Tanks on slab on grade

[JStructsteel]

I have 2 12' diameter x 30' tanks on a slab on grade. My first concern is do I take a foundation down to frost depth, or do I add a granular fill with drainage pipes under the slab? The contractor wants to do a perimeter foundation wall around the slab (1 side is against a building) but I dont see the benefit of a wall down to frost outside.

Next concern is overturning. To me a empty tank situation would be the worst case with wind, then perhaps a full situation and seismic loading.

What thoughts do you guys have?

Thanks
Jim

 

[r13]

Is this the tank?

 

[bones206]

Just received a geotech report for a tank mat foundation I'm designing (coincidentally also for a diary facility, but for chemical tanks not milk). As seen below, they provided a soil replacement option in lieu of founding the slab at the frost depth:

The on-site soils are generally classified as non-plastic, sandy gravel and gravelly sand with trace to little amounts of silt, based on the laboratory test results completed. The gravelly sand and sandy gravel soils have corresponding Unified Soil Classification System (USCS) Group symbols SM, GM, and GP-GM, and are considered moisture sensitive and frost susceptible. Mat slabs requiring frost protection should be founded a minimum of 4 feet below final exterior grade, or the on-site soils should be over excavated and replaced with non-frost susceptible
Engineered Structural Fill.

 

[JStructsteel]

That seems very similar, I dont think the thanks they are supplying are on legs.

My prelim design is a 20" thick mat footing. Thats mainly for overturning for the seismic design. Overkill, but meets code.