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Article 6: Development Standards 37 <br /> Section 6.14: Stormwater Management <br /> (N Division of Mitigation Seryices14, approved private mitigation bank, or <br /> other mitigation option as approved by the NC BVVQ DEQ and Orange County. It <br /> is the policy of NC DWQ DEQand Orange County, as well as a requirement in <br /> certain watersheds, that offset payment funds be utilized where they are <br /> generated to the maximum extent possible. <br /> (3) Offset payment fees and calculation methods are determined by the NGDWQ <br /> NCDEQ as approved by the North Carolina Environmental Management <br /> Commission (EMC). The total amount of offset payment will be determined <br /> based on current NC DWQ DEQ 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 BMPsstormwater control measures <br /> (SCMs)for nutrient reduction shall include those listed in the current NC DWQ <br /> DEQ Stormwater Best Management Practices Manual (Ste- -,wale,-BMP <br /> Manu ) ^ "^s,s 15 <br /> (2) Design, maintenance and operation of stormwater ids SCMs shall follow <br /> standards provided in the Stormwater BMP—Qesign 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 B SCMs, arA-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 16 <br /> (1) For all new development, there shall be no net increase in peak flow leaving the Formatte <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 ti Formatte <br /> flow leaving the site from the predevelopment conditions consistent with 15 A Formatte <br /> NCAC 02H.1002 (44)and the NCDEQ Stormwater Design Manual- <br /> (C) Calculating Peak Runoff Volume Formatte <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 /> 14 According to State staff NCEEP has been changed to the Division of Mitigation Services. Staff is updating the <br /> reference(s)appropriately. <br /> 15 Modification of existing language to ensure consistency with new stormwater rules(15A NCAC 02H)which went <br /> into effect on January 1,2017. <br /> 16 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 /> Orange County, North Carolina—Unified Development Ordinance Page 6-100 <br />