We are scraping the existing pond to make it deeper and larger.
Is this mud/dirt safe or good to be placed on our home garden?

Hello davespond and welcome to Pond Boss. I don't see why not but I'm no expert. Hang on for an expert opinion.

Welcome to the forum!

Do you know if your pond was ever treated with Copper Sulfate to control algae? If so, heavy metal build up may be a concern.

I seem to recall hearing that pond muck was not really good for fertilizer.

Can anyone confirm or not?

Sunil, I started to post that thought as well but IIRC, some muck won't grow anything.

Otto, et al., have mentioned that it's not nearly as fertile as one would think.

Perhaps because for terrestrial plants, the limiting factor is usually nitrogen, while for aquatic it's usually phosphorus (IIRC).

To be honest, we purchased the property 6 years ago. So i'm not sure. The pond was an old farm animal pond about 100' x 100' when full. It is located in Southern Illinois.

I'n no expert either, but I take sand (former gravel pit) from the lake and reclaim it and put it around the garden plants I have growing as a buffer zone at the water's edge. It starts off black, turns grey, then bleaches out a little more. The lake has been treated with copper sulfate and other compounds for 30 years: This process has not hurt any of my plants, in fact, I think it feeds them.

I always say they muck will grow anything when talkign to clients dredging their ponds. I hope I'm not lying but in fact sure as we say here all the time "it depends". The decompositon of organics should make the soil very fertilie. Soil type etc wil make a big difference. I have seen it spread thin after dredging and it grows grass well. If stacked thick it stays wet for a really longtime so key is thin and let it dryout like 2catmom says.

Mixed with compost material and allowed to sit long enough it should work quite well.