D.20 - Standards for Areas of Shallow Flooding (AO/AH Zones).

D.20.1

Located within the areas of special flood hazard established in Section D.7 are areas designated as shallow flooding. These areas have special flood hazards associated with flood depths of one (1) to three (3) feet 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:

A.

When a residential or nonresidential structure is intended to be constructed in an approximate A Zone, a base flood elevation must be determined by using the same engineering standards and methods that are used to develop base flood elevations in a flood insurance study (FIS).

B.

All new construction and substantial improvements of nonresidential structures:

1.

Have the lowest floor (including basement) elevated to twenty-four (24) inches above the base flood elevation or the highest adjacent grade at least as high as the depth number specified in feet on the community's FIRM (at least two (2) feet if no depth number is specified).

2.

Together with attendant utility and sanitary facilities be designed so that below the base specified flood depth in an AO Zone, or below the base flood elevation in an AH Zone level, the structure is watertight with walls substantially impermeable to the passage of water with structural components having the capability of resisting hydrostatic and hydrodynamic loads or effects of buoyancy.

C.

A registered professional engineer or architect shall submit a certification to the floodplain administrator that the standards of this section, as proposed in subsection D.15.2A, are satisfied.

D.

Require within Zones AH or AO adequate drainage paths around structures on slopes, to guide floodwaters around and away from proposed structures.

E.

At least one (1) primary entry road to a residential structure shall be elevated to or above the base flood elevation to allow entry and exit of vehicles during a base flood event.

F.

If fill material is to be used to elevate any structure in Zones A, A1-30, AE, AO, AH, AR, or A99, the following will apply:

1.

Fill material must be compacted to at least ninety-five (95) percent of standard laboratory maximum density (stand proctor) according to ASTM Standard D-698;

2.

Fill soils must be fine grained soils of low permeability, such as those classified as CH, CL, SC, or ML according to ASTM Standard D-2487, "Classification of Soils for Engineering Purposes." See Table 1804.2 in the "2000 International Building Code (IBC)" for descriptions of these soils types;

3.

The fill material must be homogeneous and isotropic; that is the soil must be all of one (1) material, and the engineering properties must be the same in all directions; and

4.

Fill material is prohibited in Zones V, V1-30, VE, or VO.

(Ord. No. 2016-61, § 1(Exh. A), 10-13-16)