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Risky reservoirs: States where aging dams pose the greatest threat

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January 9, 2024
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Risky reservoirs: States where aging dams pose the greatest threat

Record rainfall pelted parts of Iowa for 12 hours straight in July 2010, sending 10 inches of rainwater draining toward Lake Delhi, Iowa, a popular recreation destination for decades since its construction in the 1920s.

Holding back 9 miles of lake water with more precipitation flowing in by the minute was the 80-year-old Lake Delhi Dam, constructed of hundreds of feet of earth, concrete, and steel. The water punched a 30-foot-wide hole in the dam wall, spewing floodwater into the surrounding region.

Emergency and state officials ordered evacuations in time to prevent any loss of life. For safety professionals, the failure underscored the threat posed to dams by climate change (increasing the risk of flooding events), the importance of regular maintenance and inspection, and the impact of human errors in dam construction on dam integrity.

GetMyBoat analyzed data from the U.S. Army Corps of Engineers' National Inventory of Dams to identify states with the most dams at risk of failure that pose the greatest potential threat to nearby residents. The public database allowing Americans to look up the conditions of nearby dams has grown to include more than 90,000 dams.

As more dams get added to the national inventory, analyses of this database reveal a growing number of dams in poor and unsatisfactory condition, some of which have the potential to be life-threatening should they fail—dams the inventory deems "high-hazard."

States in this analysis ranked by the share of high-hazard dams that could pose a danger to human life, including those assessed to be in "poor" or "unsatisfactory" condition, those that haven't received inspections, and those where the state agency that oversees them has not reported its conditions.

A designation of "poor" is given to inspected dams showing deficiencies that threaten the dam's integrity during normal operations. "Unsatisfactory" is given to dams that require "immediate or emergency remedial action," according to the Army Corps of Engineers. About 1 in 10 of the inventory's dam listings have no condition reported by state agencies.

"It is likely most of these dams should be listed at Not Rated, but we will work with the appropriate agencies to verify the information and update the NID accordingly," Army Corps of Engineers spokesperson Gene Pawlik said in a statement.

The names of dams accompanying each state in the analysis represent the largest dams by height that were in poor or unsatisfactory condition. The total number and concentration of high-hazard dams give a sense of the stakes involved with aging infrastructure in each state, though those figures don't factor into the ranking.

The Lake Delhi Dam was reconstructed and was last inspected in 2020, receiving a "satisfactory" grade. The dam is considered one risk level below high-hazard, "significant hazard." But its failure in 2010 provides an example of the high stakes communities living near large dams face when they fail.

Illinois ranks high on this list, mainly because of what is unknown about the conditions of its dams. The Army Corps of Engineers leaves it up to state agencies to decide what information it provides or withholds from the public database. Illinois only shares info on three of its dams deemed to be high-hazard. One of its engineers has previously said that it doesn't rate dams' conditions because the process is too resource-intensive to justify.

Many state and federal agencies have chosen to keep data about those dams hidden, citing threats to national security. North Dakota and Oregon withhold data about around 40% of the dams in their states, making it difficult for locals to assess just how many are in good condition or need attention.

Other states rank poorly for their share of high-hazard dams that have gone without inspection. In Missouri, about 42% of these dams don't have a recorded date of last inspection. Another 24% were last inspected prior to 2000.

Read on to see how your state's riskiest dams fare based on publicly available data.

Aerial view of hydroelectric power plant and dam in Wisconsin.
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#50. Wisconsin

- Total high-hazard dams: 206 (3.5 per 100,000 residents)
- Share potentially dangerous: 8.7%
--- Assessed to be an immediate threat: 1.5%
--- Assessed to be in poor condition: 1.0%
--- Condition withheld: 1.9%
--- Not inspected: 4.4%
- Major examples (immediate threat): West Fork Kickapoo 1, Mlsna, Radigan
- Major examples (poor condition): Rock Falls, Rice

Red Rock Lake Iowa Dam.
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#49. Iowa

