For the purpose of this chapter, the following definitions shall apply unless the context clearly indicates or requires a different meaning.
“ADMINISTRATOR.” The Director of Urban Services or his or her designee.
“APPLICANT.” Any person, firm, corporation, or agency that submits an application for a stormwater permit. The applicant is the current owner of the property or a representative for the owner.
“BASE FLOOD.” The flood having a 1% chance of being equaled or exceeded in any given year. The base flood is also known as the 100-year frequency flood event.
“BASE FLOOD ELEVATION (BFE).” Base flood elevation.
“BEST MANAGEMENT PRACTICE (BMP).” A measure used to control the adverse stormwater-related effects of development, and includes structural devices (for example: swales, filter strips, infiltration trenches, and site runoff storage basins designed to remove pollutants, reduce runoff rates and volumes, and protect aquatic habitats) and nonstructural approaches (for example: public education efforts to prevent the dumping of household chemicals into storm drains).
“BUFFER.” An area of predominantly deeply rooted native vegetated land adjacent to channels, wetlands, lakes, or ponds for the purpose of stabilizing banks and reducing contaminants, including sediments, in stormwater that flows to such areas.
“BUILDING.” A walled and roofed structure, storage tanks, that is principally above ground, including manufactured homes, prefabricated buildings, and gas or liquid storage tank(s). The term also includes recreational vehicles and travel trailers installed on a site for more than 180 days per year.
“BULLETIN 70.” Frequency Distributions and Hydro-climatic Characteristics of Heavy Rainstorms in Illinois, by Floyd Huff and James Angel of the Illinois State Water Survey (1989).
“CAPACITY OF A STORMWATER DETENTION FACILITY.” This is the maximum volume that can be stored by a stormwater detention facility without causing damage to the public or encroachment upon private property.
“CAPACITY OF A STORMWATER DRAINAGE FACILITY.” This is the maximum flow at atmospheric pressure that can be conveyed by the facility without causing damage to the public or encroachment upon private property.
“CHANNEL.” A natural or artificial watercourse of perceptible extent which periodically or continuously contains moving water, or which forms a connecting line between two bodies of water. It has a defined bed and banks which serve to confine the water.
“CHANNEL MODIFICATION.” Alteration of a channel by changing the physical dimensions, slopes, or materials of its bed or banks. Channel modification includes damming, riprapping (or other armoring), widening, deepening, straightening, relocating, lining, and significant removal of native vegetation from the bottom or banks. Channel modification does not include the clearing of dead or dying vegetation, debris, or trash from the channel. Channelization is a severe form of channel modification involving a significant change in the channel cross-section typically involving relocation of the exiting channel (e.g., straightening).
“CITY.” The City of Danville, Vermilion County, Illinois.
“COMPENSATORY STORAGE.” An artificially excavated, hydraulically equivalent volume of storage within the floodplain used to balance the loss of natural flood storage and flow conveyance capacity when artificial fill or structures are placed within the floodplain. The uncompensated loss of natural floodplain storage and conveyance capacity can increase off-site floodwater elevations and flows.
“CONDUIT.” Any channel, pipe, sewer, or culvert used for the conveyance or movement of water, whether open or closed.
“CONSTRUCTION.” The placement, erection, or reconstruction of any building or structure, any filling or excavation, the installation of any utility, or the storage of construction materials. Construction includes, but is not limited to, modifications to any land, modifications to an existing building that would change the building’s outside dimensions, channel modifications and enclosures, roads, bridges, culverts, levees, bank protection, walls, fences, and any other man-made activity. Construction does not include normal maintenance and repair activities or farming operations such as disking and plowing.
“CONTROL STRUCTURE.” A facility constructed to regulate the volume of stormwater that is released during a specific length of time.
“CRITICAL DURATION STORM.” The design storm which provides the highest flood discharges/water surface elevation for the flooding source.
“CULVERT.” A closed conduit for the passage of surface drainage water under a roadway, railroad, canal, or other impediment.
“DEPRESSIONAL STORAGE.” The volume contained below a closed contour, the upper elevation of which is determined by the invert of a surface gravity outlet.
“DESIGN STORM EVENT.” The runoff, rainfall or flood event with a defined likelihood of occurring in any given year that is used for designing the capacity of an element in the stormwater management system.
