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On Nov 29, 2003, at 5:44 PM, Rick Valley wrote:

> > From: list@ginda.us
>
> > 2)  Lead from gasoline fumes is more prevalent than I would have
> > guessed.  I nearly bought one house that bordered a semi-major road.
> > (Not a highway, but a town road with traffic most of the day.)  There
> > was a striking gradient across the yard.  The gradient isn't nearly as
> > steep as with paint - obviously, fumes travel farther than chips.
> > Right by the road the levels were about 500 ppm which is high enough
> > that I'd prefer not to grow edible leaves, and maybe not edible roots.
> > Edible fruits would probably be okay, though.  100 feet from the road
> > the levels were down to perhaps 100-200 ppm (I don't remember 
> > exactly,)
>
> This is interesting because it contradicts findings cited in Lead in 
> Seattle
> Community Gardens, a paper from Center for Urban Hort. in Seattle from
> around '86. They said that levels correlated with intensity and length 
> of
> human (read "civilized" human) occupation of a site, not distance from 
> a
> road. Probably sampling differences, also the gardens are all tilled.
I did a dozen samples at one house, and another dozen spread over 
several houses while house-hunting, so my experience might not be 
statistically valid.  I do agree with the Community Gardens folk in 
part - the amount of lead in the soil right next to the house (a sample 
I took at every house) was very well correlated with the age of the 
house.  The only outlier was the house with more than 6 inches of mulch 
- I didn't find any lead in my sample.  I assume the lead was there, 
but below the level I dug to.  Since I was primarily interested in 
child safety right next to the house, I figured I should measure the 
stuff the kids would play in.  (I was more careful about mixing depths 
for samples I took in prospective garden spots.)
> I have, more than once, scalped an entire yard, and re-contured to 
> eliminate
> lead. I think its a very quick way to procede, if you're re-doing a
> landscape, because lead doesn't leach down, but stays in the surface 
> zone.
> I've never had a yard that couldn't spare some dirt, and it makes fine
> landfill cap.
>
> -Rick
Doesn't that remove all the top soil?

Ginda