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Washington APWA Conference

Spokane, WA

Critical Analysis – Assessing

VulnerabilityOctober, 2016

Murray, Smith & Associates, Inc.

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Contents

• Overview/Purpose of Criticality Analysis

• Criticality Analysis

– Facility

– Pipe

– Valve

• Criticality in Design

• Summary

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Water System Resiliency

“Infrastructure resilience is the ability to

reduce the magnitude and/or duration

of disruptive events. The effectiveness of

a resilient infrastructure or enterprise

depends upon its ability to anticipate,

absorb, adapt to, and/or rapidly recover

from a potentially disruptive event.”-Dr. Heather Smith, Global Water Forum, 2012

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Purpose of Criticality Analysis

• Consequences of Failure

– Strength of the system with components off-line

– Impacts to pressure and supply

– Distribution network redundancy

• Valve Criticality and Redundancy

• Supply and boosting facility “firm” capacity and

connectivity

• Storage connectivity

• Prioritization of previously identified projects

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Two-part Approach

• Mass balance

– Treatment (Source)

– Pump station

– Typically assumes largest out of service

– Storage

• Hydraulic modeling

– The largest supply is not always the critical supply

– Pipe Criticality: Strength of the pipeline network

– Valve Criticality: Availability and redundancy of valves to

isolate breaks, or failed isolation valves

– Supply and facility criticality

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Mass Balance Approach

• Required in Master

Planning

– Treatment redundancy

– Well supply redundancy

– Booster station

redundancy

– Availability of storage

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Hydraulic Model Approach - Pipelines

• Pipe Criticality – the importance of any single pipe

segment in the network

– Closes each pipe in the system and evaluates the results

– Finds “Functional” dead-ends, needed looping

– Needed tie-ins

– Service to critical customers

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Hydraulic Model Approach - Valves

• Valve Criticality

– Evaluates consequences if a

valve fails to close

– Isolates each valve in the

system and reports number

of valves required, demand

isolated

– Indicates valve redundancy

– Indicates difficulty of

isolating a valve in the field

and the impact to pressure

and supply

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Criticality Process – Criticality Goals

• Identify level of desired resiliency

– Extent of evaluation

• Single component

• Entire facility

• Analysis of dead-ends

– Context of decision

• Age of facilities

• Capital project prioritization

• Operational flexibility Redundancy Cost

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Supply and Boosting Criticality

• Supply

– Treatment

– Boosting

– Well production

• Automatic on/of capability

– SCADA

– Standby Power

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Supply Criticality

• Firm capacity: largest pump out of service

– Booster station largest pump

– Largest well pump supply to a zone

• Typically a spreadsheet analysis

• Begin with lowest level firm capacity supply

• Determine if firm boosting capacity is adequate to deliver

supply

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Firm Capacity Analysis

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Well Requirements

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Supply and Storage Criticality

• Facilities Criticality

– Well supply redundancy

– Booster station redundancy

– Automatic on/off and backup power

– Storage

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Alternate Supply Analysis

RESERVOIR

100% FULL

(HOUR)

75% FULL

(HOUR)

50% FULL

(HOUR)

MIN FULL

(HOUR)

AWBREY 0 8 37 105

OUTBACK_1 0 1 6 128

OUTBACK_2 0 3 7 129

OUTBACK_3 0 5 7 108

OVERTURF_EAST 0 7 30 105

OVERTURF_WEST 0 8 31 105

PILOT_BUTTE_1 0 8 31 128

PILOT_BUTTE_2 0 7 32 129

PILOT_BUTTE_3 0 10 24 128

ROCK_BLUFF_1 0 128 NA 129

TOWER_ROCK 0 7 32 104

COLLEGE_1 0 7 104 128

COLLEGE_2 0 31 105 128

Timing of reservoir levels at 100%, 75%, 50%, & minimum

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Alternate Supply Analysis

TANK DRAWDOWN WITH REDUCED SUPPLY

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Alternate Supply Analysis

TANK DRAWDOWN WITH REDUCED SUPPLY & EMERGENCY INTERTIE

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Criticality - Storage

• Storage is required to provide supply and pressure under

high demand and emergency conditions

– Storage provides for systems in the event of emergencies through

the use of standby storage. Requirement often two days of average

demand

– Fire flow and equalization

– Often delivered to the network through a single pipeline

– Storage requirements may sometimes be reduced or offset by

additional supply

– Storage supply is linked with redundancy in distribution network

(critical pipe analysis)

– Evaluation of storage to serve system demands must also be

hydraulic (Can the needed rate of flow be delivered without

excessive head loss through the network)

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Hydraulic + Mass Balance - Well and Booster Stations

• Firm pumping capacity

– The largest pump out of service

– MDD for zones served by storage

– The greater of MDD + Fire or PHD

for closed zones

– Automatic on/off and standby

power

• Spatially critical supply facilities

– Network weakness connecting

two parts of a pressure zone

– Network weakness connecting

storage to demand

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Closed Zone (no reservoir)

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Closed Zone (no reservoir)

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Closed Zone (no reservoir)

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• Develop hydraulic performance criteria

– Identify the target demand scenario(s)

• Average day

• Maximum day

• Peak hour

• Fire flow

– Pressure criteria

• 20 to 30 psi

• Extent of pressure drop or disconnection

– Pressure loss: Service pressure drops below criteria limits

– Disconnection: The pipeline serves a networked area, and has no parallel.

Typically at pressure zone boundaries, or extremities of the system.

• Number of customers impacted

• Amount of demand

Criticality Process – Hydraulic Criteria

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• Number of valves required to isolate a failed valve

– Valve on distribution main

– Valve on transmission main

• Demand isolated by valve closure

• Impact of critical customer to isolate failed valve

Criticality Process – Valve Criteria

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Hydraulic Model Approach - Software

• OptiCritical - Optimatics

– EPA Net-based

• Protector and VCM extension - Innovyze

– InfoWater extensions, GIS-based

• WaterCAD/WaterGEMS - Bently

• Data Intensive

– Data requirements for hydraulic models

• Calibrated Model

• GIS data for the location of system valves

• GIS data for the location of critical customers

• Data Streamlining

– Skeletonizing or phased analysis for practical run-time

(roughly 20,000 pipes)

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Criticality Process – Model Development

• Develop a calibrated hydraulic model

• Skeletonize the model (as required)

– Pipe age, material, diameter

• Create criticality scenarios

– Target demands based on developed criteria

– Alternate supply options

– Identify available facilities

• Changes to model facilities and controls to enable automated control

flexibility

• Validate the skeletonized model (as required)

– Distribution of demand

– Zone isolation maintained

– Representative elevations retained (elevation of service meters)

– Intended operations of facilities and controls

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40,000 pipes

8,000 pipes

Streamline Data

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Modeling Criticality – Pipe Criticality

• Define location of critical customers

• Locate simple dead ends

• Group results

– Categorize: disconnection or low

pressure

– Group pipe segments in series with

similar hydraulic characteristics

• Rank the importance of critical pipe

groups

• Validate project criticality with full

model

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Pipe Criticality Results

Supply Cut Off

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Critical Pipeline Scoring

• Maximum Pressure Violation- worst case pressure loss

Scoring BasisCritical Pressure Loss

PipelineDisconnection Pipeline

Critical Customer Score

(number of critical customers

with criteria violation)

10 points per critical customer,

multiplied by the pressure

violation

N/A

General Customer Score

(customers with criteria

violation)

1 point per 100 equivalent

people, multiplied by pressure

violation score

1 point per 100 equivalent

people

Pressure Violation Score

(Magnitude of pressure loss)

1 point per 10 psi pressure

violation, round up as long as

the pressure violation is 10 psi

or greater

N/A

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Ranked Critical Pipes

• Prioritization of any

existing

improvement

• Development of

improvements

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Pipeline Criticality – Rank Projects

