By BILL MARDIS, Editor Emeritus
It is no secret that residents of Music City USA have been a bit jittery the past three years while the U.S. Army Corps of Engineers is trying to plug leaks in Wolf Creek Dam.
If Wolf Creek Dam were to fail –– a highly unlikely event according to the Corps –– Nashville could suffer $2.4 billion in damage and 10,000 buildings could be flooded, according to a Corps document. Wolf Creek Dam is nearly a 100 miles as the crow flies from Nashville but 50,000 acres of water suddenly rushing down the Cumberland River would create a tide all the way to the Ohio River.
The Cumberland River starts in Letcher County on the Cumberland Plateau, flows through Southeastern Kentucky; crosses into northern Tennessee just north of Nashville; then back into Western Kentucky where it empties into the Ohio River at Smithland.
Intensive grouting was begun in January 2007 to shore up the earthen section of Wolf Creek Dam and Corps engineers assure the dam is not about to wash away. A contract has been let to insert a diaphragm wall through and some 275 feet into the bedrock below the dam to permanently repair the structure. The level of Lake Cumberland is being kept about 40 feet below normal while this work is under way.
Nashvillians no doubt are concerned as they continue to hear unsettling ripples from up the Cumberland River Basin. Teeth chattering could be heard above banjo picking when the Corps revealed a couple of years ago that the dam impounding Center Hill Lake in Middle Tennessee is in high risk of failure. This lake, also in the Cumberland River Basin, is about 63 miles from Nashville. At pool stage, Center Hill Lake is 64 miles long and has 415 miles of shoreline.
Seepage control has been a serious issue at Center Hill since construction in the 1940s due to the highly solutioned karst limestone foundation and rims. Despite various grouting programs, seepage continues around the dam and through the foundation. The first major contract has been awarded at the onset of a six-year rehabilitation of Center Hill Dam and the lake is being held lower than normal.
The latest lake news must have made Nashvillians’ nerves taut as a guitar string. The Corps said this week that J. Percy Priest Dam, located about 10 miles east of downtown Nashville, has received a Dam Safety Action Classification II Ranking (DSAC II).
Corps officials downplayed the significance of the ranking.
“There are no problems with J. Percy Priest except its proximity to Nashville,” said Mark Rankin, public affairs officer with the Corps’ Nashville District. He said the situation at J. Percy Priest is a “totally different ballgame” from seepage problems at Wolf Creek Dam and Center Hill Dam.
“We do not think that J. Percy Priest is in imminent danger of failure, and there are no signs of active seepage or leakage problems like those that exist at Wolf Creek and Center Hill dams,” said a Corps document.
“J. Percy Priest Dam was assigned the DSAC II ranking because of potential concerns with the original treatment of the limestone or karst foundation, concerns about the ability of the dam to meet current flood safety criteria, and downstream consequences in the unlikely event of a dam failure,” the document explained.
“(The DSAC II) ranking states there are ‘unconfirmed dam safety issues’ at the dam. This, combined with the dam’s proximity to Nashville confirms that the dam is not as safe as the Corps would like it to be, and that actions should be taken to reduce the risk,” the document revealed.
“Based on this ranking, the Corps will investigate further to determine the appropriate course of action to address these concerns, and will seek funding to complete the necessary studies,” it said.
“The Corps is developing an Interim Risk Reduction Measure Plan. This plan will define those measures that should be taken to reduce risk at J. Percy Priest until a permanent fix can be put in place. This plan is still in the very early stages, but could include measures such as additional instrumentation and possible lake level restrictions,” the docu-ment concluded.
