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volume of runoff by a proposed development area. The critical storm is used to calculate <br />the maximum allowable storm water discharge rate from a developed site. <br />H. DETENTION FACILITY: A basin, pond, oversized pipe, or other structure that reduces the <br />peak flow rate of storm water leaving the facility by temporarily storing a portion of the <br />storm water entering the facility. <br />I. DEVELOPMENT AREA: A parcel or contiguous parcels owned by one person or persons, <br />or operated as one development unit, and used or being developed for commercial, <br />industrial, residential, institutional, or other construction or alteration that changes runoff <br />characteristics. <br />DEVELOPMENT DRAINAGE AREA: A combination of each hydraulically unique <br />watershed with individual outlet points on the development area. <br />K. DISTURBED AREA: An area of land subject to erosion due to the removal of vegetative <br />cover and/or soil disturbing activities. <br />L. DRAINAGE: The removal of excess surface water or groundwater from land by surface or <br />subsurface drains. <br />M. EROSION: The process by which the land surface is worn away by the action of wind, <br />water, ice, gravity, or any combination of those forces. <br />N. EXTENDED CONVEYANCE: A storm water management practice that replaces and/or <br />enhances traditional open or closed storm drainage conduits by retarding flow, promoting <br />percolation of runoff into the soil, and filtering pollutants during the storm water quality <br />event. <br />O. EXTENDED DETENTION: A storm water management practice that replaces and/or <br />enhances traditional detention facilities by releasing the runoff collected during the storm <br />water quality event over at least 24 to 48 hours, retarding flow and allowing pollutants to <br />settle within the facility. <br />P. FINAL STABILIZATION: All soil disturbing activities at the site have been completed and <br />a uniform perennial vegetative cover with a density of at least 80% coverage for the area has <br />been established or equivalent stabilization practices, such as the use of mulches or <br />geotextiles, have been employed. <br />Q. GRADING: The process in which the topography of the land is altered to a new slope. <br />R. HYDROLOGIC UNIT CODE: A cataloging system developed by the United States <br />Geological Survey and the Natural Resource Conservation Service to identify <br />watersheds in the United States. <br />S. IMPERVIOUS COVER: Any surface that cannot effectively absorb or infiltrate water. This <br />may include roads, streets, parking lots, rooftops, sidewalks, and other areas not covered by <br />vegetation. <br />T. INFILTRATION: A storm water management practice that does not discharge to a water <br />resource during the storm water quality event, requiring collected runoff to either infiltrate <br />