• Critical Customer Score = 10 points per critical customer below criteria pressure multiplied by the

pressure violation

• General Customer Score = 1 point per 100 customers, multiplied by the pressure violation score

• Pressure Violation Score = 1 point per 10 psi below criteria, round up if over 10 psi

• Total Score = Critical Customer Score + General Customer Score + Pressure Violation Score

Group ID

Max

Pressure

Violation

Pressure

Violation

Score

Critical

Customers

Equivalent

People

Customer

Score

Total

ScoreRank

NH4A 40 4 - 8,990 360 364 1

NH51 5 0 5 2,217 228 228 2

H27B 21 3 - 3,579 107 110 3

NH86 19 2 - 1,235 25 27 4

L500 24 3 - 410 12 15 5

T33A 14 2 - 544 11 13 6

NT52 10 1 - 97 1 2 7

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Critical Project Prioritization

• Secondary ranking criteria

– Areas with limited capacity

• Headloss (2ft/1000 ft, 6ft/1000 ft)

• Velocity 5ft/sec

– Age/Material – older pipeline

segment based on age or pipe

material

– Joint types – pipeline segments

with leadite joints

– Identified growth areas

• Hydraulic capacity results

may inform the improvement

alternative process

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Criticality Modeling – Valve Criticality

• Skeletonized model (as

required)

• GIS valves

– Spatially located on

model pipes

– Relocate valves on

junctions

• Associate GIS valves to

hydraulic model

• Run valve criticality

Red and yellow valves are required to isolate the

black and yellow valve

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Valve Criticality - Demand Isolated

• Valves that would impact critical customers

• Valves that impact large customer demand

• Valves that require a large number of other valves to isolate

• The addition of a few valves may reduce the criticality of many valves

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Valve Criticality Results

• Transmission: Red valves require 11 or more valves to isolate

• Distribution: Yellow valves require 7 or more to isolate

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Critical Valve Database

• Operational value

– Resource requirements

– Prioritize valve maintenance program

– Identifying system improvements

• Limitations

– Complexity based on size of system

– Limited tools for operator reference

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Criticality in the Design Approach

• Pipelines

• Facilities

– Supply and pump stations

– Storage tanks

• Surge or transient analysis

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Pipelines

• New Pipe Construction Considerations:

– Distribution deficiencies (fire flow, pressure, velocity, headloss,

etc.)

– Looping, redundancy, valve isolation

– Other utility projects (i.e. road repaving or replacement)

• Additional Pipe Replacement Program Considerations:

– Condition

– Age

– Material

– Cost (rehab techniques)

– Other water system projects

How long will modern pipe materials last?

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Facilities

• Vulnerability of water wells depends on the type and location

of the earthquake, and the well construction and formation in

which well is completed

• Auxiliary power (in place or portable)

• Standby and/or redundant treatment equipment

• Seismic implications for water tanks/assessing existing

infrastructure

• Provide valves near the facilities to isolate if the piping system

is damaged

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• Transient caused by emergency pump shutdown (power

outage)

• Recommended on new and modified pumping facilities

• Mitigation

– Surge chamber OR Reservoir (risk if unavailable)

– Combination air admission/air relief valves

– Surge anticipator valve

– Surge relief valve

– Check valve

Surge or Transient Analysis

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Summary

• Mass balance

– Pump capacity

– Available storage

• Critical pipes

– Pressure loss

– Disconnection

– Prioritization

• Valve criticality

– Valves to isolate (manpower)

– Projects, maintenance priority

• Criticality in the Design Approach

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Acknowledgements

A Special Thanks to:

– City of Spokane

– Dawn Wirz/Murray, Smith & Associates

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Contact:

Joe Foote, PE

Murray, Smith & Associates, Inc.

M: 421 W Riverside Ave, Suite 762

Spokane, Washington 99201

P: 509.321.0340

E: Joe.Foote@msa-ep.com

QUESTIONS?