Existing Soil Foundation

[AAEC]

Got this existing storage tank that need to be replace with a new tank. The existing tank is smaller than the new tank 60ft diameter vs 80ft diameter and new tank is 5 ft higher than the old tank. We would like to place the new tank in the same location as the old tank. My question is do I still need to do anything with the existing soil foundation even if we did not have any problem with the old tank? What are the minimum we should do before we build the concrete foundation?

 

[civilperson]

Why do you need a concrete foundation?

 

[AAEC]

civilperson,

The old tank is seating on concrete foundation. Since the footprint will change, planning to demo the old concrete foundation and not disturb the existing soil foundation. Just need to add additional soil and new concrete foundation to accomodate the increase in footprint. The new concrete foundation will also protect the tank bottom from corrosion. Would appreciate any recommendations.

Thanks,
AAEC

 

[BigH]

Is the concrete foundation under the whole tank (raft) or is it a concrete ringwall? What is the nature of the soil supporting the tank (soil type(s); layers and their thickness; SPT N values, Undrained shear strengths, etc.)?

 

[Ron]

When you demo the old foundation, you will disturb the existing soil. Plan on recompaction/stabilization before placing a new foundation.

A concrete slab foundation will not necessary protect the tank bottom from corrosion. You will need to handle corrosion issues whether you use a concrete slab foundation or a ring wall foundation.

 

[DRC1]

I am sure this sounds like just an easy answer, but you really should have a local foundation engineer look at it. To answer your question, it does not sound like there would be a lot of work required, but since it is not the same tank, there will be some and the money invested in making sure you get the right answers is the best insurance you can get. The devil is in the details, and I don't think we will be able to get all those for you.