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This section applies to proposed development, redevelopment, site modification or building modification within a designated floodway. The designated floodway for Addison Creek and Salt Creek shall be as delineated on the designated floodway maps designated by IDNR/OWR according to and referenced in section 12-1-2 of this chapter. Only those uses and structures will be permitted which meet the criteria in this section. All floodway modifications shall be the minimum necessary to accomplish the purpose of the project. The development shall also meet the requirements of section 12-1-9 of this chapter.
A. Development Permit: No person, firm, corporation or governmental body not exempted by state law shall commence any development in a floodway without first obtaining a development permit from the building commissioner and IDNR/OWR.
B. Application For Permit: Application for a development permit shall be made on a form provided by the building commissioner. The application shall include the following information:
1. Name and address of applicant;
2. Site location (including legal description) of the property, drawn to scale, on the designated floodway map, indicating whether it is proposed to be in an incorporated or unincorporated area;
3. Name of stream or body of water affected;
4. Description of proposed activity;
5. Statement of purpose of proposed activity;
6. Anticipated dates of initiation and completion of activity;
7. Name and mailing address of the owner of the subject property if different from the applicant;
8. Signature of the applicant or the applicant's agent;
9. If the applicant is a corporation, the president or other authorized officer shall sign the application form;
10. If the applicant is a partnership, each partner shall sign the application form; and
11. If the applicant is a land trust, the trust officer shall sign the name of the trustee by him (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.
12. 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 in mean sea level (1929 adjustment) datum or NGVD or North American vertical datum, 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-year frequency flood elevation, 100-year frequency flood elevation, and graphic or numerical scales (horizontal and vertical);
d. A soil erosion and sediment 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.
e. A copy of the designated floodway map, marked to reflect any proposed change in the designated floodway location.
13. Any and all other federal, state, and local permits or approval letters that may be required for this type of development.
14. Engineering calculations and supporting data shall be submitted showing that the proposed work will meet the permit criteria of subsection D of this section.
15. If the designated floodway delineation, base flood or 100-year frequency flood elevation 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 structures may be built until a letter of map revision has been approved by FEMA.
16. The application for a structure 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 registered professional engineer, 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 section 12-1-9 of this chapter.
17. If the proposed project involves a channel modification, the applicant shall submit the following information:
a. A discussion of the purpose of and need for the proposed work;
b. A discussion of the feasibility of using alternative locations or methods (see subsection F4a of this section) to accomplish the purpose of the proposed work;
c. An analysis of the extent and permanence of the impacts each feasible alternative identified in subsection F4a of this section would have on the physical and biological conditions of the body of water affected; and
d. An analysis of the impacts of the proposed project, considering cumulative effects on the physical and biological conditions of the body of water affected.
C. Issuance Of Permit: The building commissioner 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.
The building commissioner shall not issue the development permit unless all required federal and state permits have been obtained. A registered professional engineer, under the employ or contract of the village shall review and approve applications reviewed under this section.
D. Preventing Increased Damages And A List Of Appropriate Uses: The only development in a floodway which will be allowed are appropriate uses, which will not cause a rise in the base flood elevation, and which will not create a damaging or potentially damaging increase in flood heights or velocity or be a threat to public health and safety and welfare or 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 Illinois administrative code part 3708 will be allowed. The approved appropriate uses are as follows:
1. 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.
2. 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;
3. Storm and sanitary sewer relief outfalls;
4. Underground and overhead utilities;
5. Recreational facilities such as playing fields and trail systems, including any related fencing (at least 50 percent open when viewed from any 1 direction) built parallel to the direction of flood flows, and including open air pavilions and toilet facilities (4 stall maximum) that will not block flood flows nor reduce floodway storage;
6. Detached garages, storage sheds, or other nonhabitable accessory structures that will not block flood flows nor reduce floodway storage;
7. Bridges, culverts, roadways, sidewalks, railways, runways and taxiways and any modification thereto;
8. Parking lots built at or below existing grade where either:
a. The depth of flooding at the 100-year frequency flood event will not exceed one foot (1'); or
b. 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;
9. Designated floodway regrading, without fill, to create a positive nonerosive slope toward a watercourse;
10. Floodproofing activities to protect previously existing lawful structures including the construction of watertight window wells, elevating structures, or construction of floodwalls around residential, commercial or industrial principal structures where the outside toe of the floodwall shall be no more than ten feet (10') away from the exterior wall of the existing structure, and, which are not considered substantial improvements to the structure;
11. 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 percent (50%) or more of the market value before the damage occurred, the building will be protected from flooding to the flood protection elevation;
12. Modifications to an existing building that would not increase the enclosed floor area of the building below the 100-year frequency flood elevation, 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 percent (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 flood protection elevation.
