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Assessing the Seismic Risk of Water Systems, Application of AWWA J-100
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Overview
• Introduction
• Seismicity and earthquake hazards
• Facility vulnerability
• System assessment – Portland
– Seattle
• Restoration and resiliency
• Conclusions
Water System Seismic Risk Modeling
• Seismic risk assessment of water systems developed over last 25 years
• Pushed along by Loma Prieta 1989, Northridge, 1994, and Kobe 1995
• SVA’s following 9/11
• 2011 Christchurch New Zealand and Japan/Tohoku - 40+ days water system outage
• Oregon Resilience Plan – February 2013 similar scenario based approach – focuses on Cascadia Subduction Zone scenario
AWWA J-100, Risk and Resilience Management of Water and Wastewater Systems
• Introduced in 2010
• Focus on security vulnerability with discussion on natural hazards
• 2016 version – Integrated Analysis of Natural Hazards, Nonmandatory Appendix 4
• Addresses earthquake, hurricane, tornado and flood, methodology applicable to all hazards
Oregon Resilience Plan
System Function
Event
Occurs
0-24
hours
1-3
days
3-7
days
1-2
weeks
2-4
weeks
1-3
months
3-6
monts
6-12
months
Potable water availalble at supply source XMain transmission faciliites, pipes, pump
stations and reservoirs operational XWater supply to critical facilities available XWater for fire suppression at key supply
points XWater for fire suppression at fire hydrants XWater available at community distribution
centers/points XDistribution system operational X
Desired time to restore component to 80-90% operational
Desired time to restore component to 50-60% operational
Desired time to restore component to 20-30% operational
Current state (90% operational) X
Hazard Quantification
• Scenario based • Groundmotion
• PGA, PGV, Spectral
• Spectrum
• Liquefaction probability
• Lateral spread PGD
Component Vulnerability/
Fragility • Published • Empirical • Test data • Analytical
Component Impacts
• % replacement cost
• Functionality/ reduced capacity
• Outage time
System Analysis • Functionality/
capacity • Restoration
time • Capacity
during restoration
Societal Impacts/ Business Interruption
• Daily outage per capita $ • % Gross regional product • Business specific losses
System Risk Analysis Methodology
Improve Resiliency • Mitigation • Recovery
Approaches • Emergency
Response • Cost, Schedule
Performance Goals
• Various system functions
• Immediately following event
• Outage times
Risk = Frequency x Vulnerability x Consequence
• Frequency of hazard event – Probability of occurrence in 50 years 10%, 5%, 2%
– Return period – 500, 1,000 or 2,500 years
– Lower probability results in larger intensities
• Vulnerability when subjected given intensity
• Consequence of failure – Loss of function
– Cost or repair
– Cost resulting from outages
Risk Based
• Magnitude – Richter or Moment Magnitude
– Measure of energy release
– 32 times more energy for increase of 1
• Peak ground acceleration (PGA) % of gravity
• Permanent ground deformation (PGD) - inches
Earthquake Terminology
Probabilistic Hazard - Shaking
• USGS ground motions 2% in 50 years
• IBC • ASCE 7 • AWWA D100
Seattle Fault, M6.7 Scenario
Deterministic Hazard - Shaking • Based on selected scenario
with associated return period • Maps estimated ground
motions for a given event, not probabilistic ground motions
• Does not overestimate damage
• Shaking is calculated using attenuation relationships
• Recommend using multiple scenarios with range of return periods
• Scenarios available from the USGS
Peak Ground
