Around here, shredded rubber is not worth hunting. Those shreds are made from tires and tires can contain some threads of metal wire.
KT hunted strictly totlots and you will discover several things.
Best sites on a Totlot depends on the equipment…best locations include at the base of ladders for slides…at the base of the slide where the kids come down…any equipment that the kid might hang upside down on…monkey bars, those climb on domes, any equipment that the kid may fall off of, any sets of swings, where the kids try and jump off while swinging…..perimeters of the play ground…open areas where kids might run and fall down…HA HA. In other words, most anywhere. As you hunt each one, make a mental note as to what areas yielded the most coins, jewelry, etc. Finally remember they are renewable, so come back and hunt again and again. KT had a couple of totlots that whenever He hunted them, He could always count on $3-$5 in clad, every few weeks! KT preferred elementary school totlots in depressed neighborhoods because the parents did not have lunch cards, but always sent lunch money with the kids every day. Obviously during morning recess, a certain number of kids would lose their lunch money.
Some schools have small totlots, but some have large or multiple totlots! Do not bother with kindergarten or daycare totlots, as the kids are too young to be trusted with lunch money.
As for park totlots, generally the same rules apply. Once you hunt a few, you will begin to see a pattern in each individual Totlot. If you see basketball courts in parks, if no one is actively playing, then go hunt right around the the basket pole, in the grass behind it…also check around trees nearby because sometime the players put their pocket contents at the tree base to lighten their load when playing. KT has found working cell phones, car keys, coins, even paper money around trees! Ha ha.
Finally, best of luck! Most of KT’s finds came from less than 3” deep in mulch, tho a couple of gold rings came from 8” deep!