E. Appropriate Uses: Appropriate uses do not include the construction or placement of any new structures, 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.
F. Construction Of Appropriate Uses: Within the designated floodway as identified on the floodway maps designated by IDNR/OWR, 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 professional engineer and provided that any structure meets the protection requirements of section 12-1-9 of this chapter:
1. 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 100-year frequency flood. In calculating effective designated floodway conveyance, the following factors shall be taken into consideration:
a. Designated floodway conveyance,
K = (1.486/n)(AR0.666)
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 Open Channel Hydraulics, Ven Te Chow, 1959, McGraw-Hill Book Company, New York.)
b. 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 nonvegetative land cover.
c. 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:
(1) 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 (1') horizontal for every four feet (4') of the flooded stream's length.
(2) 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 (1') horizontal for every one foot (1') of the flooded stream's length.
(3) When expanding or contracting flows in a vertical direction, a minimum of one foot (1') vertical transition for every ten feet (10') of stream length shall be used.
(4) Transition sections shall be provided between cross sections with rapid expansions and contractions and when meeting the designated floodway delineation on adjacent properties.
(5) All cross sections used in the calculations shall be located perpendicular to flood flows.
2. Preservation Of Floodway Storage So As Not To Increase Downstream Flooding: 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. Compensatory storage for fill or structures shall be equal to at least 1.0 times the volume of floodplain storage lost. Artificially created storage lost due to a reduction in head loss behind a bridge shall not be required to be replaced. The compensatory designated floodway storage shall be placed between the proposed normal water elevation and the proposed 100-year flood elevation. All designated floodway storage lost below the existing 10-year flood elevation shall be replaced below the proposed 10-year flood elevation. All designated floodway storage lost above the existing 10-year flood elevation shall be replaced above the proposed 10-year flood elevation. All such excavations shall be constructed to drain freely and openly to the watercourse. If the compensatory storage will not be placed at the location of the proposed construction, the applicant's engineer shall demonstrate to IDNR/OWR through a determination of flood discharges and water surface elevations that the compensatory storage is hydraulically equivalent. 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 existing structure.
3. Preservation Of Floodway Velocities So As Not To Increase Stream Erosion Or Flood Heights: 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 100-year frequency event. 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 riprap or other design measures.
4. Construction Of New Bridges Or Culvert Crossings And Roadway Approaches: 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 100-year frequency 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. 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 12-1-5 of this chapter. Culverts must be analyzed using the U.S. DOT, FHWA hydraulic chart for the selection of highway culverts. Bridges must be analyzed using the U.S. DOT/federal highway administration hydraulics of bridge waterways calculation procedures.
b. Lost floodway storage must be compensated for per subsection F2 of this section.
c. Velocity increases must be mitigated per subsection F3 of this section.
d. If the crossing is proposed over a public 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 subsection D of this section.
f. All excavations for the construction of the crossing shall be designed per subsection F8 of this section.
5. Reconstruction Or Modification Of Existing Bridges, Culverts, And Approach Roads:
a. 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 100-year event, if the existing structure is not a source of flood damage.
b. If the existing bridge or culvert and roadway approach is a source of flood damage to buildings or structures in the upstream floodplain, the applicant's engineer shall evaluate the feasibility of redesigning the structure to reduce the existing backwater, taking into consideration the effects on flood stages on upstream and downstream properties.
c. 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 Illinois administrative code part 3708 (floodway construction in northeastern Illinois) and submitted to IDNR/OWR for review and concurrence before a permit is issued.
6. On Stream Structures Built For The Purpose Of Backing Up Water: 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 100-year frequency 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. 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. All dams and impoundment structures as defined in section 12-1-2 of this chapter shall meet the permitting requirements of 17 Illinois administrative 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 storm water 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 presedimentation basin.
d. A nonpoint 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.
