Help with a foul smell

[Doug in Colorado]

Here's the background.
Our gravel yard was where we were feeding the flock. We used a shallow pan to hold the food and the chickens kicked a lot out on the ground.
Over the past few months we have changed how we feed and no longer use the shallow pan or the same location.
The food worked its way down into the gravel and there it fermented. We found this layer of nasty feed about three inches below the surface.
We have tried many course of action from washing to burning the gravel with a torch.
Short of scraping the yard and discarding about 2 tons of gravel I don't know how to mitigate the smell.
Anyone have any suggestions? Lime? Bleach?
Thanks, Doug

 

[paneubert]

If the smelly feed layer is contained to a smaller area of the larger gravel yard, I would probably just keep drenching that smaller area with lots of water to spread and thin out the feed so that it decomposes faster. If possible also turn the gravel so that it mixes the nasty feed into those top 3 inches that you mention.

I have in the past dealt with a pile of extremely bad smelling fermented feed and the only way to get rid of it was repeated soakings with water. Otherwise it will just dry out and become smelly every time it rains or gets wet.