I'm switching my savs substrate from mulch to dirt and sand mixed. The mulch can't hold their cute little burrows, haha. What's the ratio I should use of soil to sand? I'm thinking I'll need about 150 lbs to get 1.5 inches of substrate.

I noticed 28 people had viewed this thread with no response. I hate to see you ask a question and get no response. But, not everybody uses the soil sand thing.
I have an enclosure that I built that has a floor made of "backer board" which is a sheet of wood impregnated with concrete. It's as if he's on one big flat rock. I then put in areas for him to completely hide in. Man made burrows.
I believe in the wild, they will not dig their own burrows if there is an abandoned burrow already available to them.
I started out trying many substrates and rejected them all because everything I tried always ended up in the water bowl.
I'm a stickler about a clean water bowl.
Maybe someone who goes the all natural route will pop in and answer your question.

__________________
Git'er Done!

There really isn't a recipe for a good substrate mix. It all depends on what soil type is available in your locale. It's kind of a trial and error thing.
What makes a big difference and is probably the biggest reason people give up on this is using mesh on the enclosure. Mesh anywhere anyhow will end up in drying out the enclosure. Hence it won't matter how good your mix is, it will crumble when dried out.
First make sure you can maintain some good humidity in there and then start mixing.
The reason for burrows is to allow the monitors an area to hydrate and cool down (to a point)

__________________
Mike
"Never worry about numbers. Help one person at a time, and always start with the person nearest you." - Mother Teresa

Yea I ended up taking quarter top soil, quarter dirt from my backyard. Fertilizer free no worries, and half washed play sand. I have a screened top but I have plexiglass cut out to only allow room for the lights, everything else if covered. Humidity about 55 percent and the lower layers are staying moist, im very happy with this substrate.

The best substrate I have ever found in my area is from a dry creek bed. Where the river takes a bend it's deposited on the corners. That stuff is awesome.

__________________
Mike
"Never worry about numbers. Help one person at a time, and always start with the person nearest you." - Mother Teresa

Yea I bet that would be great. I just need to find one of those haha.