Risky reservoirs: Montana counties where aging dams pose the greatest threat

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- Total high-hazard dams: 5
- Number potentially dangerous: 1 (20.0%)
- Potentially dangerous dams include:
--- 1 in poor condition

#29. Petroleum County
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- Total high-hazard dams: 4
- Number potentially dangerous: 1 (25.0%)
- Potentially dangerous dams include:
--- 1 in poor condition

#28. Carbon County
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- Total high-hazard dams: 8
- Number potentially dangerous: 2 (25.0%)
- Potentially dangerous dams include:
--- 2 in poor condition

#27. Meagher County
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- Total high-hazard dams: 7
- Number potentially dangerous: 2 (28.6%)
- Potentially dangerous dams include:
--- 2 condition withheld

#26. Hill County
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- Total high-hazard dams: 3
- Number potentially dangerous: 1 (33.3%)
- Potentially dangerous dams include:
--- 1 in poor condition

#25. Park County
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- Total high-hazard dams: 9
- Number potentially dangerous: 3 (33.3%)
- Potentially dangerous dams include:
--- 1 in poor condition
--- 2 not rated

#24. Powell County
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- Total high-hazard dams: 5
- Number potentially dangerous: 2 (40.0%)
- Potentially dangerous dams include:
--- 2 condition withheld

#23. Missoula County
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- Total high-hazard dams: 5
- Number potentially dangerous: 2 (40.0%)
- Potentially dangerous dams include:
--- 2 in poor condition

#22. Cascade County
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- Total high-hazard dams: 2
- Number potentially dangerous: 1 (50.0%)
- Potentially dangerous dams include:
--- 1 in poor condition

#21. Granite County
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- Total high-hazard dams: 6
- Number potentially dangerous: 3 (50.0%)
- Potentially dangerous dams include:
--- 2 in poor condition
--- 1 condition withheld

#20. Lincoln County
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- Total high-hazard dams: 8
- Number potentially dangerous: 4 (50.0%)
- Potentially dangerous dams include:
--- 1 not rated
--- 3 condition withheld

#19. Flathead County
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- Total high-hazard dams: 11
- Number potentially dangerous: 6 (54.5%)
- Potentially dangerous dams include:
--- 3 in poor condition
--- 1 not rated
--- 2 condition withheld

#18. Madison County
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- Total high-hazard dams: 7
- Number potentially dangerous: 4 (57.1%)
- Potentially dangerous dams include:
--- 1 in poor condition
--- 3 not rated

#17. Jefferson County
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- Total high-hazard dams: 5
- Number potentially dangerous: 3 (60.0%)
- Potentially dangerous dams include:
--- 3 condition withheld

#16. Big Horn County
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- Total high-hazard dams: 16
- Number potentially dangerous: 10 (62.5%)
- Potentially dangerous dams include:
--- 1 in poor condition
--- 1 not rated
--- 8 condition withheld

#15. Lewis and Clark County
Christopher Boswell // Shutterstock

- Total high-hazard dams: 3
- Number potentially dangerous: 2 (66.7%)
- Potentially dangerous dams include:
--- 2 in poor condition

#14. Silver Bow County
Drew Halverson // Shutterstock

- Total high-hazard dams: 3
- Number potentially dangerous: 2 (66.7%)
- Potentially dangerous dams include:
--- 2 condition withheld

#13. Sanders County
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- Total high-hazard dams: 4
- Number potentially dangerous: 3 (75.0%)
- Potentially dangerous dams include:
--- 1 in poor condition
--- 2 not rated

#12. Gallatin County
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- Total high-hazard dams: 4
- Number potentially dangerous: 3 (75.0%)
- Potentially dangerous dams include:
--- 3 in poor condition

#11. Sweet Grass County
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- Total high-hazard dams: 9
- Number potentially dangerous: 7 (77.8%)
- Potentially dangerous dams include:
--- 2 in poor condition
--- 4 not rated
--- 1 condition withheld

#10. Ravalli County
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- Total high-hazard dams: 6
- Number potentially dangerous: 5 (83.3%)
- Potentially dangerous dams include:
--- 5 condition withheld

#9. Phillips County
Ian William Hromada // Shutterstock

- Total high-hazard dams: 12
- Number potentially dangerous: 10 (83.3%)
- Potentially dangerous dams include:
--- 1 in poor condition
--- 9 condition withheld

#8. Teton County
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- Total high-hazard dams: 7
- Number potentially dangerous: 6 (85.7%)
- Potentially dangerous dams include:
--- 5 not rated
--- 1 condition withheld

#7. Beaverhead County
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- Total high-hazard dams: 9
- Number potentially dangerous: 8 (88.9%)
- Potentially dangerous dams include:
--- 8 condition withheld

#6. Lake County
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- Total high-hazard dams: 1
- Number potentially dangerous: 1 (100.0%)
- Potentially dangerous dams include:
--- 1 condition withheld

#5. Chouteau County
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- Total high-hazard dams: 1
- Number potentially dangerous: 1 (100.0%)
- Potentially dangerous dams include:
--- 1 posing immediate threat

#4. Musselshell County
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- Total high-hazard dams: 1
- Number potentially dangerous: 1 (100.0%)
- Potentially dangerous dams include:
--- 1 condition withheld

#3. McCone County
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- Total high-hazard dams: 2
- Number potentially dangerous: 2 (100.0%)
- Potentially dangerous dams include:
--- 2 condition withheld

#2. Liberty County
Dirk Wierenga // Shutterstock

- Total high-hazard dams: 3
- Number potentially dangerous: 3 (100.0%)
- Potentially dangerous dams include:
--- 3 condition withheld

This story features data reporting by Paxtyn Merten, writing by Dom DiFurio, and is part of a series utilizing data automation across 50 states.

#1. Glacier County
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