“DETENTION STORAGE.” Temporary detention or storage of stormwater in storage basins, on rooftops, in streets, parking lots, school yards, parks, open space, or other areas under predetermined and controlled conditions, with the rate of drainage therefrom regulated by appropriately installed devices.
“DEVELOPMENT.” Any man-made change to improved or unimproved real estate, including construction, reconstruction, or placement of a building or any addition to a building, installing a manufactured home on a site, preparing a site for a manufactured home; redevelopment of a site; clearing of land as an adjunct of construction; construction or erection of levees, walls, fences, dams, or culverts, channel modification; filling, dredging, grading, excavating, paving, or other non-agricultural alterations of the ground surface; storage of materials; deposit of solid or liquid waste, any other activity of man that might change the direction, height, or velocity of flood or surface water, including extensive vegetation removal; and substantial improvement of an existing building. Development does not include routine maintenance of existing buildings and facilities such as re-roofing or re-surfacing of roads when there is no increase in elevation, or gardening, plowing, and similar agricultural practices that do not involve filling, grading, or construction of levees.
“DISCHARGE.” The rate of outflow of water from a stormwater detention facility.
“DISTURBED AREA.” The part of the project site that will be hydrologically disturbed during the construction or demolition of any facility. The disturbed area shall include all area required for site access, equipment storage and movement and the limits of the facility itself.
“DRAINAGE AREA.” The area from which water is carried off by a drainage system; a watershed or catchment area above a given point.
“DRAINAGE EASEMENT.” Authorization by a property owner allowing use of a designated portion of his or her property by others for drainage purposes.
“DRY BOTTOM STORMWATER DETENTION BASIN.” A facility that is designed to be normally dry and which accumulates stormwater runoff only during periods when the restricted stormwater runoff release rate is less than the stormwater inflow rate.
“EXCESS STORMWATER PASSAGEWAY.” A channel formed on the surface of the soil to carry excess stormwater runoff through a specific area from dominant to servient land areas.
“EASEMENT.” Grant or reservation by the owner of land for the use of such land by others for a specific purpose or purposes, and which must be included in the conveyance of land affected by such easement.
“EROSION.” The general process whereby soils are moved by wind, water, wave, or ice action.
“EXCESS STORMWATER RUNOFF.” That portion of stormwater runoff which exceeds the transportation capacity of storm sewers or natural drainage channels serving a specific watershed.
“EXEMPTION.” Land development activities that are not subject to the stormwater management permit requirements contained in this chapter.
“FIELD TILE.” An agricultural drainage system to remove excess water from soil subsurface through perforated pipes in the ground.
“FIVE-YEAR EVENT.” A runoff, rainfall, or flood event having a one in five (20%) chance of occurring in any given year.
“FLOOD ELEVATION.” The elevation of all locations delineating the maximum level of high waters for a flood of given return period.
“FLOODPLAIN.” The special flood hazard lands adjoining a watercourse, the surface elevation of which is lower than the flood elevation and which are subject to periodic inundation during floods.
“FLOODWAY.” A channel of a watercourse and those portions of the adjoining floodplain which are reasonably required to carry and discharge the design flood.
“FREEBOARD.” An increment of height added to the base flood elevation (BFE), groundwater table, or 100-year design water surface elevation to provide a factor of safety for uncertainties in calculations, unknown local conditions, wave action, non-stationary climate, and unpredictable effects such as those caused by ice or debris jams.
“GRADE.” The inclination or slope of a channel, canal, conduit, etc., or natural ground surface, usually expressed in terms of percentage the vertical rise (or fall) bears to the corresponding horizontal distance.
“GREEN INFRASTRUCTURE.” Any stormwater management technique or practice that reduces runoff volume through preserving, restoring, utilizing, or enhancing the processes of infiltration, evapotranspiration, and water reuse. These may include green roofs, naturalized detention facilities, trees and tree boxes, rain gardens, bio-retention areas, vegetated swales, vegetated buffer, wetlands, infiltration planters, porous and permeable pavements, porous piping systems, dry wells, vegetated median strips, reforestation/revegetation, rain barrels and cisterns, and protection and enhancement of riparian buffers and floodplains.
“GROUNDWATER.” Water that is located beneath the ground or pavement surface.
