(A) General standards. In all areas of special flood hazards, the following provisions are required for all new construction and substantial improvements:
(1) Design. All new construction or substantial improvements 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;
(2) Minimize flood damage. All new construction or substantial improvements shall be constructed by methods and practices that minimize flood damage;
(3) Resistant to flood damage. All new construction or substantial improvements shall be constructed with materials resistant to flood damage;
(4) Service facilities. All new construction or 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;
(5) Water supply systems. All new and replacement water supply systems shall be designed to minimize or eliminate infiltration of floodwaters into the system;
(6) Infiltration of floodwaters. New and replacement sanitary sewage systems shall be designed to minimize or eliminate infiltration of floodwaters into the systems and discharge from the systems into floodwaters; and
(7) Waste disposal systems. On-site waste disposal systems shall be located to avoid impairment to them or contamination from them during flooding.
(B) Substantial improvement. Any combination of repair, reconstruction, rehabilitation, addition, or improvement of a building or structure, if the cumulative cost of the entire project equals or exceeds 50%, unless a higher standard option is selected below, of the market value of the structure only (not of the structure and land value combined) before the improvement or repair is started then the work shall be considered as substantial improvement. If the structure has sustained substantial damage, any repairs are considered substantial improvements regardless of the actual repair work performed. For substantial damage, refer to § 154.05(C). The term does not, however, include either:
(1) Any project for improvement of a building required to correct existing health, sanitary, or safety code violations identified by the Building Official and that are the minimum necessary to assure safe living conditions; or
(2) Any alteration of a historic structure provided that the alteration will not preclude the structure's continued designation as a historic structure.
(C) Substantial damage. Substantial damage means damage of any origin sustained by a structure whereby the cost of restoring the structure to its pre-damaged condition would equal or exceed 50% of the market value of the structure only, unless a higher standard option is selected, before the damage occurred. This term also applies to structures which have incurred any damage that equals or exceeds 50% of the structure's market value regardless of the actual repair work performed. When a structure or building has been determined as substantially damaged, any work or repair on said structure or building will be considered as substantial improvement and will be required to meet the development requirements set forth within this chapter for substantial improvement.
(D) Substantial improvement and substantial damage determination. For applications for building permits to improve buildings and structures, including alterations, movement, enlargement, replacement, repair, change of occupancy, additions, rehabilitations, renovations, and any other improvement of or work on such buildings and structures, the Floodplain Administrator, in coordination with the applicable community officials and staff, shall:
(1) Estimate the market value or require the applicant to obtain an appraisal of the market value prepared by a qualified independent appraiser, of the building or structure only, not of land and building, before the start of construction of the proposed work. In the case of repair, the market value of the building or structure shall be the market value before the damage occurred and before any repairs are made.
(2) Compare the cost to perform the improvement, the cost to repair a damaged building to its pre-damaged condition, or the combined costs of improvements and repairs, if applicable, to the market value of the building or structure.
(3) Determine and document whether the proposed work constitutes substantial improvement or repair of substantial damage; the determination requires evaluation of previous permits issued for improvements and repairs as specified in § 154.05(B).
(4) If elected, utilize FEMA's Substantial Improvement/Substantial Desk Reference when making any determination on substantial improvement and/or substantial damage.
(5) The substantial improvement regulations apply to all of the work that is proposed as the improvement, even if multiple permits are issued. Therefore, the determination of the cost of the improvement should consider all costs of all phases of the work before issuance of the first permit.
(6) Notify the applicant that if it is determined that the work constitutes substantial improvement or repair of substantial damage and that compliance with the flood, this chapter is required.
(E) Specific standards. In all areas of special flood hazards where base flood elevation data has been provided as set forth in this chapter, the following provisions are required:
(1) Residential construction. New construction and substantial improvement of any residential structure shall have the lowest floor (including basement) elevated to one foot above the base flood elevation. A registered professional engineer, architect, or land surveyor shall submit a certification to the Floodplain Administrator that the standards of this chapter are satisfied.