- Total high-hazard dams: 95 (3.0 per 100,000 residents)
- Share potentially dangerous: 11.6%
--- Assessed to be an immediate threat: 0.0%
--- Assessed to be in poor condition: 1.1%
--- Condition withheld: 10.5%
--- Not inspected: 0.0%
- Major examples (immediate threat): None
- Major examples (poor condition): Glen Oaks Country Club Dam

Lock and dam on the Red River.
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#48. Louisiana

- Total high-hazard dams: 41 (0.9 per 100,000 residents)
- Share potentially dangerous: 12.2%
--- Assessed to be an immediate threat: 0.0%
--- Assessed to be in poor condition: 4.9%
--- Condition withheld: 4.9%
--- Not inspected: 2.4%
- Major examples (immediate threat): None
- Major examples (poor condition): Kincaid Reservoir, Longville Lake

Hydroelectric dam in Scotland.
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Denis Morin // Shutterstock

#47. Connecticut

- Total high-hazard dams: 274 (7.6 per 100,000 residents)
- Share potentially dangerous: 14.6%
--- Assessed to be an immediate threat: 0.0%
--- Assessed to be in poor condition: 7.3%
--- Condition withheld: 5.8%
--- Not inspected: 1.5%
- Major examples (immediate threat): None
- Major examples (poor condition): Crystal Lake Dam, Hartford Reservoir #1 Dam, Peat Swamp Reservoir Dam, Great Hill Reservior Dam

Aerial view of Smooth Lake Dam.
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#46. Michigan

- Total high-hazard dams: 162 (1.6 per 100,000 residents)
- Share potentially dangerous: 15.4%
--- Assessed to be an immediate threat: 2.5%
--- Assessed to be in poor condition: 6.8%
--- Condition withheld: 1.2%
--- Not inspected: 4.9%
- Major examples (immediate threat): Secord Dam, Edenville Dam, Smallwood Dam, Sanford Dam
- Major examples (poor condition): Cornwall Creek Dam, Little Black River Structure B, Trowbridge Dam, Manistique Papers Dam

Mill dam in autumn.
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#45. Massachusetts

- Total high-hazard dams: 329 (4.7 per 100,000 residents)
- Share potentially dangerous: 16.1%
--- Assessed to be an immediate threat: 2.1%
--- Assessed to be in poor condition: 7.3%
--- Condition withheld: 6.4%
--- Not inspected: 0.3%
- Major examples (immediate threat): Bel Air Dam, Bird Pond Dam, Moulton Pond Dam, Tremont Mill Pond
- Major examples (poor condition): Notch Reservoir Dam, Haskell Pond Dam, Mount Williams Reservoir Dam, Damon Pond Dam

Pokegama Dam on the Mississippi River.
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#44. Minnesota

- Total high-hazard dams: 55 (1.0 per 100,000 residents)
- Share potentially dangerous: 18.2%
--- Assessed to be an immediate threat: 0.0%
--- Assessed to be in poor condition: 3.6%
--- Condition withheld: 9.1%
--- Not inspected: 5.5%
- Major examples (immediate threat): None
- Major examples (poor condition): Lake Bronson, Pelican Rapids

Androscoggin River dam in Rumford.
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#43. Maine

- Total high-hazard dams: 73 (5.3 per 100,000 residents)
- Share potentially dangerous: 19.2%
--- Assessed to be an immediate threat: 6.8%
--- Assessed to be in poor condition: 12.3%
--- Condition withheld: 0.0%
--- Not inspected: 0.0%
- Major examples (immediate threat): Grand Falls, Josephine, Silver Lake, Lake Auburn
- Major examples (poor condition): Woodland, Christina, Emery Mills, Grand Lake (Matagamon)

Silver Lake spillway in Dover.
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Teresa Levite // Shutterstock

#42. Delaware

- Total high-hazard dams: 57 (5.6 per 100,000 residents)
- Share potentially dangerous: 19.3%
--- Assessed to be an immediate threat: 0.0%
--- Assessed to be in poor condition: 5.3%
--- Condition withheld: 0.0%
--- Not inspected: 14.0%
- Major examples (immediate threat): None
- Major examples (poor condition): Millsboro Pond Dam, Shoals Branch Dam, Burton Pond Dam

