B. Single-family dwellings and accessory residential, recreational and agricultural structures shall be allowed if they are allowed in the underlying or base zone, if any, only if they comply with one of the following conditions:
a. All permanent buildings will be protected from flooding by dikes, levees or other flood protection works whose design is approved by the city engineer,
b. Individual sewage systems shall be maintained outside the limits of the FP-S zone, unless protected by flood-control devices approved by the city engineer and shall not be located closer than one hundred feet to any surface water source (domestic, agricultural wells, etc.).