Open sewer port below basement floor with wood cover
House is approx 50 years old, and under the carpet (and underpad) that was on the basement floor we discovered a wood frame with a plywood access cover. It wasn't nailed down but a very tight fit and when we opened it, we could look straight down into the tile sewer line as it exits the house. We were checking the house for floor drains and was planning to install one-way traps in them to prevent possible radon entering into the house.
Measuring from the surface of the basement floor, the top of the open tile drain port is down almost 12" where you can also see the end of the foundation footing.
While I know this would be used as a cleanout, I am puzzled as to why it would have been left like this unless it was intended to possibly drain water from under the basement floor slab. I do know the house does have weeping tile around the outside perimeter, so I am not sure why they would need to leave it like this.
I am considering prying out the wood framing, scraping the sand around the tille away to install a Fernco MJ and running a piece of PVC up to floor level with a screw in access cap, then fill in around it with concrete mix.