The green infrastructure and low impact development practices provided in the BMP Manual shall be utilized for all regulated activities to the maximum extent practicable. Water volume controls shall be implemented using the Design Storm Method in subsection (a) or the Simplified Method in subsection (b) below. For regulated activity areas equal or less than one (1) acre that do not require hydrologic routing to design the stormwater facilities, this Ordinance establishes no preference for either methodology; therefore, the applicant may select either methodology on the basis of economic considerations, the intrinsic limitations on applicability of the analytical procedures associated with each methodology, and other factors.
(a) The Design Storm Method (CG-1 in the BMP Manual) is applicable to any size of regulated activity. This method requires detailed modeling based on site conditions.
(1) Do not increase the post-development total runoff volume for all storms equal to or less than the two (2)-year 24-hour duration precipitation.
(2) For modeling purposes:
A. Existing (pre-development) non-forested pervious areas must be considered meadow in good condition.
B. For computation of pre-development runoff volume, twenty percent (20%) of existing impervious areas, when present, shall be considered meadow.
(b) The Simplified Method (CG-2 in the BMP Manual) provided below is independent of site conditions and should be used if the Design Storm Method is not followed. This method is not applicable to regulated activities greater than ½ acre or for projects that require design of stormwater storage facilities.
(Ord. 44-2022. Passed 8-16-22.)