§ 164.004  DEFINITIONS.
   For the purposes of this chapter, the following definitions shall apply unless the context clearly indicates or requires a different meaning. Words and terms not defined shall have the meanings indicated by common dictionary definition.
      (1)   Is subordinate to and serves a principal building or principal use;
      (2)   Is subordinate in area, extent or purpose to the principal building or principal use served;
      (3)   Contributes to the comfort, convenience or necessity of occupants of the principal building or principal use served; and
      (4)   Is located on the same zoning lot as the principal building or potential use served with the single exception of accessory off-street parking facilities as are permitted to locate elsewhere than on the same zoning lot with the building or use served.
   ACOE.  The United States Army Corps of Engineers.
   ADMINISTRATIVE VIOLATION.  Occurs when rules and procedures regarding permit applications and site development permits are not followed.
   ADMINISTRATOR.  The person designated by the County Executive to administer and enforce this chapter.
   AGRICULTURAL PRACTICES. The use of land for agricultural purposes, including farming, dairying, pasturage, apiculture, horticulture, floriculture, viticulture and animal and poultry husbandry, and the necessary accessory uses for packing, treating or storing the produce; provided, however, that the operation of any accessory uses shall be secondary to that of the normal agricultural activities. AGRICULTURAL PRACTICES include truck farming, poultry farming, bee keeping, raising of fruit and berries, and the selling of agricultural products. AGRICULTURE PRACTICES shall not include the commercial feeding of garbage to swine or other animals. The minimum land area necessary to constitute an agricultural use is ten acres.
   AGRICULTURAL SUBSURFACE DRAINAGE.  A water management technique driven by economic and safety concerns, where the rate at which surplus groundwater should be removed is determined primarily by the moisture/air requirements of the vegetation (commonly called tiles, field tiles and the like).
   APPLICABLE ENGINEERING PRACTICE.  Procedures, methods or materials recommended in standard engineering textbooks or references as suitable for the intended purpose.
   APPLICANT.  Any person, firm or governmental agency who executes the necessary forms to procure official approval of a development or permit to carry out construction of a development from the county.
   APPROPRIATE USE.  Only uses of the designated floodway that are permissible and will be considered for permit issuance. The list of permissible uses is contained in §§ 164.060 through 164.067.
   ARMORING.  A form of channel modification which involves the placement of materials (e.g., concrete, riprap, bulkheads and the like) within a stream channel or along a shoreline to protect property above streams, lakes and ponds from erosion and wave damage caused by wave action and stream flow.
   BASE FLOOD.  The flood having a 1% probability of being equaled or exceeded in a given year. The BASE FLOOD is also known as the 100-year frequency flood event.
   BASE FLOOD ELEVATION (BFE).  The highest water surface elevation that can be expected during the base flood.
   BENCHMARK.  A permanent, stable object containing a marked point of known elevation (with respect to NAVD 88) which is used as a vertical reference point for topographic surveys.
   BEST MANAGEMENT PRACTICES (BMP).  A measure used to control the adverse stormwater-related effects of development. BMPs include structural devices (e.g., swales, filter strips, infiltration trenches and detention basins) designed to remove pollutants, reduce runoff rates and volumes, and protect aquatic habitats. BMPs also include nonstructural approaches, such as public education efforts to prevent the dumping of household chemicals into storm drains.
   BLOCKED RESTRICTOR ELEVATION. The elevation to which stormwater would rise in a basin in a 100-year storm if the restrictor is blocked. See § 164.023(F).
   BUILDING.  A structure that is principally above ground and is enclosed by walls and a roof. The term includes a gas or liquid storage tank, a manufactured home, mobile home or a prefabricated building. This term also includes recreational vehicles and travel trailers to be installed on a site for more than 180 days, unless fully licensed and ready for highway use.
   BUFFER.  An area of predominantly vegetated land located adjacent to channels, wetlands, lakes or ponds for the purpose of reducing contaminants in stormwater that flows to those areas.
   BULLETIN 70.Frequency Distributions of Heavy Precipitation in Illinois: Updated Bulletin 70 by James Angel and Momcilo Marcus of the Illinois State Water Survey, Prairie Research Institute (March 2019).
   BYPASS FLOWS.  Stormwater runoff or groundwater from upstream properties tributary to a property’s drainage system but not under its control.
   CALCULATED HIGH WATER ELEVATION.  The elevation to which stormwater would rise along an overland flow route, or similar conveyance system, in a 100-year storm.
   CHANNEL.  Any river, stream, creek, brook, branch, natural or artificial depression, ponded area, flowage, slough, ditch, conduit, culvert, gully, ravine, wash or natural or human-made drainage way, which has a definite bed and bank or shoreline, in or into which surface, groundwater, effluent or industrial discharges flow either perennially or intermittently.