(2) Non-residential construction. New construction and substantial improvements of any commercial, industrial, or other non-residential structure shall either have the lowest floor (including basement) elevated to one foot above the base flood elevation, or, 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 the effects of buoyancy. A registered professional engineer or architect shall develop and/or review structural design, specifications, and plans for the construction, and shall certify that the design and methods of construction are in accordance with accepted standards of practice as outlined in this section. A record of such certification that includes the specific elevation (in relation to mean sea level) to which such structures are floodproofed shall be maintained by the Floodplain Administrator. If the use or occupancy of the building changes in the future to residential, then the dry floodproofing of the structure cannot be used when determining compliance of the structure to the residential construction of § 154.05(E)(1). As such, the building will not be grandfathered into compliance and will be required to be brought into compliance with the residential construction requirements of this chapter.
(3) Enclosures. New construction and substantial improvements, with fully enclosed areas below the lowest floor that are to be used solely for parking of vehicles, building access, or storage in an area other than a basement, 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 must meet or exceed the following minimum 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; and
(c) Openings may be equipped with screens, louvers, valves, or other coverings or devices provided that they permit the automatic entry and exit of floodwaters. The development and construction of the structure must conform with the provision in FEMA/Federal Insurance Administration (FIA) Technical Bulletins 1 and 2. Certification and documentation from a professional, licensed engineer or architect is required if the structure's lowest floor is built below the BFE.
(4) Crawlspace. New construction and substantial improvements built on a crawlspace or sub-grade (below grade) crawlspace may be permitted if the development is designed and meets or exceeds the standards found in FEMA's Technical Bulletins 1, 2, and 11, which include but are not limited to the following:
(a) The structure must be affixed to a permanent foundation, 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. Because of hydrodynamic loads, crawlspace construction is not allowed in areas with flood velocities greater than five feet per second unless the design is reviewed by a qualified design professional, such as a registered architect or professional engineer.
(b) The crawlspace is an enclosed area below the BFE and, as such, must have openings that equalize hydrostatic pressures by allowing the automatic entry and exit of floodwaters. The bottom of each flood vent opening can be no more than one foot above the LAG.
(c) The crawlspace enclosure must have proper openings that allow equalization of hydrostatic pressure by allowing automatic entry and exit of floodwaters. To achieve this, a minimum of one square inch of flood opening is required per one square foot of the enclosed area subject to flooding.
(d) 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 crawlspace used to elevate the building, but also any joists, insulation, piers, or other materials that extend below the BFE. Ductwork, in particular, must either be placed above the BFE or sealed from floodwaters.
(e) Any building utility systems within the crawlspace must be elevated above the BFE or designed so that floodwaters cannot enter or accumulate within the system components during flood conditions.
(f) The interior grade of a crawlspace below the BFE must not be more than two feet below the LAG.
(g) The height of the below-grade crawlspace, measured from the lowest interior grade of the crawlspace floor to the bottom of the floor joist of the next higher floor cannot exceed four feet at any point.
(h) There must be an adequate drainage system that removes floodwaters from the interior area of the crawlspace. The enclosed area should be drained within a reasonable time after a flood event.
(i) Buildings with below-grade crawlspaces will have higher flood insurance premiums than buildings that have the preferred crawlspace construction, with the interior elevation at or above the LAG.
(5) Manufactured homes. All manufactured homes shall conform to the following requirements:
(a) Require that all manufactured homes to be placed within Zone A on a community's FHBM or FIRM shall be installed using methods and practices which minimize flood damage. For the purposes of this requirement, manufactured homes must be elevated and anchored to resist flotation, collapse, or lateral movement. Methods of anchoring may include, but are not limited to, use of over-the-top or frame ties to ground anchors. This requirement is in addition to applicable state and local anchoring requirements for resisting wind forces.
(b) Require that manufactured homes that are placed or substantially improved FIRM on sites:
1. Outside of a manufactured home park or subdivision;
2. On 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 which a manufactured home has incurred substantial damage as a result of a flood, be elevated on a permanent foundation such that the lowest floor of the manufactured home is elevated to or above the BFE, unless a higher standard option was selected, and be securely anchored to an adequately anchored foundation system to resist flotation, collapse, and lateral movement.
