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Glossary <br /> • Definitions are arranged alphabetically by term. For a complete reference,please see <br /> the Stormwater Management Manual for Western Washington(SWMMWW): <br /> fortress.wa.gov/ecy/ershare/wq/Permits/Flare/2019SWMMWW/2019SWMMWW.htm <br /> Best Management Practice The schedules of activities,prohibitions of practices,maintenance procedures, <br /> (BMP) and structural and/or managerial practices,that when used singly or in <br /> combination,prevent or reduce the release of pollutants and other adverse <br /> impacts to waters of Washington State. <br /> Compaction The densification,settlement,or packing of soil in such a way that permeability of <br /> the soil is reduced. <br /> Compost Organic material that has undergone biological degradation and transformation <br /> under controlled conditions designed to promote aerobic decomposition at a solid <br /> waste facility in compliance with the requirements of Chapter 173-350 WAC,or <br /> biosolids composted in compliance with Chapter 173-308 WAC.Composting is a <br /> form of organic material recycling. <br /> Critical Area At a minimum,areas which include wetlands,areas with a critical recharging effect <br /> on aquifers used for potable water,fish and wildlife habitat conservation areas, <br /> frequently flooded areas,geologically hazardous areas,including unstable slopes, <br /> and associated areas and ecosystems. <br /> Dispersion Release of surface and stormwater runoff such that the flow spreads over a wide <br /> area and is located so as not to allow flow to concentrate anywhere upstream of a <br /> drainage channel with erodible underlying granular soils. <br /> Hard Surface An impervious surface,a permeable pavement,or a vegetated roof. <br /> Impervious Surface A non-vegetated surface area which either prevents or retards the entry of water into <br /> the soil mantle as under natural conditions prior to development.A non-vegetated <br /> surface area which causes water to run off the surface in greater quantities or at an <br /> increased rate of flow from the flow present under natural conditions prior to <br /> development. Common impervious surfaces include, but are not limited to, roof <br /> tops,walkways,patios,driveways,parking lots or storage areas,concrete or asphalt <br /> paving, gravel roads, packed earthen materials, and oiled, macadam or other <br /> surfaces which similarly impede the natural infiltration of stormwater. Open, <br /> uncovered retention/ detention facilities shall not be considered as impervious <br /> surfaces for the purposes of determining whether the thresholds for application of <br /> Minimum Requirements are exceeded. Open, uncovered retention/detention <br /> facilities shall be considered impervious surfaces for purposes of runoff modeling. <br /> City of Everett Public Works <br /> Small Project Stormwater Site Plan Report-Dec 2019 21 <br />