Speedwell dam waterfall on the Whippany river.
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Mihai_Andritoiu // Shutterstock

#41. New Jersey

- Total high-hazard dams: 232 (2.5 per 100,000 residents)
- Share potentially dangerous: 20.3%
--- Assessed to be an immediate threat: 0.0%
--- Assessed to be in poor condition: 20.3%
--- Condition withheld: 0.0%
--- Not inspected: 0.0%
- Major examples (immediate threat): None
- Major examples (poor condition): Round Valley South Dam, Round Valley North Dam, Spruce Run Reservoir Dam, Round Valley Dike

Dam at Smith Mountain Lake.
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2265524729 // Shutterstocck

#40. Virginia

- Total high-hazard dams: 429 (4.9 per 100,000 residents)
- Share potentially dangerous: 22.6%
--- Assessed to be an immediate threat: 1.9%
--- Assessed to be in poor condition: 10.0%
--- Condition withheld: 3.0%
--- Not inspected: 7.7%
- Major examples (immediate threat): Lake Monroe Dam, South River Dam #19, Lake Arrowhead Dam, Killarney Dam
- Major examples (poor condition): Beaverdam Creek Dam, Little Creek Dam, Lunga Dam, Breckinridge Dam

River flowing over the Third Dam on the Logan River.
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venuswix // Shutterstock

#38. Utah

- Total high-hazard dams: 266 (7.9 per 100,000 residents)
- Share potentially dangerous: 23.3%
--- Assessed to be an immediate threat: 0.0%
--- Assessed to be in poor condition: 4.1%
--- Condition withheld: 19.2%
--- Not inspected: 0.0%
- Major examples (immediate threat): None
- Major examples (poor condition): Tony Grove Lake Dam, Alton Reservoir, Palisades Lake, Red Pine

Concrete dam and spillway.
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#38. Alaska

- Total high-hazard dams: 30 (4.1 per 100,000 residents)
- Share potentially dangerous: 23.3%
--- Assessed to be an immediate threat: 0.0%
--- Assessed to be in poor condition: 13.3%
--- Condition withheld: 6.7%
--- Not inspected: 3.3%
- Major examples (immediate threat): None
- Major examples (poor condition): Wrangell Lower, Wrangell Upper, Alitak Cannery Dam #1, Explorer Glacier Pond Dam

Elwha River Lake Dam.
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#37. Washington

- Total high-hazard dams: 320 (4.1 per 100,000 residents)
- Share potentially dangerous: 23.4%
--- Assessed to be an immediate threat: 1.3%
--- Assessed to be in poor condition: 11.3%
--- Condition withheld: 10.0%
--- Not inspected: 0.9%
- Major examples (immediate threat): Mossyrock, Mayfield, Yale Saddle Dam, Yelm Canal Dike
- Major examples (poor condition): Lower Baker, Wells, Priest Rapids, Upriver Dam

Fontana Dam in summer.
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#36. North Carolina

- Total high-hazard dams: 1533 (14.3 per 100,000 residents)
- Share potentially dangerous: 24.3%
--- Assessed to be an immediate threat: 2.9%
--- Assessed to be in poor condition: 10.2%
--- Condition withheld: 1.2%
--- Not inspected: 9.8%
- Major examples (immediate threat): Simmons Fields Lake, Young'S Lake, Mcfayden Lake, Hutaff Lake
- Major examples (poor condition): Santeetlah, Yadkin Narrows Bypass Spillway Control Structure, Mott Lake, Lake Lindsay

Kinzua Dam and Reservoir.
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#35. Pennsylvania

- Total high-hazard dams: 788 (6.1 per 100,000 residents)
- Share potentially dangerous: 24.4%
--- Assessed to be an immediate threat: 1.4%
--- Assessed to be in poor condition: 17.0%
--- Condition withheld: 5.3%
--- Not inspected: 0.6%
- Major examples (immediate threat): Ryerson Station, Indian Run, Upper Castanea Reservoir, Bernhart
- Major examples (poor condition): Little Pine Creek, Dehart, North Fork, Mill Run

Hoover Dam on a clear day.
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#34. Nevada

