Simi Valley Municipal Code Art. 6 Provisions for Flood Hazard Reduction

(a) New construction of any residential or non-residential structures in special flood hazard areas (SFHAs).

(b) Storage or processing of hazardous, flammable or explosive materials in SFHAs.

(c) New and substantially improved critical facilities within SFHAs.

(d) The change of use of non-conforming structures from a non-residential structure to a residential structure or a mixed-use structure, or an increase in the residential use area of a mixed-use structure.

(e) The change of use of any structure to a critical facility, where such a change in use will render the new critical facility in violation of Section 7-5.601(e) and 7-5.603(e)(9), Critical Facilities.

(f) Basements with finished floor elevations below the base flood elevation (BFE).

(g) Building enclosures, including breakaway walls, below the BFE.

(h) Crawl spaces greater than two (2) feet below grade, which shall be considered as basements.

(i) Installation of new and substantially-improved septic systems.

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

Properties located outside the SFHA are still subject to potential flooding caused by local drainage problems. To ensure that new development is elevated well above the street level or otherwise protected from shallow drainage flooding the following standards are required for all development in all areas of the City:

(a) These standards shall apply on all development exceeding one-half acre in size, and/or increasing impervious area by over 5,000 square feet.

(b) The lowest floor elevation of any structures shall be at least one foot above the crown of the nearest street.

(c) The site plan shall account for street flooding and local drainage from and onto adjoining properties and protects the building from local drainage flows.

(d) The site plan shall provide positive drainage away from the building site to an approved point of collection that does not create a hazard or problem on neighboring properties.

(e) All requirements of the most current NPDES stormwater permit shall be enforced including, but not limited to:

(1) Preference to the use of low-impact development techniques (instead of pipes, channels, or detention) to control the impacts of development on runoff.

(2) Include in the design of the stormwater management facilities appropriate "best management practices" that will improve the quality of surface water.

(3) At least once each year, the owners of all stormwater management facilities including, but not limited to, retention basins, detention basins, debris basins and "best management practices:"

(i) Have the facilities inspected by a licensed professional engineer;

(ii) Perform any and all necessary maintenance, repair or replacement as recommended by the engineer; and

(iii) Submit the report to the Floodplain Administrator; and

(iv) If the owner fails to perform items (i), (ii) or (iii) above, the City shall have the authority to perform the inspection, maintenance repair and/or replacement and receive reimbursement from the owner for the work performed.

(f) For all new development, the maximum storm water discharge of the ten (10), twenty-five (25), fifty (50) and 100-year storms shall be limited to the pre-developed ten-year (10-year) peak flow rate.

(1) Before development, the developer must submit hydrologic and hydraulic studies showing the nature and extent of runoff under present conditions and with the proposed development for those four (4) rainfall events. Peak runoff from new development shall be no greater than the runoff from the site in its pre-development condition.

(2) For projects of less than ten (10) acres, on-site detention in the amount of 1,000 cubic feet per acre of developed area or greater shall be provided.

(3) For projects of or greater than ten (10) acres, the required detention storage shall be based on a calculated hydrograph for a developed 100-year frequency storm.

(4) Additional detention may be considered for reduction of the discharge rate commensurate with deficiencies in downstream facilities.

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

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)

(a) All new and replacement water supply and sanitary sewage systems shall be designed to minimize or eliminate:

(1) Infiltration of flood waters into the system; and

(2) Discharge from systems into flood waters.

(b) On-site waste disposal systems shall not be located in SFHAs. See Section 7-5.601(i).

(c) Other utilities are addressed in Sections 7-5.103(e) and 7-5.605(c).

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

(a) All new subdivisions proposals and other proposed development, including proposals for manufactured home parks and subdivisions greater than one acre shall:

(1) Provide future conditions hydrologic and hydraulic engineering analysis to identify the 100-year, 500-year and floodway flood elevations and boundaries.

(i) Analysis shall use the City's most recent aerial and Quality Level 1 (QL1) or better LiDAR topography.

(ii) Analysis shall be consistent with the most current City Master Plan of Drainage models and future conditions hydrologic land use mapping.

(2) Identify the elevations of lowest floors of all proposed structures and pads on the final plans.

(3) If the site is filled above the BFE, the following as-built information for each structure shall be certified by a registered civil engineer or licensed land surveyor and provided as part of an application for a letter of map revision based on fill (LOMR-F) to the Floodplain Administrator:

(i) Lowest floor elevation.

(ii) Pad elevation.

(iii) Lowest adjacent grade.

All subdivision proposals shall be consistent with the need to minimize flood damage.

