15.04.110 Protection from inundation – Construction standards.
A. No person shall construct or substantially improve any structure within a special flood hazard area that is not in compliance with this section.
B. General Construction Standards. All new construction or substantial improvements to a structure shall be constructed using methods and practices that minimize flood damage and comply with the following standards:
1. Structures shall be constructed with electrical, heating, ventilation, plumbing and air conditioning equipment and other service facilities that are designed or located so as to prevent water from entering or accumulating within the components during conditions of flooding.
2. Fuel storage tanks and other liquid storage tanks shall be secured to prevent disturbance by floodwater. Buried tanks shall be secured to a concrete base slab of sufficient volume to prevent flotation or otherwise adequately secured. Both fill and vent pipes shall extend at least one foot above the base flood elevation.
3. On-site waste disposal systems shall be designed to minimize or eliminate infiltration of floodwaters into the systems and discharges from the systems into floodwaters and shall be located to avoid impairment to them or contamination to them during flooding.
4. All new construction and substantial improvements (including the placement of prefabricated buildings and manufactured homes) shall be designed (or modified) and adequately anchored to prevent flotation, collapse or lateral movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy.
5. All new construction and substantial improvements below the base flood elevation shall be constructed with materials resistant to flood damage.
6. New and replacement water supply systems shall be designed to minimize or eliminate infiltration of flood waters into the systems.
C. Residential Structures. All new construction of and substantial improvements to residential structures shall have:
1. The lowest floor (including basement) elevated to or above the base flood elevation; and
2. Other fully enclosed areas below the lowest floor, such as crawl spaces, that are subject to flooding, and that are usable solely for the parking of vehicles, building access, or limited storage, 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 must meet or exceed the following criteria:
a. 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 shall be provided.
b. The bottom of all openings shall be no higher than one foot above grade.
c. Openings shall be equipped with screens, louvers, valves, or other coverings or devices; provided, that they permit the automatic entry and exit of floodwaters.
D. Nonresidential Structures.
1. All new construction of and substantial improvements to nonresidential structures shall have either:
a. The lowest floor (including basement) elevated to or above the base flood elevation; or
b. Together with attendant utility and sanitary facilities, be designed so that below the base flood level the structure is watertight with walls substantially impermeable to the passage of water and with structural components having the capability of resisting hydrostatic and hydrodynamic loads and effects of buoyancy.
2. Where a nonresidential structure is intended to be made watertight below the base flood level:
a. A registered professional engineer or architect shall develop and/or review structural designs, specifications, and plans for the construction, and shall certify that the design and methods of construction are in accordance with accepted standards of practice for meeting the applicable provisions of subsection (D)(1) of this section; and
b. A record of such certificates which includes the specific elevation (in relation to mean sea level) to which such structures are floodproofed shall be maintained by the Department of Community Planning.
3. Other fully enclosed areas below the lowest floor that are usable solely for parking of vehicles, building access or storage in an area other than a basement and which are subject to flooding shall comply with the requirements of subsection (C)(2) of this section.
E. Accessory Structures. Accessory structures shall be constructed and placed on the building site so as to offer minimum resistance to the flow of floodwaters, and shall be anchored to prevent flotation which may result in damage to other structures. Services utilities such as electrical and heating equipment shall be elevated or floodproofed.
F. Recreational Vehicles. In a special flood hazard area, a recreational vehicle must be licensed and titled as a recreational vehicle or park model (not as a permanent residence) and ready for highway use (i.e., on its wheels or jacking system, have no attached deck, porch or shed, and have quick-disconnect sewage, water and electrical connectors) or be on the site for fewer than 180 consecutive days. Recreational vehicles that do not meet these conditions must obtain a permit and meet the elevation and anchoring requirements for manufactured homes.
G. Critical Facilities. The following additional standards apply to critical facilities:
1. Construction of new critical facilities shall be, to the extent possible, located outside the limits of the special flood hazard area. Construction of new critical facilities shall be permissible within the special flood hazard area if no feasible alternative site is available.
2. Critical facilities constructed within the special flood hazard area shall have the lowest floor elevated three feet above the base flood elevation or to the height of the 500-year flood, whichever is higher.
3. Access to and from the critical facility should be protected to the height utilized above.
4. Floodproofing and sealing measures must be taken to ensure that toxic substances will not be displaced by or released into floodwaters.
5. Access routes elevated to or above the level of the base flood elevation shall be provided to all critical facilities to the extent possible. (Ord. 2009-55 § 2, 2010; Ord. 92-001 §§ 4, 5, 1992; Ord. 86-019 § 5, 1986; Ord. 85-124 § 3, 1985. 2004 Code § 15.04.080.)