Contra Costa County Municipal Code Art. 82-28.10 Provisions for Flood Hazard Reduction

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

(1) Anchoring.

(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 manufactured homes shall meet the anchoring standards of Section 82-28.1008.

(2) Construction Materials and Methods.

(a) All new construction and substantial improvements shall be constructed with materials and utility equipment resistant to flood damage.

(b) All new construction and substantial improvements shall be constructed using methods and practices that minimize flood damage.

(c) All new construction and substantial improvements shall be constructed 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.

(d) In zones AH, AO or VO, adequate drainage paths around structures. To guide floodwaters around and away from proposed structures shall be constructed.

(3) Elevation and Floodproofing.

(a) New construction and substantial improvement of any structure shall have the lowest floor, including basement, elevated to or above the base flood elevation plus required freeboard. In the San Francisco Bay Delta Estuarine Region, 0.61 meters (two feet) of freeboard is required. In all other unincorporated areas of the county, 0.30 meters (one-foot) of freeboard is required. Nonresidential structures may meet the standards in Section 82-28.1002(3)(c). Upon the completion of the substructure but prior to completion of the structure, the elevation of the lowest floor, including basement, shall be certified by a registered professional engineer or surveyor, or verified by the building inspector to be properly elevated. Such certification or verification shall be provided to the floodplain administrator.

(b) New construction and substantial improvement of any structure in zone AH, AO or VO shall have the lowest floor, including basement, elevated above the highest adjacent grade at least as high as the depth number specified in meters (feet) on the FIRM plus required freeboard, or at least 0.61 meters (two feet) if no depth number is specified. In the San Francisco Bay Delta Estuarine Region, 0.61 meters (two feet) of freeboard is required. In all other unincorporated areas of the county, 0.30 meters (one-foot) of freeboard is required. Nonresidential structures may meet the standards in Section 82-28.1002(3)(c). Upon the completion of the substructure but prior to completion of the structure, the elevation of the lowest floor, including basement, shall be certified by a registered professional engineer or surveyor, or verified by the building inspector to be properly elevated. Such certification or verification shall be provided to the floodplain administrator.

(c) If the difference in elevation between the lowest floor and the ground below the lowest floor is two meters (6.6 feet) or greater, the applicant will provide the floodplain administrator with a deed restriction. This deed restriction will be recorded and will run with the property (not the applicant). This restriction will limit the area below the lowest floor to be used only for building access, storage and parking of vehicles and will not allow this area to be developed into habitable space.

(d) Nonresidential construction shall either be elevated in conformance with Section 82-28.1002 (3)(a) or (b), or together with attendant utility and sanitary facilities:

(i) Be floodproofed so that below the base flood level plus freeboard, 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 professional engineer or architect that the standards of this subsection are satisfied. Such certification shall be provided to the floodplain administrator; or

(iv) The floodplain administrator may allow the nonresidential structure to be made "flood resistant." Flood resistant structures shall comply with Section 82-28.1002(3)(e).

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

(i) Have a minimum of two openings with a total net area of not less than 6.45 square centimeters (one square inch) for every 0.09 square meters (one square foot) of enclosed area subject to flooding. The bottom of all openings shall be no higher than 0.3 meter (one foot) above grade. (Openings may be equipped with screens, louvers, valves or other coverings or devices provided that they permit the automatic entry and exit of floodwaters).

(4) Manufactured homes shall also meet the standards in Section 82-28.1008.

(Ords. 2000-33, 99-35, 96-11, 90-118, 88-50, 87-45).

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

(2) Onsite waste disposal systems shall be located to avoid impairment to them or contamination from them during flooding. All septic tanks shall be adequately anchored to resist flotation, collapse or lateral movement.

(3) Onsite water supply systems shall be located to avoid impairment to them or contamination of them during flooding.

(Ords. 2000-33, 99-35, 96-11, 90-118, 88-50, 87-45).

(1) All applications for tentative map approval are incomplete unless the tentative maps identify the flood hazard area and the elevation of the base flood. (See Section 82-28.806(2))

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

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

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

(5) All subdivisions shall provide adequate drainage to reduce exposure to flood hazards.

(Ords. 2000-33, 99-35, 96-11, 90-118, 88-50, 87-45).

