I've witnessed the soil being excavated at a small junkyard that was in bussiness since the late 20's ,and the dirt was greasy and black as coal,for the first 2 feet--after that it looked its normal color and showed no sign of the oil getting any further down...I've heard that dirt is the best "filter" known to mankind many times ,mostly by my elders...
....I guess they are right,look how water that runs off highways tainted with gas,can support life and look clean enough to drink after its passed thru enough sand...
They had to truck the soil to NH to be burned in an incinerator..the place now has new homes built on it,where once hundreds of cars met their fate...so far no one gotten MS or any other diseases from the "pollution"..but I'm sure it'll be blamed if anyone does.....
There is more than one new housing development built on former junkyard sites in local towns....one guy who bought a home at one site got his picture in the paper,when he unearthed a leaf spring with his roto-tiller when making a garden plot!--and he found a lot of car parts half buried only a few inches deep!!..he was planning to sue to get his money back after learning what the land once was used for...
One thing I noticed during a walk thru a local junkyard the other day,was the fact I haven't seen so many different animals anywhere in a long time!...even in sanctuaries near my house..I saw a rare red squirrel hoarding walnuts in a ford vans rear quarter panels. a bunch of frogs,even a painted turtle,diving into puddles when I approached..snakes too !!..

..you rarely see any around your yard any more..if they pollute so bad,why do so many animals seem to like living in the junkyards?...We had herds of deer run away every morning when we opened the gates at the junkyard I used to work at,I guess they felt safe there,and they ate all the tall grass between the cars..