Delivering Integrated, Sustainable,
Water Resources Solutions
Background on Engineering Risk
Assessments (ERA) for USACE Civil
Works Infrastructure
Robert C. Patev
North Atlantic Division – Regional Technical Specialist
(978) 318-8394
“ Building Strong “
Delivering Integrated, Sustainable,
Water Resources Solutions
Engineering Risk Assessments
“ Building Strong “
Delivering Integrated, Sustainable,
Water Resources Solutions
Risk
“ Building Strong “
Delivering Integrated, Sustainable,
Water Resources Solutions
• Background on ERA
– Major Rehabilitation Program (MR)
• ERA process started in USACE in early 1990’s
• ERA process for MR still in use today by many
USACE Districts
– Develop ERA Framework for MR
» ER 1130-2-500 – Assist MR reports for planning
studies (Section 6 and Enc 2)
» Developed ETLs on ERA
» Developed ERA specific models and examples
- Gates, Sheet piles, Piles, Gravity monolith stability
» Develop computer software
- Piles (RCPGA) and monolith stability (RCSLIDE)
“ Building Strong “
Delivering Integrated, Sustainable,
Water Resources Solutions
• Background on ERA
– System Studies
• Upper Mississippi River Illinois Waterway (1993)
– Development of more advanced reliability models
– Structural models – limited geotechnical
• Ohio River Main Stem (1996-2006)
– Development of state-of-the-art reliability models
» Using finite elements, advanced reliability techniques
– Development of hazard rate models
– System models feed back into MR reports
• Great Lakes and Saint Lawrence Seaway Study (2006
– Present)
– Continued development of new ERA models
– Extensive use of Expert Opinion Elicitation
• Panama Canal Study (2009-Present)
– Bi-national studies to set prioritization of investment decisions for
navigation lock maintenance.
“ Building Strong “
Delivering Integrated, Sustainable,
Water Resources Solutions
• Background on ERA
– Interagency Performance Evaluation
Task (IPET) Katrina – Operational Risk
and Reliability (2005 – 2009)
• Examine risks the conditions of levees and
flood walls prior to, after 1 June repairs, and
100-yr design levels
– Estimation of reliability for over 135 reaches and 197 gates and
transitions
– Full risk and reliability analysis
– 152 hurricanes, 37 sub basins
– Examine economic and loss of life
“ Building Strong “
Delivering Integrated, Sustainable,
Water Resources Solutions
• Background on ERA
• Advanced Development of Time-Dependent Models
and Response Surface Models
– Structural – Chickamauga Lock and Dam MRR –
Alkali Aggregate Reaction (AAR) growth (2000)
– Geotechnical - Wolf Creek Dam and Center Hill
Dam MRR – karst seepage (2003/2004)
• Screening Portfolio Risk Assessment (SPRA) for
Dam Safety (2005)
– Rank USACE inventory of 600+ dams
» Base rate adjustment
» Adjustment to rating – Adequate, Probably
Adequate, Probably Inadequate and Inadequate
» Relative ranking procedure
» DSAC Class (I-V) ranking
» Completed in 2009
“ Building Strong “
Delivering Integrated, Sustainable,
Water Resources Solutions
• Background on ERA
– Dam Safety Risk Assessments
• Complete risk assessment procedure for site-specific dams
with high DSAC ratings
– Potential Failure Mode Analysis (PFMA)
– Issue Evaluation Studies (IES) – more formalized ERA
than SPRA
– Dam Safety Modification (DSM) Report – a higher level MR
ERA required
– Levee Safety Risk Assessments
• Risk assessment procedure for USACE inventory of levees and
flood walls
– Levee Screening Tool (LST) – similar to SPRA, to develop
inventory and LSAC rating
– Potential Failure Mode Analysis (PFMA)
– Issue Evaluation Study (IES) – currently under
development
– Levee Safety Modification???
“ Building Strong “
Delivering Integrated, Sustainable,
Water Resources Solutions
• Where is ERA going in USACE Engineering?
– Future of ERA in USACE?
• Increased usage and development
– More major rehab studies
– More system wide studies
– More dam safety studies
– More levee safety studies
– Use in asset management (O&M)
– Use in design of civil works infrastructure
“ Building Strong “