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A. The board of trustees shall take into account flood hazards, to the extent that they are known, in all official actions related to land management, use and development.
B. New subdivisions, manufactured home parks, travel trailer parks, annexation agreements, planned unit developments (PUD) and additions to manufactured home parks and subdivisions shall meet the requirements of sections 11-1-6 and 11-1-7 of this chapter. Plats or plans for new subdivisions, manufactured home parks and a PUD shall include a signed statement by a registered professional engineer that the plat or plan accounts for changes in the drainage of surface waters in accordance with the plat act, 765 Illinois Compiled Statutes 205/2.
C. Proposals for new subdivisions, manufactured home parks, travel trailers, a PUD and additions to manufactured home parks and subdivisions shall include base flood elevation data and floodway delineations. Where this information is not available from an existing study filed with the Illinois state water survey, the applicant shall be responsible for calculating the base flood elevation and the floodway delineation and submitting it to the state water survey for review and approval as best available regulatory data. (1999 Code § 12.16)
D. The placement of site runoff storage, detention or retention facilities within floodplain areas is discouraged.
1. However, site runoff storage or detention requirements of the village may be fulfilled by providing site runoff storage within flood fringe areas provided that the following provisions are met:
a. The placement of a site runoff storage facility in a flood fringe area shall require compensatory storage for 1.1 times the volume below 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 code. The operation of the site runoff storage facility during rainfall events and periods of high stream flow and backwater events shall be considered in the design of the storage facility. The applicant shall submit the necessary hydraulic and hydrologic calculations demonstrating the proper operation of the storage facility for all stream flow and floodplain backwater conditions.
b. Excavations for compensatory storage along watercourses shall be opposite or adjacent to the area occupied by detention. All floodplain storage lost below the 10-year floodplain elevation shall be replaced below the 10-year floodplain elevation. All floodplain storage lost above the 10-year floodplain elevation shall be replaced above the 10-year floodplain elevation. All compensatory storage excavations shall be designed and constructed to have positive drainage and drain freely and openly to the watercourse.
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 allowable if they provide regional public benefits and if they meet the other provisions of this code pertaining to water quality and flood control. 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 a 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 through the upstream watershed which shall include, at minimum, runoff reduction best management practices in accordance with applicable state and federal regulations and the village environmental policy, as such regulations and policy may be amended from time to time, a permanent sediment control basin for all development sized to hold the volume of a two (2) year, twenty four (24) hour event, and a program to control nonpoint sources at the source for prior development constructed without appropriate storm water best management practices.
(6) The storage facility shall not be located downstream of any wastewater discharge.
(7) The storage facility shall comply with the provisions of Illinois regulations contained at 17 Illinois administrative code 3702 and 3708. (Ord. 2007-01, 2-13-2007)