Digging out a crawlspace

I have a contractor who wants to convert most of his crawlspace into a basement (it is his own home). Enclosed is the detail we are tossing around. The soil is pretty stiff and he is doing this in small sections so he is not worried about stability during construction. My question is how to account for the surcharge load due to the existing house footing? Part of the footing load is being used to prevent overturning of the new retaining wall, but part of the load is adding surcharge. If the computed pressure under the existing footing is, say, 750 psf (service), what would you do?
See drawing below:


Have done this often, but make the wall thickness the same as the footing width… no eccentricities… break into underpinning segments… Here is some standard detail:

Above is a snippet.

I have done this, but using Segmented underpinning and an additional full height interior 6” thick reinforced concrete wall to take the soil load. Need to trim off the interior portion of the existing strip footing too.

I would approve what is shown here if, say every 6 feet or so, a one foot wide underpin segment was placed full width of the existing strip footing to eliminate the eccentric vertical load. Otherwise, no.

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