I have been all over the forum asking questions, I hope y'all are not tired of me yet

I have a septic tank that will be emtied tomorrow just as a preventive, it has been probably 5 years since last done and it was because it was backing up. The house was build by my wife's pop, rest in peace back in the early 80's.
When they need to pump the septic tank a heavy lid needs to be lifted, approximately 27"x57". This is just part of the lids. I probed and the total length of the tank is alittle over 10 ft. I will measure the depth when he comes over tomorrow so I can approximately calculate the volume.
I remember the only pipe I saw going into the tank from the house was a small one, I think a 2-4".
I wonder if there are more pipes connected from the house that go into this tank, I assume a bigger one from the toilets???
Included is a picture from the first part of the lid where the small pipe is located.

Is it possible to get another lid for easier acces with maybe a hole in the top??

Just new into septic tanks so any advice will be appreciated. The only info about the drainage field is that there are 3 pipes drained into the field??



Ron