Dam Rehabilitation in the USA…History and Trends
Workshop on Water Security in BulgariaSofia, Bulgaria, September 18-19, 2017
Greg Paxson, P.E., D.WRE / [email protected]
Large Dam Construction
50 Years
Source: World Register of Dams
Source: National Inventory of Dams
Dam Safety in the United States
Source: National Inventory of Dams
Periods of Change… the Catalysts
Dam Safety Catalysts (1910 to 1930)
1911: Austin Dam Failure (88 Dead)
1913: Pennsylvania enacts first known
dam safety legislation
1928: St. Francis Dam Failure (600+ Dead)
1929: California enacts dam
safety legislation
Consideration of uplift pressures
More in-depth Geologic
Evaluations
The 1970s…
Teton (11) Canyon Lake (33+)
Laurel Run+ 5 (45)
Buffalo Creek (125)
Kelly Barnes (39)
1972
1977
Dam Safety Catalysts – The 1970s
Gilboa Dam, NY Photo from Achievements and Advancements in US Dam Engineering (ICOLD 2013)
Federal Guidelines & Inspection Program (1979)
Rehabilitation of Deficient Dams (1980s - today)
Teton Dam (1976)
Dam Rehabilitation
• Spillway Capacity• Spillway Integrity (lined & unlined)
• Seepage/Internal Erosion
• Stability• Embankment Slopes• Structures
• Seismic• Stability• Liquefaction
• Structural Deterioration
• Operational
Dam Safety Regulations and Standards
“Self Regulated” Federal Dams
Non Federal Hydropower Dams
The States
State Regulated Dam Rehabilitation Projects
Source: National Inventory of Dams and Association of State Dam Safety Officials
Federal Dam Rehabilitation
Source: National Inventory of Dams and FEMA
$312M
$5.3B
$1.8B
Dam Rehabilitation Strategies
Post-tensioned rock anchor stabilization
Roller Compacted Concrete (RCC) Embankment
Overtopping Protection
Cutoff Wall (Embankment and Foundation Seepage)
Labyrinth Spillway
Drains and Filters (Seepage)
Dam Rehabilitation Strategies
Sources: Bruce et al, 2013 (Anchors); Bruce et al, 2017 (Cutoff Walls), Hansen, Schnabel, 2016 (RCC); Schnabel, 2017 (Labyrinths)
Selected Projects
Bluestone Dam, WV Smith Lake Dam, VA
Wolf Creek Dam, KYLake Townsend Dam, NC
Five Phases (2000 – 2025+)• Stability thrust blocks• Penstock auxiliary spillway• 494 rock anchors (up to 61
strands, 82-m long)• New stilling basin• $500M+ US
Bluestone Dam
• Karst (limestone) foundation
• Concrete barrier wall up to 84-m deep
• $340M US
Wolf Creek Dam
• Provides 70% of water supply to Greensboro, NC
• Concrete deterioration from Alkali Silica Reactivity
• Inadequate spillway capacity
• Earthen auxiliary spillway
• Gated spillway operational issues
Lake Townsend Dam
Opportunistic Reservoir Expansion (Dam Raise)
Dam and Levee Safety Catalyst
• Hurricane Katrina and Transition to Risk informed approaches
Another Catalyst?
• The Oroville Incident
Acknowledgements
National Dam Safety Review Board &Interagency Committee on Dam Safety