(A) Site Discharge. The drainage system for a property shall be designed to control the peak rate of discharge from the property for the 2-year, 24-hour, and the 100-year, 24-hour storm events to levels which will not cause an increase in flooding or channel instability downstream when considered in aggregate with other development properties and downstream drainage capacities. The peak discharge from the developed site shall not be greater than 0.04 cfs per acre developed for events less than or equal to the 2-year event. The peak discharge from the developed site shall not be greater than 0.15 cfs per acre developed for events less than or equal to the 100-year event.
(B) Minimum Restrictor Size. In no case will discharge orifices less than two (2) inches in inside diameter be allowed. When the calculated allowable discharge for a development is exceptionally small due to the small size of the site, a two (2) inch diameter orifice may be too large to adequately restrict the discharge. In this case the following criteria may apply:
(1) The detention volume required shall be calculated according to both the theoretical maximum allowable release rate, and the actual maximum discharge utilizing the two (2) inch diameter restrictor. Detention shall be provided on site according to the actual discharge. Any difference in the detention provided, and the theoretical detention required shall be compensated for using the "Fee in Lieu of Detention" criteria described in § 151.41.
(2) If the theoretical maximum allowable release rate for the 100-year event can be accommodated with a two (2) inch diameter or larger restrictor, but the 2-year event cannot, then the 0.04 cfs per acre developed maximum release rate may be waived.
(Ord. 05-2528, passed 7-26-05; Am. Ord. 07-2622, passed 2-13-07)