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 FIRMS of Cook and Will Counties, as defined in § 152.02. Permits will only be issued for 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 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 § 152.23. No permit from IDNR/OWR shall be required if the project meets Regional Permit No. 3.
(A) Development permit.
(1) No person, firm, corporation or governmental body, shall commence any development in a floodway without first obtaining a development permit from the village, as a delegated community. Except as noted in this section, a delegation letter from IDNR/OWR is required prior to the village issuing a permit for work in the floodway.
(2) Applications for a development permit for work in a floodway shall be made by submitting an application for a development permit for work in a floodway to include, as a minimum, the following information:
(a) Name and address of applicant.
(b) Legal description of the property.
(c) Site location map of the property, drawn to scale on the FIRM, indicating whether it is proposed to be in an incorporated or unincorporated area.
(d) Name of stream or body of water affected.
(e) Description of proposed activity.
(f) Statement of purpose of proposed activity.
(g) Anticipated dates of initiation and completion of activity.
(h) Name and mailing address of the owner of the subject property if different from the applicant.
(i) Signature of the applicant or the applicant’s agent.
(j) If the applicant is a corporation, the president or other authorized officer shall sign the application form.
(k) If the applicant is a partnership, each partner shall sign the application form.
(l) If the applicant is a land trust, the trust officer shall sign the name of the trustee by him or her as trust officer. A disclosure affidavit shall be filed with the application, identifying each beneficiary of the trust by name and address and defining the respective interests therein.
(3) 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 building or work, elevations (NAVD 88), adjacent property lines and ownership, drainage and flood control easements, location of any channels and any existing or future access roads, distance between proposed activity and navigation channel (when the proposed construction is near a commercially navigable body of water), designated floodway limit, floodplain limit, specifications and dimensions of any proposed channel modifications, location and orientation of cross-sections, north arrow, and a graphic 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 plan view, existing and proposed elevations, normal water elevation, 10% annual chance flood elevation, BFE, and graphic or numerical scales (horizontal and vertical).
(d) A seeding or stabilization plan for the disturbed areas.
(e) A copy of the FIRM, marked to reflect any proposed change in the designated floodway location.
(f) Any and all other federal, state, and local permits or approval letters that may be required for this type of development.
(g) Engineering calculations and supporting data shall be submitted showing that the proposed work will meet the permit criteria of division (B) below.
(h) 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. No buildings may be built until a LOMR has been approved by FEMA.
(i) The application for a building shall be accompanied by drawings of the site, drawn to scale showing property line dimensions and existing ground elevations and all changes in grade resulting from any proposed excavation or filling, and floodplain and floodway limits; sealed by a I registered P.E., licensed architect or registered land surveyor; the location and dimensions of all buildings and additions to buildings; and the elevation of the lowest floor (including basement) of all proposed buildings subject to the requirements of § 152.23.
(j) 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 12 months 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 Department. 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.
(k) The Director of Community Development shall be responsible for obtaining from the applicant copies of all other federal, state, and local permits and approvals that may be required for this type of activity.
(l) The Building Department shall not issue the development permit unless all required federal and state permits have been obtained.
(m) 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 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-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 one 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 one foot;
(j) Designated floodway regrading, without fill, to create a positive non-erosive slop toward a watercourse.
(k) Flood proofing 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 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 50% 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 50% 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 non-appropriate 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 following engineering and mitigation criteria 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 § 152.24:
(a) Preservation of flood conveyance, so as not to increase flood stages upstream. For appropriate uses other than bridge or culvert crossings, on-stream structures or dams, all effective designated floodway conveyance lost due to the project will be replaced for all flood events up to and including the base flood. In calculating effective designated floodway conveyance, the following factors shall be taken into consideration:
1. Designated floodway conveyance, “K” = (1.486/n)(AR
2/3) where “n” is Manning’s roughness factor, “A” is the effective flow area of the cross-section, and “R” is the ratio of the area to the
wetted perimeter. (See Ven Te Chow, Open Channel Hydraulics, (McGraw-Hill, New York 1959)).
A. The same Manning’s “n” value shall be used for both existing and proposed conditions unless a recorded maintenance agreement with a federal, state, or local unit of government can assure the proposed conditions will be maintained or the land cover is changing from a vegetative to a non-vegetative land cover.
B. Transition sections shall be provided and used in calculations of effective designated floodway conveyance. The following expansion and contraction ratios shall be used unless an applicant’s engineer can prove to IDNR/OWR through engineering calculations or model tests that more abrupt transitions may be used with the same efficiency:
(i) When water is flowing from a narrow section to a wider section, the water should be assumed to expand no faster than at a rate of one foot horizontal for every four feet of the flooded stream’s length.
