Rented an electric powered Makita HR3851 rotary-hammer with a 3" wide chisel bit to break up some "hard as concrete" Caliche soil. The local Ace Hardware rental place charged $22 for 4 hours ($100 deposit).

The Makita HR3851 rotary-hammer weighs around 20 pounds with the bit installed, and has a hammer only selector knob.

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If available for rental, a Makita HM0810B hammer would be a better choice, because it lacks the rotary mechanics and weighs around 5 pounds less.

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Once the hole is at the desired depth and diameter, the bit can also be used to fracture the bottom and sides for better drainage and root growth. Planting guideline article.

This is one strategy for disposing of the excavated Caliche soil. If you have one of those garbage containers that the sanitation truck picks up with a hydraulic arm, position it at the curb. That way you only have to move buckets of excavated soil once . . from the hole to the garbage container. Keep in mind that excavated soil greatly expands, so depending on the volume, some soil may have to be "staged" and discarded on subsequent pickup days.

To get the most use out of the equipment rental period, also plan on removing/relocating other shrubs or small trees during that time.