Acceleration
Magnitude 6.7
Modeled
fault I
G
D
Earthquake Hazards
• Shaking – PGA, PGV, spectral
– PGA – Northridge 80 x gravity
• Permanent Ground Deformation (PGD) – Tectonic uplift/subsidence
– Fault offset
– Settlement
– Liquefaction
– Lateral spread
– Lurching
– Landslide
Liquefaction
San Fernando
Earthquake,
1971
Philippines, 1990
Costa
Rica,
1991
Liquefaction
Occurs due to shaking
Soil particles consolidate
squeezing out water
Water pore water pressure
increases reducing friction
between soil particles
Soil becomes a viscous liquid
Costa Rica, 1991
Consolidated
sand grains
Loosely packed
sand grains
Liquefaction – Lateral Spread
• Movement is perpendicular to pipe (A)
– Pipe can accommodate some bending
– Segmented pipe will separate at joints, shear and bend
• Movement parallel to pipe (B)
– Segmented pipe will pull apart at one end, and crush at the other
A
B
Hazard - Mapping
• Liquefaction susceptibility and landslide mapping often available from the state, DNR, DOGAMI, etc
• PGD mapping is not available
Modeled
fault I
G
D
Component Vulnerability
• Assess each system facility
• Estimate actual performance for scenario
• Understand damage state – Likelihood of Failure
– Functionality
– Recovery
– Recovery cost
• For specific earthquake
• For hazards
Buckled Steel
Tank. Northridge
Earthquake, 1994
Resources for Developing Fragilities
• HAZUS - FEMA
• ASCE Technical Council on Lifeline Earthquake Engineering
• American Lifelines Alliance
• MCEER, MAE, PEER Centers of Excellence
Burst cast iron pipe. Kobe 1995
Fragility Curves from HAZUS
Fragility Curve Development
• Date of design/building code – E.g. – improvements following 1971 San Fernando
– Progression of AWWA D100 seismic requirements
• Seismic zone designed to – Oregon increased in early 1990s
• Analysis – Capacity/demand
ratios
– Estimate damage when exceeded
Burst Wire-Wrapped
Tank, Purissima Hills,
Loma Prieta, 1989
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.10
0 10 20 30 40 50
Rep
air
Rate
(re
pair
s/1
,000 f
t)
PGV (in/sec)
ALA Pipeline Damage Relationships
Repair Rate/1000 feet = K1 * (0.00187)* PGV
ALA Repair Rate - PGD
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
0 10 20 30 40 50
PGD (inches)
Rap
air
Rate
(1,0
00 f
t) CIP
DIP
Steel
Repair Rate/1000 feet = K2* (1.06) * PGD0.319
CIP
DIP
Steel
CCP
• Using GIS, pipelines are overlaid on hazard layers
• PGV is “related” to pipe • PGD is “related” to pipe
in liquefaction areas • Pipe breaks and leaks can
be calculated within GIS • Breaks and leaks can be
calculated by pressure zone
ALA Pipe Damage Relationships K Values
Material Joint Type Soils Diameter K1 K2 Cast iron Cement All Small 1.00 1.00 Cast iron Cement Corrosive Small 1.40 Cast iron Cement Non-corrosive Small 0.70 Cast iron Rubber gasket All Small 0.80 0.80 Cast iron Mechanical
restrained 0.70
Welded steel Lap-Arc Welded All Small 0.60 Welded steel Lap-Arc Welded Corrosive Small 0.90 Welded steel Lap-Arc Welded Non-corrosive Small 0.30 Welded steel Lap-Arc Welded All Large 0.15 0.15 Welded steel Rubber gasket All Small 0.70 0.70 Welded steel Screwed All Small 1.30 Welded steel Riveted All Small 1.30 Asbestos Cement Rubber gasket All Small 0.50 0.8 Asbestos Cement Cement All Small 1.00 1.00 Concrete w/Stl Cyl. Lap-Arc Welded All Large 0.70 0.60 Concrete w/Stl Cyl. Cement All Large 1.00 1.00 Concrete w/Stl Cyl. Rubber gasket All Large 0.80 0.70 PVC – C900, C905 Rubber gasket All Small 0.50 0.80 PVC – C909 (1) Restrained All Small 0.15 Ductile Iron Rubber gasket All Small 0.50 0.50 Ductile iron (1) Restrained joint All Small 0.25 Ductile iron (1) Seismic joint All Small 0.15 HDPE (1) – C906 Fused All Small 0.15
