(A) Disclaimer. Nothing in this chapter purports to alter or affect the regulatory program administered by the IDNR-OWR. Anything in this chapter to the contrary notwithstanding, if under the rules and regulations administered by the IDNR-OWR a submittal need not be made to the IDNR-OWR, or a review, approval or permit from the IDNR-OWR need not be obtained, then nothing in this chapter shall be construed to impose a requirement that such a submittal be made or such a review, approval or permit be obtained from the IDNR-OWR. Similarly, if the IDNR-OWR has delegated its regulatory authority to another entity, then anything in this chapter to the contrary notwithstanding, or required by such entity, such submittal shall be made or such review, approval or permit shall be obtained from such entity.
(B) Statewide and regional permits. Developments that qualify for any of the self-issuing statewide or regional permits administered by the IDNR-OWR (Statewide Permits Numbers 1 through 14 and Regional Permit Number 3) are similarly permitted under this division (B). The developer need only submit to the Village Engineer such information as shall show the Village Engineer that the development qualifies for the particular statewide or regional permit in question under the regulations established by the IDNR-OWR for such permit and no further submittal need be made under this division (B). All other provisions of this chapter applicable to this development, however, continue to apply.
(C) Floodplain management.
(1) The placement of site runoff storage facilities within the floodplain is strongly discouraged due to unreliable operation during flood events. However, the site runoff storage requirements of this chapter may be fulfilled by providing site runoff storage within flood fringe areas on the project site provided the following provisions are met:
(a) 1. The placement of a site runoff storage facility in a flood fringe area shall require compensatory storage of one and one-half times the volume, below the base flood elevation occupied by the site runoff storage facility including any berms. The release from the storage facility shall still be controlled in accordance with this chapter. The operation of the site runoff storage facility during rainfall events and periods of high streamflow and backwater events shall be considered in the design of the storage facility.
2. The applicant shall submit the necessary hydraulic and hydrologic calculations demonstrating the proper operation of the storage facility for all streamflow and floodplain backwater conditions.
(b) Excavations for compensatory storage along watercourses shall be opposite or adjacent to the area occupied by detention. Excavations for compensatory storage shall be at 1.05 times the volume displaced or lost by all other types of fill operations within the floodplain. To the extent possible, all floodplain storage lost below the ten-year flood elevation should be replaced below the ten-year flood elevation and all floodplain storage lost above the ten-year flood elevation should be replaced above the ten-year flood elevation. All compensatory storage excavations shall be designed and constructed to have positive drainage and drain freely and openly to the watercourse. Notwithstanding the forgoing, all requirements of the floodplain shall conform to the requirements of the IDNR, FEMA and the NFIP.
(2) Site runoff storage facilities shall only be placed in the floodway provided the following provisions are met.
(a) On-stream storage facilities are discouraged but are allowable if they provide regional public benefits and if they meet the other provisions of this chapter with respect to water quality and control of the two-year and 100-year, 24-hour events from the property. If on-stream storage facilities are used for watershed greater than one square mile, then the applicant shall use dynamic modeling to demonstrate that the design will not increase the water surface elevation of any properties upstream or downstream of the property.
(b) Impoundment of the stream as part of on-stream storage shall meet the following provisions.
1. The migration of indigenous fish species which require access to upstream areas as part of their life cycle, such as for spawning, shall not be prevented.
2. The on-stream storage facility shall not cause or contribute to the degradation of water quality or stream aquatic habitat.
3. The design shall include gradual bank slopes, appropriate bank stabilization measures, and a sediment control basin placed upstream of the storage facility.
4. The design shall not involve any stream channelization or the filling of wetlands.
5. The design shall include the implementation of an effective nonpoint source management program throughout the upstream watershed which shall include, as a minimum, runoff reduction best management practices, a permanent sediment control basin for all development sized to hold the volume of the two-year, 24-hour event, and a program to control nonpoint sources at the source for prior development constructed without appropriate stormwater best management practices.
6. The storage facility shall not be located downstream of a wastewater discharge.
7. The storage facility shall comply with 17 Ill. Admin. Code 3702 and 3708.
(Prior Code, § 4-4-4) (Ord. 2015-17, passed 8-3-2015)