§ 7-5.603. Standards of construction within the SFHA.

In all SFHAs, the following standards are required:

(a)

Anchoring.

(1)

All new construction, substantial improvement and other proposed new development shall be adequately anchored to prevent flotation, collapse or lateral movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy.

(2)

All manufactured homes shall meet the anchoring standards of Section 7-5.605(a)(1).

(b)

Construction materials and methods. All new construction and substantial improvements of structures, including manufactured homes, shall be constructed:

(1)

With electrical, heating, ventilation, plumbing and air conditioning equipment and all other mechanical systems and service facilities located at least one foot above the BFE:

(2)

Using methods and practices that minimize flood damage;

(3)

Within Zones AH or AO, so that there is adequate drainage paths around structures on slopes to guide flood waters around and away from proposed structures; and

(4)

Must be constructed on foundations that are designed and sealed by a registered design professional as complying with the requirements of the International Building Code, the International Residential Code, or ASCE 24.

(c)

Fill. The following standards apply to all fill activities in SFHAs:

(1)

Fill sites, upon which structures will be constructed or placed, must be compacted to ninety-five (95%) percent of the maximum density obtainable with the Standard Proctor Test method or an acceptable equivalent method;

(2)

Fill slopes shall not be steeper than one foot vertical to two (2) feet horizontal;

(3)

Fill shall extend at least ten (10) feet beyond the foundation of all structures before it drops below the BFE, unless certified to be resistant against erosion and scour;

(4)

Adequate protection against erosion and scour is provided for fill slopes. When expected velocities during the occurrence of the base flood are greater than five (5) feet per second armoring with stone or rock protection shall be provided. When expected velocities during the base flood are five (5) feet per second or less protection shall be provided by covering them with vegetative cover;

(5)

Fill shall be composed of clean granular or earthen material; and

(6)

In any area that has been removed from the floodplain via a letter of map revision based on fill, any existing or new structure, addition or substantial improvement must meet the required elevation freeboard requirements.

(d)

Elevation and floodproofing.

(1)

Certification. Prior to occupancy of any structure, an elevation certificate for the lowest floor and mechanical equipment shall be certified by a registered civil engineer or licensed land surveyor, and verified by the community building inspector to be properly elevated to meet all chapter requirements. Such certification and verification shall be provided to the Floodplain Administrator. Failure to submit said certification shall be cause to issue a stop-work order for the development.

(2)

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

(i)

In AE and AH Zones, elevated at least one foot above the BFE.

(ii)

In an AO zone, elevated above the highest adjacent grade to a height at least one foot above the depth number specified in feet on the FIRM, or elevated at least two (2) feet above the highest adjacent grade if no depth number is specified.

(iii)

In an A zone, without BFEs specified on the FIRM (unnumbered A zone), elevated at least one foot above the BFE as determined under Section 7-5.402(c).

(iv)

New development proposals will be designed, to the maximum extent practicable, so residential building sites, walkways, driveways, and roadways are located on land with a natural grade with elevation not less than the BFE and with evacuation routes leading directly out of the floodplain area (dryland access).

(3)

Non-residential construction. All new construction or substantial improvements of non-residential structures shall either be elevated to conform to Section 7-5.603(e)(2); or

(i)

Be floodproofed, together with attendant utility and sanitary facilities, to at least one foot above the elevation recommended under Section 7-5.603(e)(2), so that the structure is watertight with walls substantially impermeable to the passage of water;

(ii)

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

(iii)

Be certified by a registered civil engineer or architect that the standards of Section 7-5.603(e)(3)(i) and 7-5.603(e)(3)(ii) are satisfied. Such certification shall be provided to the Floodplain Administrator.

(iv)

New development proposals will be designed, to the maximum extent practicable, so non-residential building sites, walkways, driveways, and roadways are located on land with a natural grade with elevation not less than the BFE and with evacuation routes leading directly out of the floodplain area.

(4)

Non-conversion. To put current and future tenants and owners on notice that the area below the BFE may not be architecturally finished and converted to living space and that the space may only be used as incidental material storage, building access and vehicle parking, a non-conversion agreement shall be required whenever there is a height of more than five (5) feet. The non-conversion agreement shall be in a form acceptable to the Floodplain Administrator and City Attorney. The Floodplain Administrator shall have the right to inspect for conversion with 72-hour notice. By this chapter, the Director of the Public Works shall have authority to execute the non-conversion agreements on behalf of the City of Simi Valley.

(5)

Flood openings. All new construction and substantial improvements of structures with fully enclosed areas below the lowest floor 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 meet the following minimum criteria:

(i)

For non-engineered openings:

(A)

Have a minimum of two (2) 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;

(B)

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

(C)

Openings may be equipped with screens, louvers, valves or other coverings or devices provided that they permit the automatic entry and exit of floodwater; and

(D)

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

(ii)

For engineered openings. Be certified by a registered civil engineer or architect.

(6)

Manufactured homes. See Section 7-5.605.

(7)

Garages and low cost accessory structures.

(i)

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 of flood waters. See Section 7-5.603(e)(5). Areas of the garage below the BFE must be constructed with flood resistant materials. See Section 7-5.603(b).

(B)

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

(ii)

Detached garages and accessory structures.

(A)

"Accessory structures" used solely for parking (two-car detached garages or smaller) or limited storage (small, low-cost sheds), as defined in Article 2, may be constructed such that its floor is below the BFE, provided the structure is designed and constructed in accordance with the following requirements:

(I)

Use of the accessory structure must be limited to parking or limited storage;

(II)

The portions of the accessory structure located below the BFE must be built using flood-resistant materials;

(III)

The accessory structure must be adequately anchored to prevent flotation, collapse and lateral movement;

(IV)

Any mechanical and utility equipment in the accessory structure must be elevated or floodproofed to at least one foot above the BFE;

(V)

The accessory structure must comply with floodplain encroachment provisions in Section 7-5.608; and

(VI)

The accessory structure must be designed to allow for the automatic entry of flood waters in accordance with Section 7-5.603(e)(5).

(B)

Detached garages and accessory structures not meeting the above standards must be constructed in accordance with all applicable standards in Section 7-5.603.

(8)

Crawl space construction. This sub-section applies to buildings with crawl spaces up two (2) feet below grade. Below-grade crawl space construction in accordance with the requirements listed below will not be considered basements.

(i)

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 (5) feet per second unless the design is reviewed by a qualified design professional, such as a registered architect or professional engineer;

(ii)

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;

(iii)

Portions of the building below 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 that extend below the BFE; and

(iv)

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

(v)

Requirements for all below-grade crawl space construction, in addition to the above requirements, to include the following:

(A)

The interior grade of a crawl space below the BFE must not be more than two (2) feet below the lowest adjacent exterior grade (LAG), shown as "D" in figure 3 of Technical Bulletin 11-01;

(B)

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 (4) feet (shown as L in figure 3 of Technical Bulletin 11-01) at any point;

(C)

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

(D)

The velocity of floodwaters at the site should not exceed five (5) feet per second for any crawl space. For velocities in excess of five (5) feet per second, other foundation types should be used.

(9)

Critical facilities.

(i)

Construction of new critical facilities shall be located outside the limits of the 500-year floodplain.

(A)

Critical facilities constructed adjacent to the 500-year floodplain shall have the lowest floor elevated at least one foot above the level of the 500-year flood.

(ii)

Non-substantial improvement to existing critical facilities within the SFHA shall have the lowest floor elevated at least one foot above the level of the 500-year flood.

(A)

Access to and from the critical facility should be protected to the heights utilized above.

(B)

Flood-proofing and sealing measures must be taken to ensure that toxic substances will not be displaced by or released into floodwaters.

(C)

Access routes elevated to or above the level of the BFE shall be provided to all critical facilities to the extent possible.

(§ 1 (Exh. A), Ord. No. 1268, eff. April 20, 2017)