1. Past Dam Failures with Modes of Failure
Keith Mills, P.E., G.E.
Acting State Engineer
Oregon Water Resources Dept.
2014 NWHA Annual Meeting

2. Objective – Discuss major dam incidents relevant to the PNW
Four Dams were selected because
Severe or potential severe consequences
Modes of failure applicable to Pacific Northwest
Reasonable knowledge of incident cause

3. Relevant Dam Incidents
Vaiont Northern Italy
Teton Eastern Idaho
Taum Sauk Missouri
Kaloko Kauai, Hawaii

4. Lessons Learned Comprehending geology - conditions
Design - state of the practice?
Construction practices
Non-engineered alterations
Operations, monitoring and Inspections

5. Two Historical Failures
Johnstown (South Fork) 1889
Saint Francis 1928

6. South Fork Dam Lives Lost: 2,209 Type: Embankment (earth and puddle)
10 miles SE Johnstown, PA
Constructed:
Height 72 feet
Storage 15,000 acre-ft
Date of Failure: May 31, 1889
Lives Lost: 2,209

7. South Fork Dam

8. Saint Francis Dam Lives Lost: 450+ Type: Concrete Gravity
Location:
70 miles North Los Angeles
Constructed: 1924 to 1926
Height 205 feet
Storage 38,000 acre feet
Date of Failure:
March 12, 1928
Lives Lost: 450+

9. Saint Francis Dam
Remnants after near instantaneous dam failure

10. Vaiont Dam Lives Lost: 2,500 Type: Concrete thin arch Height 869 feet
Location:
60 miles North of Venice
Constructed:
Hydroelectric
Height 869 feet
Storage 122,000 acre ft
Date of Failure:
October 9, 1963
Lives Lost: 2,500

11. Vaiont Dam
Before
After – landslide dwarfs dam

12. Vaiont Dam mode of flooding
DAM DID NOT FAIL DESPITE
OVERTOPPING BY FT
Gigantic landslide
displaced reservoir
Contributing Factors
Missed existing inactive landslide(s)
Control by changing reservoir levels
Extreme landslide size and speed (very rare)
Note reservoir level and rate of movement

13. Vaiont Dam –Lessons Learned
Comprehend the dam site geology
Unwise to rely on reservoir level to control landslide movement
Arch dams can be very stable (dam survived)
No timely independent investigation
Italian state - “the price of modernization”

14. Teton Dam Type: Zoned Embankment 40 miles NE Idaho Falls
Constructed:
Height 305 feet
Storage 288, 250 acre feet
Date of Failure: June 5, 1976
Lives Lost: 11
(middle of reported range)
Property damage: $400,000,000 -$1,000,000,000

15. Teton Dam
Picture taken at near maximum breach just past noon, first observation of problems were that morning

16. Teton Dam Mode of Failure
Primary: Development of rapid piping in right abutment with no defense or filter
Contributing Factors
Large open joints and fissures in next to key trench
Zone 1 (core) material highly prone to erosion and piping
Non standard key trench in abutment
No soil filter in abutment key trenches
Grout curtain inconsistent

17. Teton Dam Lessons Learned
Designers must understand the significance of open fractures and voids
Key trenches in the abutment can make the situation worse
A defensive design for all parts of the dam was essential
Abutment Key Trench

18. Teton Dam Lessons Learned
Incomplete grouting can be very unsafe
No compacted fill is ever homogenous
Internal erosion can be masked if rock fractured and open
Piping through erodible fill can develop to a dam breach very quickly
Cooperating agencies can complete an outstanding forensic investigation

19. Taum Sauk Dam Lives Lost: 0 (5 serious injuries)
Type: Concrete faced rock-fill with a parapet wall, liner added
90 miles Southwest of Saint Louis, MO
Constructed:
Failure: December 14, 2005
87 feet tall acre feet
Lives Lost: 0
(5 serious injuries)

20. Taum Sauk Pumped storage reservoir Inundation in yellow
Flood wave stored in lower reservoir
Camp located in inundation area
Little use in winter
Casualties could have been much higher

21. Taum Sauk Mode of Failure
Overflow eroding rockfill
Crest uneven from settlement
Improperly placed sensors
Unsafely programmed sensors
No direct observation
Differential settlement (fines)
Irregular foundation material
Improper liner placement
No spillway

22. Taum Sauk Lessons Learned
All dams need a spillway
Dams, even rock-fill, settle over time
Concrete faced dams prone to severe damage if there is settlement
Organizations need to care about safety
Largest FERC fine, at least to that point
Dam failures impact all dam owners

23. Kaloko Dam Lives Lost: 7 Property damage: Still in litigation
Type: Embankment/hydraulic fill
Location: 10 mi NW Kapaa
Built 1890, Raised 1911
Height 40 feet
Storage 1200 acre feet
Failure: March 14, 2006
Lives Lost: 7
Property damage: Still in litigation
Complex ownership pattern

24. Kaloko Dam
Inundation Area after dam breach

25. Kaloko Dam Mode of Failure
Primary: Spillway filled by new dam owner, then extended overtopping
(filled by irrigation ditch)
Contributing Factors:
Crest uneven (2 feet)
Lack of maintenance;
Trees hid erosion
Incorrect inspectors
The breach

26. Kaloko Dam Lessons Learned
DO NOT FILL IN THE SPILLWAY!!!!!!!
Incorrect hazard ratings can have serious consequences (Low when it should have been HIGH)
A red flag when dam owners and ditch operators do not talk
Inspect dams that need to be inspected
The dam regulator must inspect & investigate
Where was dam safety?

27. Key Lessons from the 6 incidents
Spillways need to handle design inflows
Understand big picture geology (rock and soil)
Old design flaws are common
As-built is different than as designed
Small dams failures have consequences on owners of large dams

28. Acknowledgements
Robert B. Jansen, USBOR Retired, author of Dams and Public Safety
J. David Rogers, Professor of Geological Engineering, Missouri University of Science and Technology
Dave Pelty, Durham University
Robert Godbey, Hawaii Special Deputy A.G.