dam safety in the 21 st century pfma as a dam safety tool – joe ehasz ferc regulator perspective...
TRANSCRIPT
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
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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
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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
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April 21, 2002April 21, 2002
The Reality of Risk
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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
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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
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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
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April 21, 2002 FailureApril 21, 2002 Failure
The Reality of Risk
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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
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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
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The Reality of Risk
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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
May 14, 2003152013 NW Hydroelectric Conference
The Reality of Risk
May 14, 2003162013 NW Hydroelectric Conference
The Reality of Risk
May 14, 2003172013 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
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Taum Sauk Pumped Storage Project
Taum Sauk Upper Reservoir
Power Tunnel
Powerhouse
The Reality of Risk
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•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
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Taum Sauk – Upper Reservoir Full
Do you ReallyOperate This Full?
The Reality of Risk
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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
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Because of that, I believe that it actually can minimize or even eliminate failures
The Reality of Risk
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Discussion Later!