(A) All buildings located within a 100-year floodplain, also known as a SFHA, shall be protected from flood damage below the flood protection elevation. This building protection criteria applies to the following situations:
(1) Construction or placement of a new building or alteration or addition to an existing building valued at more than $1,000 or 70 square feet;
(2) Substantial improvements or structural alterations made to an existing building that increase the floor area by more than 20% or equal or exceed the market value by 50%. Alteration shall be figured cumulatively subsequent to the adoption of this chapter. If substantially improved, the existing structure and the addition must meet the flood protection standards of this section;
(3) Repairs made to a substantially damaged building. These repairs shall be figured cumulatively subsequent to the adoption of this chapter. If substantially damaged, the entire structure must meet the flood protection standards of this section;
(4) Installing a manufactured home on a new site or a new manufactured home on an existing site (the building protection requirements do not apply to returning a manufactured home to the same site it lawfully occupied before it was removed to avoid flood damage);
(5) Installing a travel trailer or recreational vehicle on a site for more than 180 days per year; and
(6) Repetitive loss to an existing building as defined in § 156.002 of this chapter. This building protection requirement may be met by one of the following methods set out in this section.
(B) A residential or non-residential building, when allowed, may be constructed on permanent land fill in accordance with the following:
(1) The lowest floor (including basement) shall be at or above the flood protection elevation; and
(2) Fill requirements:
(a) The fill shall be placed in layers no greater than six inches deep before compaction and should extend at least ten feet beyond the foundation of the building before sloping below the flood protection elevation;
(b) The top of the fill shall be above the flood protection elevation. However, the ten-foot minimum may be waived if a structural engineer certifies an alternative method to protect the building from damages due to hydrostatic pressures;
(c) The fill shall be protected against erosion and scour during flooding by vegetative cover, riprap or other structural measure;
(d) The fill shall be composed of rock or soil and not incorporate debris or refuse materials; and
(e) The fill shall not adversely affect the flow or surface drainage from or onto neighboring properties, and when necessary, storm water management techniques such as swales or basins shall be incorporated.
(C) A residential or non-residential building may be elevated in accordance with the following.
(1) The building or improvements shall be elevated on crawl space, stilts, piles, walls or other foundation that is permanently open to flood waters and not subject to damage by hydrostatic pressures of the base flood or 100-year frequency flood. Designs must either be certified by a licensed professional engineer or architect or the permanent openings, one on each wall, shall be no more than one foot above existing grade, and consists of a minimum of two openings. The openings must have a total net area of not less than one square inch for every one square foot of enclosed area subject to flooding below the base flood elevation.
(2) The foundation and supporting members shall be anchored and aligned in relation to flood flows and adjoining structures so as to minimize exposure to known hydrodynamic forces such as current, waves, ice and floating debris.
(3) All areas below the flood protection elevation shall be constructed of materials resistant to flood damage.
(a) The lowest floor (including basement) and all electrical, heating, ventilating, plumbing and air conditioning equipment and utility meters shall be located at or above the flood protection elevation; and
(b) Water and sewer pipes, electrical and telephone fines, submersible pumps and other water-proofed service facilities may be located below the flood protection elevation provided they are water-proofed.
(4) The areas below the flood protection elevation may only be used for the parking of vehicles, building access or storage in an area other than a basement and not later modified or occupied as habitable space.
(5) In lieu of the above criteria, the design methods to comply with these requirements may be certified by licensed professional engineer or architect.
(6) Manufactured homes, and travel trailers to be installed on a site for more than 180 days, shall be elevated to or above the flood protection elevation; and, shall be anchored to resist flotation, collapse or lateral movement by being tied down in accordance with the Rules and Regulations for the Illinois Mobile Home Tie-Down Act, 210 ILCS 120, issued pursuant to 77 Ill. Adm. Code part 870. In addition, all manufactured homes shall meet the following elevation requirements.
(a) In the case of manufactured homes placed or substantially improved outside of a manufactured home park or subdivision; in a new manufactured home park or subdivision; in an expansion to an existing manufactured home park or subdivision; or in an existing manufactured home park or subdivision on which a manufactured home has incurred substantial damage from a flood, the top of the lowest floor shall be elevated to or above the flood protection elevation.
(b) In the case of manufactured homes placed or substantially improved in an existing manufactured home park or subdivision, the manufactured home shall be elevated so that either the top of the lowest floor is above the base flood elevation or the chassis is at least 36 inches in height above grade and supported by reinforced piers or other foundations of equivalent strength, whichever is less.
