My (wealthy) high school had a "turf" field which uses little rubber pellets as the "dirt". Those were probably shredded tires too. During football season you would see them tracked around the school, and if you were a football player or in the band they would show up at your house.

also, they would periodocially dump "more dirt" onto the field, once every year or so. Not sure if they vacuumed the old stuff up or just dumped more on top, but sometimes you would go out there and there would be a huge pile of rubber in the middle, which I guess got spread out later