Stormwater System within New Building Footprint: Effects on Foundations

I would make sure that the building foundations are founded at or preferably below the invert of the chamber. Otherwise, collapse of the chamber could cause failure of any nearby foundations.

There was a thread on here not too long ago about this. I can’t seem to find it though.

Honestly, my gut says this is a bad idea. Water usually is what you want to keep out of your building, not invite in.

My question would be, are there any concerns with the on-site soils with the potential of fines being washed deeper or having some hydrocompaction issues. Both could lead to building performance issues.

What about if the system doesn’t perform? Infiltration systems don’t always work as they are designed. System alterations and maintenance is going to be a pain.

Then there is the whole humidity/mold issue.

In my area (high water table), shallow foundations that are uniformly wet work...

shallow foundations that are uniformly dry work...

shallow foundations that uniformly alternate between wet and dry work.

IMHO, on occasion, the proposed system will result in shallow foundations where a portion will be "wet" while the remainder will be "dry"... a recipe for trouble (differential settlement).