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DRAFT 385 activity shall install such sedimentation and erosion control devices and practices as are sufficient to retain the sediment generated by the land- disturbing a~tivity within the boundaries of the tract during construction upon and development of said tract, and shall plant or otherwise provide a permanent ground cover sufficient to restrain erosion after completion of construction or development. Except as provided in Section 8(b)(5), provisions for a ground cover sufficient to restrain erosion must be accomplished within 30 working days following completion of construction or development. d. Prior Plan Approval - no person shall initiate any land-disturbing activity on a tract if more than one (1) acre except as provided in Section 6(a)(2)] is to be uncovered unless, thirty or more days prior to initiating the activity, a Plan is filed with and approved by the County. Should the Plan be filed, approved, and a grading permit issued in less than 30 days from the day of filing, the land disturbing activities and mitigation efforts. e. Pre-Submittal Conference - at least ten (10) days prior to Plan submittal, the person initiating the land-disturbing activity shall have a pre- submittal conference with the County staff to familiarize them with the proposed land-disturbing activities and mitigation efforts. f. Zoning Permits - any person requesting a Zoning Permit in association with a land-disturbing activity on a tract which involves the uncovering of more than one (1) acre of land [except as provided in Section 6(a)], shall be required to have an approved sedimentation and erosion control plan in accordance with this Ordinance. g. Subdivision Plats - any approved preliminary subdivision plat which involves the uncovering of more than one (1) acre of land [except as provided in Section 6(a)], shall become null and void unless a sedimentation and erosion control plan is submitted and approved in accordance with this Ordinance within sixty (60) days following preliminary subdivision plat approval. If such plan is not approved, preliminary plat approval for said plat shall automatically become null and void. Section 8 Design and Performance Standards a. Except as provided in Section 8(b)(2), erosion and sedimentation control measures, structures, and devices shall be so planned, designed, and constructed as 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 USDA, Natural Resources Conservation Service's "National Engineering Field Manual for Conservation Practices", or other acceptable calculation procedures. b. In High Quality Uater (HQW) zones the following design standards shall apply: 1. Uncovered areas in HQW zones shall be limited at any time to a maximum total area within ~he boundaries of the tract to twenty (20) acres. Only the portion of the land-disturbing activity within a 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. 2. Erosion and sedimentation control measures, structures, and devices within HQW zones shall be so 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 the procedures in the United States Department of Agriculture 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. 3. Sediment basins within HQW zones shall be designed and constructed such that the basin will have settling efficiency of at least 70 percent for the 40 micron (0.04mm) size soil particle transported into the basin by the runoff of that 2-year storm which produces the maximum peak rate of runoff as calculated according to procedures in the United States Department of Agriculture 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. 4. Newly constructed open channels in HQW shall be designed and constructed with side slopes no steeper than 2 horizontal to 1 vertical if a vegetative cover is used for stabilization unless soil