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Article 6: Development Standards 134 <br /> Section 6.15: Soil Erosion and Sedimentation Contro1266F <br /> (b) Erosion and Sedimentation Controls <br /> (i) 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 stormwater runoff of <br /> the 25-year storm which produces the maximum peak rate of <br /> stormwater runoff. <br /> (ii) The peak rate of stormwater runoff shall be calculated according <br /> to procedures in the latest edition of the United States <br /> Department of Agriculture Natural Resources—qofl Conservation <br /> Service's "National Engineering Field Manual Handbook 630 for <br /> Conservation Practices"or according to other calculation <br /> procedures acceptable to the Erosion Control Officer-adGpted-by <br /> any o#herogenGY of this state or the I Inner! States o <br /> r an <br /> generally re zed o zati.,n o iatien <br /> (c) Sediment Ponds313 <br /> (i) Sediment ponds (also called "sediment basins")wk4in HQW <br /> zones shall be planned, designed,and constructed to meet the <br /> following criteria: <br /> a. Use a surface withdrawal mechanism, except when the <br /> basin drainage area is less than 1.0 acre; <br /> b. Have a minimum of 1,800 cubic feet of storage area per <br /> acre of disturbed area; <br /> C. Have a minimum surface area of 325 square feet per cfs <br /> of Q25 peak inflow; <br /> d. Have a minimum dewatering time of 48 hours; and <br /> e. Incorporate 3 baffles, unless the basin is less than 20 <br /> feet in length, in which case 2 baffles shall be sufficient. <br /> a. such that the pond will have a settling efficiency of a# <br /> least 70% for the 40 micron (0.04 mm) size soil particle <br /> transported into the basin by the stormwater runoff of <br /> that 2 year storm which produces the maximum nook <br /> rate of stormwater runoff. <br /> 00 TThe peak rate of stormwater runoff shall be calculated <br /> according to procedures in the latest edition of the United States <br /> Department of Agriculture Natural Resources Conservation <br /> Service's "National Engineering Field Handbook 630 for <br /> Conservation Practices"or according to other calculation <br /> procedures acceptable to the Erosion Control Officer. <br /> (d) Alternative Sediment Pond Design314 <br /> Upon a written request of the applicant, the Director of DEMLR may <br /> allow alternative sediment pond design or control measures in lieu of <br /> meeting the conditions required in Section 6.15.7(B)(6)(c) of this <br /> Ordinance if the applicant demonstrates that meeting all of the conditions <br /> will result in design or operational hardships and that the alternative <br /> measures will provide an equal or more effective level of erosion and <br /> sedimentation control on the site. Alternative measures may include <br /> quicker application of ground cover, use of sediment flocculants, and use <br /> of enhanced ground cover practices. <br /> 313 Revised to reflect current standards within 15A NCAC Chapter 4. <br /> 3ia New section added to reflect current standards within 15A NCAC Chapter 4. <br /> Orange County, North Carolina—Unified Development Ordinance Page 6-126 <br />