First the corrugated elephant trunk is the unrelated footing drain and it seems to run (uphill?) to the shop or just really connects to shop and shop actually drains there to funklily made hole. It is well perforated and was not plugged but we teed it dropped it down to rock drain just for added drainage. There was never a problem with this drain.
The problem was out downspout and backwash water from softener - see the two white PVC perf pipes - one from shop other from house. They got plugged mainly because neither was actually capped off so ground water during the supersaturated winter of 2021 drove dirt and rocks up the pipe to meet normal debris coming down. Seems a bit counterintutive but junk worked its way up the pipe plus the junk in the gutters made a good 5-6 feet of nasty pluggage that my power washer could get past but not remove.
The drain rock is around 5 feet deep under that perf pipe.
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