“HYDROGRAPH.” A graph showing the flowrate for a given location on a stream or conduit with respect to time.
“HYDROLOGICALLY DISTURBED.” An area where the land surface or existing impervious area has been cleared, grubbed, compacted or otherwise modified, or when stormwater runoff, volumes, rates, flow direction or inundation durations are altered.
“IMPERMEABLE.” A term applied to material through which water cannot pass.
“IMPERVIOUS AREA.” Land cover such as, but not limited to, nonporous asphalt or asphalt sealants, non-porous concrete, roofing materials except planted rooftops designed to reduce runoff, and gravel surfaces used as roadways or parking lots, that prevent infiltration.
(1) “EXISTING IMPERVIOUS AREA.” The difference between the net new impervious area and the impervious area on the overall site that is present at the time of application for a SWM permit.
(2) “NET NEW IMPERVIOUS AREA.” The difference of impervious area on the overall site that is present at the time of application for a SWM permit and the amount of impervious area after improvements are made.
“INFILTRATION.” The passage or movement of water into the soil horizon.
“INLET.” An opening into a storm sewer system for the entrance of surface storm runoff, more completely described as a storm sewer inlet.
“MAJOR DRAINAGE SYSTEM.” That portion of a drainage system needed to store and convey flows beyond the capacity of the minor drainage system.
“MINOR DRAINAGE SYSTEM.” All infrastructure including curb, gutter, culverts, roadside ditches and swales, and storm sewers and subsurface drainage systems intended to convey stormwater runoff less than or equal to the design storm event required by this chapter.
“NATURAL DRAINAGE.” Water flow by gravity in channels formed by the true surface topography of the earth prior to changes made by the efforts of man.
“NATURAL DRAINAGE CONDITION.” The situation whereby water flows by gravity in channels formed by the true surface topography of the earth prior to changes made by the efforts of man.
“NEW IMPERVIOUS AREA.” The area on a site that was pervious at the time of application for SWM permit and will be impervious after improvements are made.
“ONE HUNDRED-YEAR (100-YEAR) EVENT.” A rainfall, runoff, or flood event having a one in 100 (1%) chance of occurring in any given year.
“OPEN CHANNEL.” A conveyance system with a definable bed and banks carrying the discharge from field tiles, surface drainage, and/or storm sewer system, but does not include grassed swales within farm fields under agricultural production which are ephemeral.
“OWNER.” The record title holder or a beneficiary of a land trust which is the record title holder, and includes singular or plural; if the owner is other than an individual, the term includes beneficiaries, agents, shareholders, officers and directors, partnerships, associations, firms, trusts, clubs, companies, or corporations.
“OVERALL SITE.” The entire area included in the legal description of the land upon which the land disturbing or land development activity is proposed.
“OVERLAND FLOW PATH.” A design feature of the major stormwater system which carries flows in excess of the minor stormwater system design capacity in an open channel or swale, or as sheet flow or weir flow over a feature designed to withstand the particular erosive forces involved.
“PEAK FLOW.” The maximum rate of flow of water at a given point in a channel or conduit resulting from a predetermined storm or flood.
“PERSON.” An individual, public or private corporation, government, partnership, or unincorporated association.
“POSITIVE GRAVITY OUTLET.” A term used to describe the drainage of an area in a manner that will ensure complete removal of all surface water by means of gravity.
“PROPERTY.” A parcel of real estate.
“RECOGNIZED AGENCY.” A governmental unit or agency which has statistically and consistently examined local, climatic, and geologic conditions and maintained records as they apply to stormwater runoff, e.g., U.S. Weather Bureau, University of Illinois Engineering Experiment Station, and the Illinois State Water Survey.
“RECORD.” This includes “recorded,” and “lot of record,” and shall mean a lot or parcel of land which has been recorded in the office of the County Recorder of Vermilion County, Illinois, the deed to which was of record as of the effective date of this chapter.
“REDEVELOPED IMPERVIOUS AREA.” The area on a site that was impervious at the time of application for SWM permit and will be replaced with new impervious area after improvements are made.
“RETENTION BASIN.” A structure or feature designed to retain stormwater over a period of time, with its release being positively controlled over a longer period of time than a typical “detention” storage facility.
