I know the backyard trash bit well myself. We moved in 41 years ago., the last house on the block. All the building garbage from the other homes ended up in our backyard buried under clay and cheap fill. This was also a former quarry area - you can't dig more than a few inches before you hit a boulder. That was interesing enough but the paint cans, glass, broken tiles, asphalt shingles, , boxes of nails etc. etc. are just a bonus. Still unearth crap everytime we plant a bush, bulbs or try and extricate weeds.