(c) A1-30, AH, AO, and AE Zones, require that manufactured homes to be placed or substantially improved in an existing manufactured home park to be elevated so that:
1. The lowest floor is at or above the BFE plus freeboard of one foot; or
2. The chassis is supported by reinforced piers no less than 36 inches in height above grade and securely anchored.
(6) Recreational vehicles. In all areas of special flood hazard, recreational vehicles, must either:
(a) Be on the site for fewer than 180 consecutive days;
(b) Be fully licensed and ready for highway use, on its wheels or jacking system, attached to the site only by quick disconnect type utilities and security devices, and have no permanently attached structures or addition; or
(c) The recreational vehicle must meet all the requirements for § 154.04(D), including the anchoring and elevation requirements of manufactured homes of this chapter.
(F) Standards for subdivision proposals.
(1) Development permit requirements. All proposals for the development of subdivisions, including the placement of manufactured home parks and subdivisions, shall meet development permit requirements of this chapter to minimize flood damage.
(2) All subdivision preliminary plats/development plans shall include the mapped flood hazard zones from the effective FIRM.
(3) Base flood elevation. Base flood elevation data shall be generated for subdivision proposals and other proposed developments, including the placement of manufactured home parks and subdivisions, which is greater than 50 lots or five acres, whichever is lesser.
(4) Adequate drainage. All subdivision proposals, including the placement of manufactured home parks and subdivisions, shall have adequate drainage provided to reduce exposure to flood hazards.
(5) Public utilities and facilities. All subdivision proposals, including the placement of manufactured home parks and subdivisions, shall have public utilities and facilities such as sewer, gas, electrical, and water systems located and constructed to minimize or eliminate flood damage.
(G) Standards for areas of shallow flooding (AO/AH Zones). Located within the SFHAs established in § 154.03 et seq. are areas designated as shallow flooding. These areas have special flood hazards associated with base flood depths of one to three feet where a clearly defined channel does not exist and where the path of flooding is unpredictable, and where velocity flow may be evident. Such flooding is characterized by ponding or sheet flow. Therefore, the following provisions apply:
(1) All new construction and substantial improvements of residential structures have the lowest floor (including basement) elevated above the highest adjacent grade at least as high as the depth number specified in feet on the community's FIRM (at least two feet if no depth number is specified) plus the free board height of one foot.
(2) All new construction and substantial improvements of non-residential structures:
(a) Have the lowest floor (including basement) elevated above the highest adjacent grade at least as high as the depth number specified in feet on the community's FIRM (at least two feet if no depth number is specified) plus the free board height of one foot; or
(b) Together with attendant utility and sanitary facilities be designed so that below the base flood elevation 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 of effects of buoyancy.
(3) A registered professional engineer or architect shall submit a certification to the Floodplain Administrator that the standards of this section are satisfied.
(4) Require within Zones AH or AO adequate drainage paths around structures on slopes, to guide floodwaters around and away from proposed structures.
(H) Floodways. Floodways located within SFHAs are extremely hazardous areas due to the velocity of floodwaters that carry debris, potential projectiles, and erosion potential, the following provisions shall apply:
(1) Designate a regulatory floodway that will not increase the base flood elevation more than one foot.
(2) Encroachments are prohibited, including fill, new construction, substantial improvements, and other development within the adopted regulatory floodway unless it has been demonstrated through hydrologic and hydraulic analyses performed in accordance with standard engineering practice that the proposed encroachment would not result in any increase greater than zero feet, unless higher standard option is selected, in flood levels within the community during the occurrence of the base flood discharge.
(3) All new construction and substantial improvements shall comply with all applicable flood hazard reduction provisions of this chapter.
(4) Under the provisions of 44 CFR Chapter 1, § 65.12, of the NFIP Regulations, a community may permit encroachments within the adopted regulatory floodway that would result in an increase in BFEs, provided that the community first applies for a conditional FIRM and floodway revision through FEMA.
(Prior Code, § 13.20.050) (Ord. 16-2005, passed 11-16-2005; Ord. 22-2023, passed 11-1-2023)