"Ignoramus25972" wrote in message
...
On 2011-02-10, Whole-Wit hhdh9uhh@fsb wrote:
Imagine 22,000 lbs of ground-up tires with all the steel and other crap
removed,
ground to @ 1/8" pebbles. This is the material in the backstop of a
shooting range.
There is a conservative estimate of 10,000 lbs of lead and copper to a
much lesser
degree in the rubber. This isn't the first clean-out/rebuild, the last
one was five
years ago. The idea is to remove all the material, separate it and reuse
the rubber.
One of the ideas we've had is to float the rubber in water and skim it
off. But, 1/2
of a sample amount floats, 1/3 sinks and 1/6 stays suspended. In a 1/3
cup of the
material, there was 64 grams of lead! I doubt that there is much lead in
the material
above the target line. The sample was taken at the very bottom, about 5'
below the
target line. They don't really want the range down for more than a week
to do the
clean-out and replace the front which is 4' wide x 3/4" thick conveyor
belt lengths
suspended from the ceiling and anchored to the floor and overlap by 8"
and screwed
together. The conveyor belting is bulging out close to a foot in the
center of each
of the ten lanes. It seems that this type of backstop is excellent for
stopping
bullets and keeping the dust to a minimum.

Get a air blower (like those used to dry carpets). Rig some kind of a
conveyor thing to dump that stuff in front of the blower. The blower
will blow the rubber away, but the lead will fall down.

i

I would worry that a blower would blow all sorts of lead dust everywhere.

How about a something like a gold sluice box? There are a lot of designs on
the web. You would probably want to re-circulate the water and then let it
evaporate after you are done so you do not contaminate much else.

Or, if you stick with your original idea of dumping it in a water bath, I
bet a little agitation would bring some of the sunk rubber pieces near the
surface where you could scoop them out.