7. Floodproofing Of Existing Habitable, Residential And Commercial Structures: If construction is required beyond the outside dimensions of the existing building, the outside perimeter of the floodproofing construction shall be placed no further than ten feet (10') from the outside of the building. Compensation of lost storage and conveyance will not be required for floodproofing activities.
8. Excavation In The Floodway: 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. 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 (1') horizontal for every four feet (4') of the flooded stream's length;
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 (1') horizontal for every one foot (1') of the flooded stream's length; and
c. When expanding or contracting flows in a vertical direction, a minimum of one foot (1') vertical transition for every ten feet (10') of stream length shall be used.
d. Erosion/scour protection shall be provided inland upstream and downstream of the transition sections.
9. Seeding And Stabilization Plan: For all activities located in a floodway, a seeding and stabilization plan shall be submitted by the applicant.
10. Soil Erosion And Sedimentation Measures: For all activities in the floodway, including grading, filling, and excavation, in which there is potential for erosion of exposed soil, soil erosion and sedimentation control measures shall be employed consistent with the following criteria:
a. The construction area shall be minimized to preserve the maximum vegetation possible. Construction shall be scheduled to minimize the time soil is exposed and unprotected. In no case shall the existing natural vegetation be destroyed, removed, or disturbed more than fifteen (15) days prior to the initiation of improvements.
b. Temporary and/or permanent soil stabilization shall be applied to denuded areas as soon as possible. As a minimum, soil stabilization shall be provided within fifteen (15) days after final grade is reached on any portion of the site, and within fifteen (15) days to denuded areas which may not be at final grade but will remain undisturbed for longer than sixty (60) days.
c. Sedimentation control measures shall be installed before any significant grading or filling is initiated on the site to prevent the movement of eroded sediments off site or into the channel. Potential sediment control devices include filter fences, straw bale fences, check dams, diversion ditches, and sediment traps and basins.
d. A vegetated buffer strip of at least twenty five feet (25') in width shall be preserved and/or reestablished, where possible, along existing channels (see subsection F15 of this section). Construction vehicle use of channels shall be minimized. Temporary stream crossings shall be constructed, where necessary, to minimize erosion. Necessary construction in or along channels shall be restabilized immediately.
e. Soil erosion and sedimentation control measures shall be designed and implemented consistent with "Procedures And Standards For Urban Soil Erosion And Sedimentation Control In Illinois" (1988) also known as the "Green Book" and "The Illinois Urban Manual" (NRCS,1995).
11. 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 100-year frequency event.
12. General Criteria For Analysis Of Flood Elevations:
a. The flood profiles, flows and floodway data in the designated floodway study, referenced in section 12-1-5 of this chapter, 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.
b. If the 100-year designated 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 the requirements of this section for the 100-year frequency flood elevations of the designated floodway conditions and conditions with the receiving stream at normal water elevations.
c. 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 regional flood control project is scheduled to be built, removed, constructed or modified within the next five (5) 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.
13. Conditional Letter Of Map Revision: If the appropriate use would result in a change in the designated floodway location or the 100-year frequency flood elevation, 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. 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. In the case of nongovernment 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. No filling, grading, dredging or excavating shall take place until a conditional approval is issued. After initial filling, grading, dredging or excavating, no activities shall take place until a final letter of map revision (LOMR) is issued by FEMA with concurrence from IDNR/OWR.
14. Professional Engineer's Supervision: All engineering analyses shall be performed by or under the supervision of a registered professional engineer.
15. Buffer Strip: For all activities in the floodway involving construction within twenty five feet (25') of the channel, the following criteria shall be met:
a. A natural vegetation buffer strip shall be preserved within at least twenty five feet (25') of the ordinary high water mark of the channel.
b. Where it is impossible to protect this buffer strip during the construction of an appropriate use, a vegetated buffer strip shall be established upon completion of construction.
16. Construction To Proceed With Conditional Approval: 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.
G. Development Activities In Delegated Communities Requiring State Review: For those projects listed below located in a designated floodway, the following criteria shall be submitted to IDNR/OWR for their review and concurrence and/or permit prior to the issuance of a permit by a community or county delegated state permitting authority in the floodway:
1. An engineer's analysis of the flood profile due to a proposed bridge pursuant to subsection F4 of this section.
2. 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 subsection F5 of this section.