   CHANNEL MODIFICATION.  Alteration of a channel by changing the physical dimensions or materials of its bed or banks. CHANNEL MODIFICATION includes damming, riprapping (or other armoring), widening, deepening, straightening, relocating, lining and significant removal of bottom or woody rooted vegetation but does not include the clearing of debris or removal of trash or dredging to previously documented thalwag elevations and side slopes.
   CHANNELIZATION. A severe form of channel modification involving a significant change in the channel cross-section and typically involving relocation of the existing channel (e.g., straightening).
   CHIEF SUBDIVISION ENGINEER. Stormwater Administrator for unincorporated Will County as outlined in § 164.162.
   COMMERCIAL.  Sale of goods to the public at large where the traffic generated warrants construction of site improvements.
   COMMITTEE. The Land Use and Development Committee of the County Board.
   COMMUNITY.  The county or any city or village within the county.
   COMPENSATORY STORAGE.  An excavated, hydrologically and hydraulically equivalent volume of storage created to offset the loss of existing flood storage.
   CONDITIONAL LETTER OF MAP AMENDMENT (CLOMA).  A FEMA comment letter on a development proposed to be located in, and affecting only that portion of, the area of floodplain outside the regulatory floodway and having no impact on the existing regulatory floodway or base flood elevations.
   CONDITIONAL LETTER OF MAP REVISION (CLOMR). A letter that indicates that FEMA will revise base flood elevations, flood insurance rate zones, flood boundaries or floodways as shown on an effective FIRM after the “as-built” record drawings are submitted and approved.
   COE.  The United States Army Corps of Engineers.
   CONSERVATION DESIGN.  A site design which incorporates the natural landscape, ecology, and/or historical significance of a site being developed, and which maintains the most valuable natural features and functions of the site. These natural and valuable features can be used for either passive or active recreational activity or preserved as naturally vegetated land.
   CONSERVATION PLANNING.  The practices and procedures associated with the management of soil, water, plants, plant nutrients and other elements of agricultural production. Documentation of the management system shall only be as required by the NRCS or in cases of a complaint, as requested by the Chief Subdivision Engineer in response to a notification of a complaint.
   CONSERVATION PRACTICES.  A listing of practices such as those identified in the USDA-NRCS Technical Guide § 4 that detail the standards and specifications for each practice listed. The electronic guide can be accessed at:
   CONTROL STRUCTURE.  A structure designed to control the rate of flow that passes through the structure, given a specific upstream and downstream water surface elevation.
   COUNTY.  Will County, Illinois.
   CRITICAL DURATION.  The duration of a storm event that results in the greatest peak runoff.
   CRITICAL FACILITY.  Any facility that is critical to the health and welfare of the population, and, if flooded, would create an added dimension to the disaster. Damage to these CRITICAL FACILITIES can impact the delivery of vital services, can cause greater damage to other sectors of the community, or can put special populations at risk. Examples of CRITICAL FACILITIES are: emergency services facilities (such as fire and police stations), schools, hospitals, retirement homes and senior care facilities, critical utility sites (telephone switching stations or electrical transformers), and hazardous material storage facilities (chemicals, petrochemicals, hazardous or toxic substances).
   CULVERT.  A structure designed to carry drainage water or small streams below barriers, such as roads, driveways or railroad embankments
   D-FIRM. Digital flood insurance rate map published by FEMA showing special flood hazard areas in a digital format overlaid on an aerial photograph.
   DAM.  Any obstruction, wall embankment or barrier, together with any abutments and appurtenant works, constructed to store or divert water or to create a pool. DAMS may also include weirs, restrictive culverts or impoundment structures. Underground water storage tanks are not included.
   DEPARTMENT.  The County Land Use Department.
   DEPRESSIONAL STORAGE.  The volume contained below a closed contour on a one-foot contour interval topographic map, the upper elevation which is determined by the invert of a surface gravity outlet.
   DETENTION BASIN (SITE RUNOFF STORAGE FACILITY).  A constructed structure for the temporary storage of stormwater runoff with a controlled release rate.
   DEVELOPER.  A person who creates or causes a development.
      (1)   Any constructed change to real estate including:
         (a)   Construction, reconstruction, repair or replacement of a building or an addition to a building;
         (b)   Installing a manufactured home on a site, preparing a site for a manufactured home, or installing a travel trailer or recreational vehicle on a site for more than 180 days. If the travel trailer or recreational vehicle is on-site for less than 180 days, it must be fully licensed and ready for highway use;
         (c)   Drilling, mining, installing utilities, construction of roads, bridges or similar projects;
         (d)   Construction or erection of levees, walls, fences, dams or culverts, channel modifications, filling, dredging, grading, excavating, paving or other nonagricultural alterations of the ground surface, storage materials, deposit of solids or liquid waste;
         (e)   Any other activity of humans that might change the direction, height or velocity of flood or surface water, including extensive vegetation removal; and/or
         (f)   Plowing and cultivation and other similar agricultural practices that do not involve filling, grading or construction of levees as regulated in § 164.024.
