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9/20/2016
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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
QUESTIONS?