(A) No development in the SFHA where a floodway has not been determined shall create a damaging or potentially damaging increase in flood heights or velocity or threat to public health, safety and welfare or impair the natural hydrologic and hydraulic functions of the floodway or channel, or impair existing water quality or aquatic habitat. Construction impacts shall be minimized by appropriate mitigation methods as called for in this chapter.
(B) Within all riverine SFHAs where the floodway has not been determined, the following standards shall apply.
(1) The developer shall have a licensed professional engineer state in writing and show through supporting plans, calculations and data that the project meets the engineering requirements of divisions (C)(1) through (C)(9) below for the entire floodplain as calculated under the provisions of § 156.004(D) of this chapter.
(a) As an alternative, the developer should have an engineering study performed to determine a floodway and submit that engineering study to IDNR/OWR and FEMA for acceptance as a designated floodway.
(b) Upon acceptance of the floodway by IDNR/OWR and FEMA, the developer shall then demonstrate that the project meets the requirements of this subchapter for the designated floodway. The floodway shall be defined according to the definition in § 156.002 of this chapter.
(2) A development permit shall not be issued unless the applicant first obtains a IDNR/OWR permit or a determination has been made that an IDNR/OWR permit is not required.
(3) (a) Any work involving the construction, modification or removal of a dam as defined in § 156.002 of this chapter, per 17 Ill. Adm. Code part 3702 (Rules for Construction of Dams), shall obtain an IDNR/OWR permit prior to the start of construction of a dam.
(b) If the city finds a dam that does not have an IDNR/OWR permit, the city shall immediately notify the IDNR/OWR Bartlett office.
(c) If the city finds a dam which is believed to be in unsafe condition, the city shall immediately notify the owner of the dam, the IDNR/OWR Bartlett office and the Illinois Emergency Management Agency (IEMA).
(C) The following activities may be permitted without a licensed professional engineer’s review or calculation of base flood elevation and designated floodway. Such activities shall still meet the other requirements of this chapter:
(1) Bridge and culvert crossings of streams in rural areas meeting conditions of IDNR/OWR Statewide Permit 2;
(2) Barge fleeting facilities meeting conditions of IDNR/OWR Statewide Permit 3;
(3) Aerial utility crossings meeting conditions of IDNR/OWR Statewide Permit 4;
(4) Minor boat docks meeting conditions of IDNR/OWR Statewide Permit 5;
(5) Minor, non-obstructive activities meeting conditions of IDNR/OWR Statewide Permit 6; activities (not involving fill or positive change in grade) are covered by this permit;
(6) Outfall structures and drainage ditch outlets meeting conditions of IDNR/OWR Statewide Permit 7;
(7) Underground pipeline and utility crossings meeting the conditions of IDNR/OWR Statewide Permit 8;
(8) Bank stabilization projects meeting the conditions of IDNR/OWR Statewide Permit 9;
(9) Accessory structures and additions to existing residential buildings meeting the conditions of IDNR/OWR Statewide Permit 10;
(10) Minor maintenance dredging activities meeting conditions of DNR/OWR Statewide Permit 11;
(11) Bridge and culvert replacement structures and bridge widenings meeting conditions of IDNR/OWR Statewide Permit 12;
(12) Temporary construction activities meeting conditions of IDNR/OWR Statewide Permit 13;
(13) Special uses of public waters meeting conditions of IDNR/OWR Statewide Permit 14; and
(14) Any development determined by IDNR/OWR to be located entirely within a flood fringe area shall be exempt from state floodway permit requirements.
(D) The flood carrying capacity of any altered or relocated watercourse shall be maintained.
(E) (1) Whenever any portion of a floodplain is authorized for use, the volume of space which will be occupied by the authorized fill or structure below the base flood or 100-year frequency flood elevation shall be compensated for and balanced by a hydraulically equivalent volume of excavation taken from below the base flood or 100-year frequency flood elevation.
(2) The excavation volume shall be at least equal to one times the volume of storage lost due to the fill or structure.
(3) In the case of streams and watercourses, such excavation shall be made opposite or adjacent to the areas so filled or occupied.
(4) All floodplain storage lost below the existing ten-year flood elevation shall be replaced below the proposed ten-year flood elevation. All floodplain storage lost above the existing ten-year flood elevation shall be replaced above the proposed ten-year flood elevation. All such excavations shall be constructed to drain freely and openly to the watercourse.
(Prior Code, § 157.077) (Ord. 08-023, passed 7-22-2008)