      (2)   The following are not considered DEVELOPMENT: maintenance of existing buildings and facilities such as reroofing or resurfacing of roads with an impervious surface when there is no increase in elevation.
   DIRECT DISCHARGE SITES.  Parcels of land, or portions thereof, which are immediately adjacent and naturally drain directly to the banks of the Des Plaines River, Chicago Sanitary and Ship Canal, DuPage River and Kankakee River without crossing over other private or public property.
   DIRECTOR.  The County Executive or his or her designee charged with performing the duties specified in the County Stormwater Management Ordinance, as codified in Chapter 55.
   DRAINAGE AREA. The land area above a given point that may contribute runoff flow at that point from rainfall.
   DRY BASIN.  A detention basin designed to drain completely after temporary storage of stormwater flows and to normally be dry over the majority of its bottom area.
   EFFECTIVE DATE.  The date to be determined by the County Board.
   ELEVATION CERTIFICATES. A form published by FEMA that is used to certify the base flood elevation and the lowest elevation of usable space to which a building has been constructed.
   EPHEMERAL STREAM.  A stream whose bed elevation does not intersect the groundwater table, it carries flow only during and immediately after a runoff producing rainfall event.
   EROSION.  The process whereby soil is detached by the action of water or wind.
   EXISTING MANUFACTURED HOME PARK OR SUBDIVISION.  A manufactured home park or subdivision for which the construction of facilities for servicing the lots on which the manufactured homes are to be affixed (including at a minimum the installation of utilities, the construction of streets, and either final site grading or the pouring of concrete pads) has been completed before the effective date of this chapter.
   EXPANSION TO AN EXISTING MANUFACTURED HOME PARK OR SUBDIVISION.  The preparation of additional sites by the construction of facilities for servicing the lots on which the manufactured homes are to be affixed (including the installation of utilities, the construction of streets, and either final site grading or the pouring of concrete pads).
   EXTENDED DETENTION.  A volume of runoff temporarily detained and released over a long period of time as specified in § 164.023.
   FARMED WETLAND. As determined following the procedures outlined by the Food Security Act and Chicago District of the Corps of Engineers.
   FEDERAL EMERGENCY MANAGEMENT AGENCY (FEMA).  The federal agency and its regulations, at 44 C.F.R. §§ 59 through 79, effective as of September 29, 1989, or as amended.
   FLOOD.  A general and temporary condition of partial or complete inundation of normally dry land areas from overflow of inland or tidal ways or the unusual and rapid accumulation of runoff of surface waters from any source.
   FLOOD FREQUENCY.  Normally expressed as a period of years, based on a percent chance of occurrence in any given year from statistical analysis, during which a flood of a stated magnitude may be expected to be equaled or exceeded. For example, the two-year flood frequency has a 50% chance of occurrence in any given year. Similarly, the 100-year flood frequency has a 1% chance of occurrence in any given year.
   FLOOD FRINGE.  The portion of the floodplain outside of the designated floodway.
   FLOOD INSURANCE RATE MAP (FIRM).  A map issued by FEMA that is an official community map, on which map FEMA has delineated both the special flood hazard areas and the risk premium zones applicable to the community. This map may or may not depict floodways.
   FLOOD INSURANCE STUDY (FIS).  A study of flood discharges and flood profiles for a community, adopted and published by FEMA.
   FLOOD PROTECTION ELEVATION (FPE).  The elevation of the BFE plus two feet of freeboard for structures within the plan limits of the base flood elevation. Outside the floodplain limits, the blocked restrictor elevation of any adjacent stormwater facility plus one foot of freeboard.
   FLOODPLAIN.  The land typically adjacent to a body of water with ground surface elevations at or below the base flood or the 100-year frequency flood elevation including detached special flood hazard areas, ponding areas and the like. The FLOODPLAIN is also known as the special flood hazard areas (SFHA).
   FLOODPLAIN ADMINISTRATOR.  The person designated by the County Executive to administer and enforce this chapter (Chief Subdivision Engineer).
   FLOODPROOF. Any combination of structural and nonstructural additions, changes or adjustments to structures or property which reduce or eliminate flood damage to real estate or improved real property, water and sanitary facilities, structures and their contents.
   FLOODPROOFING CERTIFICATE.  A form published by FEMA that is used to certify that a building has been designed and constructed to be structurally dry floodproofed to the FPE.
   FLOODWAY. Includes the channel, on stream lakes, and that portion of the floodplain adjacent to a stream or channel which is needed to store and convey the critical duration 100-year frequency flood discharge with no more than a one-tenth-foot increase in flood stage due to the loss of flood conveyance or storage, and no more than a 10% increase in velocities.
   FLOODWAY CONVEYANCE.  The measure of the flow carrying capacity of the floodway section and is defined using Manning’s equation as:
   K = 1.4863 AR 23 /n
where “n” is Manning’s roughness factor, “A” is the effective area of the cross-section, and “R” is ratio of the wetted area to the wetted perimeter.
