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improperly used, stored, transported or disposed of, or otherwise managed. For purposes <br />of chemical regulation by this manual, moderate to high toxicity and confirmed human <br />carcinogenicity are the criteria used to identify hazardous substances, {Note: This manual <br />does not use the Resource Conservation and Recovery Act (RCRA) definition of hazardous. <br />For the purpose of this manual, hazardous material is intended to include hazardous, toxic, <br />and other harmful substances <br />Hazardous Material Containment Zone (HMC Zone): An area where a specific individual <br />activity involving use of a hazardous material takes place, and where chemical quantities at <br />that location are expected to exceed defined thresholds. HMCs may include (but are not <br />limited to) storage and /or process areas, transportation routes, work areas, and <br />loading/unloading facilities. <br />Headwaters Area; The area within Eugene city limits that is above 500 feet <br />Headwater Shwamm Streams that (1) are identified on the Headwater Streams Map <br />(Appendix n as having all or a portion of their length located on slopes greater than 10%; <br />(2) are identified on the Sensitive Areas Map as having all or a portion of their length <br />located in areas with highly erodible soils; (3) are at least 500 feet or longer; and, (4) drain <br />at least 10 acres. <br />High Flow Bypass and /or Diversion Device: A mechanism used to route stormwater <br />runoffs which are greater than the water quality design storm around a - stDrmwater <br />management facility which is only designed to treat the water quality, design. storm. Flows <br />routed around the stormwater quality facility must be 'taken to an approved destination. <br />Hgrh -Plow Overfl An inlet located at an approved elevation and location within a <br />stormwater management facility, meant to collect overflow waters and route those waters <br />to an approved destination. <br />High- -Risk Site: - A site with characteristics and/or activities that have the potential to <br />generate pollutants that may not be addressed solely through the stornw ater quality <br />facilities presented in Chapter 2.0. High -risk site characteristics and activities are listed in <br />Chapter 4 - Source Controls. <br />InWa ious Surface /Area: Any surface area that causes water to run off the surface in <br />greater quantities or at an increased rate of flow from conditions pre - existing to <br />development. 'hypes of impervious surface include, but are not limited to, rooftops, asphalt <br />and concrete parking lots, driveways, roads, sidewalks, and pedestrian plazas: Note. Slatted <br />decks are considered pervious. Gravel surfaces are considered pervious unless they cover <br />impervious surfaces or are compacted to a degree that causes their runoff coefficient to <br />exceed O.B. <br />hnpervior s Arm Reduction Technique: implementation of a facility used to intercept <br />rainfall that would otherwise be impervious, such as a roof or sidewalk Such facilities <br />include pervious pavement, eco -roofs, contained planters, and tree credit trees. - - <br />Stormwarer Management Manual 1 -8 <br />Eugene 20714 <br />