I purchased a small house with a small lot. Most of the back yard is taken up by a detached garage which shall be removed. The garage has a dirt floor and may have been there for about 40 years. It has not been used as a car garage in at least 5 years. I'm sure the soil is contaminated with petroleum products and other chemicals from leaks. It will be half of my future dwarf fruit forest. I will be testing it and I hope, by some miracle, it will be much cleaner than I think it is, but probably not. Do I just dig it out and find a place that will take it? Do I dig it out and put it in a pile and grow bio-remediating plants on it to clean the pile (I'm thinking rain would just help the pollutants spread from this pile to the rest of the yard)? Do I leave it as is and plant bio-remediating plants in it? What would you suggest?
The problem is how deep does the contamination go? Probably not very far, because as we know, oil is lighter than water and petroleum products are going to float rather than sink. I would start off by covering the area with a foot of wood chips. Then go out and collect any and all mushrooms you can find to inoculate the pile. If you blend the mushrooms up with some water, you can work that into the wood chips so that all the surface area of the chips gets covered. Then keep it nice and wet so the fungi can do their work.
Stamets has a video where he is remediating some oil soaked ground and he did that under a tarp, but it may be better to do without the tarp, because the fungi do need to breathe. What you don't want to do is to rake or stir or turn the pile once you get it inoculated. It is NOT a compost heap, it's a fungal culture, and they don't do well when their hyphae are broken.
If you think that the contamination extends down 4" or 6" and what to remediate that volume, the time to mix that dirt in with the wood chips is at the very beginning. You could even spread down 4" of chips, rototill it in, and then cover it with another 8-12" of more chips.
You should water it every day that it doesn't rain. You want the pile to think it is living in Seattle. After a couple of weeks, you should be able to dig into the pile and see white fuzz growing on the moist chips. This is what you want. Keep it going for 3 or 4 months, and then most (>50%) of the contamination should be gone. When the pile starts sprouting mushrooms, then it has run out of food (and in this case, contaminants count as "food"), and you will be ready to use the area for a garden.
posted 5 years ago
That's a great idea. I keep thinking of it as a huge area, but really, it would just be under where the cars would have been parked and doing that to a small area would be a do-able project. Thanks. I will look for the video and check into it.