Reduce some pumping energy usage.

Potential concerns: 1. Customers sensitive to pressure;

2. Water usage and revenue might go down;

3. This district had minimum water loss and pipe break

frequencies, i.e. no need for pressure reduction.

Reduce 7 psi

OTHER ZONE

SELECTED ZONE

FOR PRESSURE MONITORING

HGL = 1,347 FT

Variable Speed Drive

Setting – 150 psi


Philadelphia Water Department – DMA5

Attributes

Length of Pipeline (all

metallic), miles

12.6

Average age of Pipelines, years 52.6

Number of Fire Hydrants 117

Number of Valves 382

Number of Customer Service

Connections

2,261

Number of separate Fire

Connections to buildings

17

Highest Elevation, ft (Critical

Point)

310 (Magnolia

St & Washington

La)

Average Zone Pressure site

elevation, ft (AZP)

254 (Mechanic

St & Morton St)

Lowest Elevation, ft 180 (Lincoln Dr

& Morris St)

Provided by George Kunkel, P.E.

Philadelphia Water Department

Pressure and Water Loss (Findings from

Philadelphia’s First Permanent District Metered Area) Primary Supply

Feed

Emergency

Standby Feed

Figure 3

Philadelphia Water Department - DMA5

Flow Modulated Supply Profile

60

65

70

75

80

85

90

95

100

0 0.5 1 1.5 2 2.5 3

Flow, Mgd

Pre

ssur

e, P

si

Profile Line

Min Flow 0.2 mgd

Max Flow 1.4 mgd

Flow Modulated

Pressure Reduction


DMA5: advanced pressure management turned

the water pressure profile “upside down”

0

20

40

60

80

100

0.0

100.0

200.0

300.0

400.0

500.0

600.0

700.0

800.0

Ave

rage

Pre

ssu

re D

MA

5 [P

SI]

Bac

kgro

und

Leak

age

[gpm

]

Time

DMA5 - Reduction in Background Leakage between April 2005 and December 2009

Savings in Background Leakage Between April 2005 and December 2009Background Leakage Component from April 5th 2005 MNF Analysis [gpm]Background Leakage Component from December 15th 2009 MNF Analysis [gpm]Average DMA5 pressure from April 5th 2005 MNF Analysis [PSI]Average DMA5 pressure from December 15th 2009 MNF Analysis [PSI]

Provided by George Kunkel, P.E. (Philadelphia Water Department)

Cost/Benefit analysis

Payback period of 6.4 years

Net Present Value (NPV) Analysis

Present worth of $112,258

Internal Rate of Return

Rate of return of 9% realized


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30 30

Pressure and Main Breaks

Case Study TN 1 – High Pressure Locations

Legend

Pressure

Less than 100 psi

100 - 200 psi

200 - 230 psi

UT TANK

[Ú PUMP

6 INCH OR LESS

8 -10 INCH

12 INCH OR MORE

Pressure Zone Boundary 30

What case studies show?

Optimized low pressure

location (~40 psi)

Optimized high pressure

location (~220 psi)


High Pressure

31 31

Spatial Analysis of Pressure and Main Breaks

31

Legend

# MAIN BREAKS

Pipe Material

CI; CI/RH; GV; GV/RH

Other materials

Pressure

Less than 100 psi

100 - 200 psi

200 - 230 psi

UT TANK

[Ú PUMP

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UT

UT

UT

UT

UT

UT

==> Main Breaks (or Main Break Hot-Spots)

High Pressure + Pipe Diameter + Pipe Material


Predicted Main Break Rate (R2=41%)

32 32

How Much High Pressure Contributes to Main Breaks?

32

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UT y = 0.0167x + 0.3669R² = 0.9938

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0 20 40 60 80 100 120 140 160

Pre

ssure

Im

pact F

acto

r (#

of bre

aks/

psi

)

Main Break Rate (#/yr/100 mile pipe)

Psi Impact Factor (#breaks/psi)Linear (Psi Impact Factor (#breaks/psi))

System average of 39 breaks/year/100 miles

Minor contribution from high pressures (mainly small diameter & cast iron pipes)

However, higher impact at higher main break rate (+3 breaks/10 psi @ zero

breaks/yr/100 mi; +10 breaks/10 psi @ 40 breaks/yr/100 mi)