(ii ) When water is flowing from a wide section to a narrow section, the water should be assumed to contract no faster than at a rate of one foot horizontal for every one foot of the flooded stream’s length.
(ii i) When expanding or contracting flows in a vertical direction, a minimum of one-foot vertical transition for every ten feet of stream length shall be used.
(iv ) Transition sections shall be provided between cross-sections with rapid expansions and contractions and when meeting the designated floodway delineation on adjacent properties.
(v) All cross-sections used in the calculations shall be located perpendicular to flood flows.
(b) 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 one and one-half times the volume of floodplain 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 10% annual chance flood elevation shall be replaced below the proposed 10-percent annual chance flood elevation. All designated floodway 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.
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.
1. The proposed structure shall not result in an increase of upstream flood stages greater than one- tenth of a 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 one-tenth of a foot, the developer must contact IDNR/OWR to obtain a permit for a dam or waiver.
3. 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 § 152.23. Bridges and culverts must be analyzed using any commonly accepted FEMA approved hydraulic models.
4. Lost floodway storage must be compensated for per division (B)(3)(b) above.
5. Velocity increases must be mitigated per division (B)(3)(c) above.
6. 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.
7. 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 division (B) above.
8. All excavations for the construction of the crossing shall be designed per division (B)(3)(h) below.
(e) Reconstruction or modification of existing bridges, culverts, and approach roads.
1. The bridge or culvert and roadway approach reconstruction or modification shall be constructed with no more than one-tenth of one 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.
1. Any increase in upstream flood stages greater than zero feet 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, as defined in § 152.02, 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 section.
(g) Excavation in the floodway.
1. When excavation is proposed in the design of bridges and culvert openings, including the modifications to and replacement of existing bridge and culvert Structures, or to compensate for lost conveyance or other appropriate uses, transition sections shall be provided for the excavation.
2. The following expansion and contraction ratios shall be used unless an applicant’s engineer can prove to IDNR/OWR through engineering calculations or model tests that more abrupt transitions may be used with the same efficiency:
A. When water is flowing from a narrow section to a wider section, the water should be assumed to expand no faster than at a rate of one foot horizontal for every four feet of the flooded stream’s length; and
B. When water is flowing from a wide section to a narrow section, the water should be assumed to contract no faster than at a rate of one foot horizontal for every one foot of the flooded stream’s length; and
C. When expanding or contracting flows in a vertical direction, a minimum of one-foot vertical transition for every ten feet of stream length shall be used; and
D. Erosion/scour protection shall be provided inland upstream and downstream of the transition sections.
(h) General criteria for analysis of flood elevations.
1. The flood profiles, flows and floodway data in the designated floodway study, referenced in § 152.20, 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:
A. The requirements of this section for the BFEs of the designated floodway conditions; and
B. Conditions with the receiving stream at normal water elevations.
3. 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 initial filling, grading, dredging or excavating no activities shall take place until a final LOMR is issued by FEMA with concurrence from IDNR/OWR.
(j) Professional engineer’s supervision. All engineering analyses shall be performed by or under the supervision of a registered P.E.
(k) 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 but no buildings - or structures - or other construction that is not an appropriate use may be placed in that area until the designated floodway map is changed and a final letter of map revision is received. The designated floodway map will be revised upon acceptance and concurrence by IDNR/OWR and FEMA of the as-built plans.
(4) Permits for dams.
(a) Any work involving the construction, modification or removal of a dam as defined in § 152,92 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 Community Development finds a dam that does not have an IDNR/OWR permit, the Director of Community Development shall immediately notify the IDNR/OWR Bartlett office.
(c) If Director of Community Development finds a dam which is believed to be in unsafe condition, the Director of Community Development 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.
(a) 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.
(b) Development activities in delegated communities requiring state review. As specified in 17 Ill. Adm. Code Part 3708, the following shall not be delegated and shall be subject to IDNR/OWR review and permits:
1. Permits issued to organizations that are exempt from village permitting authority.
2. IDNR/OWR projects, dams (as defined by 17 Ill. Adm. Code 3702) and all other state, federal or local unit of government projects, including projects of the municipalities and counties.
3. Construction and other activities in public bodies of water pursuant to 17 Ill. Adm. Code 3704.
4. An engineer’s determination that an existing bridge or culvert crossing is not a source of flood damage and the analysis indicating the proposed flood profile, pursuant to division (B)(3)(e) above.
5. An engineer’s determination that a proposed new bridge, affected by backwater from a downstream receiving stream, may be built with a smaller opening pursuant to division (B)(3)(d) above.
6. An analysis of alternative transition sections and hydraulically equivalent storage pursuant to division (B)(3)(a), (b) and (h) above.
7. Projects which revise or establish the floodway and/or flood profiles.