These regulations will typically be local (or as mentioned - specs by the railroad).
(FEMA puts out model regulations for local jusridictions to use as a guide. If the local regulations do not comply with FEMA requirements, the local body does not get FEMA subsidies.)
Our county code simply states
"All subdivision and development proposals shall have utilities and facilities such as sewer, gas, electrical, and water systems located and constructed to minimize flood damage."
and
"Dry floodproofing requirements. Dry floodproofed structures, together with attendant utility and sanitary facilities, shall:
(a) Be designed to be dry floodproofed such that the structure is watertight with walls and floors substantially impermeable to the passage of water to the level of the base flood elevation. In areas of shallow flooding (Zone AO), the structure shall be dry floodproofed at least as high above the highest adjacent grade as the depth number specified in feet on the Flood Insurance Rate Map or at least two feet if a depth number is not specified.
(b) Have structural components capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy."