Imperial County Municipal Code Ch. 5 Provisions for Flood Hazard Reduction

Footnotes:

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Editor's note— Sec. 13 of Ord. No. 1565, adopted December 15, 2020, rescinded Ch. 5, which pertained to the same subject matter, consisted of §§ 91605.00—91605.07, and derived from the prior code. Section 14 of said ordinance enacted provisions to read as herein set out.

In all areas of special flood hazards the following standards are required:

A. Anchoring.

1. All new construction and substantial improvements 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. A licensed architect or registered professional engineer shall assess all new construction and any substantial improvements.

3. All manufactured homes shall meet the anchoring standards of Section 91605.03.

B. Construction Materials and Methods. All new construction and substantial improvement shall be constructed:

1. With flood-resistant materials as specified in FEMA Technical Bulletin TB 2-93, and utility equipment resistant to flood damage;

2. Using methods and practices that minimize flood damage;

3. With electrical, heating, ventilation, plumbing and air conditioning equipment and other service facilities that are designed and/or located so as to prevent water from entering or accumulating within the components during conditions of flooding; and if

4. Within zones AH or AO, so that there are adequate drainage paths around structures on slopes to guide flood waters around and away from proposed structures.

C. Elevation and Floodproofing. (See Division 14 of Title 9 for definitions for "basement", "lowest floor", "new construction", "substantial damage" and "substantial improvement".)

1. Residential construction, new or substantial improvement, shall have the lowest floor, including basement,

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

b. In an A zone, elevated to at least two feet above the base flood elevation; said base flood elevation; said base flood elevation shall be determined by one of the methods in Section 91604.02(B) of this ordinance.

c. In all other zones, elevated at least two feet above the base flood elevation.

Upon the completion of the structure, the elevation of the lowest floor including basement shall be certified by a registered professional engineer or surveyor, and verified by the County building inspector to be properly elevated. Such certification and verification shall be provided to the Floodplain Administrator.

2. Nonresidential construction, new or substantial improvement, shall either be elevated to conform with Section 91605.00(C)(1) or together with attendant utility and sanitary facilities:

a. Be floodproofed below the elevation recommended under Section 91605.00(C)(1) so that the structure is watertight with walls substantially impermeable to the passage of water;

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

c. Be certified by a registered professional engineer or architect that the standards of this Section 91605.00(C)(2) are satisfied. Such certification shall be provided to the Floodplain Administrator.

3. All new construction or substantial improvement 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 shall follow the guidelines in FEMA Technical Bulletins TB 1-91 and TB 7-93, and must exceed the following minimum criteria:

a. Have a minimum of two openings having a total net area of not less than one square inch for every square foot of enclosed area subject to flooding. The bottom of all openings shall be no higher than one foot above grade. Openings may be equipped with screens, louvers, valves or other covering devices provided that they permit the automatic entry and exit of floodwater; or

b. Be certified by a registered professional engineer or architect.

4. Manufactured homes shall also meet the standards in Section 91605.03.

(Ord. No. 1565, §§ 13, 14, 12-15-20; Ord. No. 1576, §§ 27, 28, 2-8-22)

A. All new and replacement water supply and sanitary sewage systems shall be designed to minimize or eliminate infiltration of flood waters into the system and discharge from systems into floodwaters.

B. On-site waste disposal systems shall be located to avoid impairment to them or contamination from them during flooding.

(Ord. No. 1565, §§ 13, 14, 12-15-20)

A. All preliminary subdivision proposals shall identify the special flood hazard area and the elevation of the base flood.

B. All final subdivision plans will provide the elevation of proposed structure(s) and pads. If the site is filled above the base flood elevation, the lowest floor and pad elevations shall be certified by a registered professional engineer or surveyor and provided to the floodplain administrator.

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

D. All subdivision proposals shall have public utility and facilities such as sewer, gas, electrical and water systems located and constructed to minimize flood damage.

E. All subdivisions shall provide adequate drainage to reduce exposure to flood hazards.

(Ord. No. 1565, §§ 13, 14, 12-15-20)

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

B. All new construction and any substantial improvements shall be assessed by a licensed architect or registered professional engineer.

C. All manufactured homes that are placed or substantially improved, within Zones A1-30, AH, and AE on the County's Flood Insurance Rate Map, on sites located:

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 a site upon which a manufactured home has incurred "substantial damage" as the result of a flood,

shall be elevated on a permanent foundation such that the lowest floor of the manufactured home is elevated at least two feet above the base flood elevation and be securely fastened to an adequately anchored foundation system to resist flotation, collapse, and lateral movement.

