Agenda - 03-03-2015-13 (4) - Laserfiche WebLink

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3 It should be noted in 2014 the State Legislature adopted a temporary rule eliminating certain types of gravel from being classified as an impervious surface. This rule, however, was rescinded resulting in all forms of gravel being considered an impervious surface and calculated as same. STATE ALLOWANCES: The State has produced a stormwater manual, denoting required design elements, which can be viewed at: http: / /portal.ncdenr.org /web /ir /bmp- manual. Property owners proposing a certain level of disturbance are required to comply with established stormwater provisions as detailed within the UDO. In certain circumstances the State allows the installation of a stormwater feature, commonly referred to as a Best Management Practice (BMP), providing an opportunity for the installation of additional impervious surface area. As of the writing of this memorandum, the State recognizes only one BMP option allowing for additional impervious surface allocation, specifically: Permeable pavement - allows stormwater to infiltrate through void spaces for temporary storage and, ultimately, to be infiltrated into the soil. The total amount of additional impervious surface allotment is based on the soil type. Viability of permeable pavement is determined on a case by case basis with no guarantee(s). According to the manual, permeable pavement has the following general advantages and disadvantages: Advantages: • Replaces built upon area with materials that allow for infiltration of stormwater. • Eliminates standing water on pavement. • Helps to reduce pollutant runoff concerns from a parcel of property. Disadvantages • Without proper maintenance it can become clogged by sediment, compromising its effectiveness. • Not applicable for all site conditions. • Higher costs (i.e. installation and perpetual maintenance) County regulations, as contained in Section(s) 4.2.5 and 4.2.6 of the UDO, prohibit the use of BMPs as satisfying, or allowing for an increase in allowable, impervious surface area. UPDATE: Staff would like to offer the following: 1. Members of the Planning Department and Erosion Control / Stormwater are scheduled to review various elements of the existing stormwater program and possible use of BMPs to allow for additional impervious surface area with State officials on February 25, 2015. 2. Staff is developing potential amendment(s) to existing regulations requiring developers to address the comprehensive impact of development with respect to impervious surface limits and stormwater management.