(A) Plan requirements. The plan requirements shall be:
(1) Elevation area capacity curves for the storage facility including notation of the storage volumes allocated to runoff, and permanent residual water storage for other uses (wet basins only);
(2) Inflow hydrographs (detention volumes for rational method) for the 15-, 25-, and 100-year recurrence interval design storms;
(3) Stage-discharge rating curves for each spillway and for combined spillway discharges; and
(4) Routing curves for the 15-year and all greater criteria recurrence interval design storms with time plotted as the abscissa and the following plotted as ordinates (this item is not required for the rational method):
(a) Cumulative inflow volume;
(b) Cumulative discharge; and
(c) Stage elevation.
(1999 Code, § 34-5-65)
(B) Construction alternatives.
(1) A developer shall build, as part of his or her development, a detention basin as required by this code, unless the following sections apply.
(2) Developers of adjacent tracts may combine to build one detention site large enough to meet the requirements of all the tracts of land with approval of the city. The basin shall be located in the same drainage basin.
(3) On-site detention will be required whenever increased runoff from the proposed development creates a hazard down stream as determined by the City Engineer.
(1999 Code, § 34-5-66)