(A) Whenever any portion of a floodplain is authorized for use, the volume of space which will be occupied by the authorized fill below the base flood or 100-year frequency flood elevation shall be compensated for and balanced by a hydraulically equivalent volume of excavation taken from below the base flood or 100-year frequency flood elevation. Detention volume and associated berming within the SFHA shall be considered as fill if it occupies volume that was previously occupied by the base flood.
(B) The excavation volume shall be at least equal to one and one-half times the volume of storage lost due to the fill or structure.
(C) In the case of streams and watercourses, such excavation shall be made opposite or adjacent to the areas so filled or occupied.
(D) All floodplain storage lost below the existing ten-year flood elevation shall be replaced below the proposed 10-year flood elevation. All floodplain storage lost above the existing ten-year flood elevation shall be replaced above the proposed ten-year flood elevation.
(E) All such excavations shall be constructed to drain freely and openly to the watercourse and shall be located adjacent to the development.
(F) The fill material shall be homogeneous and isotropic and compacted to at least 95% (Standard Proctor).
(G) Finished grade shall be 4:1 maximum and 1% minimum. Retaining walls, excluding control structures, are not permitted below the BFE.
(Ord. 3187, passed 1-22-19)