   FORESTED WETLAND.  As defined by the Chicago District Corps of Engineers.
   FREEBOARD.  An increment of height added to the BFE or 100-year design water surface elevation to provide a factor of safety for uncertainties in calculations, unknown local conditions, wave actions and unpredictable effects such as those caused by ice or debris jams.
   FUNCTIONAL.  In the context of the usage in this chapter, FUNCTIONAL refers to stormwater facilities, which serve their primary purpose of meeting developed release rate requirements but do not meet all of the final design conditions. For example, a detention basin, which has been excavated but has not had the side slopes graded nor the final landscaping placed, may be considered FUNCTIONAL as a site runoff storage facility.
   GOOD HUSBANDRY.  The application of agricultural or conservation practices that minimize impacts to natural resources and neighboring landowners.
   GROUND WATER.  Water that is located within soil or rock below the surface of the earth. Same as SUBSURFACE WATER.
   GROUND WATER CONTROL SYSTEM.  A designed system which may consist of tiles, under drains, French drains or other appropriate stormwater facilities whose purpose is to lower the ground water table to a predictable elevation throughout the year.
   HISTORIC STRUCTURE.  Any structure that is:
      (1)   Listed individually in the National Register of Historic Places, or preliminarily determined by the Secretary of the Interior as meeting the requirements for individual listing on the National Register;
      (2)   Certified or preliminarily determined by the Secretary of the Interior as contributing to the historic district or a district preliminary determined by the Secretary to qualify as a registered historic district;
      (3)    Individually listed on the State Inventory of Historic Places by the State Historic Preservation Agency; and
      (4)   Individually listed on a local inventory of historic places that has been certified by the State Historic Preservation Agency.
   HQAR. High quality aquatic resource as defined by the Chicago District Corps of Engineers. These include waters of the United States or isolated waters of the county that are determined to be critical due to their uniqueness, scarcity, function and/or value. Appendix E provides further descriptions of HQARs.
   HYDRAULICS. The science and study of the mechanical behavior of water in physical systems and processes.
   HYDRAULICALLY CONNECTED IMPERVIOUS AREA.  Consists of those areas of concrete, asphalt and gravel surfaces along with roof tops which convey flows directly to an improved drainage system consisting of storm sewers or paved channels. Rooftops whose downspouts discharge to unpaved surfaces which are designed for the absorption and filtration of stormwater runoff shall not be considered as HYDRAULICALLY CONNECTED IMPERVIOUS SURFACES. Roadways whose primary conveyance is through open ditches and swales shall not be considered as HYDRAULICALLY CONNECTED IMPERVIOUS SURFACE. Roadways drained by curb and gutter and storm sewer, and driveways hydraulically connected to those roadways shall be considered as directly connected impervious surface.
   HYDRAULICALLY EQUIVALENT COMPENSATORY STORAGE.  Compensatory storage either adjacent to the floodplain fill or not located adjacent to the development but can be shown by hydrologic and hydraulic analysis to be equivalent to compensatory storage located adjacent to the development.
   HYDRIC SOIL.  A soil that is saturated, flooded or ponded long enough during the growing season to develop anaerobic conditions.
   HYDROLOGICALLY DISTURBED/ HYDROLOGIC DISTURBANCE.  An area where the land surface has been cleared, grubbed, compacted or otherwise modified that changes runoff, volumes, rates or direction.
   HYDROLOGY.  The science of the behavior of water, including its dynamics, composition and distribution in the atmosphere, on the surface of the earth, and underground.
   HYDROPHYTIC VEGETATION.  Plant life growing in water, soil or on a substrate that is at least periodically deficient in oxygen as a result of excessive water content.
   IDNR-OWR.  The State Department of Natural Resources, Office of Water Resources.
   IMPERVIOUS.  Surfaces that cause the majority of rainfall to be converted to direct runoff. Asphalt, concrete, roofing systems and gravel areas will be considered IMPERVIOUS.
   INTERIM WATERSHED PLAN.  A regional study of a watershed which does not address the entire range of purposes, goals and objectives outlined in the Countywide Stormwater Management Plan approved by the Committee and adopted by the county.
   INTERMITTENT STREAM.  A stream whose bed intersects the groundwater table for only a portion of the year on the average or any stream which flows continuously for at least one month out of the year but not the entire year.
   ISOLATED WATERS OF WILL COUNTY.  All waters such as lakes, ponds, streams, (including intermittent streams), farmed wetlands and wetlands that are located within unincorporated county but not necessarily under the United States Army Corps of Engineers jurisdiction. The limits of the ISOLATED WATERS OF WILL COUNTY extend to the ordinary high water mark or delineated wetland boundary. ISOLATED WATERS OF WILL COUNTY exclude permitted excavations created for purposes such as stormwater conveyance, detention/recreation areas as constructed as part of a stormwater management system, recreation, stock watering, irrigation, settling basins or wastewater treatment systems and roadside ditches. Compensatory wetland mitigation created to meet the requirements of this chapter or § 404 of the Clean Water Act is not excluded.
