Anyone ever heard of a hold down pit? Apparently it is a depression left at the top of an area of a foundation pad before the concrete is poured, according to a construction guy I talked to…but he could not explain the purpose.
Relief Trenches. https://profengineering.com/relief-trenches-who-needs-them/
If you talking about the deep sections, these are the beams sections that provide the strength in a waffle foundation. Look up waffle foundation.
That’s what the guy talks about in the link I shared above.
Question answered. No they are unrelated to drainage or the beam sections.
Apparently some engineers more recently have decided to install depressions at the top of foundation pads to provide additional strength/foundation thickness for framing hold downs. It’s something new I’m told.
Thanks for the help.
Good education on waffle foundations: