F. Manage Stormwater Runoff . Plans shall be designed so that any increase in velocity of stormwater runoff resulting from a land-disturbing activity will not result in accelerated erosion of the receiving stormwater conveyance or at the point of discharge. Plans shall include measures to prevent accelerated erosion within the project boundary and at the point of discharge.
(3)
Design & Performance Standard
A. Except as provided in this Ordinance, erosion and sedimentation control measures, structures, and devices shall be planned, designed, and constructed to provide protection from the calculated maximum peak rate of runoff from the 10-year storm. Runoff rates shall be calculated using the procedures in the latest edition of the United States Department of Agriculture (USDA), Soil Conservation Service’s “National Engineering Field Manual for Conservation Practices”, or other acceptable calculation procedures.
B. High Quality Water (HQW) Zones. In HQW zones, the following design standards shall apply:
i. Limit on Uncovered Area. Uncovered areas in HQW zones shall be limited at any time to a maximum total area of 20 acres within the boundaries of the tract. Only the portion of the land disturbing activity within an HQW zone shall be governed by this Section. Larger areas may be uncovered within the boundaries of the tract with the written approval of the Director of Engineering upon providing engineering justification with a construction sequence that considers phasing, limiting exposure, weekly submitted self-inspection reports, and a more conservative design than the Twenty-five Year Storm. ii. Maximum Peak Rate of Runoff Protection. Erosion and sedimentation control measures, structures, and devices within HQW zones shall be planned, designed, and constructed to provide protection from the runoff of the 25-year storm which produces the maximum peak rate of runoff as calculated according to procedures in the USDA Soil Conservation Service’s “National Engineering Field Manual for Conservation Practices” or according to procedures adopted by any other agency of this state or the United States or any generally recognized organization or association.
iii. Sediment Basin Design . Sediment basins within HQW zones shall be designed and constructed according to the following criteria:
Made with FlippingBook interactive PDF creator