(7) Recreational vehicles or travel trailers shall be required to meet the elevation and anchoring requirements of division (C)(6) above unless:
(a) They are on site for fewer than 180 consecutive days; and
(b) They are fully licensed, ready for highway use, and used only for recreation, camping, travel or seasonal use rather than as a permanent dwelling. 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 utility and service devices, and has no permanently attached additions.
(D) Only a non-residential building may be structurally dry floodproofed (in lieu of elevation); provided that:
(1) A licensed professional engineer or architect shall certify that the building has been structurally dry floodproofed below the flood protection elevation, the structure and attendant utility facilities are water-tight and capable of resisting the effects of the base flood or 100-year frequency flood;
(2) The building design shall take into account flood velocities, duration, rate of rise, hydrostatic and hydrodynamic forces, the effects of buoyancy and impacts from debris or ice; and
(3) Floodproofing measures shall be operable without human intervention and without an outside source of electricity (levees, berms, floodwalls and similar works are not considered floodproofing for the purpose of this division (D)(3)).
(E) A building may be constructed with a crawlspace located below the flood protection elevation; provided that, the following conditions are met.
(1) The building must be 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.
(2) Any enclosed area below the flood protection elevation shall have openings that equalize hydrostatic pressures by allowing for the automatic entry and exit of floodwaters. A minimum of one opening on each wall having a total net area of not less than one square inch per one square foot of enclosed area. The openings shall be no more than one foot above grade.
(3) The interior grade of the crawlspace below the flood protection elevation must not be more than two feet below the lowest adjacent exterior grade.
(4) The interior height of the crawlspace measured from the interior grade of the crawl to the top of the foundation wall must not exceed four feet at any point.
(5) An adequate drainage system must be installed to remove floodwaters from the interior area of the crawlspace within a reasonable period of time after a flood event.
(6) Portions of the building below the flood protection elevation must be constructed with materials resistant to flood damage.
(7) Utility systems within the crawlspace must be elevated above the flood protection elevation.
(F) Construction of new or substantially improved critical facilities shall be located outside the limits of the floodplain. Construction of new critical facilities shall be permissible within the floodplain if no feasible alternative site is available. Critical facilities constructed within the SFHA shall have the lowest floor (including basement) elevated or structurally dry floodproofed to the 500-year flood frequency elevation or three feet above the level of the 100-year flood frequency elevation whichever is greater. Floodproofing and sealing measures must be taken to ensure that toxic substances will not be displaced by or released into floodwaters. Access routes elevated to or above the level of the base flood elevation shall be provided to all critical facilities.
(G) Tool sheds, detached garages and other minor accessory structures on an existing single-family platted lot may be constructed with the lowest floor below the flood protection elevation in accordance with the following:
(1) The building is not used for human habitation;
(2) All areas below the base flood or 100-year frequency flood elevation shall be constructed with water-proof material. Structures located in a designated floodway shall be constructed and placed on a building site so as not to block the flow of flood waters and shall also meet the appropriate use criteria of §§ 156.060 through 156.062 of this chapter. In addition, all other requirements of §§ 156.045 through 156.047, 156.060 through 156.062 and 156.075 through 156.077 of this chapter must be met;
(3) The structure shall be anchored to prevent flotation;
(4) Service facilities such as electrical and heating equipment shall be elevated or floodproofed to the flood protection elevation;
(5) The building shall be valued at less than $10,000 and be less than 500 square feet in floor size;
(6) The building shall be used only for the storage of vehicles or tools and may not contain other rooms, workshops, greenhouses or similar uses and cannot be modified later into another use;
(7) The building shall meet the permanent opening criteria of division (C)(1) above;
(8) All flammable or toxic materials (gasoline, paint, insecticides, fertilizers and the like) shall be stored above the flood protection elevation; and
(9) The lowest floor elevation should be documented and the owner advised of the flood insurance implications.
(H) Existing buildings located within a designated floodway shall also meet the more restrictive appropriate use standards included in §§ 156.060 through 156.062 of this chapter. Non-conforming structures located in a designated floodway may remain in use and may only be enlarged, replaced or structurally altered in accordance with § 156.062 of this chapter. A non-conforming structure damaged by flood, fire, wind or other natural or human-made disaster may be restored unless the damage exceeds 50% of its market value before it was damaged, in which case it shall conform to this chapter.
(Prior Code, § 157.093) (Ord. 08-023, passed 7-22-2008)