The limestone bedrock under Wolf Creek Dam, above, has cracks and caves that allow water to seep through. The area of concern is where the earthen section of the dam wraps around the concrete portion (in distance at upper left). "The original plan was to drill a line of large holes down through the earthen part of the dam and into the limestone foundation beneath it, then fill the holes with concrete to create a wall, sealing off seepage channels in the foundation," Estep writes.
Because that plan isn't working as well as the Corps hoped, the French and Italian contractors will build a concrete wall inside the earthen dam by boring a thick steel casing into the ground, then putting the concrete inside the casing. That will "provide more support in the holes and guard against making seepage channels worse during the construction process," Estep writes. The Corps did not release a revised estimate for the cost of the project or completion date but admitted both would likely go up. "One early estimate of the cost to fix the dam was $317 million. That had climbed to $584 million before the change in construction methods," Estep writes. "A key contractor predicted at one point that the project would be done by summer 2012, and perhaps sooner, but it appears that date will be pushed back." (Read more)