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(A) Generally. The following general performance standards are applicable to all development in a regulatory floodplain. The standards of this section apply except when superseded by more stringent requirements in the subsequent sections.
(1) No development except as allowed in § 55.066 shall be allowed in the regulatory floodplain that singularly or cumulatively creates an increase in flood stage or velocity off-site, or a damaging or potentially damaging increase in flood heights or velocity on-site or threat to public health, safety and welfare.
(2) For all projects involving a channel modification, fill, stream maintenance or a levee, the flood conveyance and storage capacity of the regulatory floodplain shall not be reduced.
(3) If the proposed development would result in a change in the regulatory floodplain or BFE as indicated in Appendix A, or as adopted by each community, the applicant shall obtain a LOMR from FEMA. No buildings may be built in the existing or proposed regulatory floodplain until the LOMR receives concurrence from IDNR/OWR and is issued by FEMA and the building meets all the building protection standards (division (C) below). Proposed changes to the regulatory floodway delineation and the BFE must be submitted to IDNR/OWR for concurrence.
(4) If the development is located in a public body of water, as defined by IDNR/OWR, a permit or a waiver of a permit must also be received from IDNR/OWR.
(5) Prior to the commencement of any construction, modification or removal of a dam the developer shall obtain an IDNR/OWR permit or letter indicating a permit is not required.
(6) (a) For public flood control projects, the Floodplain Management standards will be considered met if the applicant can demonstrate to IDNR/OWR and WCSMC that each of the following conditions are met:
1. Demonstrate by hydraulic and hydrologic modeling that the proposed project will not singularly or cumulatively result in increased flood heights outside the project site or demonstrate that any increases will be contained in easements for all flood events up to and including the base flood event;
2. Demonstrate that the project will be operated and maintained by a public agency; and
3. Demonstrate that the project will reduce flood damage to an existing building or structure.
(b) These standards do not preclude the design, engineering, construction or financing, in whole or in part of a public flood control project by persons who are not public agencies.
(7) Proposals for new subdivisions, manufactured home parks, planned unit developments (PUDs) and additions to manufactured home park and additions to subdivisions shall include base flood or 100-year frequency flood elevation data and floodway delineations.
(B) Public health protection standards.
(1) New and replacement water supply systems, wells and sanitary sewer lines may be permitted if all manholes or other aboveground openings located below the FPE are watertight.
(2) New on-site waste disposal systems, such as septic systems, are allowed in the regulatory floodplain only if they meet all of the following conditions.
(a) The invert of any wastewater distribution lines shall be a minimum of two-feet above the water surface elevation of the base flow of any perennial stream.
(b) The lateral distance from a ditch, creek or other riverine source to the wastewater distribution lines shall be a minimum of 75.
(c) The elevation of any areas which are to receive wastewater distribution shall be above the ordinary high water mark.
(d) The soil of the receiving field shall be of a type suitable for septic fields.
(e) The tank shall be placed out of the floodplain with the invert of the outlet above the BFE.
(3) New, substantially improved or replacement wastewater treatment plants shall have watertight openings for those openings located below the FPE. The facilities should be located to avoid impairment to the facility or contamination of floodwaters during the base flood.
(C) Building protection standards. The building protection standards apply to all buildings located in the regulatory floodplain; however, it should be noted that most new and replacement buildings are not appropriate uses of the regulatory floodway.
(1) The lowest floor including basements of all new residential structures, substantially improved structures and additions shall be elevated up to at least the FPE. An attached garage for a structure must be elevated up to at least 0.1 feet above the BFE.
(a) If placed on fill, the top of the fill for the residential structure shall be above the FPE. The top of fill for an attached garage shall be at least 0.1 foot above the BFE. The fill shall be placed at that elevation for a distance of ten feet out from the building unless the building design is certified by a registered structural engineer to be protected from damages due to hydrostatic pressures. Additionally, the fill shall not settle below the FPE for the residential structure and not below 0.1 feet above the base flood for an attached garage, and shall be adequately protected against erosion, scour and differential settlement. The fill should not adversely affect surface drainage from or onto neighboring properties.
(b) If 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 permanent openings shall be no more than one foot above existing grade, and consist 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 BFE. The lowest inside grade must match the lowest existing outside grade adjacent to the structure. 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 of materials resistant to flood damage. The lowest floor (including basement) for the residential structure and all electrical, heating, ventilating, plumbing and air conditioning equipment and utility meters shall be located at or above the FPE. An attached garage must be elevated to at least 0.1 feet above the BFE. Water and sewer pipes, electrical and telephone lines, submersible pumps and other waterproofed service facilities may be located below the FPE. No area below the FPE shall be used for storage.
(2) The lowest floor including the basement of all new or substantially improved nonresidential buildings shall be elevated at least to the FPE as described above or be structurally dry floodproofed to at least the FPE. A nonresidential building may be structurally dry floodproofed (in lieu of elevation) provided that a professional engineer or registered structural engineer shall certify that the building has been structurally dry floodproofed below 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. 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).
(3) Manufactured homes and recreational vehicles to be installed on a site for more than 180 days shall be at or above the FPE and shall be anchored to resist flotation, collapse or lateral movement in accordance with the State Manufactured Home Tie-Down Code (77 Ill. Adm. Code 870), as amended.
(4) (a) Accessory structures, such as tool sheds and detached garages which are not substantial improvements on an existing single-family lot, may be constructed with the lowest floor below the FPE in accordance with the following criteria.
1. The building shall not be used for human habitation.
2. All areas below the FPE shall be constructed with waterproof material. Structures located in a regulatory floodway shall meet the floodway standards in § 55.064.
3. The structure shall be anchored to prevent flotation and movement.
4. Service facilities such as electrical and heating equipment shall be elevated or floodproofed to the FPE.
5. The building shall be no greater than 600 square feet in floor size and be valued at less than $7,500. The building shall meet the permanent opening criteria of division (C)(1)(b) above.
6. The building shall be used only for the storage of vehicles or tools and may not contain basements or other rooms, workshops, greenhouses or similar uses.
(b) Accessory structures that do not meet all of the above criteria may be constructed if they are dry floodproofed or elevated at least one-half of one foot above the BFE.
(D) Nonconforming structures. A nonconforming structure damaged by flood, fire, wind or other disaster may be restored unless the damage meets or exceeds 50% of its market value before it was damaged, in which case it shall conform to the building protection standards of this chapter.
(E) LOMR-F. Certified communities may utilize FEMA Technical Bulletin 10-01 for the issuance of LOMR-Fs.
(Res. 02-441, passed 10-17-2002; Res. 02-495, passed 11-21-2002; Res. 04-87, passed 3-17-2004; Ord. 18-305, passed 11-15-2018)