Dam Safety

1
Dam Safety An Opportunity for Dam Removal?
2
Dam Definitions and Clarifications
3
Dams have Exceeded their Economic Life

• 30 of dams in NID gt 50 years old (23,000)
• 80 will be gt 50 years by 2020 (60,000)
• Dams have long life if well maintained and
  operated
• 2,600 FERC licensed dams 70 gt 50 years
• Since 1981 over 600 dam safety modifications at
  FERC dams - 1 billion

4
Dam is High Hazard
5
Dam is Unsafe
6
What is a Dam?
7
What is a Dam?

• National Inventory of Dams (NID) 77,000 dams
• gt 6 feet and impound 50 acre-feet, or
• gt 25 feet and impound 15 acre-feet, or
• are Significant Hazard

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AT THE END
9
FROM THE NATIONAL INVENTORY OF DAMS DATED APRIL
2000 DAM OWNERS Federal - 3 State - 6
Local - 22 Public Utility 2.3 Private -
66 Undetermined 0.7 Total Number of Dams -
76,953
Ownership

Ownership
10
What is a Dam ?

• 49 states have dam safety legislation (Alabama
  has none Delaware just passed legislation)
• Minimum size and storage varies New Hampshire
  4 feet high or 2 acre-feet
• 90,000 state jurisdictional dams vs 77,000 in
  NID
• 9 states exempt FERC licensed dams
• 23 states include dam removal in regulations
• Source Association of State Dam Safety Officials
  and State websites

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(No Transcript)
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Aspen Recommendation

• Review all dam structures and operations
  periodically. Reviews should address
  environmental, economic, and social benefits and
  impacts in addition to dam safety.

13
Are Dams Periodically Inspected?

• 49 states have dam safety legislation (Alabama
  has none Delaware just passed legislation )
• 90,000 state jurisdictional dams total budget -
  33.4 million 401 dam safety staff
• California 1213 dams 7.9 million 65 staff
• Texas 8133 dams 300k 5 staff
• Periodic inspection by staff varies from
  annually to up to 10 years.
• 13 states require periodic inspection by
  independent engineer
• Source Association of State Dam Safety Officials
  and State websites

14
Are Dams Periodically Inspected?

• FERC dam safety inspections by staff
• Annually - High and Significant Hazard dams
• Biennially Low Hazard dams gt 25 feet high or
  50 acre-feet storage
• Triennially Smaller dams
• Every five years Independent consultant
  inspection and report for dams gt 10 m (32.8
  feet), or 2,000 acre-feet, or High Hazard

15
Dam Removal vs. Repair

• Case Study
• Two similar earth fill dams built in 1887 and
  1900
• Higher earthquake loading
• Narrow crest width, steep slopes
• Low material strength properties
• Low factors of safety under earthquake loading

16
Dam Repair Option
Built in 1887 crest raised in 1911 73 ft
high Crest width - 8 ft D/S slope 1.66 1
1981 Improvements Crest width - 30 ft D/S
slope 2.5 1 Crest raised 2.5 ft
AT THE END
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Dam Repair Option
Upstream rockfill berm added Gunite facing
AT THE END
18
Dam Repair Option
117 year old dam
Total construction cost in 1981 - 1.6 million
AT THE END
19
Dam Removal Option
32 ft high Built in 1900 Crest width 6
ft Freeboard 2 ft
AT THE END
20
Dam Removal Option
Stability improvements planned for 1977 - 1
million Foundation problems costs increased to
2.5 million
AT THE END
21
Dam Removal Option
Alternative analysis dam breach lowest cost at
70,000 Breached in 1976 final cost
150,000 Storage height lt 6 ft not under CA dam
safety jurisdiction
AT THE END
22
Dam Removal Option
28 years later
AT THE END
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Dam Removal vs. Repair

• Rising Dam Housatonic River, Massachusetts
• 300 ft long embankment, 35 ft high, built mid
  1880s
• Decision to remove in 1980s dam safety
  concerns removal less expensive liability
• PCB contaminated sediments increased costs
• 1990s dam was repaired - 3.4 million repair
  less expensive than removal easier to permit
  dam safety issues addressed sooner

24
Cost of Dam Removal

• Saeltzer Dam Clear Creek, California
• 185 ft long concrete and timber crib dam, 20 ft
  high, built in 1912
• Decision to remove dam fish passage dam
  safety concerns public safety
• Dam removed in 2000 - 6 million total cost
• Construction contract - 2.8 million
• Sediment characterization - 309,000
• Design, contract admin, environmental - 400,000
• Water rights and property interests - 2.5
  million

25
Conclusions

• Dam removal can be a viable option to dam
  safety improvements
• Most state dam safety programs are understaffed
  and under funded
• The majority of dam structures are exempt from
  state dam safety jurisdiction
• FERC licensed dams are inspected more
  frequently than most dams
• Dams can have a long life if well maintained
  and modified when necessary

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Conclusions

• Presence of contaminated sediments in reservoir
  will increase costs
• There can be more permitting uncertainty in dam
  removal than in repair
• All costs need to be considered when making a
  dam removal decision