East Baseline Risk Assessment Study Results

RACEngineers & Economists, LLC

July 20, 2017

Southeast Louisiana Flood Protection Authority - EastBaseline Risk Assessment Study Results

RACEngineers & Economists, LLCProbabilistic Performance Analysis for all Major Structures in

the HSDRRS and Redevelopment of Operations and Maintenance Manuals and Emergency Action Plans

• Project Background/History

• Review of Overall Project Objectives

• Phase 1 and Phase 2

• Risk Study Framework▪ HAZOP▪ Block Diagrams for

Each Structure▪ FTA▪ FMEA

• Risk-Informed Decision Support Tool

• Results of Analysis

• Risk Reduction Measures

• Future Applicability


Project Background/History

• How the Study was Formulated

• HUD CDBG-DR Funded

• Study Components - Nine Complex Closure Structures

• Goals of the Study –Further Reduce Risk Through:▪ Additional Spare Parts On-Hand▪ Additional Operation and Maintenance Procedures Needed▪ Emergency Contracts▪ Written Procedures▪ Maintenance Activities▪ Proposed Repairs

3


• Manage risks associated with closure of nine gates during a hurricane or tropical storm warning (HTSW).

• Identify the main risk contributors

• Identify an initial set of potential risk reduction measures

• Provide a foundation for developing a risk-informed maintenance program – Risk-Informed Decision Support Tool

Project Objectives

5

It should be noted that this study was not a system-wide risk assessment or a conditionassessment. It addressed only the performance of the nine complex gate structures and did notinclude the performance of the levees, floodwalls or other HSDRRS features. The study includedthe normal components of the risk assessment process, including risk identification, riskestimation, risk analysis, risk evaluation and risk assessment, as described in the final report. Thestudy did not identify any immediate cause for concern for public safety.


Risk Management Definition

6

Phase 1

Phase 2


HAZOP Study

Gate System Components

Initial Fault Trees

Initial Cut Sets

Block Diagrams

Event Probabilities

Workshop

Existing Fail to Close Probs.

Reviews & Inspections

Risk Reduction Fail to Close Probs.

Initial Failure Modes

Spare Parts Inventory

Potential Risk Reductions

Risk Reduction RecommendationsRisk Reduction

Measures WorkshopRecommended Risk Reductions

System Consequences & Ann. Probs.Existing System

Conseqs. & Ann. Probs.Risk Reduction System Conseqs. & Ann. Probs.

Phase 1 Phase 2

Ranked Failure Modes

Failure Modes & Effects Analysis (FMEA)

Fault Tree Analysis (FTA): Per Demand Fail to Close Probs.

Abbreviations:Ann. AnnualConseqs. ConsequencesHAZOP Hazards and OperabilityProbs. Probabilities

Project Outcomes


Risk Framework - HAZOP Overview

The HAZOP (Hazard and Operability Study) Workshop took the participants through an analysis of risks for each of the nine gated risk structures in the HSDRRS. Potential risks were categorized into four separate “risk areas” that were further broken down into “elements” and “components.”

Risk Areas•Four RISK Focus Areas•Personnel, Structure, Operational Support (Power and Communications), Procedures

Elements

•Twelve ELEMENTS -• Staff, Contractors, Controls, Hydraulics, Mechanical

Systems, Structural, Power, Communications, SOPs (Operating, Maintenance, Communication, Water Control)

Components•Sixty-one COMPONENTS•Communications: Power/Primary/Secondary/Tertiary/Generator

9 Flood Control

Systems

•549 COMBINATIONS

RACEngineers & Economists, LLCRisk Framework - Block Diagram Example

BAYOU DUPRE: Review and Inspections – Identify Gate Systems Components

9

10

Risk Framework -Functional Block Diagram

Subpanel Board 1

Subpanel Board 2

Electric Motor 1

Electric Motor 2

Gate Group A ‐ Sector (Gear): Bayou Dupre

Main HPU

Rack and Pinion

Gasoline

Gate

Portable HPUHagglund Gear Motor

Debris or Silt

Panel Board

Normal Operation

Backup

Hazard

Leaf 1 Leaf 2

Legend

Impact Damage

Same as Leaf 1

Power Supply

Generator 1 Generator 2 Diesel Tank

Manual Transfer Switch

Winch (No procedure)

Portable Generator* Diesel

Manual Transfer Switch

Manual/Auto Transfer Switch

* Kept at yard and shared with Caernarvon


FERC Risk Training CoursePhase 1Logan, Utah

Risk Framework - Fault Tree Analysis Overview

• What combination of events will cause another (top) event to occur (e.g., gates do not fully close)?

