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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 6-104 <br /> <br />(3) Jordan Lake Watershed <br />(a) The 10% rule, pursuant to15 A NCAC 02H.1002 (44). The 10% rule <br />allows for a 10% or less increase in peak stormwater runoff between pre- <br />development and post development conditions for the site for the design <br />storm. 7 <br />(4) Stormwater systems shall be designed to control and treat, at a minimum, the <br />stormwater runoff generated by one inch of rainfall from all project area surfaces. <br />The treatment volume shall be drawn down pursuant to standards specific to <br />each practice as determined by the current version of the NC DWQ stormwater <br />design manual. <br /> <br />(B) New development that would exceed the nutrient loading rates set out in subsection (A)(2) above, <br />shall include engineered stormwater controls designed to have a minimum of 85% average annual <br />removal for Total Suspended Solids (TSS). <br /> <br />(C) Proposed new development may satisfy the review criteria standards of this section by <br />meeting the post-development hydrologic criteria set out in Chapter 2 of the most recent <br />version of the North Carolina Low Impact Development Guidebook. <br />6.14.7 Nutrient Load <br />(A) Nitrogen and phosphorus loads contributed by proposed new development shall not <br />exceed the following unit-area mass loading rates: <br />(1) Falls Lake Watershed <br />(a) Nitrogen, 2.2 pounds per acre per year <br />(b) Phosphorus, 0.33 pounds per acre per year <br />(2) Jordan Lake Watershed8 <br />(a) Upper New Hope Creek Arm <br />(i) Nitrogen, 2.2 pounds per acre per year <br />(ii) Phosphorus, 0.82 pounds per acre per year <br />(b) Haw River Arm <br />(i) Nitrogen, 3.8 pounds per acre per year <br />(ii) Phosphorus, 1.43 pounds per acre per year <br />(B) The nutrient export from each new development shall be calculated in pounds per acre <br />per year (using the approved accounting tool) in accordance with the methodologies <br />approved by the NC DWQDEQ9. <br />(C) If a proposed development subject to nutrient load requirements contributes nutrients <br />greater than the standards listed above, the developer may install structural stormwater <br /> <br />7 This is to clarify what applies to the Jordan Lake watershed since the Falls Lake Watershed was specifically called <br />out in 6.14.6(A)3 <br />8 In order to ensure consistency with State regulations, staff is recommending the elimination of existing <br />regulations designed to address water quality issues within the Jordan Lake watershed. While staff can address <br />water quantity issues (i.e. how much run off has to be captured on-site) through the County we are currently <br />limited to addressing water quality issues (i.e. nutrient removal) within the Falls Lake Watershed only. <br />9 Changed to reflect North Carolina Department of Environmental Quality – name change <br /> 11