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

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

The Reality of Risk

Portland, OR February 19, 2013 12013 NW Hydroelectric Conference

Dam Safety in the 21st Century

The PFMA Process as a Dam Safety Tool

The Reality of Risk

Portland, OR February 19, 2013 22013 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

32013 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


The Reality of Risk

Three Actual Dam Failures

1. Swift 2 Forebay Dam – Washington - Failed April 21,2002

2. Silver Lake – Michigan - Failed May 14, 2003

3. Taum Sauk Upper Reservoir Dam – Missouri - Failed Dec. 14, 2005


April 21, 2002April 21, 2002

The Reality of Risk


Swift No. 2 Hydroelectric Project Forebay Dam Failure

The Reality of Risk

• Constructed - 1957 – 1958Constructed - 1957 – 1958• Length of water supply Length of water supply canal – 3 milescanal – 3 miles• Impoundment - 2400 ac-ft Impoundment - 2400 ac-ft • Embankment height in Embankment height in forebay – 93 ft forebay – 93 ft • Max water depth – 53 ftMax water depth – 53 ft


Swift No.2 Hydro Project

The Reality of Risk

Operating History

• Considerable leakage upon first fillingConsiderable leakage upon first filling

• Cracks and sinkholes in canal bottomCracks and sinkholes in canal bottom

• Mud boils below canal levelsMud boils below canal levels

• Portions of dike removed and filter placed in canal bottomPortions of dike removed and filter placed in canal bottom

• No further distress until 2002 when failure occurredNo further distress until 2002 when failure occurred


The Reality of Risk

• Sinkholes developed in forebay at 3:00 AMSinkholes 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 AMEmbankment breached at about 6:30 AM

• Flooding destroyed powerhouseFlooding destroyed powerhouse

• Discharge contained in the lower reservoirDischarge contained in the lower reservoir


April 21, 2002 FailureApril 21, 2002 Failure

The Reality of Risk


The Reality of Risk

• Sinkholes developed in Sinkholes developed in forebay at 3:00 AMforebay at 3:00 AM• Blowout followed at toe of Blowout followed at toe of embankment embankment • Orifice expanded Orifice expanded upstream upstream • Embankment breached at Embankment breached at about 6:30 AMabout 6:30 AM• Flooding destroyed Flooding destroyed powerhousepowerhouse

• Discharge contained in Discharge contained in lower reservoirlower reservoir


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


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

The Reality of Risk

May 13, 2003142013 NW Hydroelectric Conference

Silver Lake Reservoir

The Reality of Risk


The Reality of Risk


The Reality of Risk


• 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


Taum Sauk Pumped Storage Project

Taum Sauk Upper Reservoir

Power Tunnel

Powerhouse

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

The Reality of Risk


Taum Sauk – Upper Reservoir Full

Do you ReallyOperate This Full?

The Reality of Risk


The Reality of Risk

December 14, 2005222013 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


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

The Reality of Risk


Discussion Later!

Documents

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