• Also provides an estimate of the per demand probability that the top event will occur

• Utilize deductive logic, where the causative conditions and factors are deductively identified, organized in a logical manner.

• Logic represented in a fault tree diagram

RACEngineers & Economists, LLCFault Tree Diagrams

SERIES System: OR-gate (BUC)

Failure of system A occurs if one or both of the input events B and C occur

PARALLEL System: AND-gate (B∩C)

Failure of system A occurs if both of the input events B and C occur

System A Fails

Event B Occurs

Event C Occurs

Event B Occurs

Event C Occurs

System A Fails

Event B Occurs

Event C Occurs

Input OutputEvent B Occurs

Event C Occurs

Input Output

System A

System A

OR-gate AND-gate

Top Event

Fault Events


Fault Tree Diagram Illustration

ANDGate

ORGate

Emergency generatorfails to start

Fault in dieselgenerator

Mechanicalfault in diesel

generator

2

Fuel supplyproblem

Blockedfuel

intakeNofuel

Fault in start-up signalfor diesel generator

Fault insending the

signal

Fault inreception of

of signal

3

Fault intransmission

of signal

Top Event

Or-gate

Fault Events

Fault Events

Or-gateOr-gate

Or-gate

Basic Event

Transfer Event – Page 3


Fault Tree Illustration: First Order Cut Sets

ANDGate

ORGate

Emergency generatorfails to start

Fault in dieselgenerator

Mechanicalfault in diesel

generator

2

Fuel supplyproblem

Blockedfuel

intakeNofuel

Fault in start-up signalfor diesel generator

Fault insending the

signal

Fault inreception of

of signal

3

Fault intransmission

of signal

Top Event

Or-gate

Fault Events

Fault Events

Or-gateOr-gate

Or-gate

Basic Event

Transfer Event – Page 3

Cut set - the event(s) that must occur simultaneously for a system to fail

True

True

TrueTrue

True


Bayou Dupre Sector Gate Fault Tree- Index to Fault Tree Page Numbers

15


• A systematic procedure for the analysis of a system to identify the potential failure modes, their causes and effects on system performance

• The system is represented as a functional block diagram where performance of its elements can be defined

• The analysis proceeds in a bottom-up fashion until the end effect on the system is identified

• A thorough FMEA is a result of team work that stimulates the thought process, and ensures necessary expertise

• FMEA generally deals with individual failure modes and the effect of these failure modes on the system.

• Each failure mode is treated as independent.

Risk Framework - Failure Modes and Effects Analysis (FMEA) Overview

16


PFM # Failure Progression Resulting ImpactsAdverse Factors

(more likely)

Favorable

Factors

(less likely)

Fault Tree

Analysis

Order

BD1* - BD125 Operators or equipment fail to reach the site in time to close the gates during

an event.

Uncontrolled flooding of the Central Wetlands and possible failure of the

secondary protection system.

A1, A2, A3 F1, F2 Third

BD126 – BD174 The Main Hydraulic Power Unit (HPU) fails due to either; failure of shared

electric cables, panel board failure, or failure of electric motor. In addition, the

Portable HPU fails due to; bad fuel, mechanical issues, blown hose, operator

injury, lack of knowledge, or the Portable HPU is unavailable. The gate is

then, unable to be closed manually via tugboat due to; lack of knowledge, lack

of written procedure, the tug boat breaks down or is unavailable.


secondary protection system. Additional damage to the gates due to

vibration/surging

A3, A5, A8 F4, F12, F13 Third

BD174 – BD177 The Rack and Pinion fails. The gate is then, unable to be closed manually via

tugboat due to; lack of knowledge, lack of written procedure, the tug boat

breaks down or is unavailable.



vibration/surging

A3, A4 F5, F6 Second

BD178 – BD181 A hydraulic hose on one of the Hagglund Gear Motor bursts. The gate is then,

unable to be closed manually via tugboat due to; lack of knowledge, lack of

written procedure, tug boat breaks down or is unavailable.



vibration/surging

A3, A4, A5 F4, F5 Second

BD182 Debris accumulates on the sill that keep the gates from completely

closing/sealing during a storm surge or extratropical storm event. The gate is

then, unable to be closed manually via tugboat due to; lack of knowledge, lack

of written procedure, the tug boat breaks down or is unavailable.



vibration/surging.

A3, A6, A7 F6, F7, F11 First

BD183 The gate is severely damaged prior to the event by vessel or other impact and

is unable to close or seat properly. The gate is then, unable to be closed

manually via tugboat due to; lack of knowledge, lack of written procedure, the

tug boat breaks down or is unavailable.

Uncontrolled flooding of Central Wetlands and possible failure of the


vibration/surging.

