Site discharge. The drainage system for a property shall be designed to control the peak rate of discharge from the property for the less than or equal to the 100-year, 24-hour event 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 0.10 cfs per acre developed for events less than or equal to the 100-year event except that when:
(A) The sum of the added and existing impervious area does not exceed 40% but the impervious area added by the new development in the aggregate after January 1, 1995, is greater than 20,000 square feet; or
(B) The sum of the added and existing impervious area exceeds 40% of lot area but the impervious area added by the new development in the aggregate after January 1, 1995, is equal to or less than 20,000 square feet.
(C) In both cases, the restricted release rate shall be no greater than 0.1 cfs/acre of site or a greater release rate whichever will produce the lowest peak discharge from the site over the 24 hours of the 1% probability storm until the required storage is provided which will equal:
(1) One hundred percent of the storm water storage required for the additional impervious area added by the new development in the aggregate after January 1, 1995, and
(2) Storm water storage equal to storage required for the existing impervious area multiplied by one or the ratio of the impervious area added by the new development, divided by the impervious area of the existing development prior to January 1, 1995, whichever is lower in value.
(Ord. 801, passed 7-26-05) Penalty, see § 154.99