D. All manufactured homes to be placed or substantially improved on sites in an existing manufactured home park or subdivision within Zones A1-30, AH, AE, V1-30, V and VE on the County's Flood Insurance Rate Map that are not subject to the provisions of Section 91605.03.C. will be securely fastened to an adequately anchored foundation system to resist flotation, collapse, and lateral movement, and be elevated so that either the:

a. Lowest floor of the manufactured home is at or above the base flood elevation (The State of California recommends at least two feet above the base flood elevation), or

b. Manufactured homes 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 including basement shall be certified by a registered professional engineer or surveyor, and verified by the county building inspector to be properly erected. Such certification and verification shall be provided to the floodplain administrator.

(Ord. No. 1565, §§ 13, 14, 12-15-20)

A. All recreational vehicles placed on sited within Zones A1-30, AH, and AE on the County's Flood Insurance Rate Map will either:

1. Be on a site for fewer than one hundred eighty (180) consecutive days, and 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

2. Meet the permit requirements of Chapter 4 (Sections 91604.00 through 91604.03) of this division and the elevation and anchoring requirements for manufactured homes in Section 91605.03.C.

(Ord. No. 1565, §§ 13, 14, 12-15-20)

A. The floodplain administrator shall require permits for proposed construction and other development within all flood-related erosion-prone areas as known to the County.

B. Permit applications shall be reviewed to determine whether the proposed site alterations and improvements will be reasonably safe from flood-related erosion and will not cause flood-related erosion hazards or otherwise aggravate the existing hazard.

C. If a proposed improvement is found to be in the path of flood-related erosion or would increase the erosion hazard, such improvement shall be relocated or adequate protective measures shall be taken to avoid aggravating the existing erosion hazard.

D. With Zone E on the Flood Insurance Rate Map, a setback is required for all new development from the ocean, lake, bay, riverfront or other body of water to create a safety buffer consisting of a natural vegetative or contour strip. This buffer shall be designated according to the flood-related erosion hazard and erosion rate, in relation to the anticipated "useful life" of structures, and depending upon the geologic, hydrologic, topographic, and climatic characteristics of the land. The buffer may be used for suitable open space purposes, such as for agricultural, forestry, outdoor recreation and wildlife habitat areas, and for other activities using temporary and portable structures only.

(Ord. No. 1565, §§ 13, 14, 12-15-20)

Located within areas of special flood hazard established in Section 91603.01 are areas designated as floodways. Since the floodway is an extremely hazardous area due to the velocity of floodwaters which carry debris, potential projectiles, and erosion potential, the following provisions apply:

A. Prohibit encroachments, including fill, new construction, substantial improvements, and other development unless certification by a registered engineer or licensed 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 91605.06.A is satisfied, all new construction and substantial improvements shall comply with all other applicable flood hazard reduction provisions of Chapter 5 (Sections 91605.00 through 91605.07) herein.

(Ord. No. 1565, §§ 13, 14, 12-15-20)

A. The floodplain administrator shall review permits for proposed construction or other development to determine it is proposed within a mudslide area.

B. Permits shall be reviewed to determine that the proposed development is reasonably safe from mudslide hazards. Factors to be considered in making this determination include, but are not limited to:

1. The type and quality of soils.

2. Evidence of ground water or surface water problems.

3. The depth and quality of any fill.

4. The overall slope of the site.

5. The weight that any proposed development will impose on the slope.

C. Within areas which have mudslide hazards, the following requirements apply:

1. A person qualified in geology and soils engineering shall make a site investigation and further review.

2. The proposed grading, excavation, new construction and substantial improvements shall be adequately designed and protected against mudslide damages.

3. The proposed grading, excavations, new construction and substantial improvements do not aggravate the existing hazard by creating either on-site or off-site disturbance.

4. Drainage, planting, watering and maintenance shall not endanger slope stability.

D. Within Zone M on the Flood Insurance Rate Map, the County shall adopt a drainage ordinance which at least complies with the standards of Sections 7001 through 7006 and Sections 7008 through 7015 of the most recent amendment of the Uniform Building Code:

1. The location of foundation and utility systems of new construction and substantial improvements.

2. The location, drainage and maintenance of all excavations, cuts and fills and planted slopes.

3. Protective measures including but not limited to retaining walls, buttress fills, sub-drains, diverted terraces, benchings, etc.

4. Engineering drawings and specifications to be submitted for all corrective measures accompanied by supporting soils engineering and geology reports.

(Ord. No. 1565, §§ 13, 14, 12-15-20)