§ 1780-530. ELEVATION AND FLOODPROOFING

(a)

Residential Construction. All new construction or substantial improvements of residential structures shall have the lowest floor, including basement:

(1)

In AE, AH, A1-30 Zones, elevated at least one foot above the BFE.

(2)

In an AO Zone, elevated above the highest adjacent pre-construction natural grade to a height exceeding the depth number specified in feet on the FIRM by at least one foot, or elevated at least three feet above the highest adjacent pre-construction natural grade if no depth number is specified.

(3)

In an A Zone, without BFE's specified on the FIRM [unnumbered A zone], elevated at least one foot above the base flood elevation as determined under Section 1780-420(c).

(4)

In all other Zones (including A99, X, and X500) and in local flood hazard areas, elevated at least one foot above the base flood elevation shown on the flood insurance rate map or one foot above the locally-determined base flood elevation if that elevation is higher. In Zones A99, X, and X500, a condition of granting any building permit for construction outside a subdivision shall be that the lowest floor shall be placed at an elevation, as determined by a registered engineer, which will protect the structure from inundation as a result of a storm with a 100-year recurrence interval. If the Floodplain Administrator determines that developing data to establish the 100-year storm inundation elevation would be excessively expensive, the Floodplain Administrator may alternatively approve a lowest floor elevation which is one foot above the centerline of the closest county road at a point closest to the building site.

(b)

Nonresidential Construction. All new construction or substantial improvements of nonresidential structures shall either be elevated to conform with Section 1780-530(a) or:

(1)

Be floodproofed, together with attendant utility and sanitary facilities, below the elevation recommended under Section 1780-530(a), so that the structure is watertight with walls substantially impermeable to the passage of water;

(2)

Have structural components capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy; and

(3)

Be certified by a registered civil engineer or architect that the standards of Section 1780-520 and Section 1780-525 are satisfied. Such certification shall be provided to the Floodplain Administrator. Certification and verification of floodproofing design shall be in the form of a National Flood Insurance Program—Floodproofing Certificate.

(4)

In Zones A99, X, and X500, the requirement to elevate the lowest floor of detached garages, accessory buildings and/or agricultural shops to one foot above the 100-year storm inundation elevation or one foot above the centerline of the nearest County road may be waived by the Floodplain Administrator, provided that the owner executes a structure use and indemnity agreement with the County. The Floodplain Administrator may record a copy of the agreement in the Office of the Sutter County Recorder.

(c)

Flood Openings. All new construction and substantial improvements of structures with fully enclosed areas below the lowest floor (excluding basements) that are usable solely for parking of vehicles, building access or storage, and which are subject to flooding, shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of floodwater. Designs for meeting this requirement must be certified by a registered civil engineer or architect, or must meet the following minimum criteria:

(1)

Have a minimum of two openings on different sides having a total net area of not less than one square inch for every square foot of enclosed area subject to flooding;

(2)

The bottom of all openings shall be no higher than one foot above grade;

(3)

Openings must be located so that the portion of the opening intended to allow for inflow and outflow is below the BFE.

(4)

Openings may be equipped with screens, louvers, valves or other coverings or devices provided that they permit the automatic entry and exit of floodwater. The measurement of the net open area must take into consideration any coverings that have solid obstructions, such as grilles, fixed louvers, or faceplates; and

(5)

Buildings with more than one enclosed area must have openings on exterior walls for each area to allow flood water to directly enter.

(d)

Garages and Low Cost Accessory Structures.

(1)

Attached garages:

a.

A garage attached to a residential structure, constructed with the garage floor slab below the BFE, must be designed to allow for the automatic entry and exit of flood waters. Areas of the garage less than one foot above the BFE must be constructed with flood resistant materials.

b.

A garage attached to a nonresidential structure must meet the above requirements or be dry floodproofed. For guidance on below grade parking areas, see FEMA Technical Bulletin TB-6.

(2)

Detached garages and accessory structures:

a.

"Accessory structures" used solely for parking (2 car detached garages or smaller) or limited storage (small, low-cost sheds), as defined in Section 1780-210, shall be elevated or dry-floodproofed to at least one foot above the BFE. Accessory structures may be constructed such that its floor is below the BFE, provided the owner applies for and receives a wet-floodproofing variance in accordance with Section 1780-620.

(e)

Crawlspace Construction. This sub-section applies to buildings with crawl spaces up to two feet below grade. Below-grade crawl space construction in accordance with the requirements listed below will not be considered basements.

(1)

The building must be designed and adequately anchored to resist flotation, collapse, and lateral movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy. Crawl space construction is not allowed in areas with flood velocities greater than five feet per second unless the design is reviewed by a qualified design professional, such as a registered architect or professional engineer;

(2)

The crawl space is an enclosed area below the BFE and, as such, must have openings that equalize hydrostatic pressures by allowing for the automatic entry and exit of floodwaters. For guidance on flood openings, see FEMA Technical Bulletin 1-93;

(3)

Portions of the building less than one foot above the BFE must be constructed with materials resistant to flood damage. This includes not only the foundation walls of the crawl space used to elevate the building, but also any joists, insulation, or other materials less than one foot above the BFE;

(4)

Any building utility systems within the crawl space must be elevated a minimum of one foot above BFE or designed so that floodwaters cannot enter or accumulate within the system components during flood conditions.

(5)

The interior grade of a crawl space below the BFE must not be more than two feet below the lowest adjacent exterior grade (LAG), shown as D in figure 3 of Technical Bulletin 11-01;

(6)

The height of the below-grade crawl space, measured from the interior grade of the crawl space to the top of the crawl space foundation wall must not exceed four feet (shown as L in figure 3 of Technical Bulletin 11-01) at any point;

(7)

There must be an adequate drainage system that removes floodwaters from the interior area of the crawl space within a reasonable period of time after a flood event, not to exceed 72 hours; and,

(8)

The velocity of floodwaters at the site should not exceed five feet per second for any crawl space. For velocities in excess of five feet per second, other foundation types should be used.

(f)

Gas or Liquid Storage Tanks. This sub-section applies to gas or liquid storage tanks. Construction and installation shall be in accordance with the requirements listed in FEMA 348, "Protecting Building Utilities from Flood Damage - Principles and Practices for the Design and Construction of Flood Resistant Building Utility Systems" or any successor FEMA document.

(g)

Agricultural Structures. Agricultural structures shall be elevated or dry-floodproofed to at least one foot above the BFE. Agricultural structures may be constructed such that its floor is below the BFE, provided the owner applies for and receives a wet-floodproofing variance in accordance with Section 1780-620.

(h)

Elevation Certificates. Certification and verification of building elevations shall be provided for all new construction and/or substantial improvements. The certification shall be in the form of a National Flood Insurance Program—Elevation Certificate. At first form inspection, the elevation of the lowest floor including basement shall be certified by a registered professional engineer or surveyor. Such certification or verification shall be provided to the Floodplain Administrator. Upon the completion of the structure, the elevation of the lowest floor, including basement, shall be certified by a registered civil engineer or licensed land surveyor, and verified by the community building inspector to be properly elevated. Such certification and verification shall be provided to the Floodplain Administrator.

([1496, 1574] 1609, Sec. 1, March 24, 2015)