- Total high-hazard dams: 158 (5.0 per 100,000 residents)
- Share potentially dangerous: 24.7%
--- Assessed to be an immediate threat: 2.5%
--- Assessed to be in poor condition: 15.8%
--- Condition withheld: 4.4%
--- Not inspected: 1.9%
- Major examples (immediate threat): Cat Creek , Bishop Creek Dam, Sierra Sage Ponds Dam , Home Ranch Canyon Dam
- Major examples (poor condition): Cave Creek Dam, Eagle Valley Reservoir Dam, Eldorado Canyon Dam, Las Vegas Wash Upper Detention Basin Dam

Morrow Point Dam aerial view.
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#33. Colorado

- Total high-hazard dams: 472 (8.1 per 100,000 residents)
- Share potentially dangerous: 25.2%
--- Assessed to be an immediate threat: 7.8%
--- Assessed to be in poor condition: 0.2%
--- Condition withheld: 14.2%
--- Not inspected: 3.0%
- Major examples (immediate threat): Sanchez, Narraguinnep - Main Dam, Miramonte, Stillwater #1
- Major examples (poor condition): Trout Lake

J. Strom Thurmond Hudro Dam.
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#32. South Carolina

- Total high-hazard dams: 668 (12.6 per 100,000 residents)
- Share potentially dangerous: 25.6%
--- Assessed to be an immediate threat: 2.1%
--- Assessed to be in poor condition: 19.5%
--- Condition withheld: 1.3%
--- Not inspected: 2.7%
- Major examples (immediate threat): Caldwell Lake Dam, Weston Lake, Arcadia Woods Lake Dam, Whisperlake Dam
- Major examples (poor condition): Chattooga Lake Dam, Lake Lanier Dam, Silver Lake Dam, Finleys Lake Dam

Irrigation canal feeding off from a diversion dam on the Boise River.
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#31. Idaho

- Total high-hazard dams: 107 (5.5 per 100,000 residents)
- Share potentially dangerous: 26.2%
--- Assessed to be an immediate threat: 0.9%
--- Assessed to be in poor condition: 1.9%
--- Condition withheld: 23.4%
--- Not inspected: 0.0%
- Major examples (immediate threat): Saint John
- Major examples (poor condition): Fish Creek, Lost Valley

Lake McConaughy Dam aerial view.
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Hawk Eye Drone // Shutterstock

#30. Nebraska

- Total high-hazard dams: 151 (7.7 per 100,000 residents)
- Share potentially dangerous: 27.2%
--- Assessed to be an immediate threat: 0.0%
--- Assessed to be in poor condition: 7.3%
--- Condition withheld: 18.5%
--- Not inspected: 1.3%
- Major examples (immediate threat): None
- Major examples (poor condition): Beaver Lake Dam, Gering Valley B, Willow Creek Dam, Spring Creek 19-B

Sunny view of Quanah Parker Dam.
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Kit Leong // Shutterstock

#29. Oklahoma

- Total high-hazard dams: 449 (11.2 per 100,000 residents)
- Share potentially dangerous: 28.5%
--- Assessed to be an immediate threat: 2.2%
--- Assessed to be in poor condition: 6.5%
--- Condition withheld: 12.5%
--- Not inspected: 7.3%
- Major examples (immediate threat): Lake Ellsworth, Robert S. Kerr, Hominy Lake, Waxhoma Lake
- Major examples (poor condition): Chimney Rock Pump Storage, Lake Carl Blackwell, Okmulgee Lake, Shell Creek Lake Dam

The Annapolis Reservoir Dam with “Private Property No Trespassing” sign in foreground.
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JIM WATSON/AFP via Getty Images

#28. Maryland

- Total high-hazard dams: 101 (1.6 per 100,000 residents)
- Share potentially dangerous: 29.7%
--- Assessed to be an immediate threat: 9.9%
--- Assessed to be in poor condition: 18.8%
--- Condition withheld: 1.0%
--- Not inspected: 0.0%
- Major examples (immediate threat): Liberty Dam, Piney Run Dam, Warner Gap Hollow Dam, Greenbrier State Park Dam & Dike
- Major examples (poor condition): Druid Hill Lake Reservoir and Storage Tanks, Frostburg Reservoir, New Bald Eagle Road Swm, Woodlawn Railroad Embankment On Basin Run

