FOUNDATION CONTAMINATED BY PRODUCT - CRUDE OIL
Wednesday, January 11, 2017 By: CE 
Dear Tank Experts,
A happy new year wish to you all.
I have a situation with one of my jobs. It is a crude oil storage tank. Had its Single deck floating roof collapse that punctured the bottom plates and the product have seeped through the punctures. During inspection, we noticed oil weeps from underneath the annular plates from the tank external.
1. How can the foundation be inspected.
2. What code do we refer for detailed tank foundation issues?
3. Oil contamination on foundation, what does it cause?
4. If confirmed contaminated by any code/standard, what is the repair/remedy procedure?
I appreciate your usual assistance with these.
Also any other useful infor will be appreciated.
I have just completed hydrocutting the roof and discovered the holes on the bottom plates.
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Friday, January 13, 2017 By: ITS 
Well to answer your first question, I think you are already inspecting the foundation concrete annular ring. Your crude oil, which I presume is thick and out of the ground thick, will find the path of least resistance which is seeping out from under the steel bottom because of the floor lap plates. As the crude oil cools from its pour point temperature then it should thicken nicely. What has entered the ground will plug the soil or as we say - the soil sizing factor will determine the amount of soaking depth until is cools, then it will go no where.
If the concrete is in reasonable condition the crude oil will not effect the strength of the concrete ring follows what I consider a reasonably good design. You may end up core drilling the concrete ring to draw seepage if any and possibly place a slight vacuum on the soil, but this needs a professional opinion.
When repairing the floor of the AST, you may remove the plate or plates and access the soil, but I think you will find that very little saturation in the soil to any appreciable depth will be evident. Shovel it out. Sure you can get a hydrocarbon sniffer but that may not be practical or an application of good common sense until the entire tank farm is remediated if ever.
I am not sure my help represents you site conditions, but maybe someone else can assist too.
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