MS Dam Failure Deemed ‘Not Imminent’
The U.S. Army Corps of Engineers (USACE) Vicksburg District has reportedly declared that the failure or breach at Arkabutla Dam in Mississippi is not imminent.
In its first update on the concerns, USACE made their decision that the dam running along the Cold Water River was not in imminent danger of breach while assessing conditions and exploring temporary solutions for the dam’s condition.
Last week, the Vicksburg District’s Emergency Operations Center identified a potential breach at the Arkabutla Dam on the Coldwater River in Mississippi.
USACE noted that previously observed conditions led to the declaration, and the district would be providing updates as they become available. Several areas around the dam were closed, and residents were warned to stay away as it was undergoing emergency repairs.
Additionally, the National Weather Service issued a flood warning, noting that if the dam breaks, low-lying areas could be “severely affected.” Reports indicate that it is not clear how the potential breach in the dam could have occurred.
The dam itself was constructed in the 1940s, spanning 11,500 feet in length and 67 feet in height. It was built in response to floods in the area, one of which being the Great Mississippi Flood of 1927. Each year around 2 million people reportedly come to visit the dam and surrounding area.
Corps says Arkabutla Dam failure not imminent. The U.S. Army Corps of Engineers (USACE) Vicksburg District teams are assessing conditions and exploring temporary solutions at Arkabutla Dam after a May 8 emergency declaration, but dam failure or... https://t.co/I25tosq19P pic.twitter.com/aAephniwUV— HYDROVISION International (@HYDROVISIONIntl) May 16, 2023
As of May 10, officials had said that the failure of the dam is not likely. However, should that change, warnings will reportedly be issued for impacted residents.
Constructed in 1943, Arkabutla Dam is 65 feet high, 10,000 feet long and reduces flood risk for 19,000 residents. The dam protects $510 million in homes and businesses, said USACE.
A risk assessment from May of last year rated the dam with a “moderate” score, noting that it is well built and has performed as designed. However, certain large storm events could cause the lake to rise and cause downstream flooding, or increased reservoir levels could drive foundation pressure to damage the structure and cause failure.
According to the recent release, an Emergency Operations Center was activated after crews discovered a depression near the toe of the dam, where the dam meets the earth. This could result in severe foundation loss and a breach if not repaired.
USACE says that it defines an imminent breach as “the emergency level when time has run out, and the dam has breached, is breaching, or is about to breach. It is not usually possible to determine what amount of time a complete breach will take to develop. Therefore, once a decision is made that there is no time to prevent a breach, the emergency warning must be issued.”
Though the dam is not in imminent danger, the district has continued to release water from the dam into the Cold Water River in hopes of achieving an elevation of around 210 feet by June 20. This will reportedly help to significantly reduce the risk of failure and floods, particulary in low-lying areas and homes
The water from the dam is expected to crest in the river at Sarah and Marks, Mississippi, sometime this week at 12 feet and 34 feet, respectively. The district also states that this cresting will last a few weeks while they continue to monitor conditions in the area.
The district plans to monitor conditions based on future local rainfall and length of time releases are required from the dam. Property owners have been urged to plan to evacuate livestock and heavy machinery as a precaution.
The district claims it will continue to assess the repairs timeline, giving updates as they come. The current Interim Risk Reduction Measures (IRRM), or temporary solutions, include modifications to the structure, increased instrumentation and monitoring, and emergency action planning.
Cory Winders, Hydraulics Branch Chief for the District, told the DeSoto County Board of Supervisors earlier this week they won’t know the scope of repairs until the lake is low enough to examine the issue. However, he said that repairs are expected to take 2 to 3 years
“When we started getting phone calls last week, we had people thinking this was going to be done in a couple of days,” Winders said. “It’s going to take until mid-to-late June for us to get the lake level down to 210 (feet). At that point, we’re going to have to reassess to see if it is safe to get out on the dam and do our analysis or if we need to drain the lake some more.”
Winders added that the next step would then be determining what repairs need to be done on the dam.
“We’ve never released that much for that long, so Coldwater River’s going to be really full,” he said. “My concern from my standpoint is when we get local rainfall, how much is that going to back up these tributaries that drain into the Coldwater? So that is something we’ve got to monitor.”