   JURISDICTIONAL WETLAND.  A wetland that is under the jurisdiction of the Army Corps of Engineers.
   LETTER OF MAP AMENDMENT (LOMA).  The official determination by FEMA that a specific structure is not in a regulatory floodplain. A LOMA amends the effective FIRM.
   LETTER OF MAP CHANGE (LOMC). A letter from FEMA that revised base flood elevations, flood insurance rate zones, flood boundaries or floodway as shown on an effective FIRM.
   LETTER OF MAP REVISION (LOMR). A letter from FEMA that revises base flood elevations, flood insurance rate zones, flood boundaries or floodway as shown on an effective FIRM.
   LAKE. A natural or artificial body of water encompassing an area of two or more acres, which retains water throughout the year.
   LOWEST FLOOR. The lowest floor of the lowest enclosed area (including basement). An unfinished or flood resistant enclosure usable solely for parking of vehicles, building access or storage, in an area other than a basement area is not considered a building’s LOWEST FLOOR provided that the enclosure is not built so as to render the structure in violation of the applicable non-elevation design requirements of this chapter.
   MAINTENANCE SPECIAL SERVICE AREA. A backup funding mechanism which may be enacted by the County Board in the event that the person or entity charged with maintenance of the special service area fails to adequately carry out and/or provide maintenance and upkeep of the area as it relates to § 605 of this chapter.
   MAJOR STORMWATER SYSTEM.  The portion of a stormwater facility needed to store and convey flows beyond the capacity of the minor stormwater system.
   MANUFACTURED HOME.  A structure transportable in one or more sections, which is built on a permanent chassis and is designated for use with or without a permanent foundation when attached to the required utilities. The term MANUFACTURED HOME also includes park trailers, travel trailers and other similar vehicles placed on site for more than 180 consecutive days. The term MANUFACTURED HOME does not include a recreational vehicle.
   MANUFACTURED HOME PARK OR SUBDIVISION. A parcel (or contiguous parcels) of land divided into two or more manufactured home lots for rent or sale.
   MASS GRADING. Development in which the primary activity is a change in topography affected by the movement of earth materials.
   MINOR STORMWATER SYSTEM.  Consists of all infrastructure including curb, gutter, culverts, roadside ditches and swales, storm sewers and sub-surface drainage systems intended to convey stormwater runoff at less than a 100-year flood frequency. The MINOR STORMWATER SYSTEMS shall be designed to carry a ten-year storm event, or as required by the affected Highway Department jurisdiction.
   MINOR SUBDIVISION.  Any subdivision containing not more than five lots and not involving any new streets, roads or extension of municipal facilities, and not in conflict with any provision or portion of the zoning ordinance, subdivision regulations or official plan or map relating thereto.
   MITIGATION.  Measures taken to offset negative impacts from development in wetlands or the floodplain. MITIGATION includes those measures taken to eliminate or minimize damage from development activities by replacement of the resource, such as compensatory storage, soil erosion and sedimentation control, wetland replacement and channel restoration. MITIGATION may also include those activities taken to reduce a structure’s susceptibility to flooding.
   NATURAL. In reference to watercourses, those stream channels, grassed waterways and swales means those stream channels, grassed waterways, and swales formed by the existing surface topography of the earth prior to changes made by man. A natural stream tends to follow a meandering path; its floodplain is not constrained by levees; the area near the bank has not been cleared, mowed or cultivated; the stream flows over soil and geologic materials typical of the area with no substantial alteration of the course or cross-section of the stream caused by filling or excavating. A modified stream channel, grassed waterway or swale which has regained natural characteristics over time as it meanders and re-establishes vegetation may be considered NATURAL.
   NATURALIZED DETENTION BASIN.  A constructed basin for the temporary storage of stormwater runoff with a controlled release rate which creates growing conditions suitable for emergent and riparian wetland plants, and which is explicitly designed to lessen the impacts of stormwater quality and quantity in urban and urbanizing areas.
   NAVD 88 (NORTH AMERICAN VERTICAL DATUM OF 1988). The accepted standard orthometric data, referenced to the single control point at Father Point, Quebec, Canada. NAVD 88 supersedes the National Geodetic Vertical Datum of 1929 (NGVD).
   NATIONAL FLOOD INSURANCE PROGRAM (NFIP).  A federal program whose requirements are codified in C.F.R. Title 44.
   NET BENEFIT IN WATER QUALITY.  The institution of best management practices as part of a development that when compared to the pre-development condition can be judged to reduce downstream sediment loading or pollutant loadings.
