The following flood table land requirements apply to new construction only and not to additions or substantial improvements to structures within flood table lands built before August 10, 1999:
(A) Public health protection standards.
(1) No chemicals, explosives, buoyant materials, animal waste, fertilizers, flammable liquids, pollutants, or other hazardous or toxic materials shall be placed or stored below the flood protection elevation.
(2) New and replacement water supply systems, wells, and sanitary sewer lines may be permitted providing all manholes or other above-ground openings located below the FPE are watertight.
(3) On-site waste disposal systems shall be designed to avoid inundation by the base flood.
(B) Building protection requirements.
(1) The lowest floor, including basements, of all new residential structures, including additions, shall be elevated or structurally dry flood-proofed up to at least the flood protection elevation (FPE). The floor of an attached garage for a new structure must be elevated up to at least one-half of one foot above the base flood elevation (BFE). If structurally dry flood-proofed, a Licensed Professional Engineer, Licensed Structural Engineer, or Licensed Architect shall certify that the building has been structurally dry flood-proofed up to the FPE and the structure and attendant utility facilities are watertight and capable of resisting the effects of the base flood. 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. Flood-proofing measures shall be operable without human intervention and without an outside source of electricity. (Levees, berms, floodwalls. and similar works are not considered flood-proofing for the purpose of this subsection.)
(a) If the residential structure is not dry flood-proofed and is placed on compacted fill, the top of the fill for a residential structure shall be above the FPE. The top of fill for an attached garage shall be one-half of one foot above the BFE. The fill pad shall be placed at the appropriate elevation and designed to extend a minimum of ten feet out from the building’s designed footprint unless the building is certified by a Registered Structural Engineer to be protected from damages due to hydrostatic pressures. Additionally, the fill pad shall meet 95% of Standard Proctor Density in order to be demonstrated not to settle below the FPE for the residential structure and not below one-half of one foot above the BFE for an attached garage, and to be adequately protected against erosion, scour, and differential settlement. Foundation excavations shall not extend more than five feet beyond the foundation footprint. Backfill for the over excavated area does not need to meet the compaction requirements.
(b) If the residential structure is not dry flood-proofed and is elevated by means of walls, pilings, or other foundation, the building’s supporting structure must be permanently open to flood waters and not subject to damage by hydrostatic pressures of the base flood. The bottom of the permanent openings shall be no more than one foot above the lowest adjacent grade. The total net area shall be provided below the FPE, and consist of a minimum of two openings for each enclosed area with each opening of an enclosed area on a different exterior wall. 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 FPE. Any louvers, screens, or other opening covers must not block or impede the automatic flow of floodwaters into and out of the enclosed area. 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. All areas below the FPE shall be constructed with materials resistant to flood damage. The lowest floor (including basement) for the residential structure and all electrical, heating, ventilation, plumbing, air conditioning equipment, and utility meters shall be located at or above the FPE. Waterproofed service facilities, including, but not limited to, water and sewer pipes, electrical and telephone lines, and submersible pumps, may be located below the FPE. No area less than one foot above the BFE shall be used for storage of items or materials.
(2) The lowest floor including basements of all new non-residential buildings, including additions, shall be elevated at least to the FPE or be structurally dry flood-proofed to at least the FPE. A nonresidential building may be structurally dry flood-proofed (in lieu of elevation) provided that a Licensed Professional Engineer, Licensed Structural Engineer, or Licensed Architect shall certify that the building has been structurally dry flood-proofed up to the FPE and the structure and attendant utility facilities are watertight and capable of resisting the effects of the base flood. 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. Flood-proofing measures shall be operable without human intervention and without an outside source of electricity. (Levees, berms, floodwalls, and similar works are not considered flood-proofing for the purpose of this subsection.)
(a) If a non-residential structure is not dry flood-proofed and is placed on compacted fill, the top of the fill shall be above the FPE. The fill pad shall be placed at the appropriate elevation and designed to extend a minimum of ten feet out from the building’s designed footprint unless the building is certified by a Licensed Structural Engineer to be protected from damages due to hydrostatic pressures. Additionally, the fill pad shall meet 95% of Standard Proctor Density in order to be demonstrated not to settle below the FPE and to be adequately protected against erosion, scour and differential settlement. Foundation excavations shall not extend more than five feet beyond the foundation footprint. Backfill for the over excavated area does not need to meet the compaction requirements.
(b) If a non-residential structure is not dry flood-proofed and is elevated by means of walls, pilings, or other foundation, the building’s supporting structure must be permanently open to flood waters and not subject to damage by hydrostatic pressures of the base flood. The bottom of the permanent openings shall be no more than one foot above the lowest adjacent grade. The total net area shall be provided below the FPE, and consist of a minimum of two openings for each enclosed area with each opening of an enclosed area on a different exterior wall. 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 FPE. Any louvers, screens, or other opening covers must not block or impede the automatic flow of floodwaters into and out of the enclosed area. 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. All areas below the FPE shall be constructed with materials resistant to flood damage. The lowest floor (including basement) for the non-residential structure and all electrical, heating, ventilation, plumbing, air conditioning equipment, and utility meters shall be located at or above the FPE. Waterproofed service facilities, including, but not limited to, water and sewer pipes, electrical and telephone lines, and submersible pumps, may be located below the FPE. No area less than one foot above the BFE shall be used for storage of items or materials.
(3) Mobile homes and recreational vehicles to be installed on-site more than 180 days shall be elevated to or above the FPE 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 issued pursuant to 77 III. Adm. Code 870.
(4) Accessory structures and attached garages may be constructed with the lowest floor below the FPE in accordance with the following:
(a) The building shall not be used for human habitation.
(b) The structure shall be anchored to prevent flotation.
(c) Service facilities such as electrical and heating equipment shall be elevated or flood-proofed to the FPE.
(d) All areas below the FPE shall be constructed with materials resistant to flood damage.
(e) The floor must be elevated up to at least one-half (0.5) foot above the base flood elevation (BFE) unless it meets all the requirements of § 151.149(H)(6).
(Ord., § 8.9, passed 10-13-2009; Ord. passed 10-9-2012; Ord. 23-1056, passed 8-8-2023)