Thank you all for your responses. I wanted to try to further clarify what my concern regarding the the stair case.
The lumber used to make the stringer is what I am very concern about. If you were to split open the stringer horizontally, right through the middle, the insides would be black/brown. My gut feeling tells me that I should insist that the stair case be rebuilt/replaced using better quality lumber. What is there is the permanent stairs.