Depending on the amount of rain and the drainage configuration at the back of the garage, the biggest issue I see is the soil will likely spill out into the garage if it gets wet.
And, Randy, what will happen to the voided area above the garage where the soil came from…and above that? With all the mud slides/quakes I hear about from out there, it seems potentially hugely problematic to me. :shock: But, you’re the engineer.
Structurally the garage may be OK, but the wall most likely was acting like a retaining wall for the soil behind, or it would not have been a concrete wall. How much of a problem that will be will depend on the amount of rainfall that area gets and the soil type.
David, just from the photos you provided it’s seems obvious to me that the structural integrity has been compromised. I would not hesitate to refer this to a qualified contractor for corrective action.
“A portion of the rear retaining wall of garage has been removed. The structural design of this wall has been compromised and needs to be referred to a qualified contractor for any and all corrective action.”
Randy, I have great respect for you as an engineer and you have helped many, on this forum, with your expertise and drawings.
It is very possible that I misunderstood your meaning. I was just confused by this statement (when I think the potential for much more damage is possible.):
The soil behind that cutout looks dry, that’s why it is standing vertically. If the soil becomes wet it will loose its ability to support itself and will slump into the garage. This will likely create a chain reaction until the soil at the surface falls into the void created when the lower portion fell into the garage.
With all the mud slides/quakes I hear about from out there, it seems potentially hugely problematic to me. :shock: But, you’re the engineer. 