Added since ALA published
System Assessment
• Workshop setting – experts – GIS showing facility and pipeline
functionality
• Connectivity model/system probabilistic assessment – spreadsheet
• Hydraulic model – EPANET
– Academic models
– Negative pressure issues with many pipe failures
City Center
Mt. Hood
Bull Run Watershed Columbia
River
Powell Butte Reservoir
Groundwater System
Willamette River
Sandy River Landslide Area
Bull Run Watershed - some
components built in early 1900’s
Transmission 3 – 40 km conduits
Columbia Well Field – built in 1980’s
Treatment - chloramination, pH
adjustment
Distribution – primarily cast iron
Portland Water Supply System
Lusted HillTreatment
Facility
TR 3
TR 2
TR 4
BR 3
BR 2 & 4
LND 3
LND 2 &4
LND
ALL
Headworks
Building
WatershedAbbreviations:CD = Conduit TR =Trestles
BR = Bridges LND =Landslide
CD 2
CD 3
CD 4
Conduit
Headworks
Chlorine
GWS
PowellButte
Portland Supply System Schematic/ Spreadsheet Connectivity Analysis
Supply System Reliability, 500-Year Return Earthquake
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
50 100 150 200 250 300 350
Flow (mgd)
Pro
bab
ilit
y o
f su
pp
lyin
g a
t
leas
t "x
" m
gd
No Intertie
Intertie
Portland Earthquake Reliability
Supply System Reliability, 100-Year Return Earthquake
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
50 100 150 200 250 300 350
Flow (mgd)
Pro
ba
bil
ity
of
su
pp
lyin
g a
t
least
"x
" m
gd
No Intertie
Intertie
Meets 100-year return reliability of 145 mgd
Requires mitigation to meet 500-year return reliability of 95 mgd
WRF, 2009
Seattle Water – Using EPANET
Restoration Calculations • Start with damage estimate of facilities and pipelines
• Identify which are required to restore service
• Estimate repair crews available – structures, equipment, large diameter pipe, distribution pipe – Internal, Contractors, Mutual aid
• Estimate repair rate/crew
• Develop repair sequence – Restore the most people the fastest
– Restore critical services – hospitals, industries etc.
• Calculate – Restoration days (by pressure zone)
– Restoration time line
– Person outage days (by pressure zone)
Water Restoration Timeline - Sendai
Distribution area restoration
Afte
rshock
occurred
★
Earthquake o
ccurred
★
Distribution area restoration
Distribu
tion are
a resto
ration
Began
receivin
g wate
r from
th
e S
ennan
Senen
Regio
nal A
rea to
Sendai
★
Tran
smissio
n pu
mp failu
re
Main trunkline restoration
Distribution station restoration Sennan
Senen R
egio
nal A
rea
wate
r distribu
tion se
cure
d by
rero
uting wate
r system
Received water from distribution station
The n
um
ber o
f the w
ater su
spension
×1,000 h
ouse
s
Person Outage Days
Improve Resiliency
• Upgrade or replace deficient facilities and pipe
• Enhance restoration procedures
• Emergency response
• Develop costs and implementation schedule
• Loop back to reevaluate performance levels
Where’s it Being Used ?
Variations of this scenario-based methodology are being widely used in the Pacific Northwest:
• Portland (Oregon Resilience Plan)
• Sammamish Plateau W&S
• Tacoma
• Tualatin Valley WD (Oregon Resilience Plan)
• Seattle – near future
Conclusions
• AWWA J-100 effective tool for assessing system resilience
• Risk Based
• Components
– Performance Goals
– Hazards
– Vulnerability/Fragility –Parameters
– System Analysis
– Societal Impacts and Business Interruption
– Improve Resilience
Tohoku Earthquake Japan 2011
Questions ? Donald Ballantyne, PE Ballantyne Consulting LLC [email protected]
Kanigawa WTP, Tohoku Earthquake
Japan 2011