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Article 6: Development Standards Section 6.14: Stormwater Management Orange County, North Carolina – Unified Development Ordinance Page 6-96 (1) The stormwater run-off generated by one inch of rain from all project area surfaces shall be controlled to the extent possible through on-site infiltration and through the use of methods which rely on natural soil properties for absorption and treatment. (2) Run-off from roads, parking lots, and/or sidewalks shall be directed to undisturbed areas through use of berms, grassed diversion ditches or swales, or other acceptable means to reduce run-off velocity and filter out pollutants. (3) Impervious Surface Limits (a) In order to promote infiltration of stormwater runoff into the soil and minimize direct and immediate runoff into streams and water supply impoundments, the maximum percentage of the total lot area which may be covered with an impervious surface shall be specified. This limit is referred to as the "impervious surface ratio". (b) Impervious surface calculations for an individual development shall be cumulative for original construction and any subsequent additions. One- half of the width of any of any existing or proposed road adjacent to an individual lot shall be included as impervious surface for that lot, except in the case where an existing road was contained within a dedicated public right-of-way at the time that the watershed regulations were first applied to the watershed within which the development is located. (4) Infiltration Techniques (a) The benefits of infiltration techniques include: (i) Removal of both suspended and dissolved pollutants, (ii) They require less maintenance, (iii) They reduce flooding, (iv) They promote groundwater recharge, and (v) They help maintain stream flow during dry periods. (b) Where on-site infiltration methods are utilized, areas for such purposes shall be designated on the plat and shall remain undisturbed both during and after construction. (c) Undisturbed areas for infiltration of run-off shall also be located downslope from impervious surfaces and shall not include areas characterized by floodplains, highly erodible or impervious soils, steep slopes or previously disturbed areas. (d) Areas designated as suitable for septic tank nitrification fields may not be used for stormwater infiltration purposes. (B) Structural Stormwater Measures (1) In cases where non-structural methods may not adequately control the runoff from the first inch of rain due to the amount of impervious surface proposed to be developed, and other factors such as soil type, slope, presence of floodplains and erodible soils, and/or lack of vegetative cover, structural stormwater measures, which capture stormwater for slow release through an outlet, are required. (2) Where required, structural stormwater measures shall be constructed in accordance with this Section. (C) Impervious Surface and Detention Pond Requirements 6