U.S. Army Corps of Engineers Deputy Public Affairs Officer Lisa Coghlan said the dam, built in 1950 to serve seven purposes including hydropower generation and recreation, is rated No. 4 on the Dam Safety Action Classification Table.
"On a scale of one to five, it's ranked fourth, which means it's one of the safest in the country," Coghlan said. "There are annual and biannual inspections, there's daily inspections of the dam itself every day.
"[In the event of a failure], we would be working with local emergency responders on the ground, and we also have training and interaction with them all of the time because of the potential of something like this happening. It wouldn't be the first time we pick up the phone and call those people. We would have been working with them in the past over many, many years. We have drills, training where we all train together, come together and discuss potential failures and how we would respond and coordinate the messages and information to them and vice versa."
A Corps map shows what Bartow County Fire Chief Craig Millsap called "the worst case scenario." If there were a complete dam failure, flooding would arrive in the city of Cartersville in 30 minutes with the water peaking in about 3.5 hours; Euharlee in 3.5 hours with a peak at about 11 hours; Kingston in 5 hours with a peak at about 17 hours; and Rome in 10.5 hours with a peak at about 26.5 hours. At 43 river miles away, Rome would be the largest city impacted by a failure.
Bartow County Emergency Management Director Johnny Payne also called a dam failure "very unlikely," and said although Bartow County has not had an earthquake, it does experience tremors and earthquakes have occurred north and south of the area.
"The chance of failure is remote, but we could have it with an earthquake. We are prone to have earthquakes because we're on the fault line. That would be my biggest worry," Payne said. "If it turned loose totally -- that's the only time it's going to do it -- you got 30 minutes to get anything down below out of the way. The devastation is going to be: Interstate 75 is going to be gone, U.S. 41 is going to be gone, Ga. 293 is going to be gone and then you're looking at Ga. 113 covered in water. And then you're looking at Rome and Kingston and other places are going to be devastated in water. All downtown Cartersville would be flooded out into the Atco area back up into the Pumpkinvine area back all the way down to the airport. All that stuff, all those subdivisions built on the river would be gone. ... Emerson would be affected some."
Transportation would be a problem for rescue crews, but the level of devastation would depend on how much water was in the lake. Allatoona's water is low in the winter and high in the summer or when rivers reach flooding stages.
Payne estimated one third to one half of Cartersville and Bartow's populations would be affected if the dam gave way. But the county does not have an emergency evacuation plan for dam failure and flooding as does Floyd County. It would operate under the Emergency Operations Plan.
"The plan is: How are you going to get [people] out of here in 30 minutes?" Payne said. "It never has come up and as far I know we have not sit down and worked on it. We've talked with the Corps. How we're going to get all these people, I don't know yet. We're working on it, been thinking about it. I've got Public Works thinking about it. The only way we could do it would be with the alert system, but the total failure of [the dam], I don't know yet.
"I would mobilize everybody I can and get them out of here. Which way am I going to send them? North and south. Up U.S. 411, I-75, north, and them call GEMA and FEMA and tell them I've got a major disaster so they can come in here and help."
The purpose of Floyd's plan is to establish procedures for warning, evacuating and sheltering persons who would be endangered if the dam were to fail; it also addresses similar emergency response actions in the wake of flooding or emergency dam releases. Floyd would have several hours to prepare, whereas areas located closer to Allatoona Dam, such as Cartersville, would have little time to perform evacuations.
Millsap, who also serves as Bartow County EMA's deputy director, said, "The reason this has not been a high priority on planning is it's not that high of an event chance. It would take something extremely catastrophic like an earthquake to cause that kind of catastrophic failure to the dam and if that happened, we've got so many other problems going on that it's just going to add to that.
"The dam has its protections and plans for terrorism attacks, [failure] is not that great of risk. There's a lot greater risk of a tractor trailer turning over on I-75 with something bad enough to produce a cloud to kill people than this happening. Our proximity to the dam makes notification almost nothing."
The city of Cartersville, which Payne said would be submerged if the dam failed, would have little to no time to notify residents. County rescue crews would use multiple notifications systems to reach outer lying areas, Millsap said. Those south of the river would be told to travel further south and those north of the river, further north.
"The closer you are to the epicenter of the dam if that did take place, the greater risk you're at and people need to know that," Millsap said. "People need to look at where they're at and figure out they're own evacuation routes for something like that. But it doesn't just apply to this, they need to have that in place for flooding because the areas that normally flood would also be getting water. These are things we normally try to urge people to do, have your evacuation plan in place -- 'If I find out this is the problem, I'm going this way.'"
Coghlan said two July dam failures in the country -- Iowa's Lake Delhi which gave way to a rapidly rising Maquoketa River and a 16-foot-high section of Arizona's Tempe Town Lake failed -- are not structures maintained by the federal government.
Built in 1972 to produce hydroelectricity, Delhi's dam is now used solely for recreation and Lake Delhi Recreation Association members pay dues to maintain it. Heavy rains forced the river to unprecedented levels, causing earthen portions of the dam to collapse and sending a torrent of water rushing downstream.
A tear in a seam of an inflated rubber dam sent millions of gallons of water gushing from Tempe's man-made lake near Phoenix. Blazing sun and high summer temperatures coupled with cooler winters is believed to be a factor in the inflatable dam section that was supposed to last 25 to 30 years. The lake was first filled in 1999.
-- Information from the AP was used in this report.