      (1)   A finding that, when compared to the existing condition, the developed project will do one of the following:
         (a)   Substantially reduce (more than 10%) downstream peak discharges;
         (b)   Reduce downstream flood stages (more than one-tenth foot); or
         (c)   Reduce downstream damages to structures occurring in the pre-development condition.
      (2)   The demonstration of one of these conditions must be through detailed hydrologic and hydraulic analysis of watersheds on a regional scale as approved by the Stormwater Administrator.
   NEW MANUFACTURED HOME PARK OR SUBDIVISION. Manufactured home park or subdivision for which the construction of facilities for servicing the lots on which the manufactured homes are to be affixed (including at a minimum the installation of utilities, the construction of streets and either final site grading or the pouring of concrete pads) has been completed after the effective date of this chapter.
   NON-RIVERINE.  Areas not associated with a stream or river such as isolated depressional storage areas, ponds and lakes.
   NPDES.  National pollutant discharge elimination system.
   NPDES PERMIT. A permit from the State Environmental Protection Agency for discharge of stormwater associated with construction activities disturbing one acre or more.
   NRCS. The United States Department of Agriculture, Natural Resources Conservation Service.
   OBSERVATION STRUCTURES.  Structures built on a field tile where the pipe inflow and outflow is visible upon removal of a lid.
   ONE-HUNDRED YEAR EVENT. A rainfall, runoff, or flood event having a 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 and surface drainage. OPEN CHANNELS do not include grassed swales within farm fields under agricultural production, which are ephemeral in nature.
   ORDINARY HIGH WATER MARK (OHWM).  The point on the bank or shore up to which the presence and action of surface water is so continuous so as to leave a distinctive mark, such as by erosion, destruction or prevention of terrestrial vegetation, predominance of aquatic vegetation or other easily recognized characteristic.
   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.
   OVERSIGHT COMMITTEE.  The County Land Use and Development Committee. See § 164.165.
   PARCEL. A contiguous area of land under unified ownership, separately owned and capable of being separately conveyed.
   PEAK FLOW.  The maximum rate of flow of water at a given point.
   PERENNIAL STREAMS.  Riverine watercourses whose thalwag generally intersects the ground water table elevation and flows throughout the year.
   PLAN.  The  County Comprehensive Countywide Stormwater Management Plan, adopted by the  County Board on October 13, 1998, as amended from time to time.
   POND.  A body of water of less than two acres, which retains a normal water level year round.
   PRIMARY GRAVITY OUTLET. The outlet structure designed to meet the release rate requirements of this chapter.
   PROFESSIONAL ENGINEER.  An engineer registered in the state, under the State Professional Engineering Practice Act. (ILCS Ch. 225, Act 325, §§ 1 et seq.), as amended.
   PROFESSIONAL LAND SURVEYOR. A land surveyor registered in the state, under the State Land Surveyors Act. (ILCS Ch. 225, Act 330, §§ 1 et seq.), as amended.
   PROPERTY. Contiguous land under single ownership or control.
   PROPERTY OWNER’S ASSOCIATION. The legal entity created for the purpose of developing, selling, managing and maintaining a residential, commercial or industrial development which shall have the primary responsibility for providing for the care, maintenance, renewal and replacement of stormwater drainage facilities. May also known as HOMEOWNER’S ASSOCIATION.
   PUBLIC BODIES OF WATER.  All open public streams and lakes capable of being navigated by watercraft in whole or in part for commercial uses and purposes and all lakes, rivers and streams, which in their natural conditions were capable of being improved and made navigable, or that are connected with or discharge their waters into navigable lakes or rivers within, or upon the borders of the state, together with all bayous, sloughs, backwaters and submerged lands that are open to the main channel or body of water directly accessible thereto.
   PUBLIC FLOOD CONTROL PROJECT.  A flood control project, which will be operated and maintained by a public agency to reduce flood damages to existing buildings and structures, which includes a hydrologic and hydraulic study of the existing and proposed conditions of the watershed. Nothing in this definition shall preclude the design, engineering, construction or financing in whole or in part of a flood control project by persons or parties who are not public agencies.
   PUBLIC FLOOD EASEMENT.  An easement acceptable to the appropriate jurisdictional body that meets the regulations of the OWR, the Department, and the community, and that provides legal assurances that all areas subject to flooding in the created backwater of the development will remain open to allow flooding.
   QUALIFIED WETLAND PROFESSIONAL.  A person trained in natural and/or physical sciences (such as one or more of the disciplines of biology, geology, soil science, engineering or hydrology) whose training and experience ensure a competent analysis and assessment of stream, lake, pond and wetland conditions and impacts.
   RECORD DRAWINGS.  Drawings prepared, signed, and sealed by a registered professional engineer or registered land surveyor representing the final “as-built” record of the actual in-place elevations, location of structures and topography.
