Federal officials leading the 300 (M) million-dollar project say the limestone caverns -- known as karst - present unique problems for engineers.
The plan is to pour concrete into the underground gaps and build a long underground wall to seal of the seeping passages at Wolf Creek Dam. Officials say the dam is in danger of failure if the work isn't done.
But experts say the underground karst could be problematic.
Western Kentucky University geology professor Nick Crawford says it's doubtful workers will be able to seal off all the leaking water underground.
Officials with the U-S Corps of Engineers say technology has improved since the last repair project at the dam in the 1970s. They say the new work will ensure the dam is safe for another 50 years.