In floodplains, (including AE, AH, AO and unnumbered A Zones) where no floodways have been identified and no BFEs have been established by FEMA, and draining more than a square mile, no development shall be permitted unless the cumulative effect of the proposals, when combined with all other existing and anticipated uses and structures, shall not significantly impede or increase the flow and passage of the floodwaters nor significantly increase the BFE.
(A) Development permit.
(1) No person, firm, corporation, or governmental body shall commence any development in a floodplain without first obtaining a development permit from the Building Commissioner or designee.
(2) Application for a development permit shall be made on a form provided by the Building Commissioner or designee.
(a) The application shall be accompanied by drawings of the site, drawn to scale showing property line dimensions; and existing grade elevations and all changes in grade resulting from excavation or filling, sealed by a registered P.E. licensed architect or registered land surveyor; the location and dimensions of all buildings and additions to buildings; and the elevations of the lowest floor (including basement) of all proposed buildings subject to the requirements of § 153.08.
(b) The application for a development permit shall also include the following information:
1. A detailed description of the proposed activity, its purpose, and intended use;
2. Site location (including legal description) of the property, drawn to scale, on the FIRM, indicating whether it is proposed to be in an incorporated or unincorporated area;
3. Anticipated dates of initiation and completion of activity;
4. Plans of the proposed activity shall be provided which include as a minimum:
a. A vicinity map showing the site of the activity, name of the waterway, boundary lines, names of roads in the vicinity of the site, graphic or numerical scale, and north arrow;
b. A plan view of the project and engineering study reach showing existing and proposed conditions including principal dimensions of the structure or work, elevations, using the NAVD 88, adjacent property lines and ownership, drainage and flood control easements, distance between proposed activity and navigation channel (when the proposed construction is in or near a commercially navigable body of water), floodplain limit, location and orientation of cross-sections, north arrow, and a graphical or numerical scale;
c. Cross-section views of the project perpendicular to the flow of floodwater and engineering study reach showing existing and proposed conditions including principal dimensions of the work as shown in plain view, existing and proposed elevations, normal water elevation, 10% annual chance flood elevation, BFE, and graphical or numerical scales (horizontal and vertical); and
d. A seeding or stabilization plan for the disturbed areas.
(c) Engineering calculations and supporting data shall be submitted showing that the proposed work will meet the criteria of § 153.07(B).
(d) Any and all other federal, state, and local permits or approvals that may be required for this type of development.
(3) Based on the best available existing data according to federal, state or other sources, the Building Commissioner or designee shall compare the elevation of the site to the BFE.
(4) Should no BFE information exist for the site, the developer's engineer shall calculate the BFE according to § 153.04(D).
(a) Any development located on land that can be shown to have been higher than the BFE prior to the current FIRM's floodplain identification, is not in the floodplain and, therefore, not subject to the requirements of this chapter.
(b) The Building Commissioner or designee shall maintain documentation of the existing ground elevation at the development site and certification that this ground elevation existed prior to the date of the site's current FIRM's floodplain identification.
(c) The Building Commissioner or designee shall be responsible for obtaining from the applicant copies of all other federal, state, and local permits, approvals or waivers that may be required for this type of activity. The Building Commissioner or designee shall not issue the development permit unless all required federal, state, and local permits have been obtained.
(5) A development permit or approval shall become invalid unless the start of construction, for work authorized by such permit, is commenced within 180 days after its issuance, or if the work authorized is suspended or abandoned for a period of 180 days after the work commences. All permitted work shall be completed within the local permit expiration period after the date of issuance of the permit or the permit shall expire. Time extensions, of not more than 180 days each, may be granted, in writing, by the Building Commissioner or designee. Time extensions shall be granted only if the original permit is compliant with this chapter and the FIRM and FIS in effect at the time the extension is granted.
(B) Preventing increased damages.
(1) No development in the floodplain, 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.
(2) Within all riverine floodplains where the floodway has not been determined, the following standards shall apply:
(b) 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.
(d) A development permit shall not be issued unless the applicant first obtains an IDNR/OWR permit or a determination has been made that an IDNR/OWR permit is not required.
(e) Permits for dams.
1. Any work involving the construction, modification or removal of a dam as defined in § 153.02 per 17 Ill. Adm. Code Part 3702 (Rules for Construction of Dams) shall obtain an IDNR/OWR permit prior to the start of dam construction.
2. If the Building Commissioner or designee finds a dam that does not have an IDNR/OWR permit, the Building Commissioner or designee shall immediately notify the IDNR/OWR Bartlett office.
3. If the Building Commissioner or designee finds a dam which is believed to be in unsafe condition, the Building Commissioner or designee shall immediately notify the owner of the dam, the IDNR/OWR Bartlett office, and the Illinois Emergency Management Agency.
(3) The following activities may be permitted without a licensed P.E.'s review or calculation of BFE and designated floodway. Such activities shall still meet the other requirements of this chapter.
(a) Bridge and culvert crossings of streams in rural areas meeting conditions of IDNR/OWR Statewide Permit No. 2;
(b) Barge fleeting facilities meeting conditions of IDNR/OWR Statewide Permit No. 3;
(c) Aerial utility crossings meeting conditions of IDNR/OWR Statewide Permit No. 4;
(d) Minor boat docks meeting conditions of IDNR/OWR Statewide Permit No. 5;
(e) Minor, non-obstructive activities meeting conditions of IDNR/OWR Statewide Permit No. 6; activities (not involving fill or positive change in grade) are covered by this permit;
(f) Outfall structures and drainage ditch outlets meeting conditions of IDNR/OWR Statewide Permit No. 7;
(g) Underground pipeline and utility crossings meeting the conditions of IDNR/OWR Statewide Permit No. 8;
(h) Bank stabilization projects meeting the conditions of IDNR/OWR Statewide Permit No. 9;
(i) Accessory structures and additions to existing residential buildings meeting the conditions of IDNR/OWR Statewide Permit No. 10;
(j) Minor maintenance dredging activities meeting conditions of DNR/OWR Statewide Permit No. 11;
(k) Bridge and culvert replacement structures and bridge widenings meeting conditions of IDNR/OWR Statewide Permit No. 12;
(l) Temporary construction activities meeting conditions of IDNR/OWR Statewide Permit No. 13;
(m) Special uses of public waters meeting conditions of IDNR/OWR Statewide Permit No. 14; and
(n) Any development determined by IDNR/OWR to be located entirely within a flood fringe area shall be exempt from state floodway permit requirements.
(4) The flood carrying capacity of any altered or relocated watercourse shall be maintained.
(5) Compensatory storage.
(a) 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 BFE shall be compensated for and balanced by a hydraulically equivalent volume of excavation taken from below the BFE.
(b) The excavation volume shall be at least equal to 1.5 times the volume of storage lost due to the fill or structure.
(c) In the case of streams and watercourses, such excavation shall be made opposite or adjacent to the areas so filled or occupied.
(d) All floodplain storage lost below the existing 10% annual chance flood elevation shall be replaced below the proposed 10% annual chance flood elevation. All floodplain storage lost above the existing 10% annual chance flood elevation shall be replaced above the proposed 10% annual chance flood elevation. All such excavations shall be constructed to drain freely and openly to the watercourse.
(Ord. 2019-009, passed 10-30-19)