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16 <br />construction or development. Except as provided in Sectian 8 (D) (2) (e) of <br />this ordinance, provisions for a ground cover sufficient to restrain erosion <br />must be accomplished within 30 working days or 120 calendar days, <br />whichever period is shorter, following completion of construction or <br />development. <br />D. Design and Performance of Control Measures <br />1. Design Storm <br />Except as provided in Section 8(D)(2)(b) of this, Ordinance and in the <br />standard for sediment ponds in the Soil Erosion and Sediment Control <br />Manual erosion and sedimentation control measures, structures, and <br />devices shall be so planned, designed, and constructed as to provide <br />protection from accelerated erosion and sedimentation from the calculated <br />maximum peak rates of runoff from the ten-year frequency storm. Runoff <br />rates shall be calculated using the procedures in the USDA Soil <br />Conservation Service's "National Engineering Field Manual for <br />Conservation Practices," or other calculation procedures acceptable to the <br />Erosion Control Officer. <br />2. Standards for High Quality Waters <br />In High Quality Water (HQW) zones the following design standards shall <br />apply: <br />a. Uncovered areas in HQW zones shall be limited at any time to a <br />maximum total area of 20 acres within the boundaries of the <br />tract. Only the portion of the land-disturbing activity within a <br />HQW zone shall be governed by this section. Larger areas may <br />be uncovered within the boundaries of the tract with the written <br />approval of the Director of the Division of Land Resources of the <br />Department of Environment, Health, and Natural Resources. <br />b. Erosion and sedimentation control measures, structures, and <br />devices within HQW zones shall be so planned, designed, and <br />constructed to provide protection from the runoff of the 25-year <br />storm which produces the maximum peak rate of runoff. The <br />peak rate of runoff shall be calculated according to procedures,-in <br />the United States Department of Agriculture Soil Canservation <br />Service's National Engineering Field Manual for Conservation <br />Practices or according to procedures adopted by any other <br />agency of this state or the United States or any generally <br />recognized organization or association. <br />c. Sediment ponds, (also called "sediment basins") within HQW <br />zanes shall be designed and constructed such that the pond will <br />have a settling efficiency of at least 70% for the 40 micron (0.04 <br />mm) size soil particle transported into the basin by the runoff of <br />