San Leandro Municipal Code Art. 5 Provisions for Flood Hazard Reduction

(Legislative History: Ordinance No. 88-015, 8/1/88; Ordinance No. 99-07, 4/9/99 (Sections 7-9-500 — 7-9-540))

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) All manufactured homes shall meet the anchoring standards of Section 7-9-515.

(b) Construction Materials and Methods: All new construction and substantial improvements shall be constructed:

(1) With materials and utility equipment resistant to flood damage;

(2) With 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

(4) If within Zones AH or AO so that there are adequate drainage paths around structures on slopes to guide floodwaters around and away from proposed structures.

(c) Elevation and Floodproofing: (See Article 2, Definitions for "new construction," "substantial damage" and "substantial improvement.")

(1) Residential construction, new or substantial improvements, shall have the lowest floor, including basement:

(i) In an AO Zone, elevated above the highest adjacent grade to a height equal to or exceeding the depth number specified in feet on the FIRM, or elevated at least two feet above the highest adjacent grade if no depth number is specified. (The State of California recommends that the lowest floor be elevated above the highest adjacent 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 grade if no depth number is specified.)

(ii) In an A Zone, elevated to or above the base flood elevation, as determined by this community. (The State of California recommends the lowest floor be elevated at least one foot above the base flood elevation, as determined by the community).

(iii) In all other Zones, elevated to or above the base flood elevation. (The State of California recommends the lowest floor be elevated at least one foot above the base flood elevation.)

(iv) Upon the completion of the structure, the elevation of the lowest floor including basement shall be certified by a registered professional engineer or surveyor, or be properly elevated. Such certification or verification shall be provided to the Floodplain Administrator.

(2) Nonresidential construction shall either be elevated to conform with subsection (c)(1) of this section or together with attendant utility and sanitary facilities:

(i) Be floodproofed below the elevation recommended under subsection (c)(1) 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 professional engineer or architect that the standards of this subsection are satisfied. Such certification shall be provided to the Floodplain Administrator.

(3) All new construction and 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 must exceed the following minimum criteria:

(i) Be certified by a registered professional engineer or architect; or

(ii) Be certified to comply with a local floodproofing standard approved by the Federal Insurance Administration, Federal Emergency Management Agency; or

(iii) 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 coverings or devices provided that they permit the automatic entry and exit of floodwater.

(4) Manufactured. homes shall also meet the standards in Section 7-9-515.

(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 systems; and

(2) Discharge from the systems into floodwaters.

(b) On-site waste disposal systems shall be located to avoid impairment to them, or contamination from them, during flooding.

(a) All preliminary subdivision proposals shall identify the flood hazard area and the elevation of the base flood.

(b) All subdivision plans will provide the elevation of proposed structure(s) and pad(s). If the site is filled above the base flood elevation, the final first 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 utilities 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.

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

(1) Outside of a manufactured home park or subdivision;

(2) In a new manufactured home park or subdivision;

(3) In an expansion to an existing manufactured home park or subdivision; or

(4) 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 one foot above the base flood elevation and be securely anchored to an adequately anchored foundation system to resist flotation, collapse and lateral movement.

(b) All manufactured homes that are placed or substantially improved on sites located within Zones V1-30, V, and VE on the community's Flood Insurance Rate Map will meet the requirements of subsection (a) of this section and Section 7-9-530.

(c) 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 community's Flood Insurance Rate Map that are not subject to the provisions of subsection (a) of this section will be elevated so that either:

(1) The lowest floor of the manufactured home is at least one foot above the base flood elevation, 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 36 inches in height above grade and is securely anchored to an adequately anchored foundation system to resist flotation, collapse, and lateral movement.

(a) All recreational vehicles placed on sites within Zones A1-30, AH, and AE on the community's Flood Insurance Rate Map will either:

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

(2) 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, 15 attached to the site only by quick disconnect type utilities and security devices, and has no permanently attached additions; or

(3) Meet the permit requirements of Article 4 of this Chapter and the elevation and anchoring requirements for manufactured homes in Section 7-9-515(a).

(b) Recreation vehicles placed on sites within Zones V1-30, V, and VE on the community's Flood Insurance Rate Map will meet the requirements of subsection (a) of this section and Section 7-9-530.

Located within areas of special flood hazard established in Section 7-9-305 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 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 the base flood elevation during the occurrence of the base flood discharge.

(b) If subsection (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 5.

Within coastal high hazard areas as established under Section 7-9-305, the following standards shall apply:

(a) All new construction and substantial improvement 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 level. The pile or column foundation and structure attached thereto is anchored to resist flotation, collapse, and lateral movement due to the effects of wind and water loads acting simultaneously on all building components. Water loading valves used shall be those associated with the base flood. Wind loading values used shall be those required by applicable state or local building standards.

(b) All new construction and other development shall be located on the landward side of the reach of mean high tide.

(c) All new construction and substantial improvement shall have the space below the lowest floor free of obstructions or constructed with breakaway walls as defined in Article 2 of this Chapter. Such enclosed space shall not be used for human habitation and will be usable solely for parking of vehicles, building access or storage.

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

(e) Man-made alteration of sand dunes which would increase potential flood damage is prohibited.

(f) The Floodplain Administrator shall obtain and maintain the following records:

(1) Certification by a registered engineer or architect that a proposed structure complies with subsection (a) of this section.

(2) 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.

(a) The Floodplain Administrator shall review permits for proposed construction of other development to determine if it is proposed within a mudslide area.

(b) Permits shall be reviewed to determine that the proposed site and improvement will be reasonably safe from mudslide hazards. Factors to be considered in making this determination include but are not limited to:

(1) Type and quality of soils;

(2) Evidence of groundwater or surface water problems;

(3) Depth and quality of any fill;

(4) Overall slope of the site; and

(5) Weight that any proposed development will impose on the slope.

(c) Within areas which may have mudslide hazards, the Floodplain Administration shall require that:

(1) A site investigation and further review be made by persons qualified in geology and soils engineering;

(2) The proposed grading, excavation, new construction, and substantial improvement be adequately designed and protected against mudslide damages;

(3) The proposed grading, excavations, new construction, and substantial improvement not aggravate the existing hazard by creating either on-site or off-site disturbances; and

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

The Floodplain Administrator shall require permits for proposed construction and other development within all flood-related erosion-prone areas known to the community.

(a) 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.

(b) 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.

(c) Within 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 designed 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.