If flows from any upstream tributary areas are not to be detained on the applicant's site in a regional facility, the flows from upstream may bypass the applicant's site in one of two ways:
(A) The flows from upstream may be collected and conveyed around the applicant's site.
(1) The bypass conveyance system shall be separate from the system used to collect and convey stormwater on the applicant's site.
(2) The bypass conveyance system must be capable of conveying .the stormwater runoff from the 100-year storm without causing increased flood stages on the applicant's site, or in the areas upstream of the applicant's site.
(3) The point of discharge for the bypass conveyance system shall be the same as that for the undeveloped site, or as directed by the Village Engineer.
(B) Alternately, the flows from upstream may be passed through the applicant's storm drainage system.
(1) The applicant shall compute the stormwater runoff hydrograph for the site, without considering any bypass flows.
(2) The applicant shall then compute the stormwater hydrograph for the total watershed, including all upstream tributary areas.
(3) The outlet structure controlling discharge from the detention basin shall be designed as follows:
(a) The orifice, or other type restrictor shall be sized to release no more than the maximum allowable release rate for the site, as described in § 151.24. The runoff hydrograph from the site for the 100-year storm shall then be routed through the detention basin to determine a high water level, not considering any bypass flow.
(b) An overflow spillway, or other outlet structure shall be designed to discharge flow from the detention basin when the water level rises to a level higher than that determined in subsection (B)(3)(a) above. The maximum discharge rate for this outlet structure shall be the difference of the two runoff hydrographs determined in subsections (B)(1) and (B)(2).
(Ord. 05-2528, passed 7-26-05)