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These standards are for the reconstruction, modification or new construction of bridges, culvert crossings and roadway approaches that are located within the regulatory floodplain.
(A) A proposed new structure shall not result in an increase of upstream flood stages greater than one-tenth foot, when compared to the existing conditions for all flood events, up to and including the base flood event, unless contained within the channel banks or recorded easements. The evaluation must be submitted to IDNR-OWR for review and issuance of a permit.
(B) If the proposed new structure will increase upstream flood stages greater than one-tenth foot, the applicant must contact IDNR-OWR for a dam safety permit or waiver. The Administrator shall be copied on all related correspondence.
(C) A restrictive bridge or culvert may be altered to increase the conveyance of the base flood, if an impact analysis is completed and approved in writing by the Administrator, and all other required regulatory approvals are obtained.
(D) Velocity increases must be mitigated by use of appropriate measures to avoid scour, erosion and sedimentation at the structure.
(Ord. 2019-03, passed 4-15-2019)