(A) In floodplains (including AE, AH, AO, and Unnumbered A Zones) where no floodways have been identified and no base flood elevations 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 base flood elevation.
(B) Site development permit. No person, firm corporation, or governmental body, not exempted by state law, shall commence any development in a flood plain without first obtaining a site development permit from the building commissioner and city engineer. Application for a development permit shall be made on a form provided by the building commissioner. 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 licensed engineer or surveyor, the location and dimensions of all buildings and additions to buildings; and the elevation at the lowest floor (including basement) of all proposed buildings subject to the requirements of § 151.34. The application for a site 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 regulatory floodway maps, 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 roadways in the vicinity of the site, graphic or numerical shale, 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 in NAVD 88, adjacent property lines and ownership, drainage and flood control easements, distance between proposed activity and navigation channel (when the proposed construction is near a commercially navigable body of water), flood plain limit, location and orientation of cross-sections, north arrow, and a graphical or numerical scale;
(c) Cross-section views of the project and engineering study reach showing existing and proposed conditions including principal dimensions of the work as shown in the plan view, existing and proposed elevations, normal water elevation, 10% annual chance of flood elevation, base flood elevation, and graphical or numerical scales (horizontal and vertical); and
(d) A soil erosion and sedimentation control plan for disturbed areas. This plan shall include a description of the sequence of grading activities and the temporary sediment and erosion control measures to be implemented to mitigate their effects. This plan shall also include a description of final stabilization and revegetation measures, and the identification of a responsible party to ensure postconstruction maintenance.
(5) Engineering calculations and supporting data shall be submitted showing that the proposed work will meet the criteria of § 151.33.
(6) Any and all other local, state, and federal permits or approvals that may be required for this type of development.
(C) Based on the best available existing data according to the federal, state, or other sources, the building commissioner and city engineer shall compare the elevation of the site to the base flood elevation. Should no elevation information exist for a site, the developer’s engineer shall calculate the elevation according to § 151.30. Any development located on land that can be shown to have been higher than the base flood elevations of the site’s first flood insurance rate map identification is not in the floodplain, therefore, not subject to the requirements of this chapter. The building official 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 first flood insurance rate map identification.
(D) (1) The building commissioner and city engineer shall be responsible for obtaining from the applicant copies of all other local, state, and federal permits, approvals or permit-not-required letters that may be required for this type of activity. The building commissioner and city engineer shall not issue the site development permit unless all required local, state, and federal permits have been obtained.
(2) 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 a 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. Time extensions shall be granted only if the original permit is compliance with this chapter and the FIRM and FIS in effect at the time the extension is granted.
(E) Preventing increased damages. No development in the floodplain, where 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.
(F) Within all riverine floodplains 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 date that the project meets the engineering requirements of § 151.30 through (11) for the entire floodplain as calculated under the provisions of § 151.30. As an alternative, the developer should have an engineering study performed to determine a floodway and submit that engineering study to IDNR for acceptance as a regulatory floodway. Upon acceptance of their floodway by the department, the developer shall then demonstrate that the project meets the requirements of § 151.32 for the regulatory floodway. The floodway shall be defined according to the definition in § 151.03.
(2) A development permit shall not be issued unless the applicant first obtains a permit from IDNR or written documentation that a permit is not required from IDNR.
(3) No permit from IDNR shall be required if the division has delegated permit responsibility to the city per 17 Ill. Adm. Code Part 3708 for regulatory floodways, per IDNR statewide permit entitled “Construction in Flood Plains with No Designated Floodways in Northeastern Illinois.”
(4) Dam safety permits. Any work involving the construction, modification, or removal of a dam or an on-stream structure to impound water as defined in § 151.03 shall obtain an Illinois Division of Water Resources dam safety permit or letter indicating a permit is not required prior to the start of construction of a dam. If the building commissioner and city engineer finds a dam which is believed to be in unsafe condition, the building commissioner and city engineer shall immediately notify the owner of the dam and the Illinois Emergency Management Agency (IEMA), and the IDNR, Dam Safety Section in Springfield.
(5) 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 IDNR/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.
(G) Compensatory storage. Whenever any portion of a flood plain is authorized for use, the volume of space which will be occupied by the authorized fill or structure below the base flood elevation shall be compensated for and balanced by a hydraulically equivalent volume of excavation taken from below the base flood and shall be at least equal to the volume of storage lost due to the fill or structure. In the case of streams and watercourses such excavation shall be made opposite or adjacent to the areas so filled or occupied. 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. 92-23, passed 6-16-92; amend. Ord. O-13-97, passed 6-4- 97; amend. Ord. O-16-19, passed 10-15-19) Penalty, see § 151.99