How to rehabilitate damaged land

I have recently become a small part of rehabilitating a piece of property to become a permaculture site. This particular peice of property comes complete with a lot of land erosion and an abandoned automotive shop. The goal is to develope the property to be able to grow food, as well as creating a site for people to congregate and learn. The old auto shop is still sound in structure and able to be converted to a multipurpose building. My question is what about the land? I've worked in the automotive industry and can tell you from experience there is a great deal of pollution that poors into the ground around these places.

My questions regarding this are as follows

When I take soil samples how far down into the ground should I go?

Let's just say the soil samples come back looking scary. What steps should be taken to remediate that area?

How much time needs to pass before it is gone from the soil naturally?

The setting for this is in the mountains so there is a grade and water flows.

Bryan Cooper : I would start off with a call to your local soil and water district, most knowledgeable clerks can direct you to many streams of relevant information.

If this land has ever been under cultivation they probably already know more about it than you do, plus there may be regional programs that you qualify for .

For the Good of the Crafts ! Big AL

That is a good idea! I will definitely be doing that. Do you know of examples of others tackling a project like this. I have been trying to look at what others have done in the past to bring back such over abused property.

https://clu-in.org/download/Citizens/a_citizens_guide_to_phytoremediation.pdf

http://www.resilience.org/stories/2014-07-07/mycoremediation-bioremediation-with-fungi-growing-mushrooms-to-clean-the-earth-a-mini-review

http://www.motherearthnews.com/nature-and-environment/nature/paul-stamets-mycoremediation-ze0z1410zdeh.aspx

Those are some excellent resources and exactly what I was looking for. Thank you for your responses they have been very helpful!

When you test soil, you might do 2 tests, one from a mix of samples from a zone around and downhill of the building, and another one from designated area/s you think are "least likely contaminated". If the second test comes up clean, then these can be the areas where you start growing some food while remediating the others. Chemical residue testing is quite expensive, so this method might get you started with only 2 tests. For the "clean" areas, avoid gullies and drainages, any areas where you see trash lying; and also fencelines, property boundaries and other kinds of "edges"----these tend to be areas where people dump stuff!