“RETURN PERIOD.” The average interval of time within which a given rainfall event will be equaled or exceeded once. See also, “FIVE-YEAR EVENT, ONE HUNDRED-YEAR EVENT, TEN YEAR EVENT, and TWO-YEAR EVENT.
“RUNOFF COEFFICIENT.” A decimal fraction relating the amount of rain which appears as runoff and reaches the storm sewer system to the total amount of rain falling. A coefficient of 0.5 implies that 50% of the rain falling on a given surface appears as stormwater runoff.
“SEDIMENTATION.” The process that deposits soils, debris, and other materials either on other ground surfaces or in bodies of water or watercourses or stormwater drainage systems.
“SITE.” All of the land contemplated to be part of a coordinated development of one or more parcels.
“STORM SEWER.” A closed conduit for conveying collected stormwater.
“STORMWATER DRAINAGE SYSTEM.” All means, natural or man-made, used for conducting stormwater to, through or from a drainage area to the point of final outlet, including but not limited to any of the following: conduits, appurtenant features, canals, channels, ditches, streams, culverts, streets and pumping stations.
“STORMWATER MANAGEMENT FACILITY.” Something designed, built and installed to reduce the stormwater runoff flow or volume from a site or to improve the water quality of the stormwater runoff leaving the site.
“STORMWATER MANAGEMENT (SWM).” A system of vegetative, structural, non-structural, and educational measures that control the volume, rate, and pollutants of stormwater.
“STORMWATER MANAGEMENT PERMIT (SWM PERMIT).” An approval shall be issued by the Administrator prior to the approval of a building permit. Issuance of a stormwater management permit signifies conformance with the approved stormwater plan.
“STORMWATER MANAGEMENT PLAN.” A plan submitted by the applicant that demonstrates that a development meets the design requirements of this chapter. The stormwater management plan shall meet the requirements of § 162.06 of this chapter.
“STORMWATER RUNOFF.” The water that results from precipitation which is not absorbed by soil or plant material, which does not evaporate and which flows over the surface of the ground or is collected in channels, conduits or ponds.
“STORMWATER RUNOFF RELEASE RATE.” The rate at which stormwater runoff is released from dominant to servient land.
“STORMWATER STORAGE AREA.” An area designated to temporarily accumulate excess stormwater.
“STRUCTURE.” Anything which is constructed or erected with a fixed location on the ground or attached to something having a fixed location on the ground. Among other things, structures include buildings, fences, signs, mobile homes, swimming pools, and walls.
“TRADITIONAL AGRICULTURAL USES.” Uses commonly classed as agricultural or horticultural, including forestry, crop farming, truck gardening, wholesale nursery operations, animal husbandry, the operation of any machinery or vehicles incidental to said uses, and the construction of a single-family dwelling and other farm structures incidental to and typically associated with said uses.
“TRIBUTARY WATERSHED.” The entire catchment area that contributes stormwater runoff to a given point.
“TEN-YEAR EVENT.” A runoff, rainfall, or flood event having a one in ten (10%) chance of occurring in any given year.
“TWO-YEAR EVENT.” A runoff, rainfall, or flood event having a one in two (50%) chance of occurring in any given year.
“WATERCOURSE.” Any stream, creek, brook, branch, natural or artificial depression, slough, gulch, reservoir, lake, pond or natural or man-made drainageway in or into which stormwater runoff and floodwaters flow either regularly or intermittently.
“WATERSHED.” All land drained by, or contributing water to the same stream, lake, stormwater facility, or draining to a point.
“WATER QUALITY.” The biological, chemical, and physical conditions of water. It is a measure of water’s ability to support beneficial uses. The United State Environmental Protection Agency sets water quality standards for all contaminants in surface waters.
“WET BOTTOM STORMWATER STORAGE AREA.” A facility that contains a body of water and which accumulates excess stormwater during periods when the restricted stormwater runoff release rate is less than the stormwater inflow rate.
“WETLAND.” Areas which are inundated or saturated by surface or ground water (hydrology) at a frequency and duration sufficient to support, under normal circumstances, a prevalence of vegetation (hydrophytes) typically adapted for life in saturated soil conditions (hydric soils). Wetlands generally include swamps, marshes, bogs, and similar areas.
(Ord. 9097, passed 5-16-17)