(1) All manufactured homes to be placed or substantially improved within special flood hazard areas (zones A1-30, and AH), as shown on the study and maps described in Section 82-28.604, shall:

(a) Be elevated and anchored to a foundation such that the lowest floor of the manufactured home is at or above the base flood elevation, plus required freeboard. In the San Francisco Bay Delta Estuarine Region, 0.61 meters (two feet) of freeboard is required. In all other unincorporated areas of the county, 0.30 meters (one-foot) of freeboard is required; and

(b) Be securely anchored to an adequately designed foundation system to resist flotation, collapse or lateral movement in accordance with California Health and Safety Code Sections 18613.4 or 18551.

(2) Section 82-28.1008(1) shall apply to:

(a) Manufactured homes to be placed or substantially improved in an expansion to an existing manufactured home park or subdivision;

(b) Manufactured homes to be placed or substantially improved outside of a manufactured home park or subdivision; and

(c) Manufactured homes to be placed in a manufactured home park or subdivision established on or after the effective date of this ordinance.

(3) Section 82-28.1008(1)(a) shall not apply to manufactured homes to be placed or substantially improved in an existing manufactured home park or subdivision, except:

(a) Where the repair, reconstruction or improvement of the streets, utilities and pads equals or exceeds fifty percent of the streets, utilities and pads before the repair, reconstruction or improvement is commenced; or

(b) The manufactured home has incurred "substantial damage" as a result of a flood.

(Ords. 2000-33, 99-35, 96-11, 90-118, 88-50, 87-45).

(1) All recreational vehicles placed on sites within a special flood hazard area (zones A1-30, AH, and AE) on the FIRM shall:

(a) Be on the site for fewer than one hundred eighty consecutive days; or

(b) Be fully licensed, insured and ready for highway use. (A recreational vehicle is ready for highway use if it is on its wheels or integral 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 82-28.802 and the elevation and anchoring requirements for manufactured homes in Section 82-28.1008.

(Ords. 2000-33, 99-35, 96-11).

Within special flood hazard areas established in Section 82-28.604 are areas designated as floodways. A floodway is an extremely hazardous area due to the velocity of floodwaters which carry debris and potential projectiles and the potential for erosion. Floodways may or may not be specifically designated on the FIRM maps, their existence will be as determined by the floodplain administrator. Encroachments, including fill, new construction, substantial improvements and other development are not allowed in a floodway unless certification by a registered professional engineer is provided demonstrating that the encroachment(s) shall not result in any increase in flood levels during the occurrence of the base flood discharge. Allowed new construction and improvements shall comply with all applicable flood hazard reduction provisions of Article 82-28.10.

(Ords. 2000-33, 99-35, 96-11, 90-118, 88-50, 87-45).

Within coastal high hazard areas established in Section 82-28.604, the following standards shall apply:

(1) All new construction and substantial improvements shall be elevated on adequately anchored pilings or columns and securely anchored to such pilings or columns so that the lowest horizontal portion of the structural members of the lowest floor (excluding the pilings or columns) is elevated to or above the base flood elevation plus required freeboard. In the San Francisco Bay Delta Estuarine Region 0.6 meter (two feet) of freeboard is required. In all other unincorporated areas of the county, 0.3 meter (one foot) of freeboard is required. The pile or column foundation, and structure attached hereto, shall be anchored to resist flotation, collapse or lateral movement due to the effects of wind and water loads acting simultaneously on all building components. Water loading values used shall be those associated with the base flood plus freeboard. Wind loading values used shall be those required by applicable state or local building standards.

(2) All new construction shall be located on the landward side of the reach of mean high tide.

(3) All new construction and substantial improvements shall have the space below the lowest floor free of obstructions or constructed with breakaway walls. Such temporarily enclosed space shall not be used for human habitation.

(4) Fill shall not be used for structural support of buildings.

(5) Manmade alteration of sand dunes which would increase potential flood damage is prohibited.

(6) The floodplain administrator shall obtain and maintain the following records:

(a) Certification by a registered engineer or architect that a proposed structure complies with Section 82-28.1012(1); and

(b) The elevation (in relation to mean sea level) of the bottom of the lowest structural member of the lowest floor (excluding pilings or columns) of all new and substantially improved structures; and whether such structures contain a basement.

(Ords. 2000-33, 99-35, 96-11, 90-118, 88-50, 87-45).