"Whole-Wit" hhdh9uhh@fsb wrote in message
...
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.

I wouldn't touch it with a ten foot pole.