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Glossary 40 Definitions are arranged alphabetically by term. For a complete reference, please see the Stormwater Management Manual for Western Washington (SWMMWW): fortresswa.gov/.ey/ersharglwq/Permits/Flare/2019SWMMW W/2019SWMMW W.htm Best Management Practice The schedules of activities, prohibitions of practices, maintenance procedures, (BMP) and structural and/or managerial practices, that when used singly or in combination, prevent or reduce the release of pollutants and other adverse impacts to waters of Washington State, Compaction The dens cation, settlement, or packing of soil in such away that permeability of the soil isreduced. Compost Organic material that has undergone biological degradation and transformation under controlled conditions designed to promoteaerobic decomposition ata solid waste facility in compliance with the requirements of Chapter 173-350 WAC, or biosolids composted in compliancewith Chapter 173-308 WAC. Compostingisa form of organic material recycling. Critical Area Ata m in i m u m, areas which include wetlands, areaswith a critical rechargi ngeffect on aquifers usedfor potable water, fish andwildlife habitat conservation areas, frequentlyflooded areas,geo logicallyhazardous areas, inclu dingunstable slopes, and associated areas and ecosystems. Dispersion Release of surface and stormwater runoff such that the flow spreads over a wide area and is located so as notto allow flow to concentrate anywhere upstream of a drainage channel with erodible underlying granular soils. Hard Surface An impervious surface, a permeable pavement, or a vegetated roof. Impervious Surface Anon -vegetated surface areawh ich either prevents or retards the entry ofwater into the soil mantle as under natural conditions prior to development. A non -vegetated surface area which causes water to run off the surface in greater quantities or at an increased rate of flow from the flow present under natural conditions prior to development. Common impervious surfaces include, but are not limited to, roof tops, wal kways, patios, driveways, parking lots or storage areas, concrete or asphalt paving, gravel roads, packed earthen materials, and oiled, macadam or other surfaces which similarly impede the natural infiltration of stormwater. Open, uncovered retention/ detention facilities shall not be considered as impervious surfaces for the purposes of determining whether the thresholds for application of Minimum Requirements are exceeded. Open, uncovered retention/detention facilities shall be considered impervious surfaces for purposes of runoff modeling. City of Everett Public Works Small Project StormwaterSitePlan Report April 2021 21