Limestone Causes Mid-State's Dams To Leak, Slowly

[jonsdigs]

Limestone Causes Mid-State's Dams To Leak, Slowly
WKRN Nashville
December 18, 2006, 4:20 pm

If either the Center Hill Dam or Wolf Creek Dam were to fail, the flooding would be devastating. The Army Corps of Engineers said towns and cities in Middle Tennessee would be underwater if the Wolf Creek Dam in southern Kentucky or the Center Hill Dam in DeKalb County breached.

The Wolf Creek Dam is scheduled for a seven year multi million dollar renovation, but despite that, it may be just a matter of time before the dams burst.

The limestone in Middle Tennessee is about 460 million years old but the problem it creates will last longer than that.

Limestone is formed at the bottom of sea beds; it is organic and made from shells and skeletons of microscopic marine life.

The limestone in Tennessee is almost 100% calcium carbonate and it is alkaline. Acidic rainwater reacts with it causing a chemical reaction that actually producing heat, water and hydrochloric acid. In time, the rock dissolves.

Called karst geology, the limestone produces the caves that are famous in Tennessee; great for spelunkers but not so great for dams.

Center Hill Dam and the Wolf Creek Dam were built in a karst geology or limestone full of holes. Water that finds its way, allows both dams to leak. Center Hill leaks about 200 cubic feet a second.

The Corp of Engineers willstart a $240 million rehabilitation project on the dam starting next year. It will last seven years as they try to plug the seepage by filling in areas on next to the dam on the lake side.

The project will only bide time as dams in limestone are temporary structures. While they will not burst, they will slowly become moot as leakage around the dam makes it impossible to hold the water table. While no one knows how long it will take; a couple of hundred years or several lifetimes, it is more likely than in the next ten.

On Sunday, the U.S. Army Corps of Engineers called off plans to lower the level of Center Hill Lake. They thoughtthere was a breach in the dam, but determined it was just a false alarm.

Article

[Azurerana]

"The project will only bide time as dams in limestone are temporary structures. While they will not burst, they will slowly become moot as leakage around the dam makes it impossible to hold the water table. While no one knows how long it will take; a couple of hundred years or several lifetimes, it is more likely than in the next ten."

--Silly article author. *All* dams are temporary structures. Dams do not 'hold the water table' . See the thread on Wolf Creek Dam elsewhere on this board. No wonder our scientific illiteracy is so high.

[L Roebuck]

Here's the thread link

Wolf Creek Dam was built on Karst

[Brian Roebuck]

Most of the dams that TVA built in TAG are in Karst areas. The deep valleys with flowing rivers through them make up much of the Karst terrain around TAG and was perfect for the construction of dams if you ignored the fact the rock is rather porous and the whole thing would eventually leak. Cheap electric power was more important at the time and concrete was simply pumped in to fill in the gaps when they appeared. Tims Ford Dam had several karst leaks that were filled in this way not too long ago. I suspect more will follow in many of the area dams.