This Section applies to proposed Development, redevelopment, site modification or Building modification within a Designated Floodway. The Designated Floodway shall be as delineated on the countywide FIRM of Cook County. Floodplain development permits may only be issued for works that meets 17 Ill. Adm. Code Part 3708, which restricts development to Appropriate Uses of the Designated Floodway of which periodic inundation will not pose a danger to the general health and welfare of the user, or require the expenditure of public funds, or the provisions of public resources or disaster relief services, or result in increased Flood stages due to the singular or cumulative loss of regulatory Floodway storage or regulatory Designated Floodway conveyance, or increase in Flood velocities. All Floodway modifications shall be the minimum necessary to accomplish the purpose of the project. The Development shall also meet the requirements of Section 4-12-8. No application is required for an individual permit from IDNR/OWR if the project meets Regional Permit No. 3.
A. Floodway Permit :
1. In addition to a floodplain development permit, work in the Designated Floodway of an IDNR/OWR Jurisdictional Stream shall require either a floodway permit from IDNR/OWR, documentation that the projects meets Regional Permit No. 3, or a letter from IDNR/OWR stating no permit is required. An application for work in a Floodway shall be made by submitting a completed application on the form furnished by IDNR/OWR. The application for work in a Floodway, shall as a minimum meet all the requirements in 17 Ill. Adm. Code Part 3708.
a. Engineering calculations and supporting data shall be submitted showing that the proposed work will meet the permit criteria of 4-12-6(B) of this Chapter.
b. If the Designated Floodway delineation or BFE will change due to the proposed project, the application will not be considered complete until IDNR/OWR has indicated conditional approval of the Designated Floodway map change.
2. A Licensed P.E., under the employ or contract of the Village shall review and approve applications reviewed under this Section.
B. Preventing Increased Damages and a List of Appropriate Uses.
1. The only Development in a Floodway allowed are Appropriate Uses that will not cause a rise in the BFE and will not create a damaging or potentially damaging increase in Flood heights or velocity, be a threat to public health and safety and welfare, impair the natural hydrologic and hydraulic functions of the Floodway or Channel, or permanently impair existing water quality or aquatic habitat. Construction impacts shall be minimized by appropriate mitigation methods as called for in this Chapter. Only those Appropriate Uses listed in 17 Ill. Adm. Code Part 3708 will be allowed. The approved Appropriate Uses are as follows:
a. Flood Control Structures, dikes, Dams and other public works or private improvements relating to the control of drainage, Flooding, erosion, or water quality or habitat for fish and wildlife.
b. Structures or facilities relating to the use of, or requiring access to, the water or shoreline, such as pumping and treatment facilities, and facilities and improvements related to recreational boating, commercial shipping and other functionally water dependent uses;
c. Storm and sanitary sewer relief outfalls;
d. Underground and overhead utilities;
e. Recreational facilities such as playing fields and trail systems, including any related fencing (at least fifty percent (50%) open when viewed from any one direction) built parallel to the direction of Flood flows, and including open air pavilions and toilet facilities (four (4) stall maximum) that will not block Flood flows nor reduce Floodway storage.
f. Detached garages, storage sheds, or other non-habitable Accessory Structures that will not block Flood flows nor reduce Floodway storage;
g. Bridges, culverts, roadways, sidewalks, railways, runways and taxiways and any modification thereto;
h. Parking lots built at or below existing grade where either:
(1) The depth of flooding during the Base Flood will not exceed 1.0 foot; or
(2) The Applicant of a short-term recreational use facility parking lot formally agrees to restrict access during overbank flooding events and accepts liability for all damage caused by vehicular access during all overbank flooding events.
i. Aircraft parking aprons built at or below ground elevation where the depth of flooding during the Base Flood will not exceed 1.0 foot;
j. Designated Floodway regrading, without fill, to create a positive non-erosive slope toward a watercourse.
k. Floodproofing activities to protect previously existing lawful Buildings including the construction of water tight window wells, elevating Buildings, or construction of floodwalls around residential, commercial or industrial principal Buildings where the outside toe of the floodwall shall be no more than ten (10) feet away from the exterior wall of the existing Building, and, which are not considered Substantial Improvements to the Building.
l. The replacement, reconstruction, or repair of a damaged Building, provided that the outside dimensions are not increased, and if the Building was damaged to fifty (50%) percent or more of the market value before the damage occurred, the Building will be protected from flooding to the FPE.
m. Modifications to an existing Building that would not increase the enclosed floor area of the Building below the BFE, and which will not block Flood flows including but not limited to, fireplaces, bay windows, decks, patios, and second story additions. If the Building is improved to fifty (50%) percent or more of the market value before the modification occurred (i.e., a Substantial Improvement), the Building will be protected from flooding to the FPE.
2. Appropriate Uses do not include the construction or placement of any new Buildings, fill, Building additions, Buildings on stilts, excavation or Channel Modifications done to accommodate otherwise nonAppropriate Uses in the Floodway, fencing (including landscaping or planting designed to act as a fence) and storage of materials except as specifically defined above as an Appropriate Use.
