I love to hunt demolition sites... and yeah, they're hard, but you gotta stick with it... when they grate the lot off is when you'll have better luck - yeah, the trash is still gonna be there, but the good stuf will be too, and sometimes right on the surface... I found my best Barber dime by eye that way... picking thru the trash is hard, though - sometimes you just kinda have to dig the crap up and throw it to the side in order to make way for the good stuff... I've found that with my 8" coil, I have to move it really slow for it to disc. out the trash... and I dig everything when I'm on a graed lot - some things I thought were going to be really big turned out to be half- or dollar-sized things... good luck, and keep us posted!