A trick we used in the far north was to put down a foot wide strip of 2" thick foam board insulation. First, it cushioned the fall of the dirt and second was the insulation. Pick the big rocks out but we never had a problem doing it this way.
Good trick!
Or local building inspectors will approve 1' less depth for every 1" (R5) of rigid. We can use a max of 2". Normal depth here is 44-48" so we could go to 2' plus 2" of rigid in an area with a large bolder or similar that prevented digging to the standard depth- very rarely used but a vital trick!
Doing underground in my previous location we would use "sand" or "base". Then in my current location they use "crushed stone" or "stone dust".
I'd assume the concern is larger stone that could damage the pipe? Like 1/2" and above?
Thanks - I was hoping to do that - but wasn't sure how risky that would be. We are supposed to get into the mid 30s for most of next week. Hopefully the ground will thaw enough for me to add some dirt and use my box blade
What no one else has mentioned is that frozen ground is as hard as concrete. Just like you wouldn't put rocks directly on the line, you shouldn't put chunks of frozen dirt either. If the pit is 2x3 feet, six inches of sand is three cubic feet, or about 300 pounds. What I would do is go to Home Depot or Lowes -- where they keep the building supplies indoors -- and buy six 50-lb bags of sand. That will protect the pipe. You can then pile chunks of frozen ground over it. That will keep it from freezing. When the ground thaws the chunks will melt and settle, you'll have to fix it up then. I doubt you'll be able to do any landscaping until spring anyway.