(b) All subdivision proposals shall have public utilities and facilities such as sewer, gas, electrical and water systems located and constructed to minimize flood damage.

(c) All subdivisions shall provide adequate drainage to reduce exposure to flood hazards. Certification of compliance shall be required of the developer.

(d) In areas upstream of the limit of study, as delineated on the community FIRM, where BFE data is not available, a floodplain study must be performed by a professional engineer (PE) establishing the BFE and the floodplain and floodway boundaries prior to issuing a development permit.

(e) All proposed lots or parcels that will be future building sites shall have a minimum buildable area outside the natural (non-filled) one percent chance annual floodplain. The buildable area shall be large enough to accommodate any primary structure and associated structures such as sheds, barns, swimming pools, detached garages, on-site sewage disposal systems, and water supply wells, if applicable.

(f) Unless otherwise approved by the City Council, the following shall apply:

(1) All street surfaces must be located at or above the BFE; and

(2) Commercial and industrial development may not allow parking more than one foot below the BFE.

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

(a) All manufactured homes that are placed or substantially improved within a SFHA on the City's Flood Insurance Rate Map and which are either: (a) outside of a manufactured home park or subdivision, (b) in a new manufactured home park or subdivision, (c) in an expansion to an existing manufactured home park or subdivision, or (d) in an existing manufactured home park or subdivision on which a manufactured home has incurred "substantial damage" as the result of a flood shall:

(1) Within Zones AH and AE on the community's Flood Insurance Rate Map, be elevated on a permanent foundation such that the lowest floor of the manufactured home is elevated at least one foot above the BFE and be securely fastened to an adequately anchored foundation system to resist flotation, collapse, and lateral movement.

(b) All manufactured homes to be placed or substantially improved on sites in an existing manufactured home park or subdivision within Zones AH and AE on the City's Flood Insurance Rate Map that are not subject to the provisions of Section 7-5.605(a) will be securely fastened to an adequately anchored foundation system to resist flotation, collapse, and lateral movement, and be elevated so that either the:

(1) Lowest floor of the manufactured home is at least one foot above the BFE; or

(2) The manufactured home chassis is supported by reinforced piers or other foundation elements of at least equivalent strength that are no less than thirty-six (36") inches in height above grade.

Upon the completion of the structure, the elevation of the lowest floor 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.

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

All recreational vehicles placed on sites within Zones AH and AE on the City's Flood Insurance Rate Map will either:

(a) Be on the site for fewer than 180 consecutive days; or

(b) Be fully licensed and ready for highway use. A recreational vehicle is ready for highway use if it is on its wheels or jacking system, is attached to the site only by quick disconnect type utilities and security devices, and has no permanently attached additions; or

(c) Meet the permit requirements of Section 7-5.501 of this chapter and the elevation and anchoring requirements for manufactured homes in Section 7-5.605.

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

(a) In SFHAs, the storage or processing of materials that are in time of flooding, buoyant, flammable, explosive, or could be injurious to human, animal, or plant life, is prohibited.

(b) Storage of other material or equipment may be allowed if not subject to major damage by floods and firmly anchored to prevent flotation or if readily removable from the area within the time after flood warning.

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

Located within SFHAs, established in Section 7-5.302, are areas designated as floodways. The regulatory floodway shown in the Flood Insurance Study has been selected and adopted on the principle that the area chosen for the regulatory floodway must be designed to carry the waters of the base flood without increasing the water surface of that flood more than one (1) foot at any point. In accordance with this principle, and the fact that the floodway is an extremely hazardous area due to the velocity of flood waters which carry debris, potential projectiles, and erosion potential, the following provisions apply:

(a) Prohibit encroachments, including fill, new construction, substantial improvement, and other new development unless certification by a registered professional engineer or architect is provided demonstrating that encroachments shall not result in any increase in flood levels during the occurrence of the base flood discharge;

(b) If Section 7-5.608(a) of this section is satisfied, all new construction, substantial improvement, and other proposed new development shall comply with all other applicable flood hazard reduction provisions of Article 6.

(c) All new construction, substantial improvements, and other development within floodways which will cause increases in the BFE shall only be permitted if the permittee has applied to the Federal Emergency Management Agency for modification of the flood insurance rate maps and has received conditional approval of such modifications, and all other applicable provisions of this chapter are satisfied.

(d) If no floodway is identified, the applicant for a flood area development permit shall provide an engineering study to demonstrate that any new development will not increase the water surface elevation of the base flood by more than one-tenth of one foot.

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

If no floodway is identified, the applicant for a flood area development permit shall provide an engineering study to demonstrate that any new development will not increase the water surface elevation of the base flood by one-tenth of one foot or more.

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