How much basement moisture is tolerable/ normal and how to tell if a french drain or other precautions are necessary?

[Adam Olsen]

It's necessary that I replace the floor in the basement of my duplex. I'm in the process of breaking out the old concrete and the earth under is wet. I understand that there should be moisture in the dirt but how wet is too wet and how do I figure out if an interior french drain and sump pump is necessary?

A little more information

Located in Salt Lake City.

Evidence of moisture on some of the walls including under a window well.

The old floor was a really bizarre construction. There was about 2 1/2" of concrete poured and 2x4s set directly in the concrete on 16" centers and used as floor joists and a plywood sub floor on top. This was not discovered by me or my home inspector while doing due diligence. When I began tearing out the old floor about half of the wood was moldy and rotted.

With this evidence of moisture I want to make sure I proceed with the rebuild correctly to avoid problems down the road.

Thoughts, advice and recommendations greatly appreciated.

Adam