Let me preface this by noting that I am by no means a compost expert. However, I started my very first compost bin last year so I have a little experience.

In this past year I have learned that when I have the mixture out of sync (too much green, not enough brown) then I get some REALLY SMELLY compost. Adding a little something brown (shredded cardboard, newspaper, or mulch), stirring it and letting the sunlight dry it out a little, helps balance things out.

Stored excess soil isn't necessarily the same as a compost pile, but similar treatment of your dirt pile might help reduce the odor.

You might find that your plywood and plastic covering are contributing to the smell. I'm just guessing here, but I think letting a little all natural UV light in there and giving the pile a good stir would help. Dirt that smells like sewage is usually wet dirt that is not getting enough air circulation.

A good non-stinky compost pile needs air and air circulation plus rain .
The coverings probably contributed to an anaerobic environment .
Remove covers . Stir , fluff , turn - whatever you call it .
Wait a few weeks and see what happens .
Post this on the soil/compost forum and see what the experts say .

Thanks for the input and suggestion of the right forum to post this to.3

R'