3. Within the Designated Floodway, the construction of an Appropriate Use, will be considered permissible provided that the proposed project meets the criteria established in 17 Ill. Adm. Code Part 3708 and is so stated in writing with supporting plans, calculations, and data by a Registered P.E. and provided that any Building meets the protection requirements of this Chapter.
a. Preservation of Floodway Storage so as Not to Increase Downstream Flooding.
(1) Compensatory Storage shall be provided for any Designated Floodway storage lost due to the proposed work from the volume of fill or Structures placed and the impact of any related Flood control projects.
(2) Compensatory Storage for fill or Structures shall be equal to 1.1 times the volume of Designated Floodway storage lost.
(3) Artificially created storage lost due to a reduction in head loss behind a bridge shall not be required to be replaced.
(4) The compensatory Designated Floodway storage shall be placed between the proposed normal water elevation and the proposed BFE. All Designated Floodway storage lost below the existing ten percent (10%) annual chance Flood elevation shall be replaced below the proposed ten percent (10%) annual chance Flood elevation. All Designated Floodway storage lost above the existing ten percent (10%) annual chance Flood elevation shall be replaced above the proposed ten percent (10%) annual chance Flood elevation. All such excavations shall be constructed to drain freely and openly to the watercourse.
(5) If the Compensatory Storage will not be placed at the location of the proposed construction, the Applicant's engineer shall demonstrate through a determination of Flood discharges and water surface elevations that the Compensatory Storage is hydraulically equivalent.
(6) There shall be no reduction in Floodway surface area, as a result of a Floodway modification, unless such modification is necessary to reduce flooding at an existing Structure.
c. Preservation of Floodway Velocities so as Not to Increase Stream Erosion or Flood Heights.
(1) For all Appropriate Uses, except bridges or culverts or on-stream Structures, the proposed work will not result in an increase in the average Channel or Designated Floodway velocities or stage for all Flood events up to and including the Base Flood event.
(2) In the case of bridges or culverts or on-stream Structures built for the purpose of backing up water in the stream during normal or Flood flows, velocities may be increased at the Structure site if scour, erosion and sedimentation will be avoided by the use of rip-rap or other design measures.
d. Construction of new bridges or culvert crossings and roadway approaches shall meet 17 Ill. Adm. Code Part 3708.
(1) The proposed Structure shall not result in an increase of upstream Flood stages greater than 0.1 foot when compared to the existing conditions for all Flood events up to and including the Base Flood event; or the upstream Flood stage increases will be contained within the Channel banks (or within existing vertical extensions of the Channel banks) such as within the design protection grade of existing levees or floodwalls or within recorded Flood easements.
(2) If the proposed construction will increase upstream Flood stages greater than 0.1 feet, the developer must contact IDNR/OWR to obtain a permit for a Dam or waiver.
A. The engineering analysis of upstream Flood stages must be calculated using the Flood study flows, and corresponding Flood elevations for tailwater conditions for the Flood study specified in Section 4-12-4 of this Chapter. Bridges and Culverts must be analyzed using any commonly accepted FEMA approved hydraulic models.
B. Lost Floodway storage must be compensated for per Section 4-12-6 of this Chapter.
C. Velocity increases must be mitigated per Section 4-12-7(B)(1).
D. If the crossing is proposed over a Public Body of Water that is used for recreational or commercial navigation, an IDNR/OWR permit must be received.
E. The hydraulic analysis for the backwater caused by the bridge showing the existing condition and proposed regulatory profile must be submitted to IDNR/OWR for concurrence that a CLOMR is not required by this Chapter.
F. All excavations for the construction of the crossing shall be designed per 4-12-6(B)(3)(h) of this Chapter.
e. Reconstruction or Modification of Existing Bridges, Culverts, and Approach Roads shall meet 17 Ill. Adm. Code Part 3708.
(1) The bridge or culvert and roadway approach reconstruction or modification shall be constructed with no more than 0.1-foot increase in backwater over the existing Flood profile for all Flood frequencies up to and including the Base Flood event, if the existing Structure is not a source of Flood damage.
(2) If the existing bridge or culvert and roadway approach is a source of Flood damage to Structures in the upstream Floodplain, the Applicant's engineer shall evaluate the feasibility of redesigning the existing bridge or culvert and roadway approach to reduce the existing backwater, taking into consideration the effects on Flood stages on upstream and downstream properties.
(3) The determination as to whether or not the existing crossing is a source of Flood damage and should be redesigned must be prepared in accordance with 17 Ill. Adm. Code Part 3708 (Floodway Construction in Northeastern Illinois) and submitted to IDNR/OWR for review and concurrence before a permit is issued.
f. On-Stream Structures Built for the Purpose of Backing Up Water shall meet 17 Ill. Adm. Code Part 3708.
(1) Any increase in upstream Flood stages greater than 0.0 foot when compared to the existing conditions, for all Flood events up to and including the Base Flood event shall be contained within the Channel banks (or within existing vertical extensions of the Channel banks) such as within the design protection grade of existing levees or Floodwalls or within recorded Flood easements.
