@Listerational
We are using a "pit-of-doom" underground enclosure for a muffler on our listeroid. It is constructed of concrete blocks with a few pieces of concrete slab cast on site as a top. The whole thing is covered with about 18" of dirt. The dirt is glacial till, and has little or no nutritional value for plants. I figured that area would remain barren as exhaust and by-products leached into the soil.
I was amazed to find that the pit-o-doom and its immediate area have become covered with deep lush green grass, while the area a few feet away remains scraggley as the rest of the farther away areas. If you are using the garden for edibles, maybe the exhaust is a concern, otherwise it seems to actually promote growth here!
Cheers,
Hugh