Plumbing Engineer and Building Codes for sewer pipe to city sewer line

Last summer, my first floor condo had major flooding in the basement. I think the root cause of the flooding was that a tropical storm overloaded the city sewer system and that the storm water accumulating around our building had no where to go and just flowed back towards our basement. I’ve had several plumbers and basement specialists come and look at the problem. The proposal that makes the most sense to me came from a plumber. His assessment is that the sewer line going from our building to the city sewer line is too low so when the city sewer’s combined storm and sewer line is full, there is nowhere for the water to go. He is suggesting that we move the line from our building up higher so it connects to the city sewer line at a higher point so the storm water from our building will have a place to flow.

He also says that this is a new requirement for new sewer lines extending from buildings to the city sewer lines. Would anyone know where I can find the building codes that would specify how high the sewer line would need to be? Or would know a licensed plumbing eng ineer be able to tell me if that is a requirement? If an engineer would be able to answer this question, would anyone be able to recommend one? Also, I am hoping to talk to an engineer to confirm that this is the right path.