The first two pictures are blurred, yea I know. I'm trying to get used to this I-Phone 5 camera.
What you are looking at is a sewer filled with pebbles and dirt. The riser came loose enough to allow the stuff to fill the pipe over the course of years. The third picture is the riser.
What makes matters worse is the sewer makes a u-turn to go all the way across the front lawn to join a shared sewer before it goes into the city sewer.