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Article 6: Development Standards <br /> Section 6.14: Stormwater Management <br /> <br /> <br />Orange County, North Carolina – Unified Development Ordinance Page 6-100 <br /> <br />extent possible. <br />(3) Offset payment fees and calculation methods are determined by the NCDWQ as <br />approved by the North Carolina Environmental Management Commission (EMC). <br />The total amount of offset payment will be determined based on current NC <br />DWQ policy and regulation on a case by case basis. <br />(E) Permanent Nutrient Export Reduction Best Management Practices <br />(1) Allowable on-site structural stormwater BMPs for nutrient reduction shall include <br />those listed in the current NC DWQ DEQ Stormwater Best Management <br />Practices Manual (Stormwater BMP Manual)Design Manual (Minimum Design <br />Criteria) or others approved on a case by case basis.10 <br />(2) Design, maintenance and operation of stormwater BMPs SCMs shall follow <br />standards provided in the Stormwater BMP Design Manual. <br />(3) Deviations from these standards may be allowed as approved on a case by case <br />basis. <br />(F) Total Nutrient Removal Rates <br />Total nutrient removal rates of stormwater BMPsSCMs, and as well as BMPs SCMs in a <br />series, will be calculated pursuant to the approved accounting tool. <br />6.14.8 Peak Runoff Volume <br />(A) StandardStandards for Falls Lake Watershed 11 <br />(1) For all new development, there shall be no net increase in peak flow leaving the <br />site from the predevelopment conditions for the 1 year, 24 hour storm. <br />(B) Standards for Jordan Lake Watershed <br />(B)(1) For all new development there shall be no net increase greater than 10% in peak <br />flow leaving the site from the predevelopment conditions consistent with 15 A <br />NCAC 02H.1002 (44) and the NCDEQ Stormwater Design Manual.. <br />(C) Calculating Peak Runoff Volume <br />(1) The following are acceptable methodologies for computing the pre- and post- <br />development conditions for the 1 year, 24 hour storm: <br />(a) Rational Method, <br />(b) Peak Discharge Method as described in the USDA Soil Conservation <br />Service’s Technical Release Number 55 (TR-55), <br />(c) Alternative methods must be approved by the County. <br />(2) The same method must be used for both the pre- and post- development <br />conditions. <br />6.14.9 Stormwater Management Plan <br />(A) Required Approval <br />The Erosion Control Officer shall not issue any permits for new development on any land <br />within Orange County subject to the provisions of this Section, unless and until a <br /> <br />10 Modification of existing language to ensure consistency with new stormwater rules (15A NCAC 02H) which went  <br />into effect on January 1, 2017.  <br />11 Clarification of existing language to reference peak runoff requirements are only enforceable within the Falls  <br />Lake Watershed.  Development of property within the Jordan Lake Watershed is required to abide by 15 A NCAC  <br />02H.1002 (44) as previously indicated.  <br /> 10