A3, A7 F8, F9, F10 First

FMEA Example – Bayou Dupre

17

From Initial FTA Cut Set

First Discussion of Consequences

Outside the HAZOP

Risk Elements to Possibly Mitigate

F6 – Regular Exercising, Operation and Maintenance

of Gates

Verbal Description of The Failure Mode –

Based on Block Diagram

Existing Risk Reduction Measures


Basic Event Probability Estimation

Event Reliability (per demand) Descriptor

10-1 1 in 10 Critical

10-2 1 in 100 Low-Poor

10-3 1 in 1,000 Moderate

10-4 1 in 10,000 Moderate-High

10-5 1 in 100,000 High

10-6 1 in 1,000,000 Very High

• Initial Probability Estimates

• Expert elicitation▪ Probability mapping table

• Snap Shot in Time

• Resources: ▪ Project information▪ Off Shore (OREDA)▪ USACE: Age and frequency of

use-testing for flood control projects

▪ Industry failure rate data for mechanical hardware, electrical equipment

▪ Human reliability – available for individual actions –considered critical actions

• Life Safety and Operator Injuries are not accounted for

18


• Estimated for each event as:▪ Zero hours for “Quick Fix” = Diagnosis plus repair is less than 1 hour

▪ Hours for diagnosis, decision and resolution

▪ “No” for times exceeding time available during gate closing – assigned a nominal value of “1,000” hours

• Estimates considered:▪ Diagnosis of problem

▪ Decision to repair

▪ Resources and Available Spare Parts

▪ Getting parts to site

▪ Repair

▪ Feasibility during emergency within total 96 hr. window

▪ Procedure Available/in-place

• Assume very low nominal probability for quick fixes under current situation = 1 in 10,000

• Sum Repair Times for each cut set and reduce gate unavailability to account for repairs

• Are repair times reasonable?

• Are spares or other resources (equipment, special skills) currently available or do procedures/contracts need to be developed?

• Are there opportunities for faster diagnosis and repair (based on importance) as risk reduction measures (RRMs)

Repair/Recovery Time

19


Repair/Recovery Time Impacts on Failure to Close Probability

20

1 in 1 inPercent

Reduction1 in

Bayou Bienvenue Sector 2.91E‐04 3,440 1.45E‐04 6,897 50% 1.46E‐04 6,863 0.00143Bayou Bienvenue VLG 2.60E‐03 384 1.38E‐03 726 53% 1.23E‐03 816 0.00183Bayou Dupre Sector 8.74E‐04 1,144 2.45E‐04 4,082 28% 6.29E‐04 1,590 0.00203

Bayou St John 4.12E‐04 2,427 1.60E‐04 6,246 39% 2.52E‐04 3,968 0.00153Caernarvon Sector 8.74E‐04 1,144 2.45E‐04 4,082 28% 6.29E‐04 1,590 0.00203GIWW Barge Gate 3.32E‐02 30 1.74E‐03 576 5% 3.15E‐02 32 0.01018GIWW Sector Gate 3.18E‐03 314 2.19E‐03 457 69% 9.96E‐04 1,004 0.03505

Seabrook Sector Gate 1.93E‐03 518 1.16E‐03 862 60% 7.69E‐04 1,301 0.03093Seabrook VLG #1 2.50E‐02 40 2.42E‐02 41 97% 7.33E‐04 1,364 0.04153Seabrook VLG #2 2.50E‐02 40 2.42E‐02 41 97% 7.33E‐04 1,364 0.04153

All Gates 9.33E‐02 11 5.57E‐02 18 60% 3.76E‐02 27 0.16805

Gate

Expected Value of Cut Set Repair

Time (hrs)

Total Unavailability (per demand)

Reduction in Unavailability Due to Repair (per demand)

Net Unavailability (per demand)


Per Demand Failure to Close Probabilities - Unavailabilities

21

0.E+0

2.E‐2

4.E‐2

6.E‐2

8.E‐2

1.E‐1

Gate System Unavailabilities ‐ Linear Scale

Total Unavailability (per demand) Net Unavailability (per demand)


Per Demand Failure to Close Probabilities - Unavailabilities

22

1.E‐4

1.E‐3

1.E‐2

1.E‐1

1.E+0

Gate System Unavailabilities ‐ Log Scale

Total Unavailability (per demand) Net Unavailability (per demand)


HAZOP Study


Initial Fault Trees

Initial Cut Sets

Block Diagrams

Event Probabilities

Workshop











Phase 1 Phase 2





Project Outcomes


• Objective:▪ Quantify flooding and economic

impacts due to failure of gate to close under various loading conditions (50-year, 100-year, 500-year events)