Weather, soil conditions, etc. not modeled

Legend

Pressure Zone Boundary

UT TANK

[Ú PUMP

Pipefishnet_w_pipelen_05_Gwr

Predicted

-1.897922 - 1.312926

1.312927 - 3.192876

3.192877 - 5.435046

5.435047 - 7.908231

7.908232 - 10.754786

10.754787 - 14.554317

14.554318 - 30.968855


33

Pressure and Insurance Claim Cost

Case Study – PA 1

Reduced peak pressures

from 179 psi to 145 psi

60% reduction in main breaks

30% reduction in non revenue

water loss

$1.4 million per year cost savings $0

$500,000

$1,000,000

$1,500,000

$2,000,000

$2,500,000

2003 2004 2005*

Year

An

nu

al C

os

t ($

)

Paving Labor & Mat* Claims

Overlay system pressure

contours

Insurance claims due to

main breaks

Size of the circle related to

cost of the claim


Pressure = Energy

Large area of water supplied at high pressure

System topography allowed

To create a new pressure gradient/zone

34 34

Pressure and Energy Analysis (Case Study – AZ 1)

34

Cost & Benefit

Capital, O&M costs, etc.

Reduce main breaks and

NRW

Reduce energy

consumption

New Boundary

(4 Alternatives)

GROUND

RESERVOIR

SELECTED ZONE FOR PRESSURE MONITORING

ADD = 2.0 MGD

HGL = 238-270 FT

3Q

254 FT

224 FT

3.0 MG

PS 01

#1 - 2,100 GPM @ 160 FT

#2 - 2,100 GPM @ 160 FT

#3 - 1,200 GPM @ 160 FT

#4 - 1,200 GPM @ 160 FT

#1

#2

#3

#4

SET AT 143.5 PSI


35 35

Pressure and Energy (Case Study – AZ 1)

35

Reduced Pressure by ~40 psi and Less Energy Usage New PS & Boundary

[Ú

Description Energy usage (kWh/MG) Energy cost ($/YR)

Baseline Average day demand (ADD) 3,344 $1.2 M

Alt01 ADD with a VFD at the treatment plant 2,000 $0.69 M

Alt02 ADD after pressure zone realign with no new pump station

added 3,344

$1.2 M

Alt03 ADD after pressure zone realign 3,523 $1.2 M

Alt04 ADD after pressure zone realign and a VFD at the

treatment plant 1,404 $0.49 M


36 36

The Future of Pressure Management

Some states are placing greater emphasis on requirements for pressure management

The USEPA Research & Information Collection Partnership includes emphasis on pressure management:

Survey of Distribution System Pressure Management Practices

Characterize Propagation of Pressure Events through Water Distribution Systems to Improve Pressure Management Approaches

Develop Strategies to Diagnose and Monitor Pressure Fluctuations in Water Distribution Systems

Toolkit for Pressure Management

Partnership for Safe Water

Distribution System Optimization

www.awwa.org/Resources/PartnershipDistribution


37 37

Summary

Pressure management is fundamental to protecting public health,

maintaining infrastructure and effective utility management

Although pressure monitoring is required by regulations, implementation

varies across the inductry

Permanently installed monitors do not exist in all pressure zones

Routine pressure monitoring is mostly at convenient locations

Most pressure monitors either never calibrated or calibrated annually

Monitoring frequency will not capture short-term events

Negative pressure events may occur

Main breaks, power outages may occur routinely

Power outages may cause regional depressurization events

Pressure management has been identified by USEPA as an important topic

for distribution system research

A program for optimized distribution systems, including pressure

management has been formulated by the Partnership Program


38

Acknowledgements

• Funding provided by Water Research Foundation and in-kind

contributions from 30 water utilities; American Water

• Frank Blaha (Water Research Foundation) and PAC:

Bill Soucie

Graham MacDonald

Steve Rupar

• Technical Advisors:

Dave Hughes and Norm Ansell (AW)

George Kunkel (PWD)

Mike Hotaling (NNW)

• Water utility participants (36) of this survey


39 39

Questions??

Mark W. LeChevallier, Ph.D.

Director, Innovation & Environmental Stewardship

American Water

1025 Laurel Oak Road

Voorhees, NJ 08043

phone: (856) 346-8261

fax: (856) 782-3603

e-mail: [email protected]

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

Innovation & Environmental Stewardship

1025 Laurel Oak Road

Voorhees, NJ 08043 USA

phone: (856) 309-4858

e-mail: [email protected]

Contact Information


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