(2) A permit or letter indicating a permit is not required must be obtained from IDNR/OWR for any Structure built for the purpose of backing up water in the stream during normal or Flood flow.
(3) All Dams and impoundment Structures, shall meet the permitting requirements of 17 Ill. Adm. Code Part 3702 (Construction and Maintenance of Dams). If the proposed activity involves a modification of the Channel or Floodway to accommodate an impoundment, it shall be demonstrated that:
A. The impoundment is determined to be in the public interest by providing Flood control, public recreation, or regional stormwater detention;
B. The impoundment will not prevent the migration of indigenous fish species, which require access to upstream areas as part of their life cycle, such as for spawning;
C. The impoundment will not cause or contribute to degraded water quality or habitat conditions. Impoundment design should include gradual bank slopes, appropriate bank stabilization measures and a pre-sedimentation basin;
D. A non-point source control plan has been implemented in the upstream watershed to control the effects of sediment runoff as well as minimize the input of nutrients, oil and grease, metals, and other pollutants. If there is more than one municipality in the upstream watershed, the municipality in which the impoundment is constructed should coordinate with upstream municipalities to ensure comprehensive watershed control;
E. The project otherwise complies with the requirements of this Chapter.
g. Excavation in the Floodway shall meet 17 Ill. Adm. Code Part 3708.
h. General Criteria for Analysis of Flood Elevations.
(1) The Flood profiles, flows and Floodway data in the Designated Floodway study, referenced in Section 4-12-5, must be used for analysis of the base conditions. If the study data appears to be in error or conditions have changed, IDNR/OWR shall be contacted for approval and concurrence on the appropriate base conditions data to use.
(2) If the Floodway elevation at the site of the proposed construction is affected by backwater from a downstream receiving stream with a larger drainage area, the proposed construction shall be shown to meet:
(3) The requirements of this section for the BFEs of the Designated Floodway conditions; and
(4) Conditions with the receiving stream at normal water elevations.
(5) If the Applicant learns from IDNR/OWR, local governments, or a private owner that a downstream restrictive bridge or culvert is scheduled to be removed, reconstructed, modified, or a Public Flood Control Project is scheduled to be built, removed, constructed or modified within the next five years, the proposed construction shall be analyzed and shown to meet the requirements of this section for both the existing conditions and the expected Flood profile conditions when the bridge, culvert or Flood control project is built.
i. Conditional Letter of Map Revision.
(1) If the Appropriate Use would result in a change in the Designated Floodway location or the BFE, the Applicant shall submit to IDNR/OWR and FEMA all information, calculations and documents necessary to be issued a conditional Designated Floodway map revision and receive from IDNR/OWR a conditional concurrence of the Designated Floodway change before a permit is issued.
(2) The final Designated Floodway map will not be changed by FEMA until as-built plans or record drawings of initial filling, grading, dredging, or excavating activities are submitted and accepted by FEMA and IDNR/OWR. All field surveys shall be conducted under the supervision of a Registered P.E. or Registered Land Surveyor and shall be sealed. All required engineering analyses shall be conducted under the supervision of a Registered P. E., or in the case of a federal project, by the federal agency and shall be so sealed or stated.
(3) In the case of non-government projects, the municipality in incorporated areas and the county in unincorporated areas shall concur with the proposed conditional Designated Floodway map revision before IDNR/OWR approval can be given.
(4) No filling, grading, dredging, or excavating shall take place until a conditional approval is issued.
(5) After receipt of conditional approval of the Designated Floodway change and issuance of a permit and a Conditional Letter of Map Revision, construction as necessary to change the Floodway designation may proceed including filling, grading, dredging, and excavating, No additional Development activities, including the construction of Buildings, shall take place in the Floodplain or Designated Floodway until a final LOMR is issued by FEMA with concurrence from IDNR/OWR.
j. Public Flood Control Projects. For Public Flood Control Projects, the permitting requirements of this Section will be considered met if the applicant can demonstrate to IDNR/OWR through hydraulic and hydrologic calculations that the proposed project will not singularly or cumulatively result in increased flood heights outside the project right-of-way or easements for all flood events up to and including the 100year frequency event.
k. Professional Engineer's Supervision. All engineering analyses shall be performed by or under the supervision of a Registered P.E.
4. Permits for Dams:
a. Any work involving the construction, modification, or removal of a Dam 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.
b. If the Director of Public Works finds a Dam that does not have an IDNR/OWR permit, the Director of Public Works shall immediately notify the IDNR/OWR Bartlett office.
c. If the Director of Public Works finds a Dam which is believed to be in unsafe condition, the Director of Public Works shall immediately notify the owner of the Dam, the IDNR/OWR Bartlett office, and the Illinois Emergency Management Agency.
5. Activities that do not Require a Registered Professional Engineer's Review: Regional Permit No. 3, which authorizes, for example, underground and overhead utilities, storm and sanitary sewer outfalls, sidewalks, patios, athletic fields, playground equipment and streambank protection activities; may be permitted without a Registered P.E.'s review. Such activities shall still meet the other requirements of this Chapter, including the mitigation requirements. (Ord. 3852, 1-10-2022)