• Consider event duration to estimate inflows

• Estimated Values▪ Frequency of surge levels in IHNC

basin and on exterior gates▪ Overtopping / breach assumptions of

IHNC floodwalls▪ Flood depths within polders▪ Converting flood depths to damage

estimates

System Consequences & Annual Probabilities

24


0

1

2

3

4

5

6

7

8

‐15 ‐10 ‐5 0 5 10 15 20 25

Econ

omic Dam

ages ($m)

Innudation Elevation (ft. NAVD88)

SB5

Gate Fails to Close

Gate Closes

Event Tree - Bayou Dupre Sector

4

6

8

10

12

14

16

18

20

22

24

10 100 1000

Su

rge

SW

L (f

t NA

VD88

)

Return Period (years)

Adjusted Exterior Surge HazardsGeneral curve shape taken from 2007 JPM Study; a log-linear adustment was added to make the 100- and 500-yr values equal to

USACE's 2014 HSDRRS Hydraulic Design for 2007 Base Case; a 10-yr value was also added.

Bayou St. John Sector Gate

Seabrook Complex Structure

GIWW East Closure Sector Gate

Bayou Bienvenue Vertical Lift Gate

Bayou Dupre Sector Gate

Caervarvon Sector Gate

‐

50,000

100,000

150,000

200,000

250,000

300,000

350,000

‐10 ‐5 0 5 10 15 20

Polder Volum

e (acre‐ft)

Innudation Elevation (ft. NAVD88)

SB5

Probability (Unavailability) from Fault Tree


Economic Consequences

26

1 inBayou Bienvenue Sector BB Sec 1.46E‐05 68,617 $2 $66,666 137,234$ $215,472Bayou Bienvenue VLG BB VLG 1.23E‐04 8,157 $126 $288,166 1,027,732$ $1,256,240Bayou Dupre Sector BD Sec 6.29E‐05 15,898 $18 $205,924 286,169$ $307,069Bayou St John Sector BSJ Sec 1.26E‐06 793,227 $2,233 $1,201,620,841 1,771,666,667$ $1,938,080,748Caernarvon Sector C Sec 6.29E‐05 15,898 $1,234 $3,859,879 19,618,442$ $51,863,347GIWW Barge Gate GIWW Barge 3.15E‐03 318 $695,410 $1,536,002 220,889,138$ $808,387,498GIWW Sector Gate GIWW Sec 9.96E‐05 10,045 $21,991 $1,536,002 220,889,138$ $808,387,498Seabrook Sector Gate SB Sec 7.69E‐05 13,009 $25 $224,100 330,950$ $2,254,937Seabrook VLG #1 SB VLG 7.33E‐05 13,639 $19 $224,100 259,138$ $1,146,104Seabrook VLG #2 SB VLG 7.33E‐05 13,639 $19 $224,100 259,138$ $1,146,104

Figure 12 Abbreviated Gate Name

Gate

Annual Probability (/yr)

Average Annual Incremental Economic

Consequences (AAEC) ($/yr)

Minimum Incremental Economic

Consequences (Min EC) ($)

Weighted Average

Incremental Economic

Consequenecs ($)

Maximum Incremental Economic

Consequences (Max EC) ($)


BB Sec

BB VLG

BD Sec

BSJ Sec

C Sec

GIWW Barge

GIWW SecSB Sec

SB VLG

SB VLG

1.E‐6

1.E‐5

1.E‐4

1.E‐3

1.E‐2

0.1 1.0 10.0 100.0 1,000.0 10,000.0

Annu

al Probability

Weighted Average Incremental Economic Consequences ($million)

Annual Probability vs. Weighted Average Incremental Economic Consequences

Probability

Consequences

Av Ann Econ Risk = Prob * Conseq


HAZOP Study


Initial Fault Trees

Initial Cut Sets

Block Diagrams

Event Probabilities

Workshop











Phase 1 Phase 2





Project Outcomes


Risk Reduction Measures


• Potential Future Benefits ▪ Periodic Update and Assessment▪ Modular

• Maintaining and Improving the Risk-Informed Decision Support Tool/Approach ▪ Maintenance Database Feedback

▪ System Performance

▪ Expand to System-Wide Application

▪ Updated Information – Economics, Fragility, CLARA Model

Risk-Informed Decision Support ToolRealizing Value Into the Future


Robert Turner, Executive Director, Southeast Louisiana Flood Protection Authority – East

David Moore, PE (Tetra Tech)

[email protected]

614-289-0118

Questions?

32

East Baseline Risk Assessment Study Results

Documents

Transcript of East Baseline Risk Assessment Study Results