      (1)   Built on a single chassis;
      (2)   Four hundred square feet or less when measured at the largest horizontal projection;
      (3)   Designed to be self propelled or permanently towable by a light duty truck; and
      (4)   Designed primarily not for use as a permanent dwelling, but as a temporary living quarters for recreational camping travel or seasonal use.
   REDEVELOPMENT.  Development on a parcel upon which the existing condition is buildings, parking lots and/or infrastructure.
   REGIONAL PERMITS. Offered for pre- approved projects that are considered minor projects that are permissible per IDNR/OWR Part 3708 rules for Northeastern Illinois regulatory floodways. A complete listing of the terms and conditions for specific project types can be obtained from the IDNR/OWR website. However, a regional permit from IDNR/OWR does not exempt a project from securing a site development permit.
   REGISTERED STRUCTURAL ENGINEER.  A person licensed under the laws of the state as a structural engineer.
   REGULATORY FLOODPLAIN. The floodplain as depicted on maps recognized by FEMA as defining the limits of the SFHA.
   REGULATORY FLOODWAY.  Those portions of the floodplain depicted on maps as floodway and recognized by the IDNR-OWR for regulatory purposes.
   REPAIR, REMODELING OR MAINTENANCE.  Development activities that do not result in any increases in the outside dimensions of a building or any changes to the dimensions of a structure.
   REPETITIVE LOSS.  Flood-related damages sustained by a structure on two separate occasions during a ten-year period for which the cost of repairs at the time of each flood event, on the average, equals or exceeds 25% of the market value of the structure before the damage occurred.
   RETENTION FACILITY.  Stores stormwater runoff without a gravity release.
   RIPRAP. Large size, coarse aggregate with angular edges normally placed at end sections of storm sewer inlets or outlets, culverts or along shorelines to reduce soil erosion.
   RIVER FRONTAGE.  The property that is immediately adjacent to and naturally drains directly to the Des Plaines River, Chicago Sanitary and Ship Canal, DuPage River or Kankakee River without crossing over other private or public property.
   RIVERINE.  Related to, formed by or resembling a channel (including creeks and rivers).
   RIVERINE SFHA.  Any SFHA subject to flooding from a river, creek, intermittent stream, ditch, on-stream lake system or any other identified channel. This term does not include areas subject to flooding from lakes, ponding areas, areas of sheet flow or other areas not subject to over bank flooding.
   RUNOFF.  The waters derived from melting snow or rain falling within a tributary drainage basin that exceeds the infiltration capacity of the soils of that basin.
   RUNOFF POLLUTANTS. Sediment, heavy metals, petroleum-based organic compounds, nutrients, oxygen-demanding organics (BOD), pesticides, salt and pathogens which may be present in stormwater runoff.
   SEASONAL HIGH GROUND WATER TABLE.  The upper limits of the soil temporarily saturated with water.
   SEDIMENTATION. The process that deposits hydraulically moved soils, debris and other materials either on other ground surfaces or in bodies of water, watercourses or stormwater drainage systems.
   SEDIMENT TRAP.  A structure or area that allows for the temporary deposit and removal or disposal of sediment materials from stormwater runoff.
   SEEPAGE. The movement of drainable water through soil and rock.
   SITE. A lot or a parcel of land where grading work is performed as a single unified operation.
   SITE DEVELOPMENT PERMIT.  A permit issued by the County Land Use Department for the construction or alteration of ground improvements and structures for the control of erosion, runoff and grading, or for the clearing, grading, stripping, excavating or filling of land.
   STORMWATER ADMINISTRATOR. The person designated by the County Executive to administer and enforce this chapter in the unincorporated areas of the county.
   STORMWATER DRAINAGE SYSTEM.  All means, natural or human-made, used for conducting stormwater to, through or from, a drainage area to the point of final outlet from a property. The STORMWATER DRAINAGE SYSTEM includes, but is not limited to, any of the following: conduits, appurtenance features, canals, channels, ditches, streams, culverts, streets, storm sewers, detention basins, swales and pumping stations.
   STORMWATER FACILITY.  All ditches, channels, conduits, bridges, culverts, levees, ponds, natural and human-made impoundments, wetlands, riparian environment, tile, swales, sewers or other natural or artificial structures or measures which serve as a means of draining surface and subsurface water from land.
   STORMWATER MANAGEMENT PERMIT.  The permit issued under §§ 164.080 through 164.085. Also called a SITE DEVELOPMENT PERMIT.
   STORMWATER RUNOFF. The waters derived from melting snow or rain falling within a tributary drainage basin which are in excess of the infiltration capacity of the soils of that basin, which flow over the surface of the ground or are collected in channels or conduits.
   STORM SEWER. A closed conduit for conveying collected stormwater.
   STREAM. Any river, creek, brook, branch, flowage, ravine or natural or human-made drainage way which has a definite bed and banks or shoreline, in or into which surface or groundwater flows, either perennially or intermittently.