Small breach in a dam at a Kansas river.
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Picunique // Shutterstock

#27. Kansas

- Total high-hazard dams: 323 (11.0 per 100,000 residents)
- Share potentially dangerous: 31.3%
--- Assessed to be an immediate threat: 0.6%
--- Assessed to be in poor condition: 8.4%
--- Condition withheld: 9.3%
--- Not inspected: 13.0%
- Major examples (immediate threat): Rogers Dam, Willow Lake
- Major examples (poor condition): Lake Dabinawa, Lake Estates West, Bayer Pond Dam, Frd No T-4

Aerial view of Lake Hodges Dam.
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Unwind // Shutterstock

#26. California

- Total high-hazard dams: 867 (2.2 per 100,000 residents)
- Share potentially dangerous: 32.6%
--- Assessed to be an immediate threat: 0.2%
--- Assessed to be in poor condition: 2.2%
--- Condition withheld: 29.4%
--- Not inspected: 0.8%
- Major examples (immediate threat): Lake Hodges, Double U Fish Ranch
- Major examples (poor condition): Castaic, El Capitan, Morena, Matilija

Middlebury Falls after heavy rain.
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Jon Bilous // Shutterstock

#25. Vermont

- Total high-hazard dams: 62 (9.6 per 100,000 residents)
- Share potentially dangerous: 33.9%
--- Assessed to be an immediate threat: 0.0%
--- Assessed to be in poor condition: 16.1%
--- Condition withheld: 9.7%
--- Not inspected: 8.1%
- Major examples (immediate threat): None
- Major examples (poor condition): Waterbury, Sugar Hill, Windsor Upper, Institute Pond

Croton Dam Waterfall and reservoir bridge walkway.
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yuriyt // Shutterstock

#24. New York

- Total high-hazard dams: 438 (2.2 per 100,000 residents)
- Share potentially dangerous: 37.7%
--- Assessed to be an immediate threat: 1.4%
--- Assessed to be in poor condition: 21.5%
--- Condition withheld: 1.8%
--- Not inspected: 13.0%
- Major examples (immediate threat): Toronto, Seneca Falls, Stillwell, Lake Jefferson
- Major examples (poor condition): Inghams Dam, Mill Brook Site 2 Dam, 60 Foot Dam, Deruyter Dam

An angled view of the Franklin Locks in Alva Florida.
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Anthony George Visuals // Shutterstock

#23. Florida

- Total high-hazard dams: 94 (0.4 per 100,000 residents)
- Share potentially dangerous: 39.4%
--- Assessed to be an immediate threat: 7.4%
--- Assessed to be in poor condition: 3.2%
--- Condition withheld: 3.2%
--- Not inspected: 25.5%
- Major examples (immediate threat): Lake Asbury Dam, L.P.Hill Dam #3, L.P.Hill Dam 1, Herbert Hicks Dam 1
- Major examples (poor condition): Lake Asbury South Dam, Lake Ryan Dam, Meadow View Lake Dam

Lake Travis Dam.
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Ric Schafer // Shutterstock

#22. Texas

- Total high-hazard dams: 1587 (5.3 per 100,000 residents)
- Share potentially dangerous: 43.5%
--- Assessed to be an immediate threat: 5.8%
--- Assessed to be in poor condition: 6.1%
--- Condition withheld: 2.2%
--- Not inspected: 29.4%
- Major examples (immediate threat): Williamson Dam, Chambers Creek WS SCS Site 42 Dam, Lake Comanche Dam, Hamilton City Lake Dam
- Major examples (poor condition): Amistad Dam, Robert Lee Dam, Sorrells Reservoir Dam, Livingston

Aerial view of Steele Bayou Control structure.
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Justin Wilkens // Shutterstock

