Well the suggestion that you use the native clay for back fill right at the wall is a sound one. Adding sand will just let the water from the surrounding clay collect where you went thru the wall.
Thank you. I am NOT a professional on utilities and ditches but fortunately for me, my brother-in-law is (and sounds like you have a lot of experience in this area too). It just "made sense" to me.
Backfill Methodology/Thoughts: Although I did not mention it in previous posts, but the Logstor is fully supported with 8"-10" flume sand right up to the 90° turn and 2 feet straight piece that go into the pipe. The flume sand was then compacted the entire trench length with a hand tamp. The Logstor was laid onto this flume sand foundation, straightened, and then covered with another 12 inches of flume sand and hand tamped again. About 6-7" of flume sand over the top of the Logstor.
The 1" electrical conduit was then laid on that flume sand foundation and covered with 3 inches more of flume sand. and tamped. The main run was backfilled over the electrical conduit and flume sand with many loader buckets of clay using the New Holland TC33D tractor. I completed compaction with the weight of the loader, tractor, and a 1600 lbs 4-in1 box blade. Many runs back and forth squishing it all down for good compaction.
I am certain "the turn" and main run (90 feet) were fully supported with good, compacted base.
Backfill up to a couple feet of the wall, then for expected heavy rains you can place planks over it and a tarp to shed excess water.
This is a really good suggestion that I am going to use.

...Now if replacing or installing a new pipe they hand dig the last several inches to be even with the bottom of the hole in the wall so the bottom of the trench is never disturbed. Soil can't fall away from the bottom of the pipe if it doesn't have to settle in the first place.
Because I core-drilled from the outside of the wall into the interior, I had to dig down 8 inches below the lower, 6" core-drilled hole (in order to mount the core drill mounting plate to the wall). I dig fill that back up with heavy clay and hand tamped the heck out of it.... all the way up and just over the top of the Logstor as it enters the house. I am hoping this will eliminate/minimize and major settling at the wall itself (but your point on clay settling
slowly over years of time is well-known by me; it happened during the original, lackluster backfill job of the original build some 14 years ago).