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3. Raleigh Rainfall Depths <br />a) 1 year, 24 hour depth: 3.00 inches <br />b) 1 year, 24 hour intensity: under development by DWQ staff <br />E. Exemptions to the Peak Flow Requirements <br />Peak flow requirements are waived for development that meets the following criteria: <br />1. Increase in peak flow between pre- and post- development conditions does not <br />exceed 10% (ten percent). <br />2. Proposed new development meets all of the following criteria: <br />a) total impervious surface is less than 15% (fifteen percent), and <br />b) remaining pervious surface maximizes stormwater runoff control and <br />conveyance. <br />3. Detention will cause further flooding on lands that have experience flooding <br />during previous storm events. This request for exemption must be prepared by a <br />North Carolina registered professional engineer and submitted in writing to the <br />Planning Director or Designee. Appeals of this decision will follow Section 7 -E <br />of this Ordinance. <br />Section 7 Stormwater Management Plan <br />A. Plan Requirements <br />1. Permanent on -site BMPs must be shown as part of the Stormwater <br />Management Plan and accompany the Land - Disturbing Plan submittal. BMPs are <br />to be in accordance with the NC and MD design manuals. <br />2. All calculations for Nitrogen Export, Peak Run -off Volume, and permanent <br />BMPs designed for Nitrogen Removal must be included in the submittal of the <br />Stormwater Development Plan. <br />B. Plan Approval <br />The Enforcement Officer is authorized to approve any Stormwater Management Plan <br />which is in conformance with the performance standards specified in the Orange County <br />Design Manual, and other requirements of this Ordinance. <br />C. Approved Plan a Prerequisite <br />The Enforcement Officer is not authorized to issue any permits for development on any <br />land within the Neuse River Basin that is defined as new development under Section 5 of <br />this Ordinance unless and until a Stormwater Development Plan in compliance with the <br />requirements of this Section has been approved. <br />D. Design of Permanent Nitrogen Export Reduction BMPs <br />When a permanent nitrogen export reduction BMP is required for new development to <br />meet the requirements of this Ordinance, a North Carolina registered professional <br />engineer shall prepare the plan with the Engineer's Certification of Stormwater <br />Management as shown in Appendix 3 affixed, signed, sealed and dated. <br />E. Fees <br />The Stormwater Management Plan Review Fee shall be paid at the time of submittal. The <br />fee shall be based upon the current Orange County Planning Fee Schedule. <br />25 <br />