I noticed noone had responded to your inquiry on a couple forums for many days. While it is admittedly not directed at your specific application, you may be interested is a sort of contour-appearance map of “Extreme Frost Penetration…” in the USA that appears (along with a lot of other stuff!), specifically in the “Foundation Depth” discussion area of standard ANSI/AWWA D100 Welded Carbon Steel Tanks for Water Storage. [I would further caution that this map was probably put together in the days before Algore brought “global warming” amongst us. ;>)]
