Concrete – What are the dimensions of the steel in the concrete slabs on the upper floors of the house

Let's not over complicate this little project. I have seen these open sump holes hundreds of times. I am absolutely sure there are no structural issues here, how long has the house stood without concrete in the hole? There was probably not a concrete floor when it was built and for many years after. If you want to simply keep stuff out and hide the dirt then let's do it simple. Dig out to about a total of 4 inches below your water pipe and valve. Mix up a small bag of Sacrete concrete mix and fill the hole to about 1 inch under the pipe. Float it smooth, you're done. There is no need to get carried away with a special base etc. The size and weight of the concrete patch is negligible as far as settling or shrinking is concerned. Get the stuff and be done with it in an hour!

I'd use a setting-type compound (like Easysand 45) for this. Premix compound will take a long time to dry and will shrink quite a bit. Mix to a consistency of thick peanut butter.

I'd also try to not disturb the surrounding area, filling only the hole itself as deeply as possible. Finish by dabbing compound on the patch with a small paintbrush or the corner of a rag to replicate the nearby texture. The smaller the patch, the less noticeable it will be.

If you don't have touchup paint on hand, flat white from a spray can may work. Test on a scrap of cardboard to check the match.