Dam Safety in the 21 st Century

1. The Reality of Risk Dam Safety in the 21st Century • PFMA as a Dam Safety Tool – Joe Ehasz • FERC Regulator Perspective – Doug Johnson • USACE Perspective – Doug Boyer • Owner Perspective - Bill Christman 2013 NW Hydroelectric Conference Portland, OR February 19, 2013

2. The Reality of Risk Dam Safety in the 21st Century The PFMA Process as a Dam Safety Tool Joe Ehasz URS Energy & Construction, Inc 2013 NW Hydroelectric Conference Portland, OR February 19, 2013

3. The Reality of Risk Potential Failure Mode Analysis (PFMA) • The process utilized to determine the Potential Failure Modes • pertinent to the dam under investigation • Essentially asks the Question: • How could this dam fail • What happens if it does • Are the identified potential failure modes recognized • What actions can be taken to reduce the dam failure likelihood 2013 NW Hydroelectric Conference

4. The Reality of Risk • Presentation of Three Actual Dam Failures that : • Were scheduled to have PFMA performed • Failed prior to PFMA • Failure could have been avoided if PFMA process had been done 2013 NW Hydroelectric Conference

5. The Reality of Risk • Three Actual Dam Failures • Swift 2 Forebay Dam – Washington - Failed April 21,2002 • Silver Lake – Michigan - Failed May 14, 2003 • Taum Sauk Upper Reservoir Dam – Missouri - Failed Dec. 14, 2005 2013 NW Hydroelectric Conference

6. The Reality of Risk Swift No. 2 Hydroelectric Project Forebay Dam Failure April 21, 2002 2013 NW Hydroelectric Conference

7. The Reality of Risk Swift No.2 Hydro Project • Constructed - 1957 – 1958 • Length of water supply canal – 3 miles • Impoundment - 2400 ac-ft • Embankment height in forebay – 93 ft • Max water depth – 53 ft 2013 NW Hydroelectric Conference

8. The Reality of Risk Operating History • Considerable leakage upon first filling • Cracks and sinkholes in canal bottom • Mud boils below canal levels • Portions of dike removed and filter placed in canal bottom • No further distress until 2002 when failure occurred 2013 NW Hydroelectric Conference

9. The Reality of Risk • Sinkholes developed in forebay at 3:00 AM • Blowout followed at toe of embankment • Orifice expanded upstream • Embankment breached at about 6:30 AM • Flooding destroyed powerhouse • Discharge contained in the lower reservoir 2013 NW Hydroelectric Conference

10. The Reality of Risk April 21, 2002 Failure 2013 NW Hydroelectric Conference

11. The Reality of Risk • Sinkholes developed in forebay at 3:00 AM • Blowout followed at toe of embankment • Orifice expanded upstream • Embankment breached at about 6:30 AM • Flooding destroyed powerhouse • Discharge contained in lower reservoir 2013 NW Hydroelectric Conference

12. The Reality of Risk Potential Things That Could Have Been Done to Recognize the Problem? • Periodic (annual) draining and inspection of the forebay and canal • Install piezometers beneath the basalt to measure pressures • Develop a complete water balance to establish the total loss of canal water • More study and critical review of construction conditions and photos • Perform a PFMA to develop the possible failure modes with consideration of the construction and series of repairs that were required upon first filling and later 2013 NW Hydroelectric Conference

13. The Reality of Risk Silver Lake Failure – May 14, 2003 • High Rainfall Period • Fuse Plug Failure • Fuse Plug Foundation Eroded • Entire Lake Empted • Flooding Downstream Facilities 2013 NW Hydroelectric Conference

14. The Reality of Risk Silver Lake Reservoir May 13, 2003 2013 NW Hydroelectric Conference

15. The Reality of Risk May 14, 2003 2013 NW Hydroelectric Conference

16. The Reality of Risk May 14, 2003 2013 NW Hydroelectric Conference

17. The Reality of Risk May 14, 2003 2013 NW Hydroelectric Conference

18. The Reality of Risk Taum Sauk Pumped Storage Project • 450 MW Pumped Storage Project • Located in Reynolds County, Missouri • One of the First PSP, Started in 1963 • Licensed by FPC in August 1965 • Owned and Operated by Ameren UE • Upper Dam is a Continuous Dike 6,562 Ft. Long • Upper Reservoir Water Level Overtopped the Dam • Upper Reservoir Dam Failed on December 14, 2005 2013 NW Hydroelectric Conference

19. The Reality of Risk Taum Sauk Upper Reservoir Power Tunnel Powerhouse 2013 NW Hydroelectric Conference

20. The Reality of Risk • Dumped and Sluced Rockfill • Upstream Reinforced Concrete Lining • Parapet Wall Placed atop the Rockfill Dam • Underdrainage Concerns Upon First Filling • Continued High Levels of Leakage Through Dam • Large Settlements and Movements of Dam and Wall • Relining in 2004 to Reduce Seepage • Revised Water Level Instrumentation in 2004 2013 NW Hydroelectric Conference

21. The Reality of Risk Do you Really Operate This Full? Taum Sauk – Upper Reservoir Full 2013 NW Hydroelectric Conference

22. The Reality of Risk December 14, 2005 2013 NW Hydroelectric Conference

23. The Reality of Risk Potential Failure Mode Analysis (PFMA) • Is a Good process because it does ask the tough questions • How could this dam fail • What happens if it does • Are the identified potential failure modes recognized • What actions can be taken to reduce the dam failure likelihood Because of that, I believe that it actually can minimize or even eliminate failures 2013 NW Hydroelectric Conference

24. The Reality of Risk Discussion Later! 2013 NW Hydroelectric Conference