#20. Mississippi

- Total high-hazard dams: 347 (11.8 per 100,000 residents)
- Share potentially dangerous: 43.8%
--- Assessed to be an immediate threat: 17.0%
--- Assessed to be in poor condition: 23.1%
--- Condition withheld: 2.3%
--- Not inspected: 1.4%
- Major examples (immediate threat): Indian Creek WS Str Y-9a-14 Dam, Lake Hilda, Big Sand Watershed Structure Y-32-11 Dam, Chuquatonchee WS Str 07 Dam
- Major examples (poor condition): Kelly Greenwood Lake Dam, Second Creek WS Str #6a Dam, Second Creek WS Str #7 Dam, Big Sand Watershed Structure Y-32-10 Dam

Jackson Falls Dam on Nashua River
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Wangkun Jia // Shutterstock

#20. New Hampshire

- Total high-hazard dams: 160 (11.5 per 100,000 residents)
- Share potentially dangerous: 43.8%
--- Assessed to be an immediate threat: 0.0%
--- Assessed to be in poor condition: 34.4%
--- Condition withheld: 8.1%
--- Not inspected: 1.3%
- Major examples (immediate threat): None
- Major examples (poor condition): Baker River Site 6a Dam, Baker River Site 5 Dam, Lake Gloriette Dike, Weare Reservoir Dam

Maumee River Dam in Fort Wayne.
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Nicholas J Klein // Shutterstock

#19. Indiana

- Total high-hazard dams: 281 (4.1 per 100,000 residents)
- Share potentially dangerous: 44.1%
--- Assessed to be an immediate threat: 0.7%
--- Assessed to be in poor condition: 31.7%
--- Condition withheld: 4.6%
--- Not inspected: 7.1%
- Major examples (immediate threat): Upper Peoga Lake Dam, Log Cabin Lake Dam
- Major examples (poor condition): Eagle Creek Reservoir Dam, Twin-Rush Creek Dam #3, Hood Lake Dam, Delaney Creek Dam #1

Lake Hartwell hydro dam power plant.
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Williams Photography 365 // Shutterstock

#18. Georgia

- Total high-hazard dams: 542 (5.0 per 100,000 residents)
- Share potentially dangerous: 45.2%
--- Assessed to be an immediate threat: 0.7%
--- Assessed to be in poor condition: 36.3%
--- Condition withheld: 4.2%
--- Not inspected: 3.9%
- Major examples (immediate threat): Butler Reservoir, Cochran Lake Dam, Aug. Canal Left Embkmnt + Structures (Below + Bulkhead Structure), Gordon Lake
- Major examples (poor condition): Bartletts Ferry, Main Dam, Tallulah Falls, Tara Lake Dam, Talking Rock Creek WS Str #13

Hoover Dam in Westerville.
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Kenneth Bradford // Shutterstock

#17. Ohio

- Total high-hazard dams: 425 (3.6 per 100,000 residents)
- Share potentially dangerous: 47.1%
--- Assessed to be an immediate threat: 0.9%
--- Assessed to be in poor condition: 30.6%
--- Condition withheld: 13.9%
--- Not inspected: 1.6%
- Major examples (immediate threat): Southern Silica Pond No. 1 Dam, Upper Shaker Lake Dam, Shreve Lake Dam, Blanchester Reservoir No. 4 Dam
- Major examples (poor condition): Marge Schott Lake Dam, Apple Valley Lake Dam, Barnesville Reservoir No. 3 Dam, Rocky Fork Lake Dam

Hoover Dam, Black Canyon of the Colorado River.
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Ian Kennedy // Shutterstock

#16. Arizona

- Total high-hazard dams: 162 (2.2 per 100,000 residents)
- Share potentially dangerous: 47.5%
--- Assessed to be an immediate threat: 3.1%
--- Assessed to be in poor condition: 6.8%
--- Condition withheld: 34.0%
--- Not inspected: 3.7%
- Major examples (immediate threat): Fredonia, Cook Reservoir, Green Road Basin, Maricopa Road Basin
- Major examples (poor condition): Frye Mesa, Jaques, Black Canyon, Fool Hollow

Aerial view of dam at Hawk’s Nest State Park.
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#15. West Virginia

