[mrrec]

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well... If the vault was full how could the level of water gone down if there was no dranage in the vault?

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It's pretty tuff to make concrete watertight and it obviously leaked at the joint of floor and walls. Groundwater could enter this way, too, but looking at the top of the walls and the goo in the bottom, it appears the lid was not sealed properly - a major mistake. A drainage system around the peremiter would have done a lot.....

So water enters at top and does not drain out unless the groundwater is low enough to allow it to escape through the floor/side joint.

I think it will take more than a 5 gal can of Safest Rust Remover on this one......

Dave