I'm working on designing a two story building (same as the attached sketch) & here are the conditions:- The building is 72 ft x 32 ft;- The lower level should be all concrete & waterproof, the top level is CMU with an A-frame roof;- The building is in a flood zone & the first floor will be completely submersed in water when it floods;- This is an industrial structure in a water plant.I have not designed a structure like this before & I have concerns about the lower level; What are the main things to look out for or be concerned about in my design? Do I need drainage? Or a retaining wall (or other methods of stabilizing the soil) so the soil on the bottom of the building wouldn't be washed off over time? Is it a concern for the passive pressure of the soil behind the building causing overturning or sliding down the slope?What would you recommend for the foundation? A slab? Piles?...I'd appreciate your advise and help!

