Our backfill has been stored on our backyard in a large triangular pile about 12' high> there's about 150 cu yds.

Its rained for 5 days_ light for 3 and then heavy (about an inch a day) for 2.

Is the backfill too wet to use? How can I tell? It's a sandy clay.

I would have covered it by tarps, but I was more worried about the excavation near the neighbours house and used them there instead.

Thanks

We have to guess a bit here since we don't know what you built. Guessing a foundation wall, only way to tell is to plow into the pile to see how far in the dirt is soaked. I think it should be OK but be sure to lay gravel down in the trench first and do not push backfill againist the foundation wall perpendicular to the wall, you can buckle the wall.

Soil compacts best when it is at optimum moisture content, which varies with soil types. Unless you have access to testing and analysis equipment, an educated guess is about the only option.
Molding a sample (taken from well into the pile) in your hand will provide some clues. Form a ball with the sample in your hand. Is it firm or spongy? This is the best "seat of the pants guess" to indicate how the material will react when compacted.
If it really is sandy clay (and not clayey sand) it will probably be too wet considering the recent weather you have described.
The amount of residue left on the hand after molding a ball is also a clue--a lot, is an indication of too wet.
Soil engineering is a science. The foregoing is not but it is as close as we can get under these circumstances.

Thanks Guys. Yes, it's the foundation for a new house.

The backfill was in the sun for a couple of days and completely dried out on the top. There was a wet layer about a foot down, and then it was relatively dry under that. I had the excavator mix the pile up by moving it, and then we used it.

Hopefully there will be no problems.