Lakeboy2004! Hi again. I read the follow up posts and would like to add my nickel.
Piles - (I will call mech devices "pushed" or "driven" into the ground to develop skin friction and end bearing)
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The piles that you install whether steel, PVC...
I would like to add a possibile variation to your choices. You may wish to investigate the cost and validity of using a deep compaction grouting process to bridge that softer soil strata.