3. Alternative transition sections and hydraulically equivalent storage pursuant to subsections F1, F2 and F8 of this section.
4. The construction of any IDNR/OWR projects, dams (as defined in section 12-1-2 of this chapter) and all other state, federal, or local units of government projects, including projects of the municipality or county.
5. An engineer's determination that a proposed bridge affected by backwater from a downstream receiving stream may be built with a smaller opening.
6. Projects which revise or establish the floodway and/or flood profiles.
7. Projects in public bodies of water.
H. Other Permits: In addition to the other requirements of this chapter, a development permit for a site located in a floodway shall not be issued unless the applicant first obtains a permit or written documentation that a permit is not required from IDNR/OWR, issued pursuant to 615 Illinois Compiled Statutes 5/5 et seq. No permit from IDNR/OWR shall be required if IDNR/OWR has delegated this responsibility to the village.
I. Permits For Dams: Any work involving the construction, modification or removal of a "dam" as defined in section 12-1-2 of this chapter per 17 Illinois administrative code part 3702 (rules for construction of dams) shall obtain an IDNR/OWR permit prior to the start of construction of a dam. If the building commissioner finds a dam that does not have an IDNR/OWR permit, the building commissioner shall immediately notify the IDNR/OWR Schaumburg office. If the building commissioner finds a dam which is believed to be in unsafe condition, the building commissioner shall immediately notify the owner of the dam, the IDNR/OWR Schaumburg office, and the Illinois emergency management agency (IEMA).
J. Activities That Do Not Require A Registered Professional Engineer's Review: The following activities may be permitted without a registered professional engineer's review. Such activities shall still meet the other requirements of this chapter, including the mitigation requirements.
1. Underground and overhead utilities that:
a. Do not result in any increase in existing ground elevations, or
b. Do not require the placement of aboveground structures in the floodway, or
c. In the case of underground stream crossings, the top of the pipe or encasement is buried a minimum of three feet (3') below the existing streambed, and
d. Overhead utility lines shall be constructed above the estimated 100-year frequency flood elevation or attached above the low chord of an existing bridge (with the permission of the bridge owner). No supporting towers shall be placed in the watercourse and shall be designed so as to not catch debris.
e. Disturbance of stream side vegetation shall be kept to a minimum during construction to prevent erosion and sedimentation. All disturbed floodway areas, including the stream banks shall be restored to their original contours and seeded or otherwise stabilized upon completion of construction.
f. A utility crossing carrying material which may cause water pollution as defined by the environmental protection act 415 Illinois Compiled Statutes 5 (1992 state bar edition) shall be provided with shutoff valves on each side of the body of water to be crossed.
g. All Illinois commerce commission, national electric safety codes, and federal requirements for clearance must be met.
2. Storm and sanitary sewer relief outfalls that:
a. Do not extend riverward or lakeward of the existing adjacent natural bank slope, and
b. Do not result in an increase in ground elevation, and
c. Are designed so as not to cause stream erosion at the outfall location.
3. Construction of sidewalks, athletic fields (excluding fences), properly anchored playground equipment and patios at grade.
4. Construction of shoreline and stream bank protection that:
a. Does not exceed one thousand feet (1,000') in length.
b. Materials are not placed higher than the existing top of bank.
c. Materials are placed so as not to reduce the cross sectional area of the stream channel or bank of the lake.
d. Stabilization utilizing native vegetation and gradual side slopes are the preferred mitigation methods for existing erosion problems. Where high channel velocities, sharp bends or wave action necessitate the use of alternative stabilization measures, soil bioengineering techniques, natural rock or riprap are preferred materials. Artificial materials such as concrete, construction rubble, and gabions should be avoided unless there are no practicable alternatives.
5. Temporary stream crossings in which:
a. The approach roads will be one-half foot (1/2') or less above natural grade.
b. The crossing will allow stream flow to pass without backing up the water above the stream bank vegetation line or above any drainage tile or outfall invert.
c. The top of the roadway fill in the channel will be at least two feet (2') below the top of the lowest bank. Any fill in the channel shall be nonerosive material, such as riprap or gravel.
d. All disturbed stream banks will be seeded or otherwise stabilized as soon as possible upon installation and again upon removal of construction.
e. The access road and temporary crossings will be removed within one year after authorization. (Ord. 2005-11, 5-16-2005)