Background on Engineering Risk Assessments (ERA) for USACE Civil Works Infrastructure

1. Background on Engineering Risk Assessments (ERA) for USACE Civil Works Infrastructure Robert C. Patev North Atlantic Division – Regional Technical Specialist (978) 318-8394

2. Engineering Risk Assessments

3. Risk

4. 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)

5. 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.

6. 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

7. 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

8. 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???

9. 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