Located within the areas of special flood hazard are areas designated as shallow flooding. These areas have special flood hazards associated with base flood depths of one (1') to three feet (3') where a clearly defined channel does not exist and where the path of flooding is unpredictable and where velocity flow may be evident. Such flooding is characterized by ponding or sheet flow; therefore, the following provisions apply:
1. Require within Zone AO that all new construction and substantial improvements of residential structures have the lowest floor (including basement) elevated above the highest adjacent grade at least as high as the depth number specified in feet on the community’s flood insurance rate map (FIRM) (at least two feet (2') if no depth number is specified).
a. Have the lowest floor (including basement) elevated above the highest adjacent grade at least as high as the depth number specified in feet on the community’s FIRM (at least two feet (2') if no depth number is specified); or
b. Together with attendant utility and sanitary facilities be designed so that below the base flood level the structure is watertight with walls substantially impermeable to the passage of water and with structural components having the capability of resisting hydrostatic and hydrodynamic loads of effects of buoyancy.
3. A registered professional engineer or architect shall submit a certification to the floodplain administrator that the standards of this section and Section 17.62.200 are satisfied.