For related stories about this dam's problems, and photos, see the following site and click on the headlines on the left margin:
"JAMESTOWN, Ky. (CBS) - There are more than 80,000 dams protecting communities across the nation from floods.
Many were built more than 50 years ago using outdated technology. About 3,500 are deemed unsafe; some are classified as being on the verge of collapse.
Wolf Creek Dam, one of the country's largest dams, in Kentucky is in danger and so are the people who live within the region.
Stretching a mile from end to end, the gigantic Wolf Creek Dam is vital to southern Kentucky and northern Tennessee, preventing the periodic flooding that once plagued the cities and towns along the 700 mile Cumberland River. But Wolf Creek Dam is in trouble.
"The problem is about 250-300 feet below us in the rock," said Mike Zoccola of the U.S. Army Corps of Engineers.
The Corps of Engineers recently designated the dam at "high risk" for failure, requiring "emergency measures" to reduce an "imminent risk of human life".
"We estimated a range somewhere between about 50 and 120 people, the loss of life - people who live downstream, and possibly fishermen or campers that may be down there," Zoccola said.
The devil is in the design. Wolf Creek Dam was built on porous limestone. Over time, water has seeped into cracks in the rock, eroding a Swiss cheese of holes and caves. A sinkhole could cause this entire earthen embankment to collapse.
The first town downstream is Burkesville, Ky. The state has handed out warning radios to all 1,700 residents.
"I've heard four to six hours," said a restaurant manager when asked how much time he'd have if the radio started to go off.
There are currently 3,500 dams in the United States listed as unsafe and the list is growing faster than the rate of repair. They may not all be as big as Wolf Creek Dam, but when they fail, the results can be catastrophic.
In recent years, fears about dams giving way have forced evacuations in Maryland, Massachusetts and Missouri. Seven lives were lost last year when a dam broke in Hawaii.
The American Society of Civil Engineers gives the infrastructure report card of the nation's dams a "D" and called for fully funded dam safety programs in all 50 states.
"If you live downstream from the dam, it doesn't matter whether the dam was attacked by terrorists or whether it failed because of fatigue and age and lack of repair. The people downstream are all impacted the same," said Patrick Natale of the American Society of Civil Engineers.
At Wolf Creek Dam, lake levels have been lowered to reduce pressure and crews are working 24 hours-a-day to fill the underwater holes with grout.
Because while the potential damage to Burkesville would be in the millions, the damage to Nashville, located further downstream, would be measured in the billions.
The U.S. Army Corps of Engineers is in the process of updating evacuation plans for those in danger."
Note: As the article says, "The devil is in the design". Dix Dam was also built on porous limestone, known as karst, with caverns, underground streams and sinkholes. We know that their are caverns under the Dix Dam because there are numerous "boils" in the river below, where water literally comes to the surface after traveling under tremendous pressure through the caverns under the dam. Studies have shown that these caverns enlarge at a very rapid rate with highly pressurized water. Over time, water has seeped into cracks in the rock, eroding a Swiss cheese of holes and caves. The collapse of these caves under the tremendous pressure and weight of the dam could cause severe structural integrity problems, according to the Corps of Engineers.