adjacent pile cap

huangyhg

adjacent pile cap
more specific question regarding adjacent foundation element.  example, 120 ton compression capacity auger cast in place pile system, two pile caps 8'-0 square with four piles each, face to face of pile cap dimension is 16'-0 (center to center of columns 20'-0).pile cap a is under basement wall top of slab elevation 2'-0, top of pile cap elevation 0'-6.  pile cap b is supporting a column of the first floor, top of slab elevation 18'-0.  what would you make the top of pile cap elevaion for pile cap b?  soil is sand with silt.
thanks for your quick replies.

based on the proximity of the two pile caps, the contractor will need to excavate the area to place the lower pile, so it would only make sense to have them both at the lower elevation.
auce98