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

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

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 NW Hydroelectric Conference

The Reality of Risk Presentation of Three Actual Dam Failures that : 1.Were scheduled to have PFMA performed 2.Failed prior to PFMA 3.Failure could have been avoided if PFMA process had been done NW Hydroelectric Conference

The Reality of Risk Three Actual Dam Failures 1.Swift 2 Forebay Dam – Washington - Failed April 21, Silver Lake – Michigan - Failed May 14, Taum Sauk Upper Reservoir Dam – Missouri - Failed Dec. 14, NW Hydroelectric Conference

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

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

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

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

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

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

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 NW Hydroelectric Conference

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

The Reality of Risk May 13, NW Hydroelectric Conference Silver Lake Reservoir

The Reality of Risk May 14, NW Hydroelectric Conference

The Reality of Risk May 14, NW Hydroelectric Conference

The Reality of Risk May 14, NW Hydroelectric Conference

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 The Reality of Risk NW Hydroelectric Conference Taum Sauk Pumped Storage Project

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

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 The Reality of Risk NW Hydroelectric Conference

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

The Reality of Risk December 14, NW Hydroelectric Conference

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 NW Hydroelectric Conference Because of that, I believe that it actually can minimize or even eliminate failures

The Reality of Risk NW Hydroelectric Conference Discussion Later!