- Total high-hazard dams: 419 (23.6 per 100,000 residents)
- Share potentially dangerous: 47.7%
--- Assessed to be an immediate threat: 0.0%
--- Assessed to be in poor condition: 6.7%
--- Condition withheld: 11.9%
--- Not inspected: 29.1%
- Major examples (immediate threat): None
- Major examples (poor condition): Horton Dam, Lake Stephens Dam, Elk Two Mile #14 Dam, Upper Smith Dam

Kerr Dam on the Flathead River.
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#14. Montana

- Total high-hazard dams: 206 (18.3 per 100,000 residents)
- Share potentially dangerous: 48.1%
--- Assessed to be an immediate threat: 0.5%
--- Assessed to be in poor condition: 12.1%
--- Condition withheld: 26.2%
--- Not inspected: 9.2%
- Major examples (immediate threat): Melstone Detention Dam
- Major examples (poor condition): West Fork Bitterroot (Painted Rocks), Kootenai Dvlpmnt Impoundment Dam, Newlan Creek Dam, Willow Creek Dam

Nickajack hydroelectric dam.
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#13. Tennessee

- Total high-hazard dams: 274 (3.9 per 100,000 residents)
- Share potentially dangerous: 51.5%
--- Assessed to be an immediate threat: 1.5%
--- Assessed to be in poor condition: 0.4%
--- Condition withheld: 20.4%
--- Not inspected: 29.2%
- Major examples (immediate threat): Fall Creek Falls, Radnor, Leisure Lake, Pressmans Home
- Major examples (poor condition): Grundy #1

Bonneville dam on the Columbia river.
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#12. Oregon

- Total high-hazard dams: 171 (4.0 per 100,000 residents)
- Share potentially dangerous: 55.6%
--- Assessed to be an immediate threat: 7.0%
--- Assessed to be in poor condition: 9.4%
--- Condition withheld: 38.0%
--- Not inspected: 1.2%
- Major examples (immediate threat): Smith, Hosler (Reeder Gulch, Clear Branch, Willow Creek 3 (Malheur)
- Major examples (poor condition): Bear Creek, Currant Creek, Mercer, Walch Dam

Jackson Lake Dam.
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#11. Wyoming

- Total high-hazard dams: 108 (18.6 per 100,000 residents)
- Share potentially dangerous: 57.4%
--- Assessed to be an immediate threat: 1.9%
--- Assessed to be in poor condition: 12.0%
--- Condition withheld: 25.9%
--- Not inspected: 17.6%
- Major examples (immediate threat): Laprele, Snyder Creek Det Dam X
- Major examples (poor condition): Upper Van Tassell, Hawk Springs, Leavitt, Cardine Keith

Gavins Point Dam on the Missouri River.
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Rick L. Saint John // Shutterstock

#10. South Dakota

- Total high-hazard dams: 88 (9.7 per 100,000 residents)
- Share potentially dangerous: 64.8%
--- Assessed to be an immediate threat: 0.0%
--- Assessed to be in poor condition: 15.9%
--- Condition withheld: 36.4%
--- Not inspected: 12.5%
- Major examples (immediate threat): None
- Major examples (poor condition): Marindahl, Richmond, Rank Dam, Lake Corsica Dam

Kentucky hydroelectric Dam over Tennessee River.
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#9. Kentucky

- Total high-hazard dams: 275 (6.1 per 100,000 residents)
- Share potentially dangerous: 65.5%
--- Assessed to be an immediate threat: 4.0%
--- Assessed to be in poor condition: 27.6%
--- Condition withheld: 33.5%
--- Not inspected: 0.4%
- Major examples (immediate threat): Rice Lake Dam, Elkhorn Lake Dam, Melvin Stinson Lake, Otter Lake Dam No 2
- Major examples (poor condition): Cranks Creek Lake Dam, Cedar Creek Dam, Willisburg Lake Dam, Red Lick Creek FRS 2

Garrison dam hydroelectric generating station.
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northlight // Shutterstock

#8. North Dakota

- Total high-hazard dams: 54 (6.9 per 100,000 residents)
- Share potentially dangerous: 66.7%
--- Assessed to be an immediate threat: 0.0%
--- Assessed to be in poor condition: 18.5%
--- Condition withheld: 38.9%
--- Not inspected: 9.3%
- Major examples (immediate threat): None
- Major examples (poor condition): Senator Young Dam, Matejcek Dam, Olson Dam, Bylin Dam