   STRUCTURE.  The results of a built change to the land constructed on or below the ground, including the 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 or installing a travel trailer on a site for more than 180 days unless they are fully licensed and ready for highway use.
   SUBSTANTIAL IMPROVEMENT.  Any reconstruction, rehabilitation, addition or improvement of a structure taking place during a ten-year period, in which the cumulative percentage of improvements equals or exceeds 50% of the market value of the structure before the improvement or repair is started. SUBSTANTIAL IMPROVEMENT is considered to occur when the first alteration of any wall, ceiling, floor or other structural part of the building commences, whether or not that alteration affects the external dimensions of the building. This term includes structures that have incurred repetitive loss or substantial damage, regardless of the actual work done. This term does not, however, include any project for improvement of a structure to comply with existing state or local health, sanitary or safety code specifications which are solely necessary to assure safe living conditions, or any alteration of a historic structure listed on the National Register of historic Places or the State Register of historic places, provided that the alteration will not preclude the structure’s continued designation as a historic structure.
   SUBSURFACE DRAINAGE.  The removal of excess soil water to control water table levels at predetermined elevations for structural, environmental or other reasons in areas already developed or being developed for agricultural, residential, industrial, commercial or recreational uses.
   SUBSURFACE WATER.  Water beneath the ground or pavement surface. Sometimes referred to as GROUND WATER or SOIL WATER.
   T FACTOR.  The soil loss tolerance. It is defined as the maximum amount of erosion at which the quality of a soil as a medium for plant growth can be maintained. Erosion losses are estimated by Universal Soil Loss Equation (USLE) and Revised Universal Soil Loss Equation (RUSLE).
   TECHNICAL GUIDANCE MANUAL.  The manual adopted by the County Board, which refers to the County Stormwater Management Ordinance, as codified in Chapter 55, and provides additional explanations and examples.
   THALWAG. A line along the lowest point in a channel.
   TRANSITION SECTION.  Reaches of the stream or floodway where water flows from a narrow cross-section to a wide cross-section, or vice versa.
      (1)   Built on a single chassis;
      (2)   Four hundred square feet or less when measured at the largest horizontal projection;
      (3)   Designed to be self propelled or permanently towable by a light duty truck; and
      (4)   Designed primarily not for use as a permanent dwelling, but as a temporary living quarters for recreational camping travel or seasonal use.
   TWO-YEAR EVENT. A runoff, rainfall, or flood event having a 50% chance of occurring in any given year.
   USABLE SPACE.  Space used for dwelling, storage, utilities or other beneficial purposes, including, without limitation, basements.
   VIOLATION. The failure of a structure or other development to be fully compliant with the community’s floodplain management regulations. A structure or other development without the elevation certificate, other certifications or other evidence of compliance is presumed to be in violation until a time as that documentation is provided.
   WATER TABLE. The upper limit of a free water surface in a saturated soil or underlying material.
   WATERS OF THE UNITED STATES.  As defined by the United States Army Corps of Engineers in their Federal Methodology for the Regulation of Wetlands. For purposes of this chapter, WATERS OF THE UNITED STATES include wetlands, lakes, rivers, streams, creeks, bogs, fens and ponds. WATERS OF THE UNITED STATES do not include maintained stormwater facilities.
   WATERSHED.  All land area drained by, or contributing water to, the same stream, lake, stormwater facility or draining to a point.
   WATERSHED CHARACTERISTICS.  Includes land use, physiology, habitat, climate, drainage system and community profile.
   WATERSHED PLAN.  A study and evaluation of an individual drainage basin’s stormwater management, floodplain management, water quality and flood control needs and capabilities.
   WET BASIN.  A detention basin designed to maintain a permanent pool of water after the temporary storage of stormwater runoff.
      (1)   As defined in current federal methodology recognized by the United States Army Corps of Engineers for regulatory purposes. WETLANDS are areas that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions (known as hydrophytic vegetation).
      (2)   A WETLAND is identified based upon the three attributes:
         (a)   Hydrology;
         (b)   Soils; and
         (c)   Vegetation as mandated by the current federal wetland determination methodology.
      (3)   Classification of areas shall follow the United States Army Corps of Engineers Wetlands Delineation Manual, Technical Report Y-87-1.
   WETLAND BASIN.  A detention basin designed with all or a portion of its bottom area as a wetland.
   WETLAND IMPACT. Wetlands that are hydrologically disturbed or otherwise adversely affected by flooding, filling, excavation or drainage that results from implementation of a development activity.
   WETLAND MITIGATION CREDITS.  A credit is equal to one acre of wetland mitigation. The value of mitigation to generate credit is calculated differently depending the form of the mitigation.
   WOODLANDS. An area with a contiguous tree canopy area, including younger understory trees, of at least one acre that contains healthy deciduous coniferous trees as determined by a qualified professional.
(Ord. 10-164, passed 6-17-2010; Ord. 19-238, passed 9-19-2019)