Percha Dam on Rio Grande in New Mexico.
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#7. New Mexico

- Total high-hazard dams: 222 (10.5 per 100,000 residents)
- Share potentially dangerous: 68.0%
--- Assessed to be an immediate threat: 1.4%
--- Assessed to be in poor condition: 45.5%
--- Condition withheld: 20.7%
--- Not inspected: 0.5%
- Major examples (immediate threat): San Mateo Lake Dam, Gardner Dam, Power Lake Dam
- Major examples (poor condition): Mcclure Dam, Lake Maloya Dam, T Or C Site 8c Dam, Nichols Dam

Table Rock Dam in Branson.
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Gerlach Photos // Shutterstock

#6. Missouri

- Total high-hazard dams: 1493 (24.2 per 100,000 residents)
- Share potentially dangerous: 69.9%
--- Assessed to be an immediate threat: 2.3%
--- Assessed to be in poor condition: 0.1%
--- Condition withheld: 0.9%
--- Not inspected: 66.7%
- Major examples (immediate threat): Fletcher Tailings Dam, Gun Club Lake Dam, Upper Little Black D-2, Lake Waukomis Dam
- Major examples (poor condition): Sterling Hollow

Woonsocket Mill and dam.
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#5. Rhode Island

- Total high-hazard dams: 95 (8.7 per 100,000 residents)
- Share potentially dangerous: 74.7%
--- Assessed to be an immediate threat: 0.0%
--- Assessed to be in poor condition: 55.8%
--- Condition withheld: 0.0%
--- Not inspected: 18.9%
- Major examples (immediate threat): None
- Major examples (poor condition): Gainer Memorial, Woonsocket Reservoir #1, Lawton Valley Reservoir, Harris Pond

Water flowing over dam.
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Canva

#4. Hawaii

- Total high-hazard dams: 120 (8.3 per 100,000 residents)
- Share potentially dangerous: 77.5%
--- Assessed to be an immediate threat: 12.5%
--- Assessed to be in poor condition: 64.2%
--- Condition withheld: 0.0%
--- Not inspected: 0.8%
- Major examples (immediate threat): Puu Lua Reservoir, Ku Tree Reservoir, Wailuku Water Reservoir 10, Twin Reservoirs
- Major examples (poor condition): Wahiawa Dam, Horner Reservoir, Waikoloi Reservoir, Kahoma Reservoir

Metal and concrete dam in Alabama.
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#3. Alabama

- Total high-hazard dams: 228 (4.5 per 100,000 residents)
- Share potentially dangerous: 89.9%
--- Assessed to be an immediate threat: 0.4%
--- Assessed to be in poor condition: 0.4%
--- Condition withheld: 5.7%
--- Not inspected: 83.3%
- Major examples (immediate threat): Cone Reservoir
- Major examples (poor condition): Logan Martin

Detail of light on concrete dam structure.
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Canva

#2. Arkansas

- Total high-hazard dams: 194 (6.4 per 100,000 residents)
- Share potentially dangerous: 98.5%
--- Assessed to be an immediate threat: 0.0%
--- Assessed to be in poor condition: 1.0%
--- Condition withheld: 13.4%
--- Not inspected: 84.0%
- Major examples (immediate threat): None
- Major examples (poor condition): Paris Dam, Broadmoor Lake Dam

Seagulls at the Melvin Price Locks and Dam No. 26 in Alton.
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MShipphoto // Shutterstock

#1. Illinois

- Total high-hazard dams: 252 (2.0 per 100,000 residents)
- Share potentially dangerous: 98.8%
--- Assessed to be an immediate threat: 0.0%
--- Assessed to be in poor condition: 0.0%
--- Condition withheld: 98.8%
--- Not inspected: 0.0%
- Major examples (immediate threat): None
- Major examples (poor condition): None available

This story originally appeared on GetMyBoat and was produced and distributed in partnership with Stacker Studio.

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